Discussion:
Small battery bank vs too large array
(too old to reply)
Drake
2012-07-19 21:20:45 UTC
Permalink
Hello Wrenches,

Where can I get a device that will measure current through a shunt
and create a signal to trigger a relay?

We want to be able to use a 2 kW array with four, 200 AH sealed
batteries on an Outback system. 2 kW of PV would be too much
amperage for the batteries. The idea is to open relays to disengage
strings in conditions of high current to the batteries.

The reason for this is to create backup systems where power will be
abundantly available when the sun shines. The system will normally
connect to the grid, except during outages. In normal charging
conditions the power will go straight to the grid. When the grid is
down, power will be available for loads and battery charging, but
batteries will be protected from overcharge?

Any suggestions on ways to accomplish this are welcome!

Thanks

Drake


Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
<http://athens-electric.com/>http://athens-electric.com/
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Jason Szumlanski
2012-07-19 21:53:04 UTC
Permalink
I could be wrong, but I thought the FM60 and FM80 charge controllers have
adjustable current limits that apply to battery charging, and I think when
integrated with GVFX inverters in sell mode and a Mate controller, you will
be able to accomplish what you need to do without a relay. I always thought
when the charge controller indicated GT Mode and was in bulk charging mode
that the current limit would be essentially ignored because the battery
voltage is above the sell voltage and any available DC current would be
inverted and sold to the grid. In other words, the batteries are full, so
they are not being charged - the FM60 and GVFX communicate and balance the
current available for selling.

You may want to talk to Outback about that, because I don't think it is
documented all that well, and again, I could be wrong. I've never installed
that much solar on a small battery, so it never came up! Incidentally, I
have someone that came in today looking for a 5kW grid-interactive system
and a small battery to handle critical loads. I was leaning to an AC
coupled system to get away from the issue you describe, but now I am
second-guessing that theory. I'd be interested to learn what you discover.

Most inverter manufacturer's have a minimum battery size, but that
seemingly is there to address the maximum possible current out of the
battery, not the charging rate because that can be limited, too.

Jason Szumlanski
Fafco Solar


On Thu, Jul 19, 2012 at 5:20 PM, Drake <drake.chamberlin at redwoodalliance.org
Post by Drake
Hello Wrenches,
Where can I get a device that will measure current through a shunt and
create a signal to trigger a relay?
We want to be able to use a 2 kW array with four, 200 AH sealed batteries
on an Outback system. 2 kW of PV would be too much amperage for the
batteries. The idea is to open relays to disengage strings in conditions
of high current to the batteries.
The reason for this is to create backup systems where power will be
abundantly available when the sun shines. The system will normally connect
to the grid, except during outages. In normal charging conditions the
power will go straight to the grid. When the grid is down, power will be
available for loads and battery charging, but batteries will be protected
from overcharge?
Any suggestions on ways to accomplish this are welcome!
Thanks
Drake
Drake Chamberlin
*Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
*http://athens-electric.com/
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
www.re-wrenches.org/etiquette.htm
www.members.re-wrenches.org
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Brian Teitelbaum
2012-07-19 23:35:14 UTC
Permalink
Drake,

I've been hounding a couple of the charge controller manufactures about this issue, but so far I just haven't seen a light bulb go off in their heads, but I'll keep trying, and maybe this is a better forum to do it.

MPPT controllers can be adjusted to current limit at amperage values below their rating, but if you do that, you are also limiting the output of the array in general, and the amount of PV power available to run the loads directly from the array (through the inverter). Not the best use of available PV power.

Say you have an 80A controller and a 200AH battery. With current technology, you have two choices:

Let the controller operate at 80A. If you have loads to draw off some of the current (or sell to the grid), great, but if not you could be seeing a charge rate of C/2.5, which would be pretty hard on a sealed 200AH battery, to say the least. Granted, the battery voltage would rise pretty quickly, and the controller would start to taper off, but it would still see high currents especially if the absorption time is set long. Not a happy scenario.

Or, you can set the current limiting on the controller to 20A for a C/10 charge rate. But if you had loads drawing 60A, you would be pulling that additional 40A from the battery and not using the array's full power. Also not a happy scenario.

What we need is a controller that can read the signal from a shunt at the battery, and use that as the basis of current limiting control.

For example, if we have an array that can produce 80A of current, but we want to limit the battery to 20A of charge, there would be 60A of potential current there to run loads without drawing on the battery. If there are no loads running, the controller should current limit at 20A (reading from a shunt), but if loads are turned on, the controller should be able to let more current through while still limiting the battery to 20A. When loads are shut off, the controller should go back to a 20A limit.

This doesn't all have to happen very quickly as a battery can take a heavier charge for a short period of time, but I think that this would be a major improvement of controller function.

Of course, if you are grid-tied you can sell all the excess power, but if the grid goes down, or you are off-grid....?

Because of the low cost of PV and the high cost of batteries these days, I'm seeing more and more requests for large arrays with smaller batteries. I also think that PV is now cheap enough to allow for oversizing of arrays for better battery charging on cloudy days, which can reduce generator run times. We need smarter controllers.

What say ye, charge controller gurus?

Brian Teitelbaum
AEE Solar

From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Drake
Sent: Thursday, July 19, 2012 2:21 PM
To: RE-wrenches
Subject: [RE-wrenches] Small battery bank vs too large array

Hello Wrenches,

Where can I get a device that will measure current through a shunt and create a signal to trigger a relay?

We want to be able to use a 2 kW array with four, 200 AH sealed batteries on an Outback system. 2 kW of PV would be too much amperage for the batteries. The idea is to open relays to disengage strings in conditions of high current to the batteries.

The reason for this is to create backup systems where power will be abundantly available when the sun shines. The system will normally connect to the grid, except during outages. In normal charging conditions the power will go straight to the grid. When the grid is down, power will be available for loads and battery charging, but batteries will be protected from overcharge?

Any suggestions on ways to accomplish this are welcome!

Thanks

Drake


Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
http://athens-electric.com/
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toddcory
2012-07-20 00:02:58 UTC
Permalink
what is the point of having battery backup if is is so small as to not really be able to back anything up (except when the sun is shining)?

this seems like a system design error rather than a charge controller problem.

my .02

todd




On Thursday, July 19, 2012 4:35pm, "Brian Teitelbaum" <bteitelbaum at aeesolar.com> said:




Drake,

I?ve been hounding a couple of the charge controller manufactures about this issue, but so far I just haven?t seen a light bulb go off in their heads, but I?ll keep trying, and maybe this is a better forum to do it.

MPPT controllers can be adjusted to current limit at amperage values below their rating, but if you do that, you are also limiting the output of the array in general, and the amount of PV power available to run the loads directly from the array (through the inverter). Not the best use of available PV power.

Say you have an 80A controller and a 200AH battery. With current technology, you have two choices:

Let the controller operate at 80A. If you have loads to draw off some of the current (or sell to the grid), great, but if not you could be seeing a charge rate of C/2.5, which would be pretty hard on a sealed 200AH battery, to say the least. Granted, the battery voltage would rise pretty quickly, and the controller would start to taper off, but it would still see high currents especially if the absorption time is set long. Not a happy scenario.

Or, you can set the current limiting on the controller to 20A for a C/10 charge rate. But if you had loads drawing 60A, you would be pulling that additional 40A from the battery and not using the array?s full power. Also not a happy scenario.

What we need is a controller that can read the signal from a shunt at the battery, and use that as the basis of current limiting control.

For example, if we have an array that can produce 80A of current, but we want to limit the battery to 20A of charge, there would be 60A of potential current there to run loads without drawing on the battery. If there are no loads running, the controller should current limit at 20A (reading from a shunt), but if loads are turned on, the controller should be able to let more current through while still limiting the battery to 20A. When loads are shut off, the controller should go back to a 20A limit.

This doesn?t all have to happen very quickly as a battery can take a heavier charge for a short period of time, but I think that this would be a major improvement of controller function.

Of course, if you are grid-tied you can sell all the excess power, but if the grid goes down, or you are off-grid?.?

Because of the low cost of PV and the high cost of batteries these days, I?m seeing more and more requests for large arrays with smaller batteries. I also think that PV is now cheap enough to allow for oversizing of arrays for better battery charging on cloudy days, which can reduce generator run times. We need smarter controllers.

What say ye, charge controller gurus?

Brian Teitelbaum
AEE Solar



From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Drake
Sent: Thursday, July 19, 2012 2:21 PM
To: RE-wrenches
Subject: [RE-wrenches] Small battery bank vs too large array

Hello Wrenches,

Where can I get a device that will measure current through a shunt and create a signal to trigger a relay?

We want to be able to use a 2 kW array with four, 200 AH sealed batteries on an Outback system. 2 kW of PV would be too much amperage for the batteries. The idea is to open relays to disengage strings in conditions of high current to the batteries.

The reason for this is to create backup systems where power will be abundantly available when the sun shines. The system will normally connect to the grid, except during outages. In normal charging conditions the power will go straight to the grid. When the grid is down, power will be available for loads and battery charging, but batteries will be protected from overcharge?

Any suggestions on ways to accomplish this are welcome!

Thanks

Drake


Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
[http://athens-electric.com/] http://athens-electric.com/


Sent from Finest Planet WebMail.
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Jason Szumlanski
2012-09-05 13:11:22 UTC
Permalink
This thread is a little stale, but I have an application to bring it back
to life.

Has anyone designed a solar powered go-kart? There is a high school
challenge here sponsored by the local University. This seems like an
application that could use a large array with a small battery to keep
weight down. I'm considering a 69aH-85aH AGM battery range @ 48V with three
SunPower 327W modules wired in series with a Midnite 250 controller.

Any advice would be appreciated, especially regarding:

- Safety
- Monitoring
- Maximizing endurance (ties into monitoring)


Jason Szumlanski
Fafco Solar
Post by toddcory
what is the point of having battery backup if is is so small as to not
really be able to back anything up (except when the sun is shining)?
this seems like a system design error rather than a charge controller problem.
my .02
todd
On Thursday, July 19, 2012 4:35pm, "Brian Teitelbaum" <
Drake,
I?ve been hounding a couple of the charge controller manufactures about
this issue, but so far I just haven?t seen a light bulb go off in their
heads, but I?ll keep trying, and maybe this is a better forum to do it.
MPPT controllers can be adjusted to current limit at amperage values
below their rating, but if you do that, you are also limiting the output of
the array in general, and the amount of PV power available to run the loads
directly from the array (through the inverter). Not the best use of
available PV power.
Say you have an 80A controller and a 200AH battery. With current
Let the controller operate at 80A. If you have loads to draw off some of
the current (or sell to the grid), great, but if not you could be seeing a
charge rate of C/2.5, which would be pretty hard on a sealed 200AH battery,
to say the least. Granted, the battery voltage would rise pretty quickly,
and the controller would start to taper off, but it would still see high
currents especially if the absorption time is set long. Not a happy
scenario.
Or, you can set the current limiting on the controller to 20A for a C/10
charge rate. But if you had loads drawing 60A, you would be pulling that
additional 40A from the battery and not using the array?s full power. Also
not a happy scenario.
What we need is a controller that can read the signal from a shunt at
the battery, and use that as the basis of current limiting control.
For example, if we have an array that can produce 80A of current, but we
want to limit the battery to 20A of charge, there would be 60A of potential
current there to run loads without drawing on the battery. If there are no
loads running, the controller should current limit at 20A (reading from a
shunt), but if loads are turned on, the controller should be able to let
more current through while still limiting the battery to 20A. When loads
are shut off, the controller should go back to a 20A limit.
This doesn?t all have to happen very quickly as a battery can take a
heavier charge for a short period of time, but I think that this would be a
major improvement of controller function.
Of course, if you are grid-tied you can sell all the excess power, but
if the grid goes down, or you are off-grid?.?
Because of the low cost of PV and the high cost of batteries these days,
I?m seeing more and more requests for large arrays with smaller batteries.
I also think that PV is now cheap enough to allow for oversizing of arrays
for better battery charging on cloudy days, which can reduce generator run
times. We need smarter controllers.
What say ye, charge controller gurus?
Brian Teitelbaum
AEE Solar
re-wrenches-bounces at lists.re-wrenches.org] *On Behalf Of *Drake
*Sent:* Thursday, July 19, 2012 2:21 PM
*To:* RE-wrenches
*Subject:* [RE-wrenches] Small battery bank vs too large array
Hello Wrenches,
Where can I get a device that will measure current through a shunt and
create a signal to trigger a relay?
We want to be able to use a 2 kW array with four, 200 AH sealed batteries
on an Outback system. 2 kW of PV would be too much amperage for the
batteries. The idea is to open relays to disengage strings in conditions
of high current to the batteries.
The reason for this is to create backup systems where power will be
abundantly available when the sun shines. The system will normally connect
to the grid, except during outages. In normal charging conditions the
power will go straight to the grid. When the grid is down, power will be
available for loads and battery charging, but batteries will be protected
from overcharge?
Any suggestions on ways to accomplish this are welcome!
Thanks
Drake
Drake Chamberlin
*Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
*http://athens-electric.com/
Sent from Finest Planet WebMail.
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
www.re-wrenches.org/etiquette.htm
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Jason Szumlanski
2012-09-05 13:11:22 UTC
Permalink
This thread is a little stale, but I have an application to bring it back
to life.

Has anyone designed a solar powered go-kart? There is a high school
challenge here sponsored by the local University. This seems like an
application that could use a large array with a small battery to keep
weight down. I'm considering a 69aH-85aH AGM battery range @ 48V with three
SunPower 327W modules wired in series with a Midnite 250 controller.

Any advice would be appreciated, especially regarding:

- Safety
- Monitoring
- Maximizing endurance (ties into monitoring)


Jason Szumlanski
Fafco Solar
Post by toddcory
what is the point of having battery backup if is is so small as to not
really be able to back anything up (except when the sun is shining)?
this seems like a system design error rather than a charge controller problem.
my .02
todd
On Thursday, July 19, 2012 4:35pm, "Brian Teitelbaum" <
Drake,
I?ve been hounding a couple of the charge controller manufactures about
this issue, but so far I just haven?t seen a light bulb go off in their
heads, but I?ll keep trying, and maybe this is a better forum to do it.
MPPT controllers can be adjusted to current limit at amperage values
below their rating, but if you do that, you are also limiting the output of
the array in general, and the amount of PV power available to run the loads
directly from the array (through the inverter). Not the best use of
available PV power.
Say you have an 80A controller and a 200AH battery. With current
Let the controller operate at 80A. If you have loads to draw off some of
the current (or sell to the grid), great, but if not you could be seeing a
charge rate of C/2.5, which would be pretty hard on a sealed 200AH battery,
to say the least. Granted, the battery voltage would rise pretty quickly,
and the controller would start to taper off, but it would still see high
currents especially if the absorption time is set long. Not a happy
scenario.
Or, you can set the current limiting on the controller to 20A for a C/10
charge rate. But if you had loads drawing 60A, you would be pulling that
additional 40A from the battery and not using the array?s full power. Also
not a happy scenario.
What we need is a controller that can read the signal from a shunt at
the battery, and use that as the basis of current limiting control.
For example, if we have an array that can produce 80A of current, but we
want to limit the battery to 20A of charge, there would be 60A of potential
current there to run loads without drawing on the battery. If there are no
loads running, the controller should current limit at 20A (reading from a
shunt), but if loads are turned on, the controller should be able to let
more current through while still limiting the battery to 20A. When loads
are shut off, the controller should go back to a 20A limit.
This doesn?t all have to happen very quickly as a battery can take a
heavier charge for a short period of time, but I think that this would be a
major improvement of controller function.
Of course, if you are grid-tied you can sell all the excess power, but
if the grid goes down, or you are off-grid?.?
Because of the low cost of PV and the high cost of batteries these days,
I?m seeing more and more requests for large arrays with smaller batteries.
I also think that PV is now cheap enough to allow for oversizing of arrays
for better battery charging on cloudy days, which can reduce generator run
times. We need smarter controllers.
What say ye, charge controller gurus?
Brian Teitelbaum
AEE Solar
re-wrenches-bounces at lists.re-wrenches.org] *On Behalf Of *Drake
*Sent:* Thursday, July 19, 2012 2:21 PM
*To:* RE-wrenches
*Subject:* [RE-wrenches] Small battery bank vs too large array
Hello Wrenches,
Where can I get a device that will measure current through a shunt and
create a signal to trigger a relay?
We want to be able to use a 2 kW array with four, 200 AH sealed batteries
on an Outback system. 2 kW of PV would be too much amperage for the
batteries. The idea is to open relays to disengage strings in conditions
of high current to the batteries.
The reason for this is to create backup systems where power will be
abundantly available when the sun shines. The system will normally connect
to the grid, except during outages. In normal charging conditions the
power will go straight to the grid. When the grid is down, power will be
available for loads and battery charging, but batteries will be protected
from overcharge?
Any suggestions on ways to accomplish this are welcome!
Thanks
Drake
Drake Chamberlin
*Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
*http://athens-electric.com/
Sent from Finest Planet WebMail.
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
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maverick
2012-07-20 02:34:24 UTC
Permalink
I say it is waste of time.

1. AGM batteries can take the high current and you are right, the absorb voltage is reached and the absorb current is tapered rather quickly. Current generation charge controllers are rather fast at the transitions. I have a bunch of data from a system with a PentaMetric that shows the battery bank going to absorb voltage at grid tie, during cloud events, but only for a few seconds at a time.

2. A properly designed GTBB system should cover the connected loads for 24 hours of each sunny day, at a minimum. Keep in mind, off grid systems are designed for that, and 3 days + of backup, etc.

3. I would say, based on my experience, the minimum battery bank should be 400Ah. I personally try to set it at 600Ah (48V). It is a backup system after all. But the key is the customer's expectations...who are they going to call after the lights go out?


Thank you,

Maverick


Maverick Brown
BSEET, NABCEP Certified Solar PV Installer ?
President & CEO
Maverick Solar Enterprises, Inc.
Office: 512-919-4493
Cell: 512-460-9825

Sent from my HondaJet!
Post by Brian Teitelbaum
Drake,
I?ve been hounding a couple of the charge controller manufactures about this issue, but so far I just haven?t seen a light bulb go off in their heads, but I?ll keep trying, and maybe this is a better forum to do it.
MPPT controllers can be adjusted to current limit at amperage values below their rating, but if you do that, you are also limiting the output of the array in general, and the amount of PV power available to run the loads directly from the array (through the inverter). Not the best use of available PV power.
Let the controller operate at 80A. If you have loads to draw off some of the current (or sell to the grid), great, but if not you could be seeing a charge rate of C/2.5, which would be pretty hard on a sealed 200AH battery, to say the least. Granted, the battery voltage would rise pretty quickly, and the controller would start to taper off, but it would still see high currents especially if the absorption time is set long. Not a happy scenario.
Or, you can set the current limiting on the controller to 20A for a C/10 charge rate. But if you had loads drawing 60A, you would be pulling that additional 40A from the battery and not using the array?s full power. Also not a happy scenario.
What we need is a controller that can read the signal from a shunt at the battery, and use that as the basis of current limiting control.
For example, if we have an array that can produce 80A of current, but we want to limit the battery to 20A of charge, there would be 60A of potential current there to run loads without drawing on the battery. If there are no loads running, the controller should current limit at 20A (reading from a shunt), but if loads are turned on, the controller should be able to let more current through while still limiting the battery to 20A. When loads are shut off, the controller should go back to a 20A limit.
This doesn?t all have to happen very quickly as a battery can take a heavier charge for a short period of time, but I think that this would be a major improvement of controller function.
Of course, if you are grid-tied you can sell all the excess power, but if the grid goes down, or you are off-grid?.?
Because of the low cost of PV and the high cost of batteries these days, I?m seeing more and more requests for large arrays with smaller batteries. I also think that PV is now cheap enough to allow for oversizing of arrays for better battery charging on cloudy days, which can reduce generator run times. We need smarter controllers.
What say ye, charge controller gurus?
Brian Teitelbaum
AEE Solar
From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Drake
Sent: Thursday, July 19, 2012 2:21 PM
To: RE-wrenches
Subject: [RE-wrenches] Small battery bank vs too large array
Hello Wrenches,
Where can I get a device that will measure current through a shunt and create a signal to trigger a relay?
We want to be able to use a 2 kW array with four, 200 AH sealed batteries on an Outback system. 2 kW of PV would be too much amperage for the batteries. The idea is to open relays to disengage strings in conditions of high current to the batteries.
The reason for this is to create backup systems where power will be abundantly available when the sun shines. The system will normally connect to the grid, except during outages. In normal charging conditions the power will go straight to the grid. When the grid is down, power will be available for loads and battery charging, but batteries will be protected from overcharge?
Any suggestions on ways to accomplish this are welcome!
Thanks
Drake
Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
http://athens-electric.com/
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
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Allan Sindelar
2012-07-20 02:53:58 UTC
Permalink
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boB
2012-07-20 02:56:43 UTC
Permalink
I didn't see that Brian T had the same idea until after I sent that
email off to Allan...
boB
Post by Drake
Wrenches,
I forwarded Brian's post on to Robin at Midnite, as I thought it was
an interesting idea. Below is his response, as well as boB's.
Allan
*Allan Sindelar*
_Allan at positiveenergysolar.com_ <mailto:Allan at positiveenergysolar.com>
NABCEP Certified Photovoltaic Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder and Chief Technology Officer
*Positive Energy, Inc.*
3209 Richards Lane (note new address)
Santa Fe, New Mexico 87507
*505 424-1112*
_www.positiveenergysolar.com_ <http://www.positiveenergysolar.com/>
Allan, It is simpler than what is being suggested. The reason they
want to limit to 20 amps is because the battery doesn't need anymore
than that. The controller will automatically limit the charge current
as the battery gets full. If a large load is turned on, the controller
will try to refill the battery up to its capacity. The 80 amps will
quickly be reduced because the voltage will rise to the point where
the charge tapers off.
There is nothing else that needs to be done. If the problem is that
the battery bank is too small for a big controller, the best answer is
to get more batteries. A 80 amp charger into a 200 amp hour battery is
going to raise the battery voltage so quick, it will not affect the
battery at all. By the way, discharging a battery at 60 or 80 amps is
probably going to do damage to a small battery also. We do have an
input on the Classic that could probably be programmed to do as
requested. That input feature has yet to be implemented. I'm sure we
will have discussions about this when the time comes to write the
input code. Maybe this feature will be designed in, but it doesn't
sound like it is a very good feature to spend a bunch of time on.
After all, the main problem is that the battery bank is just too
darned small.
Bob, Tom and Ryan do you have any comments on the subject?
Thanks,
Robin
*
*
One idea I had in mind was to have an option, in software, to limit
the current into the battery,
when the charging current goes above some set threshold. The
controller would have to get its information from
the battery monitor over the network.
If it is a grid tie system and grid is there and GT inverter is
selling, then no problem... The controller
can work at its full output. If grid or loads go away, then the CC
will know and it can throttle back at
that time.
We don't have a battery monitor yet, but we will have one. This will
be one of the settings as well as
Re-Bulk based on state of charge, ending amps and those types of things.
boB
Post by maverick
I say it is waste of time.
1. AGM batteries can take the high current and you are right, the
absorb voltage is reached and the absorb current is tapered rather
quickly. Current generation charge controllers are rather fast at the
transitions. I have a bunch of data from a system with a PentaMetric
that shows the battery bank going to absorb voltage at grid tie,
during cloud events, but only for a few seconds at a time.
2. A properly designed GTBB system should cover the connected loads
for 24 hours of each sunny day, at a minimum. Keep in mind, off grid
systems are designed for that, and 3 days + of backup, etc.
3. I would say, based on my experience, the minimum battery bank
should be 400Ah. I personally try to set it at 600Ah (48V). It is a
backup system after all. But the key is the customer's
expectations...who are they going to call after the lights go out?
Thank you,
Maverick
Maverick Brown
BSEET, NABCEP Certified Solar PV Installer ?
President & CEO
Maverick Solar Enterprises, Inc.
Office: 512-919-4493
Cell: 512-460-9825
Sent from my HondaJet!
On Jul 19, 2012, at 6:35 PM, Brian Teitelbaum
Post by Brian Teitelbaum
Drake,
I've been hounding a couple of the charge controller manufactures
about this issue, but so far I just haven't seen a light bulb go off
in their heads, but I'll keep trying, and maybe this is a better
forum to do it.
MPPT controllers can be adjusted to current limit at amperage values
below their rating, but if you do that, you are also limiting the
output of the array in general, and the amount of PV power available
to run the loads directly from the array (through the inverter). Not
the best use of available PV power.
Say you have an 80A controller and a 200AH battery. With current
Let the controller operate at 80A. If you have loads to draw off
some of the current (or sell to the grid), great, but if not you
could be seeing a charge rate of C/2.5, which would be pretty hard
on a sealed 200AH battery, to say the least. Granted, the battery
voltage would rise pretty quickly, and the controller would start to
taper off, but it would still see high currents especially if the
absorption time is set long. Not a happy scenario.
Or, you can set the current limiting on the controller to 20A for a
C/10 charge rate. But if you had loads drawing 60A, you would be
pulling that additional 40A from the battery and not using the
array's full power. Also not a happy scenario.
What we need is a controller that can read the signal from a shunt
at the battery, and use that as the basis of current limiting control.
For example, if we have an array that can produce 80A of current,
but we want to limit the battery to 20A of charge, there would be
60A of potential current there to run loads without drawing on the
battery. If there are no loads running, the controller should
current limit at 20A (reading from a shunt), but if loads are turned
on, the controller should be able to let more current through while
still limiting the battery to 20A. When loads are shut off, the
controller should go back to a 20A limit.
This doesn't all have to happen very quickly as a battery can take a
heavier charge for a short period of time, but I think that this
would be a major improvement of controller function.
Of course, if you are grid-tied you can sell all the excess power,
but if the grid goes down, or you are off-grid....?
Because of the low cost of PV and the high cost of batteries these
days, I'm seeing more and more requests for large arrays with
smaller batteries. I also think that PV is now cheap enough to allow
for oversizing of arrays for better battery charging on cloudy days,
which can reduce generator run times. We need smarter controllers.
What say ye, charge controller gurus?
Brian Teitelbaum
AEE Solar
*From:*re-wrenches-bounces at lists.re-wrenches.org
<mailto:re-wrenches-bounces at lists.re-wrenches.org>
[mailto:re-wrenches-bounces at lists.re-wrenches.org] *On Behalf Of *Drake
*Sent:* Thursday, July 19, 2012 2:21 PM
*To:* RE-wrenches
*Subject:* [RE-wrenches] Small battery bank vs too large array
Hello Wrenches,
Where can I get a device that will measure current through a shunt
and create a signal to trigger a relay?
We want to be able to use a 2 kW array with four, 200 AH sealed
batteries on an Outback system. 2 kW of PV would be too much
amperage for the batteries. The idea is to open relays to disengage
strings in conditions of high current to the batteries.
The reason for this is to create backup systems where power will be
abundantly available when the sun shines. The system will normally
connect to the grid, except during outages. In normal charging
conditions the power will go straight to the grid. When the grid is
down, power will be available for loads and battery charging, but
batteries will be protected from overcharge?
Any suggestions on ways to accomplish this are welcome!
Thanks
Drake
Drake Chamberlin
/Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
/http://athens-electric.com/
_______________________________________________
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Phil Undercuffler
2012-07-20 04:34:32 UTC
Permalink
OutBack implemented Global Charge Control in the FM charge controllers
a while back, based on the input of the good folk at SELF who worked
to power a number of hospitals and clinics in Haiti after the
earthquake. In some of those systems, the PV array was based on the
typical running consumption of the hospital, in the 30 - 100 kW if I
remember right, and the battery bank was relatively modest. However,
on the weekends and holidays without the normal AC loads the PV input
was considerably more than the battery could absorb without
destructive heating, something like a C2 or C5 rate.

Global Charge Control is implemented using the MATE3, a FN-DC and FM
charge controllers set to GT mode. You set a high charge current
limit in the M3, and then it monitors the charge current going to the
batteries. In normal operating mode the controllers stay in wide open
mode, harvesting as much power as possible. However if the loads drop
and the total current from the charging sources begin exceed the
global charge limit, the system compensates and the controllers back
off to prevent sending too much current to the batteries.

In today's world of PV modules being cheaper than diesel, we're seeing
a lot more systems that can use this tool.

Hope this helps,

Phil



On Thu, Jul 19, 2012 at 7:56 PM, boB at midnitesolar.com
I didn't see that Brian T had the same idea until after I sent that email
off to Allan...
boB
Wrenches,
I forwarded Brian's post on to Robin at Midnite, as I thought it was an
interesting idea. Below is his response, as well as boB's.
Allan
Allan Sindelar
Allan at positiveenergysolar.com
NABCEP Certified Photovoltaic Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder and Chief Technology Officer
Positive Energy, Inc.
3209 Richards Lane (note new address)
Santa Fe, New Mexico 87507
505 424-1112
www.positiveenergysolar.com
Allan, It is simpler than what is being suggested. The reason they want to
limit to 20 amps is because the battery doesn?t need anymore than that. The
controller will automatically limit the charge current as the battery gets
full. If a large load is turned on, the controller will try to refill the
battery up to its capacity. The 80 amps will quickly be reduced because the
voltage will rise to the point where the charge tapers off.
There is nothing else that needs to be done. If the problem is that the
battery bank is too small for a big controller, the best answer is to get
more batteries. A 80 amp charger into a 200 amp hour battery is going to
raise the battery voltage so quick, it will not affect the battery at all.
By the way, discharging a battery at 60 or 80 amps is probably going to do
damage to a small battery also. We do have an input on the Classic that
could probably be programmed to do as requested. That input feature has yet
to be implemented. I?m sure we will have discussions about this when the
time comes to write the input code. Maybe this feature will be designed in,
but it doesn?t sound like it is a very good feature to spend a bunch of time
on. After all, the main problem is that the battery bank is just too darned
small.
Bob, Tom and Ryan do you have any comments on the subject?
Thanks,
Robin
One idea I had in mind was to have an option, in software, to limit the
current into the battery,
when the charging current goes above some set threshold. The controller
would have to get its information from
the battery monitor over the network.
If it is a grid tie system and grid is there and GT inverter is selling,
then no problem... The controller
can work at its full output. If grid or loads go away, then the CC will
know and it can throttle back at
that time.
We don't have a battery monitor yet, but we will have one. This will be one
of the settings as well as
Re-Bulk based on state of charge, ending amps and those types of things.
boB
I say it is waste of time.
1. AGM batteries can take the high current and you are right, the absorb
voltage is reached and the absorb current is tapered rather quickly. Current
generation charge controllers are rather fast at the transitions. I have a
bunch of data from a system with a PentaMetric that shows the battery bank
going to absorb voltage at grid tie, during cloud events, but only for a few
seconds at a time.
2. A properly designed GTBB system should cover the connected loads for 24
hours of each sunny day, at a minimum. Keep in mind, off grid systems are
designed for that, and 3 days + of backup, etc.
3. I would say, based on my experience, the minimum battery bank should be
400Ah. I personally try to set it at 600Ah (48V). It is a backup system
after all. But the key is the customer's expectations...who are they going
to call after the lights go out?
Thank you,
Maverick
Maverick Brown
BSEET, NABCEP Certified Solar PV Installer ?
President & CEO
Maverick Solar Enterprises, Inc.
Office: 512-919-4493
Cell: 512-460-9825
Sent from my HondaJet!
Drake,
I?ve been hounding a couple of the charge controller manufactures about this
issue, but so far I just haven?t seen a light bulb go off in their heads,
but I?ll keep trying, and maybe this is a better forum to do it.
MPPT controllers can be adjusted to current limit at amperage values below
their rating, but if you do that, you are also limiting the output of the
array in general, and the amount of PV power available to run the loads
directly from the array (through the inverter). Not the best use of
available PV power.
Say you have an 80A controller and a 200AH battery. With current technology,
Let the controller operate at 80A. If you have loads to draw off some of the
current (or sell to the grid), great, but if not you could be seeing a
charge rate of C/2.5, which would be pretty hard on a sealed 200AH battery,
to say the least. Granted, the battery voltage would rise pretty quickly,
and the controller would start to taper off, but it would still see high
currents especially if the absorption time is set long. Not a happy
scenario.
Or, you can set the current limiting on the controller to 20A for a C/10
charge rate. But if you had loads drawing 60A, you would be pulling that
additional 40A from the battery and not using the array?s full power. Also
not a happy scenario.
What we need is a controller that can read the signal from a shunt at the
battery, and use that as the basis of current limiting control.
For example, if we have an array that can produce 80A of current, but we
want to limit the battery to 20A of charge, there would be 60A of potential
current there to run loads without drawing on the battery. If there are no
loads running, the controller should current limit at 20A (reading from a
shunt), but if loads are turned on, the controller should be able to let
more current through while still limiting the battery to 20A. When loads are
shut off, the controller should go back to a 20A limit.
This doesn?t all have to happen very quickly as a battery can take a heavier
charge for a short period of time, but I think that this would be a major
improvement of controller function.
Of course, if you are grid-tied you can sell all the excess power, but if
the grid goes down, or you are off-grid?.?
Because of the low cost of PV and the high cost of batteries these days, I?m
seeing more and more requests for large arrays with smaller batteries. I
also think that PV is now cheap enough to allow for oversizing of arrays for
better battery charging on cloudy days, which can reduce generator run
times. We need smarter controllers.
What say ye, charge controller gurus?
Brian Teitelbaum
AEE Solar
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Drake
Sent: Thursday, July 19, 2012 2:21 PM
To: RE-wrenches
Subject: [RE-wrenches] Small battery bank vs too large array
Hello Wrenches,
Where can I get a device that will measure current through a shunt and
create a signal to trigger a relay?
We want to be able to use a 2 kW array with four, 200 AH sealed batteries on
an Outback system. 2 kW of PV would be too much amperage for the batteries.
The idea is to open relays to disengage strings in conditions of high
current to the batteries.
The reason for this is to create backup systems where power will be
abundantly available when the sun shines. The system will normally connect
to the grid, except during outages. In normal charging conditions the power
will go straight to the grid. When the grid is down, power will be
available for loads and battery charging, but batteries will be protected
from overcharge?
Any suggestions on ways to accomplish this are welcome!
Thanks
Drake
Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
http://athens-electric.com/
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
www.re-wrenches.org/etiquette.htm
www.members.re-wrenches.org
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
www.re-wrenches.org/etiquette.htm
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Drake
2012-07-20 14:11:34 UTC
Permalink
Thank you Phil,

That is the solution. Your wealth of knowledge has proven itself again.

Drake
Post by Phil Undercuffler
OutBack implemented Global Charge Control in the FM charge controllers
a while back, based on the input of the good folk at SELF who worked
to power a number of hospitals and clinics in Haiti after the
earthquake. In some of those systems, the PV array was based on the
typical running consumption of the hospital, in the 30 - 100 kW if I
remember right, and the battery bank was relatively modest. However,
on the weekends and holidays without the normal AC loads the PV input
was considerably more than the battery could absorb without
destructive heating, something like a C2 or C5 rate.
Global Charge Control is implemented using the MATE3, a FN-DC and FM
charge controllers set to GT mode. You set a high charge current
limit in the M3, and then it monitors the charge current going to the
batteries. In normal operating mode the controllers stay in wide open
mode, harvesting as much power as possible. However if the loads drop
and the total current from the charging sources begin exceed the
global charge limit, the system compensates and the controllers back
off to prevent sending too much current to the batteries.
In today's world of PV modules being cheaper than diesel, we're seeing
a lot more systems that can use this tool.
Hope this helps,
Phil
On Thu, Jul 19, 2012 at 7:56 PM, boB at midnitesolar.com
I didn't see that Brian T had the same idea until after I sent that email
off to Allan...
boB
Wrenches,
I forwarded Brian's post on to Robin at Midnite, as I thought it was an
interesting idea. Below is his response, as well as boB's.
Allan
Allan Sindelar
Allan at positiveenergysolar.com
NABCEP Certified Photovoltaic Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder and Chief Technology Officer
Positive Energy, Inc.
3209 Richards Lane (note new address)
Santa Fe, New Mexico 87507
505 424-1112
www.positiveenergysolar.com
Allan, It is simpler than what is being suggested. The reason they want to
limit to 20 amps is because the battery doesn?t need anymore than that. The
controller will automatically limit the charge current as the battery gets
full. If a large load is turned on, the controller will try to refill the
battery up to its capacity. The 80 amps will quickly be reduced because the
voltage will rise to the point where the charge tapers off.
There is nothing else that needs to be done. If the problem is that the
battery bank is too small for a big controller, the best answer is to get
more batteries. A 80 amp charger into a 200 amp hour battery is going to
raise the battery voltage so quick, it will not affect the battery at all.
By the way, discharging a battery at 60 or 80 amps is probably going to do
damage to a small battery also. We do have an input on the Classic that
could probably be programmed to do as requested. That input feature has yet
to be implemented. I?m sure we will have discussions about this when the
time comes to write the input code. Maybe this feature will be designed in,
but it doesn?t sound like it is a very good
feature to spend a bunch of time
on. After all, the main problem is that the battery bank is just too darned
small.
Bob, Tom and Ryan do you have any comments on the subject?
Thanks,
Robin
One idea I had in mind was to have an option, in software, to limit the
current into the battery,
when the charging current goes above some set threshold. The controller
would have to get its information from
the battery monitor over the network.
If it is a grid tie system and grid is there and GT inverter is selling,
then no problem... The controller
can work at its full output. If grid or loads go away, then the CC will
know and it can throttle back at
that time.
We don't have a battery monitor yet, but we
will have one. This will be one
of the settings as well as
Re-Bulk based on state of charge, ending amps and those types of things.
boB
I say it is waste of time.
1. AGM batteries can take the high current and you are right, the absorb
voltage is reached and the absorb current is
tapered rather quickly. Current
generation charge controllers are rather fast at the transitions. I have a
bunch of data from a system with a PentaMetric that shows the battery bank
going to absorb voltage at grid tie, during
cloud events, but only for a few
seconds at a time.
2. A properly designed GTBB system should cover the connected loads for 24
hours of each sunny day, at a minimum. Keep in mind, off grid systems are
designed for that, and 3 days + of backup, etc.
3. I would say, based on my experience, the minimum battery bank should be
400Ah. I personally try to set it at 600Ah (48V). It is a backup system
after all. But the key is the customer's expectations...who are they going
to call after the lights go out?
Thank you,
Maverick
Maverick Brown
BSEET, NABCEP Certified Solar PV Installer ?
President & CEO
Maverick Solar Enterprises, Inc.
Office: 512-919-4493
Cell: 512-460-9825
Sent from my HondaJet!
Drake,
I?ve been hounding a couple of the charge
controller manufactures about this
issue, but so far I just haven?t seen a light bulb go off in their heads,
but I?ll keep trying, and maybe this is a better forum to do it.
MPPT controllers can be adjusted to current limit at amperage values below
their rating, but if you do that, you are also limiting the output of the
array in general, and the amount of PV power available to run the loads
directly from the array (through the inverter). Not the best use of
available PV power.
Say you have an 80A controller and a 200AH
battery. With current technology,
Let the controller operate at 80A. If you
have loads to draw off some of the
current (or sell to the grid), great, but if not you could be seeing a
charge rate of C/2.5, which would be pretty hard on a sealed 200AH battery,
to say the least. Granted, the battery voltage would rise pretty quickly,
and the controller would start to taper off, but it would still see high
currents especially if the absorption time is set long. Not a happy
scenario.
Or, you can set the current limiting on the controller to 20A for a C/10
charge rate. But if you had loads drawing 60A, you would be pulling that
additional 40A from the battery and not using the array?s full power. Also
not a happy scenario.
What we need is a controller that can read the signal from a shunt at the
battery, and use that as the basis of current limiting control.
For example, if we have an array that can produce 80A of current, but we
want to limit the battery to 20A of charge, there would be 60A of potential
current there to run loads without drawing on the battery. If there are no
loads running, the controller should current limit at 20A (reading from a
shunt), but if loads are turned on, the controller should be able to let
more current through while still limiting the
battery to 20A. When loads are
shut off, the controller should go back to a 20A limit.
This doesn?t all have to happen very quickly
as a battery can take a heavier
charge for a short period of time, but I think that this would be a major
improvement of controller function.
Of course, if you are grid-tied you can sell all the excess power, but if
the grid goes down, or you are off-grid
.?
Post by Phil Undercuffler
Because of the low cost of PV and the high
cost of batteries these days, I?m
seeing more and more requests for large arrays with smaller batteries. I
also think that PV is now cheap enough to
allow for oversizing of arrays for
better battery charging on cloudy days, which can reduce generator run
times. We need smarter controllers.
What say ye, charge controller gurus?
Brian Teitelbaum
AEE Solar
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Drake
Sent: Thursday, July 19, 2012 2:21 PM
To: RE-wrenches
Subject: [RE-wrenches] Small battery bank vs too large array
Hello Wrenches,
Where can I get a device that will measure current through a shunt and
create a signal to trigger a relay?
We want to be able to use a 2 kW array with
four, 200 AH sealed batteries on
an Outback system. 2 kW of PV would be too
much amperage for the batteries.
The idea is to open relays to disengage strings in conditions of high
current to the batteries.
The reason for this is to create backup systems where power will be
abundantly available when the sun shines. The system will normally connect
to the grid, except during outages. In
normal charging conditions the power
will go straight to the grid. When the grid is down, power will be
available for loads and battery charging, but batteries will be protected
from overcharge?
Any suggestions on ways to accomplish this are welcome!
Thanks
Drake
Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
http://athens-electric.com/
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
www.re-wrenches.org/etiquette.htm
www.members.re-wrenches.org
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
www.re-wrenches.org/etiquette.htm
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Brian Teitelbaum
2012-07-20 17:23:03 UTC
Permalink
Phil,

Thanks for the very thorough explanation of the Global Charge Control. That setup would certainly provide the level of control that I was getting at.

I can see how the FN-DC could do that since it utilizes multiple shunts and can therefore use discrete amperage readings to provide better charge controlling functions. This will be very useful, not only for the type of system that you describe in Haiti, but for off-grid systems employing large PV arrays to provide adequate charging in foggy or overcast weather. With PV at a buck-a-Watt, this is starting to become a viable way to reduce battery size and cost without resorting to running a generator. PV lasts substantially longer than batteries, so is a better investment in my opinion

Brian Teitelbaum
AEE Solar



-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Phil Undercuffler
Sent: Thursday, July 19, 2012 9:35 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Small battery bank vs too large array

OutBack implemented Global Charge Control in the FM charge controllers a while back, based on the input of the good folk at SELF who worked to power a number of hospitals and clinics in Haiti after the earthquake. In some of those systems, the PV array was based on the typical running consumption of the hospital, in the 30 - 100 kW if I remember right, and the battery bank was relatively modest. However, on the weekends and holidays without the normal AC loads the PV input was considerably more than the battery could absorb without destructive heating, something like a C2 or C5 rate.

Global Charge Control is implemented using the MATE3, a FN-DC and FM charge controllers set to GT mode. You set a high charge current limit in the M3, and then it monitors the charge current going to the batteries. In normal operating mode the controllers stay in wide open mode, harvesting as much power as possible. However if the loads drop and the total current from the charging sources begin exceed the global charge limit, the system compensates and the controllers back off to prevent sending too much current to the batteries.

In today's world of PV modules being cheaper than diesel, we're seeing a lot more systems that can use this tool.

Hope this helps,

Phil
Post by boB
I didn't see that Brian T had the same idea until after I sent that
email off to Allan...
boB
Wrenches,
I forwarded Brian's post on to Robin at Midnite, as I thought it was
an interesting idea. Below is his response, as well as boB's.
Allan
Allan Sindelar
Allan at positiveenergysolar.com
NABCEP Certified Photovoltaic Installer NABCEP Certified Technical
Sales Professional New Mexico EE98J Journeyman Electrician Founder and
Chief Technology Officer Positive Energy, Inc.
3209 Richards Lane (note new address)
Santa Fe, New Mexico 87507
505 424-1112
www.positiveenergysolar.com
Allan, It is simpler than what is being suggested. The reason they
want to limit to 20 amps is because the battery doesn't need anymore
than that. The controller will automatically limit the charge current
as the battery gets full. If a large load is turned on, the controller
will try to refill the battery up to its capacity. The 80 amps will
quickly be reduced because the voltage will rise to the point where the charge tapers off.
There is nothing else that needs to be done. If the problem is that
the battery bank is too small for a big controller, the best answer is
to get more batteries. A 80 amp charger into a 200 amp hour battery is
going to raise the battery voltage so quick, it will not affect the battery at all.
By the way, discharging a battery at 60 or 80 amps is probably going
to do damage to a small battery also. We do have an input on the
Classic that could probably be programmed to do as requested. That
input feature has yet to be implemented. I'm sure we will have
discussions about this when the time comes to write the input code.
Maybe this feature will be designed in, but it doesn't sound like it
is a very good feature to spend a bunch of time on. After all, the
main problem is that the battery bank is just too darned small.
Bob, Tom and Ryan do you have any comments on the subject?
Thanks,
Robin
One idea I had in mind was to have an option, in software, to limit
the current into the battery, when the charging current goes above
some set threshold. The controller would have to get its information
from the battery monitor over the network.
If it is a grid tie system and grid is there and GT inverter is
selling, then no problem... The controller can work at its full
output. If grid or loads go away, then the CC will know and it can
throttle back at that time.
We don't have a battery monitor yet, but we will have one. This will
be one of the settings as well as Re-Bulk based on state of charge,
ending amps and those types of things.
boB
I say it is waste of time.
1. AGM batteries can take the high current and you are right, the
absorb voltage is reached and the absorb current is tapered rather
quickly. Current generation charge controllers are rather fast at the
transitions. I have a bunch of data from a system with a PentaMetric
that shows the battery bank going to absorb voltage at grid tie,
during cloud events, but only for a few seconds at a time.
2. A properly designed GTBB system should cover the connected loads
for 24 hours of each sunny day, at a minimum. Keep in mind, off grid
systems are designed for that, and 3 days + of backup, etc.
3. I would say, based on my experience, the minimum battery bank
should be 400Ah. I personally try to set it at 600Ah (48V). It is a
backup system after all. But the key is the customer's
expectations...who are they going to call after the lights go out?
Thank you,
Maverick
Maverick Brown
BSEET, NABCEP Certified Solar PV Installer (r) President & CEO Maverick
Solar Enterprises, Inc.
Office: 512-919-4493
Cell: 512-460-9825
Sent from my HondaJet!
On Jul 19, 2012, at 6:35 PM, Brian Teitelbaum
<bteitelbaum at aeesolar.com>
Drake,
I've been hounding a couple of the charge controller manufactures
about this issue, but so far I just haven't seen a light bulb go off
in their heads, but I'll keep trying, and maybe this is a better forum to do it.
MPPT controllers can be adjusted to current limit at amperage values
below their rating, but if you do that, you are also limiting the
output of the array in general, and the amount of PV power available
to run the loads directly from the array (through the inverter). Not
the best use of available PV power.
Say you have an 80A controller and a 200AH battery. With current
Let the controller operate at 80A. If you have loads to draw off some
of the current (or sell to the grid), great, but if not you could be
seeing a charge rate of C/2.5, which would be pretty hard on a sealed
200AH battery, to say the least. Granted, the battery voltage would
rise pretty quickly, and the controller would start to taper off, but
it would still see high currents especially if the absorption time is
set long. Not a happy scenario.
Or, you can set the current limiting on the controller to 20A for a
C/10 charge rate. But if you had loads drawing 60A, you would be
pulling that additional 40A from the battery and not using the array's
full power. Also not a happy scenario.
What we need is a controller that can read the signal from a shunt at
the battery, and use that as the basis of current limiting control.
For example, if we have an array that can produce 80A of current, but
we want to limit the battery to 20A of charge, there would be 60A of
potential current there to run loads without drawing on the battery.
If there are no loads running, the controller should current limit at
20A (reading from a shunt), but if loads are turned on, the controller
should be able to let more current through while still limiting the
battery to 20A. When loads are shut off, the controller should go back to a 20A limit.
This doesn't all have to happen very quickly as a battery can take a
heavier charge for a short period of time, but I think that this would
be a major improvement of controller function.
Of course, if you are grid-tied you can sell all the excess power, but
if the grid goes down, or you are off-grid....?
Because of the low cost of PV and the high cost of batteries these
days, I'm seeing more and more requests for large arrays with smaller
batteries. I also think that PV is now cheap enough to allow for
oversizing of arrays for better battery charging on cloudy days, which
can reduce generator run times. We need smarter controllers.
What say ye, charge controller gurus?
Brian Teitelbaum
AEE Solar
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Drake
Sent: Thursday, July 19, 2012 2:21 PM
To: RE-wrenches
Subject: [RE-wrenches] Small battery bank vs too large array
Hello Wrenches,
Where can I get a device that will measure current through a shunt and
create a signal to trigger a relay?
We want to be able to use a 2 kW array with four, 200 AH sealed
batteries on an Outback system. 2 kW of PV would be too much amperage for the batteries.
The idea is to open relays to disengage strings in conditions of high
current to the batteries.
The reason for this is to create backup systems where power will be
abundantly available when the sun shines. The system will normally
connect to the grid, except during outages. In normal charging
conditions the power will go straight to the grid. When the grid is
down, power will be available for loads and battery charging, but
batteries will be protected from overcharge?
Any suggestions on ways to accomplish this are welcome!
Thanks
Drake
Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
http://athens-electric.com/
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Chris Mason
2012-07-20 23:11:30 UTC
Permalink
Phil,
Good explanation of the feature. When did GCC make it into the firmware,
and can the older ones be updated? It sounds like a perfect solution for
some of my installations.
Post by Phil Undercuffler
OutBack implemented Global Charge Control in the FM charge controllers
a while back, based on the input of the good folk at SELF who worked
to power a number of hospitals and clinics in Haiti after the
earthquake. In some of those systems, the PV array was based on the
typical running consumption of the hospital, in the 30 - 100 kW if I
remember right, and the battery bank was relatively modest. However,
on the weekends and holidays without the normal AC loads the PV input
was considerably more than the battery could absorb without
destructive heating, something like a C2 or C5 rate.
Global Charge Control is implemented using the MATE3, a FN-DC and FM
charge controllers set to GT mode. You set a high charge current
limit in the M3, and then it monitors the charge current going to the
batteries. In normal operating mode the controllers stay in wide open
mode, harvesting as much power as possible. However if the loads drop
and the total current from the charging sources begin exceed the
global charge limit, the system compensates and the controllers back
off to prevent sending too much current to the batteries.
In today's world of PV modules being cheaper than diesel, we're seeing
a lot more systems that can use this tool.
Hope this helps,
Phil
On Thu, Jul 19, 2012 at 7:56 PM, boB at midnitesolar.com
I didn't see that Brian T had the same idea until after I sent that email
off to Allan...
boB
Wrenches,
I forwarded Brian's post on to Robin at Midnite, as I thought it was an
interesting idea. Below is his response, as well as boB's.
Allan
Allan Sindelar
Allan at positiveenergysolar.com
NABCEP Certified Photovoltaic Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder and Chief Technology Officer
Positive Energy, Inc.
3209 Richards Lane (note new address)
Santa Fe, New Mexico 87507
505 424-1112
www.positiveenergysolar.com
Allan, It is simpler than what is being suggested. The reason they want
to
limit to 20 amps is because the battery doesn?t need anymore than that.
The
controller will automatically limit the charge current as the battery
gets
full. If a large load is turned on, the controller will try to refill the
battery up to its capacity. The 80 amps will quickly be reduced because
the
voltage will rise to the point where the charge tapers off.
There is nothing else that needs to be done. If the problem is that the
battery bank is too small for a big controller, the best answer is to get
more batteries. A 80 amp charger into a 200 amp hour battery is going to
raise the battery voltage so quick, it will not affect the battery at
all.
By the way, discharging a battery at 60 or 80 amps is probably going to
do
damage to a small battery also. We do have an input on the Classic that
could probably be programmed to do as requested. That input feature has
yet
to be implemented. I?m sure we will have discussions about this when the
time comes to write the input code. Maybe this feature will be designed
in,
but it doesn?t sound like it is a very good feature to spend a bunch of
time
on. After all, the main problem is that the battery bank is just too
darned
small.
Bob, Tom and Ryan do you have any comments on the subject?
Thanks,
Robin
One idea I had in mind was to have an option, in software, to limit the
current into the battery,
when the charging current goes above some set threshold. The controller
would have to get its information from
the battery monitor over the network.
If it is a grid tie system and grid is there and GT inverter is selling,
then no problem... The controller
can work at its full output. If grid or loads go away, then the CC will
know and it can throttle back at
that time.
We don't have a battery monitor yet, but we will have one. This will be
one
of the settings as well as
Re-Bulk based on state of charge, ending amps and those types of things.
boB
I say it is waste of time.
1. AGM batteries can take the high current and you are right, the absorb
voltage is reached and the absorb current is tapered rather quickly.
Current
generation charge controllers are rather fast at the transitions. I have
a
bunch of data from a system with a PentaMetric that shows the battery
bank
going to absorb voltage at grid tie, during cloud events, but only for a
few
seconds at a time.
2. A properly designed GTBB system should cover the connected loads for
24
hours of each sunny day, at a minimum. Keep in mind, off grid systems are
designed for that, and 3 days + of backup, etc.
3. I would say, based on my experience, the minimum battery bank should
be
400Ah. I personally try to set it at 600Ah (48V). It is a backup system
after all. But the key is the customer's expectations...who are they
going
to call after the lights go out?
Thank you,
Maverick
Maverick Brown
BSEET, NABCEP Certified Solar PV Installer ?
President & CEO
Maverick Solar Enterprises, Inc.
Office: 512-919-4493
Cell: 512-460-9825
Sent from my HondaJet!
Drake,
I?ve been hounding a couple of the charge controller manufactures about
this
issue, but so far I just haven?t seen a light bulb go off in their heads,
but I?ll keep trying, and maybe this is a better forum to do it.
MPPT controllers can be adjusted to current limit at amperage values
below
their rating, but if you do that, you are also limiting the output of the
array in general, and the amount of PV power available to run the loads
directly from the array (through the inverter). Not the best use of
available PV power.
Say you have an 80A controller and a 200AH battery. With current
technology,
Let the controller operate at 80A. If you have loads to draw off some of
the
current (or sell to the grid), great, but if not you could be seeing a
charge rate of C/2.5, which would be pretty hard on a sealed 200AH
battery,
to say the least. Granted, the battery voltage would rise pretty quickly,
and the controller would start to taper off, but it would still see high
currents especially if the absorption time is set long. Not a happy
scenario.
Or, you can set the current limiting on the controller to 20A for a C/10
charge rate. But if you had loads drawing 60A, you would be pulling that
additional 40A from the battery and not using the array?s full power.
Also
not a happy scenario.
What we need is a controller that can read the signal from a shunt at the
battery, and use that as the basis of current limiting control.
For example, if we have an array that can produce 80A of current, but we
want to limit the battery to 20A of charge, there would be 60A of
potential
current there to run loads without drawing on the battery. If there are
no
loads running, the controller should current limit at 20A (reading from a
shunt), but if loads are turned on, the controller should be able to let
more current through while still limiting the battery to 20A. When loads
are
shut off, the controller should go back to a 20A limit.
This doesn?t all have to happen very quickly as a battery can take a
heavier
charge for a short period of time, but I think that this would be a major
improvement of controller function.
Of course, if you are grid-tied you can sell all the excess power, but if
the grid goes down, or you are off-grid?.?
Because of the low cost of PV and the high cost of batteries these days,
I?m
seeing more and more requests for large arrays with smaller batteries. I
also think that PV is now cheap enough to allow for oversizing of arrays
for
better battery charging on cloudy days, which can reduce generator run
times. We need smarter controllers.
What say ye, charge controller gurus?
Brian Teitelbaum
AEE Solar
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Drake
Sent: Thursday, July 19, 2012 2:21 PM
To: RE-wrenches
Subject: [RE-wrenches] Small battery bank vs too large array
Hello Wrenches,
Where can I get a device that will measure current through a shunt and
create a signal to trigger a relay?
We want to be able to use a 2 kW array with four, 200 AH sealed
batteries on
an Outback system. 2 kW of PV would be too much amperage for the
batteries.
The idea is to open relays to disengage strings in conditions of high
current to the batteries.
The reason for this is to create backup systems where power will be
abundantly available when the sun shines. The system will normally
connect
to the grid, except during outages. In normal charging conditions the
power
will go straight to the grid. When the grid is down, power will be
available for loads and battery charging, but batteries will be protected
from overcharge?
Any suggestions on ways to accomplish this are welcome!
Thanks
Drake
Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
http://athens-electric.com/
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
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--
Chris Mason
President, Comet Systems Ltd
www.cometenergysystems.com
Cell: 264.235.5670
Skype: netconcepts
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Phil Undercuffler
2012-07-21 01:28:46 UTC
Permalink
Hi all, I just got a correction from Darren - global charge control is in
the Mate3, and therefore works with any FM or MX controller that has the GT
mode. It uses the current sense from the FN-DC and the GT mode signal to
control the output of the controllers.

Sorry for any confusion

Phil
Post by Chris Mason
Phil,
Good explanation of the feature. When did GCC make it into the firmware,
and can the older ones be updated? It sounds like a perfect solution for
some of my installations.
Post by Phil Undercuffler
OutBack implemented Global Charge Control in the FM charge controllers
a while back, based on the input of the good folk at SELF who worked
to power a number of hospitals and clinics in Haiti after the
earthquake. In some of those systems, the PV array was based on the
typical running consumption of the hospital, in the 30 - 100 kW if I
remember right, and the battery bank was relatively modest. However,
on the weekends and holidays without the normal AC loads the PV input
was considerably more than the battery could absorb without
destructive heating, something like a C2 or C5 rate.
Global Charge Control is implemented using the MATE3, a FN-DC and FM
charge controllers set to GT mode. You set a high charge current
limit in the M3, and then it monitors the charge current going to the
batteries. In normal operating mode the controllers stay in wide open
mode, harvesting as much power as possible. However if the loads drop
and the total current from the charging sources begin exceed the
global charge limit, the system compensates and the controllers back
off to prevent sending too much current to the batteries.
In today's world of PV modules being cheaper than diesel, we're seeing
a lot more systems that can use this tool.
Hope this helps,
Phil
On Thu, Jul 19, 2012 at 7:56 PM, boB at midnitesolar.com
Post by boB
I didn't see that Brian T had the same idea until after I sent that
email
Post by boB
off to Allan...
boB
Wrenches,
I forwarded Brian's post on to Robin at Midnite, as I thought it was an
interesting idea. Below is his response, as well as boB's.
Allan
Allan Sindelar
Allan at positiveenergysolar.com
NABCEP Certified Photovoltaic Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder and Chief Technology Officer
Positive Energy, Inc.
3209 Richards Lane (note new address)
Santa Fe, New Mexico 87507
505 424-1112
www.positiveenergysolar.com
Allan, It is simpler than what is being suggested. The reason they want
to
Post by boB
limit to 20 amps is because the battery doesn?t need anymore than that.
The
Post by boB
controller will automatically limit the charge current as the battery
gets
Post by boB
full. If a large load is turned on, the controller will try to refill
the
Post by boB
battery up to its capacity. The 80 amps will quickly be reduced because
the
Post by boB
voltage will rise to the point where the charge tapers off.
There is nothing else that needs to be done. If the problem is that the
battery bank is too small for a big controller, the best answer is to
get
Post by boB
more batteries. A 80 amp charger into a 200 amp hour battery is going to
raise the battery voltage so quick, it will not affect the battery at
all.
Post by boB
By the way, discharging a battery at 60 or 80 amps is probably going to
do
Post by boB
damage to a small battery also. We do have an input on the Classic that
could probably be programmed to do as requested. That input feature has
yet
Post by boB
to be implemented. I?m sure we will have discussions about this when the
time comes to write the input code. Maybe this feature will be designed
in,
Post by boB
but it doesn?t sound like it is a very good feature to spend a bunch of
time
Post by boB
on. After all, the main problem is that the battery bank is just too
darned
Post by boB
small.
Bob, Tom and Ryan do you have any comments on the subject?
Thanks,
Robin
One idea I had in mind was to have an option, in software, to limit the
current into the battery,
when the charging current goes above some set threshold. The controller
would have to get its information from
the battery monitor over the network.
If it is a grid tie system and grid is there and GT inverter is selling,
then no problem... The controller
can work at its full output. If grid or loads go away, then the CC will
know and it can throttle back at
that time.
We don't have a battery monitor yet, but we will have one. This will
be one
Post by boB
of the settings as well as
Re-Bulk based on state of charge, ending amps and those types of things.
boB
I say it is waste of time.
1. AGM batteries can take the high current and you are right, the absorb
voltage is reached and the absorb current is tapered rather quickly.
Current
Post by boB
generation charge controllers are rather fast at the transitions. I
have a
Post by boB
bunch of data from a system with a PentaMetric that shows the battery
bank
Post by boB
going to absorb voltage at grid tie, during cloud events, but only for
a few
Post by boB
seconds at a time.
2. A properly designed GTBB system should cover the connected loads for
24
Post by boB
hours of each sunny day, at a minimum. Keep in mind, off grid systems
are
Post by boB
designed for that, and 3 days + of backup, etc.
3. I would say, based on my experience, the minimum battery bank should
be
Post by boB
400Ah. I personally try to set it at 600Ah (48V). It is a backup system
after all. But the key is the customer's expectations...who are they
going
Post by boB
to call after the lights go out?
Thank you,
Maverick
Maverick Brown
BSEET, NABCEP Certified Solar PV Installer ?
President & CEO
Maverick Solar Enterprises, Inc.
Office: 512-919-4493
Cell: 512-460-9825
Sent from my HondaJet!
On Jul 19, 2012, at 6:35 PM, Brian Teitelbaum <bteitelbaum at aeesolar.com
Drake,
I?ve been hounding a couple of the charge controller manufactures about
this
Post by boB
issue, but so far I just haven?t seen a light bulb go off in their
heads,
Post by boB
but I?ll keep trying, and maybe this is a better forum to do it.
MPPT controllers can be adjusted to current limit at amperage values
below
Post by boB
their rating, but if you do that, you are also limiting the output of
the
Post by boB
array in general, and the amount of PV power available to run the loads
directly from the array (through the inverter). Not the best use of
available PV power.
Say you have an 80A controller and a 200AH battery. With current
technology,
Post by boB
Let the controller operate at 80A. If you have loads to draw off some
of the
Post by boB
current (or sell to the grid), great, but if not you could be seeing a
charge rate of C/2.5, which would be pretty hard on a sealed 200AH
battery,
Post by boB
to say the least. Granted, the battery voltage would rise pretty
quickly,
Post by boB
and the controller would start to taper off, but it would still see high
currents especially if the absorption time is set long. Not a happy
scenario.
Or, you can set the current limiting on the controller to 20A for a C/10
charge rate. But if you had loads drawing 60A, you would be pulling that
additional 40A from the battery and not using the array?s full power.
Also
Post by boB
not a happy scenario.
What we need is a controller that can read the signal from a shunt at
the
Post by boB
battery, and use that as the basis of current limiting control.
For example, if we have an array that can produce 80A of current, but we
want to limit the battery to 20A of charge, there would be 60A of
potential
Post by boB
current there to run loads without drawing on the battery. If there are
no
Post by boB
loads running, the controller should current limit at 20A (reading from
a
Post by boB
shunt), but if loads are turned on, the controller should be able to let
more current through while still limiting the battery to 20A. When
loads are
Post by boB
shut off, the controller should go back to a 20A limit.
This doesn?t all have to happen very quickly as a battery can take a
heavier
Post by boB
charge for a short period of time, but I think that this would be a
major
Post by boB
improvement of controller function.
Of course, if you are grid-tied you can sell all the excess power, but
if
Post by boB
the grid goes down, or you are off-grid?.?
Because of the low cost of PV and the high cost of batteries these
days, I?m
Post by boB
seeing more and more requests for large arrays with smaller batteries. I
also think that PV is now cheap enough to allow for oversizing of
arrays for
Post by boB
better battery charging on cloudy days, which can reduce generator run
times. We need smarter controllers.
What say ye, charge controller gurus?
Brian Teitelbaum
AEE Solar
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Drake
Sent: Thursday, July 19, 2012 2:21 PM
To: RE-wrenches
Subject: [RE-wrenches] Small battery bank vs too large array
Hello Wrenches,
Where can I get a device that will measure current through a shunt and
create a signal to trigger a relay?
We want to be able to use a 2 kW array with four, 200 AH sealed
batteries on
Post by boB
an Outback system. 2 kW of PV would be too much amperage for the
batteries.
Post by boB
The idea is to open relays to disengage strings in conditions of high
current to the batteries.
The reason for this is to create backup systems where power will be
abundantly available when the sun shines. The system will normally
connect
Post by boB
to the grid, except during outages. In normal charging conditions the
power
Post by boB
will go straight to the grid. When the grid is down, power will be
available for loads and battery charging, but batteries will be
protected
Post by boB
from overcharge?
Any suggestions on ways to accomplish this are welcome!
Thanks
Drake
Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
http://athens-electric.com/
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--
Chris Mason
President, Comet Systems Ltd
www.cometenergysystems.com
Cell: 264.235.5670
Skype: netconcepts
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Chris Mason
2012-07-21 02:49:44 UTC
Permalink
Is there a document available on how this world?
Post by Phil Undercuffler
Hi all, I just got a correction from Darren - global charge control is in
the Mate3, and therefore works with any FM or MX controller that has the GT
mode. It uses the current sense from the FN-DC and the GT mode signal to
control the output of the controllers.
Post by Phil Undercuffler
Sorry for any confusion
Phil
Phil,
Good explanation of the feature. When did GCC make it into the firmware,
and can the older ones be updated? It sounds like a perfect solution for
some of my installations.
Post by Phil Undercuffler
On Fri, Jul 20, 2012 at 12:34 AM, Phil Undercuffler <solarphil at gmail.com>
OutBack implemented Global Charge Control in the FM charge controllers
a while back, based on the input of the good folk at SELF who worked
to power a number of hospitals and clinics in Haiti after the
earthquake. In some of those systems, the PV array was based on the
typical running consumption of the hospital, in the 30 - 100 kW if I
remember right, and the battery bank was relatively modest. However,
on the weekends and holidays without the normal AC loads the PV input
was considerably more than the battery could absorb without
destructive heating, something like a C2 or C5 rate.
Global Charge Control is implemented using the MATE3, a FN-DC and FM
charge controllers set to GT mode. You set a high charge current
limit in the M3, and then it monitors the charge current going to the
batteries. In normal operating mode the controllers stay in wide open
mode, harvesting as much power as possible. However if the loads drop
and the total current from the charging sources begin exceed the
global charge limit, the system compensates and the controllers back
off to prevent sending too much current to the batteries.
In today's world of PV modules being cheaper than diesel, we're seeing
a lot more systems that can use this tool.
Hope this helps,
Phil
On Thu, Jul 19, 2012 at 7:56 PM, boB at midnitesolar.com
I didn't see that Brian T had the same idea until after I sent that email
off to Allan...
boB
Wrenches,
I forwarded Brian's post on to Robin at Midnite, as I thought it was an
interesting idea. Below is his response, as well as boB's.
Allan
Allan Sindelar
Allan at positiveenergysolar.com
NABCEP Certified Photovoltaic Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder and Chief Technology Officer
Positive Energy, Inc.
3209 Richards Lane (note new address)
Santa Fe, New Mexico 87507
505 424-1112
www.positiveenergysolar.com
Allan, It is simpler than what is being suggested. The reason they want to
limit to 20 amps is because the battery doesn?t need anymore than that. The
controller will automatically limit the charge current as the battery gets
full. If a large load is turned on, the controller will try to refill the
battery up to its capacity. The 80 amps will quickly be reduced because the
voltage will rise to the point where the charge tapers off.
There is nothing else that needs to be done. If the problem is that the
battery bank is too small for a big controller, the best answer is to get
more batteries. A 80 amp charger into a 200 amp hour battery is going to
raise the battery voltage so quick, it will not affect the battery at all.
By the way, discharging a battery at 60 or 80 amps is probably going to do
damage to a small battery also. We do have an input on the Classic that
could probably be programmed to do as requested. That input feature has yet
to be implemented. I?m sure we will have discussions about this when the
time comes to write the input code. Maybe this feature will be designed in,
but it doesn?t sound like it is a very good feature to spend a bunch of time
on. After all, the main problem is that the battery bank is just too
darned<
--
Chris Mason
President, Comet Systems Ltd
www.cometenergysystems.com
Cell: 264.235.5670
Skype: netconcepts
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Philip
2012-07-21 05:11:41 UTC
Permalink
Page 127 of the Mate3 manual.

Phil
Post by Chris Mason
Is there a document available on how this world?
Hi all, I just got a correction from Darren - global charge control is in the Mate3, and therefore works with any FM or MX controller that has the GT mode. It uses the current sense from the FN-DC and the GT mode signal to control the output of the controllers.
Sorry for any confusion
Phil
Phil,
Good explanation of the feature. When did GCC make it into the firmware, and can the older ones be updated? It sounds like a perfect solution for some of my installations.
OutBack implemented Global Charge Control in the FM charge controllers
a while back, based on the input of the good folk at SELF who worked
to power a number of hospitals and clinics in Haiti after the
earthquake. In some of those systems, the PV array was based on the
typical running consumption of the hospital, in the 30 - 100 kW if I
remember right, and the battery bank was relatively modest. However,
on the weekends and holidays without the normal AC loads the PV input
was considerably more than the battery could absorb without
destructive heating, something like a C2 or C5 rate.
Global Charge Control is implemented using the MATE3, a FN-DC and FM
charge controllers set to GT mode. You set a high charge current
limit in the M3, and then it monitors the charge current going to the
batteries. In normal operating mode the controllers stay in wide open
mode, harvesting as much power as possible. However if the loads drop
and the total current from the charging sources begin exceed the
global charge limit, the system compensates and the controllers back
off to prevent sending too much current to the batteries.
In today's world of PV modules being cheaper than diesel, we're seeing
a lot more systems that can use this tool.
Hope this helps,
Phil
On Thu, Jul 19, 2012 at 7:56 PM, boB at midnitesolar.com
I didn't see that Brian T had the same idea until after I sent that email
off to Allan...
boB
Wrenches,
I forwarded Brian's post on to Robin at Midnite, as I thought it was an
interesting idea. Below is his response, as well as boB's.
Allan
Allan Sindelar
Allan at positiveenergysolar.com
NABCEP Certified Photovoltaic Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder and Chief Technology Officer
Positive Energy, Inc.
3209 Richards Lane (note new address)
Santa Fe, New Mexico 87507
505 424-1112
www.positiveenergysolar.com
Allan, It is simpler than what is being suggested. The reason they want to
limit to 20 amps is because the battery doesn?t need anymore than that. The
controller will automatically limit the charge current as the battery gets
full. If a large load is turned on, the controller will try to refill the
battery up to its capacity. The 80 amps will quickly be reduced because the
voltage will rise to the point where the charge tapers off.
There is nothing else that needs to be done. If the problem is that the
battery bank is too small for a big controller, the best answer is to get
more batteries. A 80 amp charger into a 200 amp hour battery is going to
raise the battery voltage so quick, it will not affect the battery at all.
By the way, discharging a battery at 60 or 80 amps is probably going to do
damage to a small battery also. We do have an input on the Classic that
could probably be programmed to do as requested. That input feature has yet
to be implemented. I?m sure we will have discussions about this when the
time comes to write the input code. Maybe this feature will be designed in,
but it doesn?t sound like it is a very good feature to spend a bunch of time
on. After all, the main problem is that the battery bank is just too darned<
--
Chris Mason
President, Comet Systems Ltd
www.cometenergysystems.com
Cell: 264.235.5670
Skype: netconcepts
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
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Drake
2012-08-02 20:06:04 UTC
Permalink
Hello Wrenches,

Thanks for your help with this question.

I've had a breakthrough on the design of this system. I talked with
Tom at Midnight Solar, and he explained that Concord batteries can be
charged at C X 5 if necessary, i.e., 5 X AH capacity of the
bank. The batteries like a fast charge. They are a bit spendy, but
will simplify the overall system design.

From the Manual:
"The charging current during the Bulk stage should be set as high as
practical; higher current mean faster recharge time. For repetitive
deep cycling, chargers should have an output current of at least 0.2C
(20 Amps for a 100 Ah battery). If the output current is less than
this value, the cycle life of the battery may be negatively
affected. Due to low impedance design, Sun Xtender batteries can
tolerate in-rush current levels as high as 5C (500 A for a 100 Ah battery). "

It is imperative to keep the system voltage at the required set
point. The CC regulation will prevent the batteries from being
harmed, as the voltage will rise quickly.

Drake

Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
<http://athens-electric.com/>http://athens-electric.com/



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Larry Crutcher, Starlight Solar Power Systems
2012-08-02 21:16:21 UTC
Permalink
Drake,

The ability to charge at much higher amperage is typical of all AGM batteries. The recombinant technology does not produce much heat before the internal resistance rises and the current naturally drops. AGM's require up to 20% less energy to recharge as very little is wasted as heat.

For me, the important aspect of AGM's is that with higher initial current (over sizing the PV system or the ability to use a large charger) and higher efficiency, you reach the absorb set point earlier in the day. For off grid systems, this means you will have more sun hours left to achieve 100% SoC. For these reasons I generally recommend AGM's.

Larry Crutcher
Starlight Solar Power Systems
(928) 342-9103



On Aug 2, 2012, at 2:06 PM, Drake wrote:


Hello Wrenches,

Thanks for your help with this question.

I've had a breakthrough on the design of this system. I talked with Tom at Midnight Solar, and he explained that Concord batteries can be charged at C X 5 if necessary, i.e., 5 X AH capacity of the bank. The batteries like a fast charge. They are a bit spendy, but will simplify the overall system design.

From the Manual:
"The charging current during the Bulk stage should be set as high as practical; higher current mean faster recharge time. For repetitive deep cycling, chargers should have an output current of at least 0.2C (20 Amps for a 100 Ah battery). If the output current is less than this value, the cycle life of the battery may be negatively affected. Due to low impedance design, Sun Xtender batteries can tolerate in-rush current levels as high as 5C (500 A for a 100 Ah battery). "

It is imperative to keep the system voltage at the required set point. The CC regulation will prevent the batteries from being harmed, as the voltage will rise quickly.

Drake

Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
http://athens-electric.com/

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Vince McClellan
2012-08-03 21:01:10 UTC
Permalink
Post by Drake
Hello Wrenches,
Thanks for your help with this question.
I've had a breakthrough on the design of this system. I talked with
Tom at Midnight Solar, and he explained that Concord batteries can be
charged at C X 5 if necessary, i.e., 5 X AH capacity of the bank. The
batteries like a fast charge. They are a bit spendy, but will
simplify the overall system design.
"The charging current during the Bulk stage should be set as high as
practical; higher current mean faster recharge time. For repetitive
deep cycling, chargers should have an output current of at least 0.2C
(20 Amps for a 100 Ah battery). If the output current is less than
this value, the cycle life of the battery may be negatively affected.
Due to low impedance design, Sun Xtender batteries can tolerate
in-rush current levels as high as 5C (500 A for a 100 Ah battery). "
It is imperative to keep the system voltage at the required set
point. The CC regulation will prevent the batteries from being
harmed, as the voltage will rise quickly.
Drake
Drake Chamberlin
/Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
/http://athens-electric.com/
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Just a word of caution on the AGM batteries. AGM's do have some
vulnerabilities compared to deep cycle wet filled batteries. We had a
bank of 20, 8A8D running a Buddhist Retreat compound and were unable to
convince our clients that there were limitations to the amount of power
that they could run at one time. They managed to overheat and destroy
the whole bank of batteries we think by using too much power during a
retreat camp. People had brought there own appliances to use at the camp
and we still don't know what the total load was on the 4, Outback VFX
3648 inverters. I'm guessing it was up there close to the 14.4 kW limit
of the Outback inverters. We also petitioned our client for a larger
battery bank but they didn't think they would ever need that much power.
--
--
*Vince McClellan
Energy Design
_www.solarenergydesign.com <http://www.solarenergydesign.com/>_
p: 541.485.8122; f: 541.338.3168*
Energy Design Logo
This email and any files transmitted with it are confidential and
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Larry Crutcher, Starlight Solar Power Systems
2012-08-03 22:03:59 UTC
Permalink
Vince,

I know of no such "vulnerability". In fact, an AGM can provide much more instant current than any flooded battery. Concorde (Lifeline, SunXtender, etc.) and Fullriver AGM's are very robust designs. On the other hand, Deka AGM's, specifically the 12 volt 8A8D, are not to be trusted at all. We have stopped selling all Deka/MK AGM's due to very high failure rate.

One other point to consider, having 5 parallel strings of 12 volt batteries is generally asking for short battery life, especially with an AGM since you can not check the SG to be sure all are charged fully. Cells do not charge at the same rate and having parallel paths for current will leave some cells deficit charged. Having many parallel strings exacerbate this issue. If you do upgrade the bank, opt for lower voltage, higher capacity batteries.

Larry Crutcher
Starlight Solar Power Systems
(928) 342-9103


Just a word of caution on the AGM batteries. AGM's do have some vulnerabilities compared to deep cycle wet filled batteries. We had a bank of 20, 8A8D running a Buddhist Retreat compound and were unable to convince our clients that there were limitations to the amount of power that they could run at one time. They managed to overheat and destroy the whole bank of batteries we think by using too much power during a retreat camp. People had brought there own appliances to use at the camp and we still don't know what the total load was on the 4, Outback VFX 3648 inverters. I'm guessing it was up there close to the 14.4 kW limit of the Outback inverters. We also petitioned our client for a larger battery bank but they didn't think they would ever need that much power.
--
--
Vince McClellan
Energy Design
www.solarenergydesign.com
p: 541.485.8122; f: 541.338.3168
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Allan Sindelar
2012-08-04 13:08:33 UTC
Permalink
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Gary Willett
2012-08-04 19:18:36 UTC
Permalink
Larry:

Are the problems you have encountered with the Deka/MK 12V AGMs also an
issue with the 8AGC2 6V AGM? Are the problems you're seeing with climate
controlled batteries, or with outside cabinet mounted batteries?

I have an application having I believe heat related failures with one
48V string of outside cabinet 8AGC2 batteries in an off-grid battery
based inverter/charger with generator charging (6kw LP generator).
Temperature compensated bulk charging of 60A DC is delivered to the bank
(0.3 x C20).

Gary
Post by Larry Crutcher, Starlight Solar Power Systems
Vince,
I know of no such "vulnerability". In fact, an AGM can provide much
more instant current than any flooded battery. Concorde (Lifeline,
SunXtender, etc.) and Fullriver AGM's are very robust designs. On the
other hand, Deka AGM's, specifically the 12 volt 8A8D, are not to be
trusted at all. We have stopped selling all Deka/MK AGM's due to very
high failure rate.
One other point to consider, having 5 parallel strings of 12 volt
batteries is generally asking for short battery life, especially with
an AGM since you can not check the SG to be sure all are charged
fully. Cells do not charge at the same rate and having parallel paths
for current will leave some cells deficit charged. Having many
parallel strings exacerbate this issue. If you do upgrade the bank,
opt for lower voltage, higher capacity batteries.
Larry Crutcher
Starlight Solar Power Systems
(928) 342-9103
_
_
Just a word of caution on the AGM batteries. AGM's do have some
vulnerabilities compared to deep cycle wet filled batteries. We had a
bank of 20, 8A8D running a Buddhist Retreat compound and were unable
to convince our clients that there were limitations to the amount of
power that they could run at one time. They managed to overheat and
destroy the whole bank of batteries we think by using too much power
during a retreat camp. People had brought there own appliances to use
at the camp and we still don't know what the total load was on the 4,
Outback VFX 3648 inverters. I'm guessing it was up there close to the
14.4 kW limit of the Outback inverters. We also petitioned our client
for a larger battery bank but they didn't think they would ever need
that much power.
--
--
*Vince McClellan
Energy Design
_www.solarenergydesign.com <http://www.solarenergydesign.com/>_
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Larry Crutcher, Starlight Solar Power Systems
2012-08-04 20:52:39 UTC
Permalink
We also have experienced very low life from some of the 8AGC2 6 volt AGM but more of the 8A8D's failed than anything. Over the years that we sold Deka, we also sold Lifeline and Sun Xtender (Concorde) batteries. Zero failure with the Concorde made; far too many failures with Deka.

Larry Crutcher
Starlight Solar Power Systems




On Aug 4, 2012, at 1:18 PM, Gary Willett wrote:

Larry:

Are the problems you have encountered with the Deka/MK 12V AGMs also an issue with the 8AGC2 6V AGM? Are the problems you're seeing with climate controlled batteries, or with outside cabinet mounted batteries?

I have an application having I believe heat related failures with one 48V string of outside cabinet 8AGC2 batteries in an off-grid battery based inverter/charger with generator charging (6kw LP generator). Temperature compensated bulk charging of 60A DC is delivered to the bank (0.3 x C20).

Gary
Post by Larry Crutcher, Starlight Solar Power Systems
Vince,
I know of no such "vulnerability". In fact, an AGM can provide much more instant current than any flooded battery. Concorde (Lifeline, SunXtender, etc.) and Fullriver AGM's are very robust designs. On the other hand, Deka AGM's, specifically the 12 volt 8A8D, are not to be trusted at all. We have stopped selling all Deka/MK AGM's due to very high failure rate.
One other point to consider, having 5 parallel strings of 12 volt batteries is generally asking for short battery life, especially with an AGM since you can not check the SG to be sure all are charged fully. Cells do not charge at the same rate and having parallel paths for current will leave some cells deficit charged. Having many parallel strings exacerbate this issue. If you do upgrade the bank, opt for lower voltage, higher capacity batteries.
Larry Crutcher
Starlight Solar Power Systems
(928) 342-9103
Just a word of caution on the AGM batteries. AGM's do have some vulnerabilities compared to deep cycle wet filled batteries. We had a bank of 20, 8A8D running a Buddhist Retreat compound and were unable to convince our clients that there were limitations to the amount of power that they could run at one time. They managed to overheat and destroy the whole bank of batteries we think by using too much power during a retreat camp. People had brought there own appliances to use at the camp and we still don't know what the total load was on the 4, Outback VFX 3648 inverters. I'm guessing it was up there close to the 14.4 kW limit of the Outback inverters. We also petitioned our client for a larger battery bank but they didn't think they would ever need that much power.
--
--
Vince McClellan
Energy Design
www.solarenergydesign.com
p: 541.485.8122; f: 541.338.3168
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
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Larry Crutcher, Starlight Solar Power Systems
2012-08-04 20:52:39 UTC
Permalink
We also have experienced very low life from some of the 8AGC2 6 volt AGM but more of the 8A8D's failed than anything. Over the years that we sold Deka, we also sold Lifeline and Sun Xtender (Concorde) batteries. Zero failure with the Concorde made; far too many failures with Deka.

Larry Crutcher
Starlight Solar Power Systems




On Aug 4, 2012, at 1:18 PM, Gary Willett wrote:

Larry:

Are the problems you have encountered with the Deka/MK 12V AGMs also an issue with the 8AGC2 6V AGM? Are the problems you're seeing with climate controlled batteries, or with outside cabinet mounted batteries?

I have an application having I believe heat related failures with one 48V string of outside cabinet 8AGC2 batteries in an off-grid battery based inverter/charger with generator charging (6kw LP generator). Temperature compensated bulk charging of 60A DC is delivered to the bank (0.3 x C20).

Gary
Post by Larry Crutcher, Starlight Solar Power Systems
Vince,
I know of no such "vulnerability". In fact, an AGM can provide much more instant current than any flooded battery. Concorde (Lifeline, SunXtender, etc.) and Fullriver AGM's are very robust designs. On the other hand, Deka AGM's, specifically the 12 volt 8A8D, are not to be trusted at all. We have stopped selling all Deka/MK AGM's due to very high failure rate.
One other point to consider, having 5 parallel strings of 12 volt batteries is generally asking for short battery life, especially with an AGM since you can not check the SG to be sure all are charged fully. Cells do not charge at the same rate and having parallel paths for current will leave some cells deficit charged. Having many parallel strings exacerbate this issue. If you do upgrade the bank, opt for lower voltage, higher capacity batteries.
Larry Crutcher
Starlight Solar Power Systems
(928) 342-9103
Just a word of caution on the AGM batteries. AGM's do have some vulnerabilities compared to deep cycle wet filled batteries. We had a bank of 20, 8A8D running a Buddhist Retreat compound and were unable to convince our clients that there were limitations to the amount of power that they could run at one time. They managed to overheat and destroy the whole bank of batteries we think by using too much power during a retreat camp. People had brought there own appliances to use at the camp and we still don't know what the total load was on the 4, Outback VFX 3648 inverters. I'm guessing it was up there close to the 14.4 kW limit of the Outback inverters. We also petitioned our client for a larger battery bank but they didn't think they would ever need that much power.
--
--
Vince McClellan
Energy Design
www.solarenergydesign.com
p: 541.485.8122; f: 541.338.3168
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
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Allan Sindelar
2012-08-04 13:08:33 UTC
Permalink
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Gary Willett
2012-08-04 19:18:36 UTC
Permalink
Larry:

Are the problems you have encountered with the Deka/MK 12V AGMs also an
issue with the 8AGC2 6V AGM? Are the problems you're seeing with climate
controlled batteries, or with outside cabinet mounted batteries?

I have an application having I believe heat related failures with one
48V string of outside cabinet 8AGC2 batteries in an off-grid battery
based inverter/charger with generator charging (6kw LP generator).
Temperature compensated bulk charging of 60A DC is delivered to the bank
(0.3 x C20).

Gary
Post by Larry Crutcher, Starlight Solar Power Systems
Vince,
I know of no such "vulnerability". In fact, an AGM can provide much
more instant current than any flooded battery. Concorde (Lifeline,
SunXtender, etc.) and Fullriver AGM's are very robust designs. On the
other hand, Deka AGM's, specifically the 12 volt 8A8D, are not to be
trusted at all. We have stopped selling all Deka/MK AGM's due to very
high failure rate.
One other point to consider, having 5 parallel strings of 12 volt
batteries is generally asking for short battery life, especially with
an AGM since you can not check the SG to be sure all are charged
fully. Cells do not charge at the same rate and having parallel paths
for current will leave some cells deficit charged. Having many
parallel strings exacerbate this issue. If you do upgrade the bank,
opt for lower voltage, higher capacity batteries.
Larry Crutcher
Starlight Solar Power Systems
(928) 342-9103
_
_
Just a word of caution on the AGM batteries. AGM's do have some
vulnerabilities compared to deep cycle wet filled batteries. We had a
bank of 20, 8A8D running a Buddhist Retreat compound and were unable
to convince our clients that there were limitations to the amount of
power that they could run at one time. They managed to overheat and
destroy the whole bank of batteries we think by using too much power
during a retreat camp. People had brought there own appliances to use
at the camp and we still don't know what the total load was on the 4,
Outback VFX 3648 inverters. I'm guessing it was up there close to the
14.4 kW limit of the Outback inverters. We also petitioned our client
for a larger battery bank but they didn't think they would ever need
that much power.
--
--
*Vince McClellan
Energy Design
_www.solarenergydesign.com <http://www.solarenergydesign.com/>_
p: 541.485.8122; f: 541.338.3168*
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
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Jonathan Hill
2012-08-04 03:40:33 UTC
Permalink
Is this the case with gel batteries as well?

Jonathan Hill, senior system engineer and founder
Sierra Solar Systems
Post by Larry Crutcher, Starlight Solar Power Systems
Post by Drake
Hello Wrenches,
Thanks for your help with this question.
I've had a breakthrough on the design of this system. I talked with Tom at Midnight Solar, and he explained that Concord batteries can be charged at C X 5 if necessary, i.e., 5 X AH capacity of the bank. The batteries like a fast charge. They are a bit spendy, but will simplify the overall system design.
"The charging current during the Bulk stage should be set as high as practical; higher current mean faster recharge time. For repetitive deep cycling, chargers should have an output current of at least 0.2C (20 Amps for a 100 Ah battery). If the output current is less than this value, the cycle life of the battery may be negatively affected. Due to low impedance design, Sun Xtender batteries can tolerate in-rush current levels as high as 5C (500 A for a 100 Ah battery). "
It is imperative to keep the system voltage at the required set point. The CC regulation will prevent the batteries from being harmed, as the voltage will rise quickly.
Drake
Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
http://athens-electric.com/
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
www.re-wrenches.org/etiquette.htm
www.members.re-wrenches.org
Just a word of caution on the AGM batteries. AGM's do have some vulnerabilities compared to deep cycle wet filled batteries. We had a bank of 20, 8A8D running a Buddhist Retreat compound and were unable to convince our clients that there were limitations to the amount of power that they could run at one time. They managed to overheat and destroy the whole bank of batteries we think by using too much power during a retreat camp. People had brought there own appliances to use at the camp and we still don't know what the total load was on the 4, Outback VFX 3648 inverters. I'm guessing it was up there close to the 14.4 kW limit of the Outback inverters. We also petitioned our client for a larger battery bank but they didn't think they would ever need that much power.
--
--
Vince McClellan
Energy Design
www.solarenergydesign.com
p: 541.485.8122; f: 541.338.3168
This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the sender. If you are not the intended recipient you are notified that disclosing, copying, or distributing the contents of this email is strictly prohibited.
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
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Larry Crutcher, Starlight Solar Power Systems
2012-08-03 22:03:59 UTC
Permalink
Vince,

I know of no such "vulnerability". In fact, an AGM can provide much more instant current than any flooded battery. Concorde (Lifeline, SunXtender, etc.) and Fullriver AGM's are very robust designs. On the other hand, Deka AGM's, specifically the 12 volt 8A8D, are not to be trusted at all. We have stopped selling all Deka/MK AGM's due to very high failure rate.

One other point to consider, having 5 parallel strings of 12 volt batteries is generally asking for short battery life, especially with an AGM since you can not check the SG to be sure all are charged fully. Cells do not charge at the same rate and having parallel paths for current will leave some cells deficit charged. Having many parallel strings exacerbate this issue. If you do upgrade the bank, opt for lower voltage, higher capacity batteries.

Larry Crutcher
Starlight Solar Power Systems
(928) 342-9103


Just a word of caution on the AGM batteries. AGM's do have some vulnerabilities compared to deep cycle wet filled batteries. We had a bank of 20, 8A8D running a Buddhist Retreat compound and were unable to convince our clients that there were limitations to the amount of power that they could run at one time. They managed to overheat and destroy the whole bank of batteries we think by using too much power during a retreat camp. People had brought there own appliances to use at the camp and we still don't know what the total load was on the 4, Outback VFX 3648 inverters. I'm guessing it was up there close to the 14.4 kW limit of the Outback inverters. We also petitioned our client for a larger battery bank but they didn't think they would ever need that much power.
--
--
Vince McClellan
Energy Design
www.solarenergydesign.com
p: 541.485.8122; f: 541.338.3168
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Jonathan Hill
2012-08-04 03:40:33 UTC
Permalink
Is this the case with gel batteries as well?

Jonathan Hill, senior system engineer and founder
Sierra Solar Systems
Post by Larry Crutcher, Starlight Solar Power Systems
Post by Drake
Hello Wrenches,
Thanks for your help with this question.
I've had a breakthrough on the design of this system. I talked with Tom at Midnight Solar, and he explained that Concord batteries can be charged at C X 5 if necessary, i.e., 5 X AH capacity of the bank. The batteries like a fast charge. They are a bit spendy, but will simplify the overall system design.
"The charging current during the Bulk stage should be set as high as practical; higher current mean faster recharge time. For repetitive deep cycling, chargers should have an output current of at least 0.2C (20 Amps for a 100 Ah battery). If the output current is less than this value, the cycle life of the battery may be negatively affected. Due to low impedance design, Sun Xtender batteries can tolerate in-rush current levels as high as 5C (500 A for a 100 Ah battery). "
It is imperative to keep the system voltage at the required set point. The CC regulation will prevent the batteries from being harmed, as the voltage will rise quickly.
Drake
Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
http://athens-electric.com/
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
www.re-wrenches.org/etiquette.htm
www.members.re-wrenches.org
Just a word of caution on the AGM batteries. AGM's do have some vulnerabilities compared to deep cycle wet filled batteries. We had a bank of 20, 8A8D running a Buddhist Retreat compound and were unable to convince our clients that there were limitations to the amount of power that they could run at one time. They managed to overheat and destroy the whole bank of batteries we think by using too much power during a retreat camp. People had brought there own appliances to use at the camp and we still don't know what the total load was on the 4, Outback VFX 3648 inverters. I'm guessing it was up there close to the 14.4 kW limit of the Outback inverters. We also petitioned our client for a larger battery bank but they didn't think they would ever need that much power.
--
--
Vince McClellan
Energy Design
www.solarenergydesign.com
p: 541.485.8122; f: 541.338.3168
This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the sender. If you are not the intended recipient you are notified that disclosing, copying, or distributing the contents of this email is strictly prohibited.
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
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Larry Crutcher, Starlight Solar Power Systems
2012-08-02 21:16:21 UTC
Permalink
Drake,

The ability to charge at much higher amperage is typical of all AGM batteries. The recombinant technology does not produce much heat before the internal resistance rises and the current naturally drops. AGM's require up to 20% less energy to recharge as very little is wasted as heat.

For me, the important aspect of AGM's is that with higher initial current (over sizing the PV system or the ability to use a large charger) and higher efficiency, you reach the absorb set point earlier in the day. For off grid systems, this means you will have more sun hours left to achieve 100% SoC. For these reasons I generally recommend AGM's.

Larry Crutcher
Starlight Solar Power Systems
(928) 342-9103



On Aug 2, 2012, at 2:06 PM, Drake wrote:


Hello Wrenches,

Thanks for your help with this question.

I've had a breakthrough on the design of this system. I talked with Tom at Midnight Solar, and he explained that Concord batteries can be charged at C X 5 if necessary, i.e., 5 X AH capacity of the bank. The batteries like a fast charge. They are a bit spendy, but will simplify the overall system design.

From the Manual:
"The charging current during the Bulk stage should be set as high as practical; higher current mean faster recharge time. For repetitive deep cycling, chargers should have an output current of at least 0.2C (20 Amps for a 100 Ah battery). If the output current is less than this value, the cycle life of the battery may be negatively affected. Due to low impedance design, Sun Xtender batteries can tolerate in-rush current levels as high as 5C (500 A for a 100 Ah battery). "

It is imperative to keep the system voltage at the required set point. The CC regulation will prevent the batteries from being harmed, as the voltage will rise quickly.

Drake

Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
http://athens-electric.com/

-------------- next part --------------
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Vince McClellan
2012-08-03 21:01:10 UTC
Permalink
Post by Drake
Hello Wrenches,
Thanks for your help with this question.
I've had a breakthrough on the design of this system. I talked with
Tom at Midnight Solar, and he explained that Concord batteries can be
charged at C X 5 if necessary, i.e., 5 X AH capacity of the bank. The
batteries like a fast charge. They are a bit spendy, but will
simplify the overall system design.
"The charging current during the Bulk stage should be set as high as
practical; higher current mean faster recharge time. For repetitive
deep cycling, chargers should have an output current of at least 0.2C
(20 Amps for a 100 Ah battery). If the output current is less than
this value, the cycle life of the battery may be negatively affected.
Due to low impedance design, Sun Xtender batteries can tolerate
in-rush current levels as high as 5C (500 A for a 100 Ah battery). "
It is imperative to keep the system voltage at the required set
point. The CC regulation will prevent the batteries from being
harmed, as the voltage will rise quickly.
Drake
Drake Chamberlin
/Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
/http://athens-electric.com/
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
www.re-wrenches.org/etiquette.htm
www.members.re-wrenches.org
Just a word of caution on the AGM batteries. AGM's do have some
vulnerabilities compared to deep cycle wet filled batteries. We had a
bank of 20, 8A8D running a Buddhist Retreat compound and were unable to
convince our clients that there were limitations to the amount of power
that they could run at one time. They managed to overheat and destroy
the whole bank of batteries we think by using too much power during a
retreat camp. People had brought there own appliances to use at the camp
and we still don't know what the total load was on the 4, Outback VFX
3648 inverters. I'm guessing it was up there close to the 14.4 kW limit
of the Outback inverters. We also petitioned our client for a larger
battery bank but they didn't think they would ever need that much power.
--
--
*Vince McClellan
Energy Design
_www.solarenergydesign.com <http://www.solarenergydesign.com/>_
p: 541.485.8122; f: 541.338.3168*
Energy Design Logo
This email and any files transmitted with it are confidential and
intended solely for the use of the individual or entity to whom they are
addressed. If you have received this email in error please notify the
sender. If you are not the intended recipient you are notified that
disclosing, copying, or distributing the contents of this email is
strictly prohibited.

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Drake
2012-08-02 20:06:04 UTC
Permalink
Hello Wrenches,

Thanks for your help with this question.

I've had a breakthrough on the design of this system. I talked with
Tom at Midnight Solar, and he explained that Concord batteries can be
charged at C X 5 if necessary, i.e., 5 X AH capacity of the
bank. The batteries like a fast charge. They are a bit spendy, but
will simplify the overall system design.

From the Manual:
"The charging current during the Bulk stage should be set as high as
practical; higher current mean faster recharge time. For repetitive
deep cycling, chargers should have an output current of at least 0.2C
(20 Amps for a 100 Ah battery). If the output current is less than
this value, the cycle life of the battery may be negatively
affected. Due to low impedance design, Sun Xtender batteries can
tolerate in-rush current levels as high as 5C (500 A for a 100 Ah battery). "

It is imperative to keep the system voltage at the required set
point. The CC regulation will prevent the batteries from being
harmed, as the voltage will rise quickly.

Drake

Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
<http://athens-electric.com/>http://athens-electric.com/



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Philip
2012-07-21 05:11:41 UTC
Permalink
Page 127 of the Mate3 manual.

Phil
Post by Chris Mason
Is there a document available on how this world?
Hi all, I just got a correction from Darren - global charge control is in the Mate3, and therefore works with any FM or MX controller that has the GT mode. It uses the current sense from the FN-DC and the GT mode signal to control the output of the controllers.
Sorry for any confusion
Phil
Phil,
Good explanation of the feature. When did GCC make it into the firmware, and can the older ones be updated? It sounds like a perfect solution for some of my installations.
OutBack implemented Global Charge Control in the FM charge controllers
a while back, based on the input of the good folk at SELF who worked
to power a number of hospitals and clinics in Haiti after the
earthquake. In some of those systems, the PV array was based on the
typical running consumption of the hospital, in the 30 - 100 kW if I
remember right, and the battery bank was relatively modest. However,
on the weekends and holidays without the normal AC loads the PV input
was considerably more than the battery could absorb without
destructive heating, something like a C2 or C5 rate.
Global Charge Control is implemented using the MATE3, a FN-DC and FM
charge controllers set to GT mode. You set a high charge current
limit in the M3, and then it monitors the charge current going to the
batteries. In normal operating mode the controllers stay in wide open
mode, harvesting as much power as possible. However if the loads drop
and the total current from the charging sources begin exceed the
global charge limit, the system compensates and the controllers back
off to prevent sending too much current to the batteries.
In today's world of PV modules being cheaper than diesel, we're seeing
a lot more systems that can use this tool.
Hope this helps,
Phil
On Thu, Jul 19, 2012 at 7:56 PM, boB at midnitesolar.com
I didn't see that Brian T had the same idea until after I sent that email
off to Allan...
boB
Wrenches,
I forwarded Brian's post on to Robin at Midnite, as I thought it was an
interesting idea. Below is his response, as well as boB's.
Allan
Allan Sindelar
Allan at positiveenergysolar.com
NABCEP Certified Photovoltaic Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder and Chief Technology Officer
Positive Energy, Inc.
3209 Richards Lane (note new address)
Santa Fe, New Mexico 87507
505 424-1112
www.positiveenergysolar.com
Allan, It is simpler than what is being suggested. The reason they want to
limit to 20 amps is because the battery doesn?t need anymore than that. The
controller will automatically limit the charge current as the battery gets
full. If a large load is turned on, the controller will try to refill the
battery up to its capacity. The 80 amps will quickly be reduced because the
voltage will rise to the point where the charge tapers off.
There is nothing else that needs to be done. If the problem is that the
battery bank is too small for a big controller, the best answer is to get
more batteries. A 80 amp charger into a 200 amp hour battery is going to
raise the battery voltage so quick, it will not affect the battery at all.
By the way, discharging a battery at 60 or 80 amps is probably going to do
damage to a small battery also. We do have an input on the Classic that
could probably be programmed to do as requested. That input feature has yet
to be implemented. I?m sure we will have discussions about this when the
time comes to write the input code. Maybe this feature will be designed in,
but it doesn?t sound like it is a very good feature to spend a bunch of time
on. After all, the main problem is that the battery bank is just too darned<
--
Chris Mason
President, Comet Systems Ltd
www.cometenergysystems.com
Cell: 264.235.5670
Skype: netconcepts
_______________________________________________
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http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
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Chris Mason
2012-07-21 02:49:44 UTC
Permalink
Is there a document available on how this world?
Post by Phil Undercuffler
Hi all, I just got a correction from Darren - global charge control is in
the Mate3, and therefore works with any FM or MX controller that has the GT
mode. It uses the current sense from the FN-DC and the GT mode signal to
control the output of the controllers.
Post by Phil Undercuffler
Sorry for any confusion
Phil
Phil,
Good explanation of the feature. When did GCC make it into the firmware,
and can the older ones be updated? It sounds like a perfect solution for
some of my installations.
Post by Phil Undercuffler
On Fri, Jul 20, 2012 at 12:34 AM, Phil Undercuffler <solarphil at gmail.com>
OutBack implemented Global Charge Control in the FM charge controllers
a while back, based on the input of the good folk at SELF who worked
to power a number of hospitals and clinics in Haiti after the
earthquake. In some of those systems, the PV array was based on the
typical running consumption of the hospital, in the 30 - 100 kW if I
remember right, and the battery bank was relatively modest. However,
on the weekends and holidays without the normal AC loads the PV input
was considerably more than the battery could absorb without
destructive heating, something like a C2 or C5 rate.
Global Charge Control is implemented using the MATE3, a FN-DC and FM
charge controllers set to GT mode. You set a high charge current
limit in the M3, and then it monitors the charge current going to the
batteries. In normal operating mode the controllers stay in wide open
mode, harvesting as much power as possible. However if the loads drop
and the total current from the charging sources begin exceed the
global charge limit, the system compensates and the controllers back
off to prevent sending too much current to the batteries.
In today's world of PV modules being cheaper than diesel, we're seeing
a lot more systems that can use this tool.
Hope this helps,
Phil
On Thu, Jul 19, 2012 at 7:56 PM, boB at midnitesolar.com
I didn't see that Brian T had the same idea until after I sent that email
off to Allan...
boB
Wrenches,
I forwarded Brian's post on to Robin at Midnite, as I thought it was an
interesting idea. Below is his response, as well as boB's.
Allan
Allan Sindelar
Allan at positiveenergysolar.com
NABCEP Certified Photovoltaic Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder and Chief Technology Officer
Positive Energy, Inc.
3209 Richards Lane (note new address)
Santa Fe, New Mexico 87507
505 424-1112
www.positiveenergysolar.com
Allan, It is simpler than what is being suggested. The reason they want to
limit to 20 amps is because the battery doesn?t need anymore than that. The
controller will automatically limit the charge current as the battery gets
full. If a large load is turned on, the controller will try to refill the
battery up to its capacity. The 80 amps will quickly be reduced because the
voltage will rise to the point where the charge tapers off.
There is nothing else that needs to be done. If the problem is that the
battery bank is too small for a big controller, the best answer is to get
more batteries. A 80 amp charger into a 200 amp hour battery is going to
raise the battery voltage so quick, it will not affect the battery at all.
By the way, discharging a battery at 60 or 80 amps is probably going to do
damage to a small battery also. We do have an input on the Classic that
could probably be programmed to do as requested. That input feature has yet
to be implemented. I?m sure we will have discussions about this when the
time comes to write the input code. Maybe this feature will be designed in,
but it doesn?t sound like it is a very good feature to spend a bunch of time
on. After all, the main problem is that the battery bank is just too
darned<
--
Chris Mason
President, Comet Systems Ltd
www.cometenergysystems.com
Cell: 264.235.5670
Skype: netconcepts
-------------- next part --------------
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Phil Undercuffler
2012-07-21 01:28:46 UTC
Permalink
Hi all, I just got a correction from Darren - global charge control is in
the Mate3, and therefore works with any FM or MX controller that has the GT
mode. It uses the current sense from the FN-DC and the GT mode signal to
control the output of the controllers.

Sorry for any confusion

Phil
Post by Chris Mason
Phil,
Good explanation of the feature. When did GCC make it into the firmware,
and can the older ones be updated? It sounds like a perfect solution for
some of my installations.
Post by Phil Undercuffler
OutBack implemented Global Charge Control in the FM charge controllers
a while back, based on the input of the good folk at SELF who worked
to power a number of hospitals and clinics in Haiti after the
earthquake. In some of those systems, the PV array was based on the
typical running consumption of the hospital, in the 30 - 100 kW if I
remember right, and the battery bank was relatively modest. However,
on the weekends and holidays without the normal AC loads the PV input
was considerably more than the battery could absorb without
destructive heating, something like a C2 or C5 rate.
Global Charge Control is implemented using the MATE3, a FN-DC and FM
charge controllers set to GT mode. You set a high charge current
limit in the M3, and then it monitors the charge current going to the
batteries. In normal operating mode the controllers stay in wide open
mode, harvesting as much power as possible. However if the loads drop
and the total current from the charging sources begin exceed the
global charge limit, the system compensates and the controllers back
off to prevent sending too much current to the batteries.
In today's world of PV modules being cheaper than diesel, we're seeing
a lot more systems that can use this tool.
Hope this helps,
Phil
On Thu, Jul 19, 2012 at 7:56 PM, boB at midnitesolar.com
Post by boB
I didn't see that Brian T had the same idea until after I sent that
email
Post by boB
off to Allan...
boB
Wrenches,
I forwarded Brian's post on to Robin at Midnite, as I thought it was an
interesting idea. Below is his response, as well as boB's.
Allan
Allan Sindelar
Allan at positiveenergysolar.com
NABCEP Certified Photovoltaic Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder and Chief Technology Officer
Positive Energy, Inc.
3209 Richards Lane (note new address)
Santa Fe, New Mexico 87507
505 424-1112
www.positiveenergysolar.com
Allan, It is simpler than what is being suggested. The reason they want
to
Post by boB
limit to 20 amps is because the battery doesn?t need anymore than that.
The
Post by boB
controller will automatically limit the charge current as the battery
gets
Post by boB
full. If a large load is turned on, the controller will try to refill
the
Post by boB
battery up to its capacity. The 80 amps will quickly be reduced because
the
Post by boB
voltage will rise to the point where the charge tapers off.
There is nothing else that needs to be done. If the problem is that the
battery bank is too small for a big controller, the best answer is to
get
Post by boB
more batteries. A 80 amp charger into a 200 amp hour battery is going to
raise the battery voltage so quick, it will not affect the battery at
all.
Post by boB
By the way, discharging a battery at 60 or 80 amps is probably going to
do
Post by boB
damage to a small battery also. We do have an input on the Classic that
could probably be programmed to do as requested. That input feature has
yet
Post by boB
to be implemented. I?m sure we will have discussions about this when the
time comes to write the input code. Maybe this feature will be designed
in,
Post by boB
but it doesn?t sound like it is a very good feature to spend a bunch of
time
Post by boB
on. After all, the main problem is that the battery bank is just too
darned
Post by boB
small.
Bob, Tom and Ryan do you have any comments on the subject?
Thanks,
Robin
One idea I had in mind was to have an option, in software, to limit the
current into the battery,
when the charging current goes above some set threshold. The controller
would have to get its information from
the battery monitor over the network.
If it is a grid tie system and grid is there and GT inverter is selling,
then no problem... The controller
can work at its full output. If grid or loads go away, then the CC will
know and it can throttle back at
that time.
We don't have a battery monitor yet, but we will have one. This will
be one
Post by boB
of the settings as well as
Re-Bulk based on state of charge, ending amps and those types of things.
boB
I say it is waste of time.
1. AGM batteries can take the high current and you are right, the absorb
voltage is reached and the absorb current is tapered rather quickly.
Current
Post by boB
generation charge controllers are rather fast at the transitions. I
have a
Post by boB
bunch of data from a system with a PentaMetric that shows the battery
bank
Post by boB
going to absorb voltage at grid tie, during cloud events, but only for
a few
Post by boB
seconds at a time.
2. A properly designed GTBB system should cover the connected loads for
24
Post by boB
hours of each sunny day, at a minimum. Keep in mind, off grid systems
are
Post by boB
designed for that, and 3 days + of backup, etc.
3. I would say, based on my experience, the minimum battery bank should
be
Post by boB
400Ah. I personally try to set it at 600Ah (48V). It is a backup system
after all. But the key is the customer's expectations...who are they
going
Post by boB
to call after the lights go out?
Thank you,
Maverick
Maverick Brown
BSEET, NABCEP Certified Solar PV Installer ?
President & CEO
Maverick Solar Enterprises, Inc.
Office: 512-919-4493
Cell: 512-460-9825
Sent from my HondaJet!
On Jul 19, 2012, at 6:35 PM, Brian Teitelbaum <bteitelbaum at aeesolar.com
Drake,
I?ve been hounding a couple of the charge controller manufactures about
this
Post by boB
issue, but so far I just haven?t seen a light bulb go off in their
heads,
Post by boB
but I?ll keep trying, and maybe this is a better forum to do it.
MPPT controllers can be adjusted to current limit at amperage values
below
Post by boB
their rating, but if you do that, you are also limiting the output of
the
Post by boB
array in general, and the amount of PV power available to run the loads
directly from the array (through the inverter). Not the best use of
available PV power.
Say you have an 80A controller and a 200AH battery. With current
technology,
Post by boB
Let the controller operate at 80A. If you have loads to draw off some
of the
Post by boB
current (or sell to the grid), great, but if not you could be seeing a
charge rate of C/2.5, which would be pretty hard on a sealed 200AH
battery,
Post by boB
to say the least. Granted, the battery voltage would rise pretty
quickly,
Post by boB
and the controller would start to taper off, but it would still see high
currents especially if the absorption time is set long. Not a happy
scenario.
Or, you can set the current limiting on the controller to 20A for a C/10
charge rate. But if you had loads drawing 60A, you would be pulling that
additional 40A from the battery and not using the array?s full power.
Also
Post by boB
not a happy scenario.
What we need is a controller that can read the signal from a shunt at
the
Post by boB
battery, and use that as the basis of current limiting control.
For example, if we have an array that can produce 80A of current, but we
want to limit the battery to 20A of charge, there would be 60A of
potential
Post by boB
current there to run loads without drawing on the battery. If there are
no
Post by boB
loads running, the controller should current limit at 20A (reading from
a
Post by boB
shunt), but if loads are turned on, the controller should be able to let
more current through while still limiting the battery to 20A. When
loads are
Post by boB
shut off, the controller should go back to a 20A limit.
This doesn?t all have to happen very quickly as a battery can take a
heavier
Post by boB
charge for a short period of time, but I think that this would be a
major
Post by boB
improvement of controller function.
Of course, if you are grid-tied you can sell all the excess power, but
if
Post by boB
the grid goes down, or you are off-grid?.?
Because of the low cost of PV and the high cost of batteries these
days, I?m
Post by boB
seeing more and more requests for large arrays with smaller batteries. I
also think that PV is now cheap enough to allow for oversizing of
arrays for
Post by boB
better battery charging on cloudy days, which can reduce generator run
times. We need smarter controllers.
What say ye, charge controller gurus?
Brian Teitelbaum
AEE Solar
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Drake
Sent: Thursday, July 19, 2012 2:21 PM
To: RE-wrenches
Subject: [RE-wrenches] Small battery bank vs too large array
Hello Wrenches,
Where can I get a device that will measure current through a shunt and
create a signal to trigger a relay?
We want to be able to use a 2 kW array with four, 200 AH sealed
batteries on
Post by boB
an Outback system. 2 kW of PV would be too much amperage for the
batteries.
Post by boB
The idea is to open relays to disengage strings in conditions of high
current to the batteries.
The reason for this is to create backup systems where power will be
abundantly available when the sun shines. The system will normally
connect
Post by boB
to the grid, except during outages. In normal charging conditions the
power
Post by boB
will go straight to the grid. When the grid is down, power will be
available for loads and battery charging, but batteries will be
protected
Post by boB
from overcharge?
Any suggestions on ways to accomplish this are welcome!
Thanks
Drake
Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
http://athens-electric.com/
_______________________________________________
List sponsored by Home Power magazine
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List Address: RE-wrenches at lists.re-wrenches.org
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List Address: RE-wrenches at lists.re-wrenches.org
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--
Chris Mason
President, Comet Systems Ltd
www.cometenergysystems.com
Cell: 264.235.5670
Skype: netconcepts
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Drake
2012-07-20 14:11:34 UTC
Permalink
Thank you Phil,

That is the solution. Your wealth of knowledge has proven itself again.

Drake
Post by Phil Undercuffler
OutBack implemented Global Charge Control in the FM charge controllers
a while back, based on the input of the good folk at SELF who worked
to power a number of hospitals and clinics in Haiti after the
earthquake. In some of those systems, the PV array was based on the
typical running consumption of the hospital, in the 30 - 100 kW if I
remember right, and the battery bank was relatively modest. However,
on the weekends and holidays without the normal AC loads the PV input
was considerably more than the battery could absorb without
destructive heating, something like a C2 or C5 rate.
Global Charge Control is implemented using the MATE3, a FN-DC and FM
charge controllers set to GT mode. You set a high charge current
limit in the M3, and then it monitors the charge current going to the
batteries. In normal operating mode the controllers stay in wide open
mode, harvesting as much power as possible. However if the loads drop
and the total current from the charging sources begin exceed the
global charge limit, the system compensates and the controllers back
off to prevent sending too much current to the batteries.
In today's world of PV modules being cheaper than diesel, we're seeing
a lot more systems that can use this tool.
Hope this helps,
Phil
On Thu, Jul 19, 2012 at 7:56 PM, boB at midnitesolar.com
I didn't see that Brian T had the same idea until after I sent that email
off to Allan...
boB
Wrenches,
I forwarded Brian's post on to Robin at Midnite, as I thought it was an
interesting idea. Below is his response, as well as boB's.
Allan
Allan Sindelar
Allan at positiveenergysolar.com
NABCEP Certified Photovoltaic Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder and Chief Technology Officer
Positive Energy, Inc.
3209 Richards Lane (note new address)
Santa Fe, New Mexico 87507
505 424-1112
www.positiveenergysolar.com
Allan, It is simpler than what is being suggested. The reason they want to
limit to 20 amps is because the battery doesn?t need anymore than that. The
controller will automatically limit the charge current as the battery gets
full. If a large load is turned on, the controller will try to refill the
battery up to its capacity. The 80 amps will quickly be reduced because the
voltage will rise to the point where the charge tapers off.
There is nothing else that needs to be done. If the problem is that the
battery bank is too small for a big controller, the best answer is to get
more batteries. A 80 amp charger into a 200 amp hour battery is going to
raise the battery voltage so quick, it will not affect the battery at all.
By the way, discharging a battery at 60 or 80 amps is probably going to do
damage to a small battery also. We do have an input on the Classic that
could probably be programmed to do as requested. That input feature has yet
to be implemented. I?m sure we will have discussions about this when the
time comes to write the input code. Maybe this feature will be designed in,
but it doesn?t sound like it is a very good
feature to spend a bunch of time
on. After all, the main problem is that the battery bank is just too darned
small.
Bob, Tom and Ryan do you have any comments on the subject?
Thanks,
Robin
One idea I had in mind was to have an option, in software, to limit the
current into the battery,
when the charging current goes above some set threshold. The controller
would have to get its information from
the battery monitor over the network.
If it is a grid tie system and grid is there and GT inverter is selling,
then no problem... The controller
can work at its full output. If grid or loads go away, then the CC will
know and it can throttle back at
that time.
We don't have a battery monitor yet, but we
will have one. This will be one
of the settings as well as
Re-Bulk based on state of charge, ending amps and those types of things.
boB
I say it is waste of time.
1. AGM batteries can take the high current and you are right, the absorb
voltage is reached and the absorb current is
tapered rather quickly. Current
generation charge controllers are rather fast at the transitions. I have a
bunch of data from a system with a PentaMetric that shows the battery bank
going to absorb voltage at grid tie, during
cloud events, but only for a few
seconds at a time.
2. A properly designed GTBB system should cover the connected loads for 24
hours of each sunny day, at a minimum. Keep in mind, off grid systems are
designed for that, and 3 days + of backup, etc.
3. I would say, based on my experience, the minimum battery bank should be
400Ah. I personally try to set it at 600Ah (48V). It is a backup system
after all. But the key is the customer's expectations...who are they going
to call after the lights go out?
Thank you,
Maverick
Maverick Brown
BSEET, NABCEP Certified Solar PV Installer ?
President & CEO
Maverick Solar Enterprises, Inc.
Office: 512-919-4493
Cell: 512-460-9825
Sent from my HondaJet!
Drake,
I?ve been hounding a couple of the charge
controller manufactures about this
issue, but so far I just haven?t seen a light bulb go off in their heads,
but I?ll keep trying, and maybe this is a better forum to do it.
MPPT controllers can be adjusted to current limit at amperage values below
their rating, but if you do that, you are also limiting the output of the
array in general, and the amount of PV power available to run the loads
directly from the array (through the inverter). Not the best use of
available PV power.
Say you have an 80A controller and a 200AH
battery. With current technology,
Let the controller operate at 80A. If you
have loads to draw off some of the
current (or sell to the grid), great, but if not you could be seeing a
charge rate of C/2.5, which would be pretty hard on a sealed 200AH battery,
to say the least. Granted, the battery voltage would rise pretty quickly,
and the controller would start to taper off, but it would still see high
currents especially if the absorption time is set long. Not a happy
scenario.
Or, you can set the current limiting on the controller to 20A for a C/10
charge rate. But if you had loads drawing 60A, you would be pulling that
additional 40A from the battery and not using the array?s full power. Also
not a happy scenario.
What we need is a controller that can read the signal from a shunt at the
battery, and use that as the basis of current limiting control.
For example, if we have an array that can produce 80A of current, but we
want to limit the battery to 20A of charge, there would be 60A of potential
current there to run loads without drawing on the battery. If there are no
loads running, the controller should current limit at 20A (reading from a
shunt), but if loads are turned on, the controller should be able to let
more current through while still limiting the
battery to 20A. When loads are
shut off, the controller should go back to a 20A limit.
This doesn?t all have to happen very quickly
as a battery can take a heavier
charge for a short period of time, but I think that this would be a major
improvement of controller function.
Of course, if you are grid-tied you can sell all the excess power, but if
the grid goes down, or you are off-grid
.?
Post by Phil Undercuffler
Because of the low cost of PV and the high
cost of batteries these days, I?m
seeing more and more requests for large arrays with smaller batteries. I
also think that PV is now cheap enough to
allow for oversizing of arrays for
better battery charging on cloudy days, which can reduce generator run
times. We need smarter controllers.
What say ye, charge controller gurus?
Brian Teitelbaum
AEE Solar
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Drake
Sent: Thursday, July 19, 2012 2:21 PM
To: RE-wrenches
Subject: [RE-wrenches] Small battery bank vs too large array
Hello Wrenches,
Where can I get a device that will measure current through a shunt and
create a signal to trigger a relay?
We want to be able to use a 2 kW array with
four, 200 AH sealed batteries on
an Outback system. 2 kW of PV would be too
much amperage for the batteries.
The idea is to open relays to disengage strings in conditions of high
current to the batteries.
The reason for this is to create backup systems where power will be
abundantly available when the sun shines. The system will normally connect
to the grid, except during outages. In
normal charging conditions the power
will go straight to the grid. When the grid is down, power will be
available for loads and battery charging, but batteries will be protected
from overcharge?
Any suggestions on ways to accomplish this are welcome!
Thanks
Drake
Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
http://athens-electric.com/
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Brian Teitelbaum
2012-07-20 17:23:03 UTC
Permalink
Phil,

Thanks for the very thorough explanation of the Global Charge Control. That setup would certainly provide the level of control that I was getting at.

I can see how the FN-DC could do that since it utilizes multiple shunts and can therefore use discrete amperage readings to provide better charge controlling functions. This will be very useful, not only for the type of system that you describe in Haiti, but for off-grid systems employing large PV arrays to provide adequate charging in foggy or overcast weather. With PV at a buck-a-Watt, this is starting to become a viable way to reduce battery size and cost without resorting to running a generator. PV lasts substantially longer than batteries, so is a better investment in my opinion

Brian Teitelbaum
AEE Solar



-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Phil Undercuffler
Sent: Thursday, July 19, 2012 9:35 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Small battery bank vs too large array

OutBack implemented Global Charge Control in the FM charge controllers a while back, based on the input of the good folk at SELF who worked to power a number of hospitals and clinics in Haiti after the earthquake. In some of those systems, the PV array was based on the typical running consumption of the hospital, in the 30 - 100 kW if I remember right, and the battery bank was relatively modest. However, on the weekends and holidays without the normal AC loads the PV input was considerably more than the battery could absorb without destructive heating, something like a C2 or C5 rate.

Global Charge Control is implemented using the MATE3, a FN-DC and FM charge controllers set to GT mode. You set a high charge current limit in the M3, and then it monitors the charge current going to the batteries. In normal operating mode the controllers stay in wide open mode, harvesting as much power as possible. However if the loads drop and the total current from the charging sources begin exceed the global charge limit, the system compensates and the controllers back off to prevent sending too much current to the batteries.

In today's world of PV modules being cheaper than diesel, we're seeing a lot more systems that can use this tool.

Hope this helps,

Phil
Post by boB
I didn't see that Brian T had the same idea until after I sent that
email off to Allan...
boB
Wrenches,
I forwarded Brian's post on to Robin at Midnite, as I thought it was
an interesting idea. Below is his response, as well as boB's.
Allan
Allan Sindelar
Allan at positiveenergysolar.com
NABCEP Certified Photovoltaic Installer NABCEP Certified Technical
Sales Professional New Mexico EE98J Journeyman Electrician Founder and
Chief Technology Officer Positive Energy, Inc.
3209 Richards Lane (note new address)
Santa Fe, New Mexico 87507
505 424-1112
www.positiveenergysolar.com
Allan, It is simpler than what is being suggested. The reason they
want to limit to 20 amps is because the battery doesn't need anymore
than that. The controller will automatically limit the charge current
as the battery gets full. If a large load is turned on, the controller
will try to refill the battery up to its capacity. The 80 amps will
quickly be reduced because the voltage will rise to the point where the charge tapers off.
There is nothing else that needs to be done. If the problem is that
the battery bank is too small for a big controller, the best answer is
to get more batteries. A 80 amp charger into a 200 amp hour battery is
going to raise the battery voltage so quick, it will not affect the battery at all.
By the way, discharging a battery at 60 or 80 amps is probably going
to do damage to a small battery also. We do have an input on the
Classic that could probably be programmed to do as requested. That
input feature has yet to be implemented. I'm sure we will have
discussions about this when the time comes to write the input code.
Maybe this feature will be designed in, but it doesn't sound like it
is a very good feature to spend a bunch of time on. After all, the
main problem is that the battery bank is just too darned small.
Bob, Tom and Ryan do you have any comments on the subject?
Thanks,
Robin
One idea I had in mind was to have an option, in software, to limit
the current into the battery, when the charging current goes above
some set threshold. The controller would have to get its information
from the battery monitor over the network.
If it is a grid tie system and grid is there and GT inverter is
selling, then no problem... The controller can work at its full
output. If grid or loads go away, then the CC will know and it can
throttle back at that time.
We don't have a battery monitor yet, but we will have one. This will
be one of the settings as well as Re-Bulk based on state of charge,
ending amps and those types of things.
boB
I say it is waste of time.
1. AGM batteries can take the high current and you are right, the
absorb voltage is reached and the absorb current is tapered rather
quickly. Current generation charge controllers are rather fast at the
transitions. I have a bunch of data from a system with a PentaMetric
that shows the battery bank going to absorb voltage at grid tie,
during cloud events, but only for a few seconds at a time.
2. A properly designed GTBB system should cover the connected loads
for 24 hours of each sunny day, at a minimum. Keep in mind, off grid
systems are designed for that, and 3 days + of backup, etc.
3. I would say, based on my experience, the minimum battery bank
should be 400Ah. I personally try to set it at 600Ah (48V). It is a
backup system after all. But the key is the customer's
expectations...who are they going to call after the lights go out?
Thank you,
Maverick
Maverick Brown
BSEET, NABCEP Certified Solar PV Installer (r) President & CEO Maverick
Solar Enterprises, Inc.
Office: 512-919-4493
Cell: 512-460-9825
Sent from my HondaJet!
On Jul 19, 2012, at 6:35 PM, Brian Teitelbaum
<bteitelbaum at aeesolar.com>
Drake,
I've been hounding a couple of the charge controller manufactures
about this issue, but so far I just haven't seen a light bulb go off
in their heads, but I'll keep trying, and maybe this is a better forum to do it.
MPPT controllers can be adjusted to current limit at amperage values
below their rating, but if you do that, you are also limiting the
output of the array in general, and the amount of PV power available
to run the loads directly from the array (through the inverter). Not
the best use of available PV power.
Say you have an 80A controller and a 200AH battery. With current
Let the controller operate at 80A. If you have loads to draw off some
of the current (or sell to the grid), great, but if not you could be
seeing a charge rate of C/2.5, which would be pretty hard on a sealed
200AH battery, to say the least. Granted, the battery voltage would
rise pretty quickly, and the controller would start to taper off, but
it would still see high currents especially if the absorption time is
set long. Not a happy scenario.
Or, you can set the current limiting on the controller to 20A for a
C/10 charge rate. But if you had loads drawing 60A, you would be
pulling that additional 40A from the battery and not using the array's
full power. Also not a happy scenario.
What we need is a controller that can read the signal from a shunt at
the battery, and use that as the basis of current limiting control.
For example, if we have an array that can produce 80A of current, but
we want to limit the battery to 20A of charge, there would be 60A of
potential current there to run loads without drawing on the battery.
If there are no loads running, the controller should current limit at
20A (reading from a shunt), but if loads are turned on, the controller
should be able to let more current through while still limiting the
battery to 20A. When loads are shut off, the controller should go back to a 20A limit.
This doesn't all have to happen very quickly as a battery can take a
heavier charge for a short period of time, but I think that this would
be a major improvement of controller function.
Of course, if you are grid-tied you can sell all the excess power, but
if the grid goes down, or you are off-grid....?
Because of the low cost of PV and the high cost of batteries these
days, I'm seeing more and more requests for large arrays with smaller
batteries. I also think that PV is now cheap enough to allow for
oversizing of arrays for better battery charging on cloudy days, which
can reduce generator run times. We need smarter controllers.
What say ye, charge controller gurus?
Brian Teitelbaum
AEE Solar
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Drake
Sent: Thursday, July 19, 2012 2:21 PM
To: RE-wrenches
Subject: [RE-wrenches] Small battery bank vs too large array
Hello Wrenches,
Where can I get a device that will measure current through a shunt and
create a signal to trigger a relay?
We want to be able to use a 2 kW array with four, 200 AH sealed
batteries on an Outback system. 2 kW of PV would be too much amperage for the batteries.
The idea is to open relays to disengage strings in conditions of high
current to the batteries.
The reason for this is to create backup systems where power will be
abundantly available when the sun shines. The system will normally
connect to the grid, except during outages. In normal charging
conditions the power will go straight to the grid. When the grid is
down, power will be available for loads and battery charging, but
batteries will be protected from overcharge?
Any suggestions on ways to accomplish this are welcome!
Thanks
Drake
Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
http://athens-electric.com/
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Chris Mason
2012-07-20 23:11:30 UTC
Permalink
Phil,
Good explanation of the feature. When did GCC make it into the firmware,
and can the older ones be updated? It sounds like a perfect solution for
some of my installations.
Post by Phil Undercuffler
OutBack implemented Global Charge Control in the FM charge controllers
a while back, based on the input of the good folk at SELF who worked
to power a number of hospitals and clinics in Haiti after the
earthquake. In some of those systems, the PV array was based on the
typical running consumption of the hospital, in the 30 - 100 kW if I
remember right, and the battery bank was relatively modest. However,
on the weekends and holidays without the normal AC loads the PV input
was considerably more than the battery could absorb without
destructive heating, something like a C2 or C5 rate.
Global Charge Control is implemented using the MATE3, a FN-DC and FM
charge controllers set to GT mode. You set a high charge current
limit in the M3, and then it monitors the charge current going to the
batteries. In normal operating mode the controllers stay in wide open
mode, harvesting as much power as possible. However if the loads drop
and the total current from the charging sources begin exceed the
global charge limit, the system compensates and the controllers back
off to prevent sending too much current to the batteries.
In today's world of PV modules being cheaper than diesel, we're seeing
a lot more systems that can use this tool.
Hope this helps,
Phil
On Thu, Jul 19, 2012 at 7:56 PM, boB at midnitesolar.com
I didn't see that Brian T had the same idea until after I sent that email
off to Allan...
boB
Wrenches,
I forwarded Brian's post on to Robin at Midnite, as I thought it was an
interesting idea. Below is his response, as well as boB's.
Allan
Allan Sindelar
Allan at positiveenergysolar.com
NABCEP Certified Photovoltaic Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder and Chief Technology Officer
Positive Energy, Inc.
3209 Richards Lane (note new address)
Santa Fe, New Mexico 87507
505 424-1112
www.positiveenergysolar.com
Allan, It is simpler than what is being suggested. The reason they want
to
limit to 20 amps is because the battery doesn?t need anymore than that.
The
controller will automatically limit the charge current as the battery
gets
full. If a large load is turned on, the controller will try to refill the
battery up to its capacity. The 80 amps will quickly be reduced because
the
voltage will rise to the point where the charge tapers off.
There is nothing else that needs to be done. If the problem is that the
battery bank is too small for a big controller, the best answer is to get
more batteries. A 80 amp charger into a 200 amp hour battery is going to
raise the battery voltage so quick, it will not affect the battery at
all.
By the way, discharging a battery at 60 or 80 amps is probably going to
do
damage to a small battery also. We do have an input on the Classic that
could probably be programmed to do as requested. That input feature has
yet
to be implemented. I?m sure we will have discussions about this when the
time comes to write the input code. Maybe this feature will be designed
in,
but it doesn?t sound like it is a very good feature to spend a bunch of
time
on. After all, the main problem is that the battery bank is just too
darned
small.
Bob, Tom and Ryan do you have any comments on the subject?
Thanks,
Robin
One idea I had in mind was to have an option, in software, to limit the
current into the battery,
when the charging current goes above some set threshold. The controller
would have to get its information from
the battery monitor over the network.
If it is a grid tie system and grid is there and GT inverter is selling,
then no problem... The controller
can work at its full output. If grid or loads go away, then the CC will
know and it can throttle back at
that time.
We don't have a battery monitor yet, but we will have one. This will be
one
of the settings as well as
Re-Bulk based on state of charge, ending amps and those types of things.
boB
I say it is waste of time.
1. AGM batteries can take the high current and you are right, the absorb
voltage is reached and the absorb current is tapered rather quickly.
Current
generation charge controllers are rather fast at the transitions. I have
a
bunch of data from a system with a PentaMetric that shows the battery
bank
going to absorb voltage at grid tie, during cloud events, but only for a
few
seconds at a time.
2. A properly designed GTBB system should cover the connected loads for
24
hours of each sunny day, at a minimum. Keep in mind, off grid systems are
designed for that, and 3 days + of backup, etc.
3. I would say, based on my experience, the minimum battery bank should
be
400Ah. I personally try to set it at 600Ah (48V). It is a backup system
after all. But the key is the customer's expectations...who are they
going
to call after the lights go out?
Thank you,
Maverick
Maverick Brown
BSEET, NABCEP Certified Solar PV Installer ?
President & CEO
Maverick Solar Enterprises, Inc.
Office: 512-919-4493
Cell: 512-460-9825
Sent from my HondaJet!
Drake,
I?ve been hounding a couple of the charge controller manufactures about
this
issue, but so far I just haven?t seen a light bulb go off in their heads,
but I?ll keep trying, and maybe this is a better forum to do it.
MPPT controllers can be adjusted to current limit at amperage values
below
their rating, but if you do that, you are also limiting the output of the
array in general, and the amount of PV power available to run the loads
directly from the array (through the inverter). Not the best use of
available PV power.
Say you have an 80A controller and a 200AH battery. With current
technology,
Let the controller operate at 80A. If you have loads to draw off some of
the
current (or sell to the grid), great, but if not you could be seeing a
charge rate of C/2.5, which would be pretty hard on a sealed 200AH
battery,
to say the least. Granted, the battery voltage would rise pretty quickly,
and the controller would start to taper off, but it would still see high
currents especially if the absorption time is set long. Not a happy
scenario.
Or, you can set the current limiting on the controller to 20A for a C/10
charge rate. But if you had loads drawing 60A, you would be pulling that
additional 40A from the battery and not using the array?s full power.
Also
not a happy scenario.
What we need is a controller that can read the signal from a shunt at the
battery, and use that as the basis of current limiting control.
For example, if we have an array that can produce 80A of current, but we
want to limit the battery to 20A of charge, there would be 60A of
potential
current there to run loads without drawing on the battery. If there are
no
loads running, the controller should current limit at 20A (reading from a
shunt), but if loads are turned on, the controller should be able to let
more current through while still limiting the battery to 20A. When loads
are
shut off, the controller should go back to a 20A limit.
This doesn?t all have to happen very quickly as a battery can take a
heavier
charge for a short period of time, but I think that this would be a major
improvement of controller function.
Of course, if you are grid-tied you can sell all the excess power, but if
the grid goes down, or you are off-grid?.?
Because of the low cost of PV and the high cost of batteries these days,
I?m
seeing more and more requests for large arrays with smaller batteries. I
also think that PV is now cheap enough to allow for oversizing of arrays
for
better battery charging on cloudy days, which can reduce generator run
times. We need smarter controllers.
What say ye, charge controller gurus?
Brian Teitelbaum
AEE Solar
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Drake
Sent: Thursday, July 19, 2012 2:21 PM
To: RE-wrenches
Subject: [RE-wrenches] Small battery bank vs too large array
Hello Wrenches,
Where can I get a device that will measure current through a shunt and
create a signal to trigger a relay?
We want to be able to use a 2 kW array with four, 200 AH sealed
batteries on
an Outback system. 2 kW of PV would be too much amperage for the
batteries.
The idea is to open relays to disengage strings in conditions of high
current to the batteries.
The reason for this is to create backup systems where power will be
abundantly available when the sun shines. The system will normally
connect
to the grid, except during outages. In normal charging conditions the
power
will go straight to the grid. When the grid is down, power will be
available for loads and battery charging, but batteries will be protected
from overcharge?
Any suggestions on ways to accomplish this are welcome!
Thanks
Drake
Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
http://athens-electric.com/
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
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Chris Mason
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Cell: 264.235.5670
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Phil Undercuffler
2012-07-20 04:34:32 UTC
Permalink
OutBack implemented Global Charge Control in the FM charge controllers
a while back, based on the input of the good folk at SELF who worked
to power a number of hospitals and clinics in Haiti after the
earthquake. In some of those systems, the PV array was based on the
typical running consumption of the hospital, in the 30 - 100 kW if I
remember right, and the battery bank was relatively modest. However,
on the weekends and holidays without the normal AC loads the PV input
was considerably more than the battery could absorb without
destructive heating, something like a C2 or C5 rate.

Global Charge Control is implemented using the MATE3, a FN-DC and FM
charge controllers set to GT mode. You set a high charge current
limit in the M3, and then it monitors the charge current going to the
batteries. In normal operating mode the controllers stay in wide open
mode, harvesting as much power as possible. However if the loads drop
and the total current from the charging sources begin exceed the
global charge limit, the system compensates and the controllers back
off to prevent sending too much current to the batteries.

In today's world of PV modules being cheaper than diesel, we're seeing
a lot more systems that can use this tool.

Hope this helps,

Phil



On Thu, Jul 19, 2012 at 7:56 PM, boB at midnitesolar.com
I didn't see that Brian T had the same idea until after I sent that email
off to Allan...
boB
Wrenches,
I forwarded Brian's post on to Robin at Midnite, as I thought it was an
interesting idea. Below is his response, as well as boB's.
Allan
Allan Sindelar
Allan at positiveenergysolar.com
NABCEP Certified Photovoltaic Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder and Chief Technology Officer
Positive Energy, Inc.
3209 Richards Lane (note new address)
Santa Fe, New Mexico 87507
505 424-1112
www.positiveenergysolar.com
Allan, It is simpler than what is being suggested. The reason they want to
limit to 20 amps is because the battery doesn?t need anymore than that. The
controller will automatically limit the charge current as the battery gets
full. If a large load is turned on, the controller will try to refill the
battery up to its capacity. The 80 amps will quickly be reduced because the
voltage will rise to the point where the charge tapers off.
There is nothing else that needs to be done. If the problem is that the
battery bank is too small for a big controller, the best answer is to get
more batteries. A 80 amp charger into a 200 amp hour battery is going to
raise the battery voltage so quick, it will not affect the battery at all.
By the way, discharging a battery at 60 or 80 amps is probably going to do
damage to a small battery also. We do have an input on the Classic that
could probably be programmed to do as requested. That input feature has yet
to be implemented. I?m sure we will have discussions about this when the
time comes to write the input code. Maybe this feature will be designed in,
but it doesn?t sound like it is a very good feature to spend a bunch of time
on. After all, the main problem is that the battery bank is just too darned
small.
Bob, Tom and Ryan do you have any comments on the subject?
Thanks,
Robin
One idea I had in mind was to have an option, in software, to limit the
current into the battery,
when the charging current goes above some set threshold. The controller
would have to get its information from
the battery monitor over the network.
If it is a grid tie system and grid is there and GT inverter is selling,
then no problem... The controller
can work at its full output. If grid or loads go away, then the CC will
know and it can throttle back at
that time.
We don't have a battery monitor yet, but we will have one. This will be one
of the settings as well as
Re-Bulk based on state of charge, ending amps and those types of things.
boB
I say it is waste of time.
1. AGM batteries can take the high current and you are right, the absorb
voltage is reached and the absorb current is tapered rather quickly. Current
generation charge controllers are rather fast at the transitions. I have a
bunch of data from a system with a PentaMetric that shows the battery bank
going to absorb voltage at grid tie, during cloud events, but only for a few
seconds at a time.
2. A properly designed GTBB system should cover the connected loads for 24
hours of each sunny day, at a minimum. Keep in mind, off grid systems are
designed for that, and 3 days + of backup, etc.
3. I would say, based on my experience, the minimum battery bank should be
400Ah. I personally try to set it at 600Ah (48V). It is a backup system
after all. But the key is the customer's expectations...who are they going
to call after the lights go out?
Thank you,
Maverick
Maverick Brown
BSEET, NABCEP Certified Solar PV Installer ?
President & CEO
Maverick Solar Enterprises, Inc.
Office: 512-919-4493
Cell: 512-460-9825
Sent from my HondaJet!
Drake,
I?ve been hounding a couple of the charge controller manufactures about this
issue, but so far I just haven?t seen a light bulb go off in their heads,
but I?ll keep trying, and maybe this is a better forum to do it.
MPPT controllers can be adjusted to current limit at amperage values below
their rating, but if you do that, you are also limiting the output of the
array in general, and the amount of PV power available to run the loads
directly from the array (through the inverter). Not the best use of
available PV power.
Say you have an 80A controller and a 200AH battery. With current technology,
Let the controller operate at 80A. If you have loads to draw off some of the
current (or sell to the grid), great, but if not you could be seeing a
charge rate of C/2.5, which would be pretty hard on a sealed 200AH battery,
to say the least. Granted, the battery voltage would rise pretty quickly,
and the controller would start to taper off, but it would still see high
currents especially if the absorption time is set long. Not a happy
scenario.
Or, you can set the current limiting on the controller to 20A for a C/10
charge rate. But if you had loads drawing 60A, you would be pulling that
additional 40A from the battery and not using the array?s full power. Also
not a happy scenario.
What we need is a controller that can read the signal from a shunt at the
battery, and use that as the basis of current limiting control.
For example, if we have an array that can produce 80A of current, but we
want to limit the battery to 20A of charge, there would be 60A of potential
current there to run loads without drawing on the battery. If there are no
loads running, the controller should current limit at 20A (reading from a
shunt), but if loads are turned on, the controller should be able to let
more current through while still limiting the battery to 20A. When loads are
shut off, the controller should go back to a 20A limit.
This doesn?t all have to happen very quickly as a battery can take a heavier
charge for a short period of time, but I think that this would be a major
improvement of controller function.
Of course, if you are grid-tied you can sell all the excess power, but if
the grid goes down, or you are off-grid?.?
Because of the low cost of PV and the high cost of batteries these days, I?m
seeing more and more requests for large arrays with smaller batteries. I
also think that PV is now cheap enough to allow for oversizing of arrays for
better battery charging on cloudy days, which can reduce generator run
times. We need smarter controllers.
What say ye, charge controller gurus?
Brian Teitelbaum
AEE Solar
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Drake
Sent: Thursday, July 19, 2012 2:21 PM
To: RE-wrenches
Subject: [RE-wrenches] Small battery bank vs too large array
Hello Wrenches,
Where can I get a device that will measure current through a shunt and
create a signal to trigger a relay?
We want to be able to use a 2 kW array with four, 200 AH sealed batteries on
an Outback system. 2 kW of PV would be too much amperage for the batteries.
The idea is to open relays to disengage strings in conditions of high
current to the batteries.
The reason for this is to create backup systems where power will be
abundantly available when the sun shines. The system will normally connect
to the grid, except during outages. In normal charging conditions the power
will go straight to the grid. When the grid is down, power will be
available for loads and battery charging, but batteries will be protected
from overcharge?
Any suggestions on ways to accomplish this are welcome!
Thanks
Drake
Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
http://athens-electric.com/
_______________________________________________
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boB
2012-07-20 02:56:43 UTC
Permalink
I didn't see that Brian T had the same idea until after I sent that
email off to Allan...
boB
Post by Drake
Wrenches,
I forwarded Brian's post on to Robin at Midnite, as I thought it was
an interesting idea. Below is his response, as well as boB's.
Allan
*Allan Sindelar*
_Allan at positiveenergysolar.com_ <mailto:Allan at positiveenergysolar.com>
NABCEP Certified Photovoltaic Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder and Chief Technology Officer
*Positive Energy, Inc.*
3209 Richards Lane (note new address)
Santa Fe, New Mexico 87507
*505 424-1112*
_www.positiveenergysolar.com_ <http://www.positiveenergysolar.com/>
Allan, It is simpler than what is being suggested. The reason they
want to limit to 20 amps is because the battery doesn't need anymore
than that. The controller will automatically limit the charge current
as the battery gets full. If a large load is turned on, the controller
will try to refill the battery up to its capacity. The 80 amps will
quickly be reduced because the voltage will rise to the point where
the charge tapers off.
There is nothing else that needs to be done. If the problem is that
the battery bank is too small for a big controller, the best answer is
to get more batteries. A 80 amp charger into a 200 amp hour battery is
going to raise the battery voltage so quick, it will not affect the
battery at all. By the way, discharging a battery at 60 or 80 amps is
probably going to do damage to a small battery also. We do have an
input on the Classic that could probably be programmed to do as
requested. That input feature has yet to be implemented. I'm sure we
will have discussions about this when the time comes to write the
input code. Maybe this feature will be designed in, but it doesn't
sound like it is a very good feature to spend a bunch of time on.
After all, the main problem is that the battery bank is just too
darned small.
Bob, Tom and Ryan do you have any comments on the subject?
Thanks,
Robin
*
*
One idea I had in mind was to have an option, in software, to limit
the current into the battery,
when the charging current goes above some set threshold. The
controller would have to get its information from
the battery monitor over the network.
If it is a grid tie system and grid is there and GT inverter is
selling, then no problem... The controller
can work at its full output. If grid or loads go away, then the CC
will know and it can throttle back at
that time.
We don't have a battery monitor yet, but we will have one. This will
be one of the settings as well as
Re-Bulk based on state of charge, ending amps and those types of things.
boB
Post by maverick
I say it is waste of time.
1. AGM batteries can take the high current and you are right, the
absorb voltage is reached and the absorb current is tapered rather
quickly. Current generation charge controllers are rather fast at the
transitions. I have a bunch of data from a system with a PentaMetric
that shows the battery bank going to absorb voltage at grid tie,
during cloud events, but only for a few seconds at a time.
2. A properly designed GTBB system should cover the connected loads
for 24 hours of each sunny day, at a minimum. Keep in mind, off grid
systems are designed for that, and 3 days + of backup, etc.
3. I would say, based on my experience, the minimum battery bank
should be 400Ah. I personally try to set it at 600Ah (48V). It is a
backup system after all. But the key is the customer's
expectations...who are they going to call after the lights go out?
Thank you,
Maverick
Maverick Brown
BSEET, NABCEP Certified Solar PV Installer ?
President & CEO
Maverick Solar Enterprises, Inc.
Office: 512-919-4493
Cell: 512-460-9825
Sent from my HondaJet!
On Jul 19, 2012, at 6:35 PM, Brian Teitelbaum
Post by Brian Teitelbaum
Drake,
I've been hounding a couple of the charge controller manufactures
about this issue, but so far I just haven't seen a light bulb go off
in their heads, but I'll keep trying, and maybe this is a better
forum to do it.
MPPT controllers can be adjusted to current limit at amperage values
below their rating, but if you do that, you are also limiting the
output of the array in general, and the amount of PV power available
to run the loads directly from the array (through the inverter). Not
the best use of available PV power.
Say you have an 80A controller and a 200AH battery. With current
Let the controller operate at 80A. If you have loads to draw off
some of the current (or sell to the grid), great, but if not you
could be seeing a charge rate of C/2.5, which would be pretty hard
on a sealed 200AH battery, to say the least. Granted, the battery
voltage would rise pretty quickly, and the controller would start to
taper off, but it would still see high currents especially if the
absorption time is set long. Not a happy scenario.
Or, you can set the current limiting on the controller to 20A for a
C/10 charge rate. But if you had loads drawing 60A, you would be
pulling that additional 40A from the battery and not using the
array's full power. Also not a happy scenario.
What we need is a controller that can read the signal from a shunt
at the battery, and use that as the basis of current limiting control.
For example, if we have an array that can produce 80A of current,
but we want to limit the battery to 20A of charge, there would be
60A of potential current there to run loads without drawing on the
battery. If there are no loads running, the controller should
current limit at 20A (reading from a shunt), but if loads are turned
on, the controller should be able to let more current through while
still limiting the battery to 20A. When loads are shut off, the
controller should go back to a 20A limit.
This doesn't all have to happen very quickly as a battery can take a
heavier charge for a short period of time, but I think that this
would be a major improvement of controller function.
Of course, if you are grid-tied you can sell all the excess power,
but if the grid goes down, or you are off-grid....?
Because of the low cost of PV and the high cost of batteries these
days, I'm seeing more and more requests for large arrays with
smaller batteries. I also think that PV is now cheap enough to allow
for oversizing of arrays for better battery charging on cloudy days,
which can reduce generator run times. We need smarter controllers.
What say ye, charge controller gurus?
Brian Teitelbaum
AEE Solar
*From:*re-wrenches-bounces at lists.re-wrenches.org
<mailto:re-wrenches-bounces at lists.re-wrenches.org>
[mailto:re-wrenches-bounces at lists.re-wrenches.org] *On Behalf Of *Drake
*Sent:* Thursday, July 19, 2012 2:21 PM
*To:* RE-wrenches
*Subject:* [RE-wrenches] Small battery bank vs too large array
Hello Wrenches,
Where can I get a device that will measure current through a shunt
and create a signal to trigger a relay?
We want to be able to use a 2 kW array with four, 200 AH sealed
batteries on an Outback system. 2 kW of PV would be too much
amperage for the batteries. The idea is to open relays to disengage
strings in conditions of high current to the batteries.
The reason for this is to create backup systems where power will be
abundantly available when the sun shines. The system will normally
connect to the grid, except during outages. In normal charging
conditions the power will go straight to the grid. When the grid is
down, power will be available for loads and battery charging, but
batteries will be protected from overcharge?
Any suggestions on ways to accomplish this are welcome!
Thanks
Drake
Drake Chamberlin
/Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
/http://athens-electric.com/
_______________________________________________
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Allan Sindelar
2012-07-20 02:53:58 UTC
Permalink
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Drake
2012-07-20 02:52:49 UTC
Permalink
Brian: Thanks for the clarification, it saved a
phone call to Outback. That is how I think it
works also. It seems that a current activated
relay to disconnect strings, to bring the charge
rate into line with the battery bank, could be
an answer. I don't know what equipment is
available. A device that could read the current
from a shunt and generate a signal could be a solution.

Jason: The regulation of the CC might take care
of things but I'm concerned that the C/2.5 would
occur for too long before the voltage got high
enough to activate the charge control. AC
coupling could be a problem, since the full
output of a direct grid-tie inverter goes
straight to the batter without any controls
(unless dump or other loads are present). A
coordinated system of dump loads, using a Morningstar Relay driver could work.

Todd: We just got done with an extended power
outage here, and people with direct grid tie PV
are looking for ways to have power when the sun
shines. Many people ran their generators for a
couple of hours at a time to cool their
refrigerators and freezers, then lent them to
their neighbors to do the same. Having power
during the day would have been a great help. A
bank of 4, 220 AH AGM batteries would allow for
CF lights, music and computers after dark.
Batteries are expensive and have a shelf
life. They also take up a lot of space. We are
trying to minimize these issues.

Cheers,

Drake
Content-Language: en-US
Content-Type: multipart/alternative;
boundary="_000_8961DF9D3453CF41A4A5B6E6BECA4C770B17874813VSSJEXCH01rec_"
Drake,
I?ve been hounding a couple of the charge
controller manufactures about this issue, but so
far I just haven?t seen a light bulb go off in
their heads, but I?ll keep trying, and maybe this is a better forum to do it.
MPPT controllers can be adjusted to current
limit at amperage values below their rating, but
if you do that, you are also limiting the output
of the array in general, and the amount of PV
power available to run the loads directly from
the array (through the inverter). Not the best use of available PV power.
Say you have an 80A controller and a 200AH
Let the controller operate at 80A. If you have
loads to draw off some of the current (or sell
to the grid), great, but if not you could be
seeing a charge rate of C/2.5, which would be
pretty hard on a sealed 200AH battery, to say
the least. Granted, the battery voltage would
rise pretty quickly, and the controller would
start to taper off, but it would still see high
currents especially if the absorption time is set long. Not a happy scenario.
Or, you can set the current limiting on the
controller to 20A for a C/10 charge rate. But if
you had loads drawing 60A, you would be pulling
that additional 40A from the battery and not
using the array?s full power. Also not a happy scenario.
What we need is a controller that can read the
signal from a shunt at the battery, and use that
as the basis of current limiting control.
For example, if we have an array that can
produce 80A of current, but we want to limit the
battery to 20A of charge, there would be 60A of
potential current there to run loads without
drawing on the battery. If there are no loads
running, the controller should current limit at
20A (reading from a shunt), but if loads are
turned on, the controller should be able to let
more current through while still limiting the
battery to 20A. When loads are shut off, the
controller should go back to a 20A limit.
This doesn?t all have to happen very quickly as
a battery can take a heavier charge for a short
period of time, but I think that this would be a
major improvement of controller function.
Of course, if you are grid-tied you can sell all
the excess power, but if the grid goes down, or you are off-grid
.?
Because of the low cost of PV and the high cost
of batteries these days, I?m seeing more and
more requests for large arrays with smaller
batteries. I also think that PV is now cheap
enough to allow for oversizing of arrays for
better battery charging on cloudy days, which
can reduce generator run times. We need smarter controllers.
What say ye, charge controller gurus?
Brian Teitelbaum
AEE Solar
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Drake
Sent: Thursday, July 19, 2012 2:21 PM
To: RE-wrenches
Subject: [RE-wrenches] Small battery bank vs too large array
Hello Wrenches,
Where can I get a device that will measure
current through a shunt and create a signal to trigger a relay?
We want to be able to use a 2 kW array with
four, 200 AH sealed batteries on an Outback
system. 2 kW of PV would be too much amperage
for the batteries. The idea is to open relays
to disengage strings in conditions of high current to the batteries.
The reason for this is to create backup systems
where power will be abundantly available when
the sun shines. The system will normally connect
to the grid, except during outages. In normal
charging conditions the power will go straight
to the grid. When the grid is down, power will
be available for loads and battery charging, but
batteries will be protected from overcharge?
Any suggestions on ways to accomplish this are welcome!
Thanks
Drake
Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
<http://athens-electric.com/>http://athens-electric.com/
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
www.re-wrenches.org/etiquette.htm
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toddcory
2012-07-20 00:02:58 UTC
Permalink
what is the point of having battery backup if is is so small as to not really be able to back anything up (except when the sun is shining)?

this seems like a system design error rather than a charge controller problem.

my .02

todd




On Thursday, July 19, 2012 4:35pm, "Brian Teitelbaum" <bteitelbaum at aeesolar.com> said:




Drake,

I?ve been hounding a couple of the charge controller manufactures about this issue, but so far I just haven?t seen a light bulb go off in their heads, but I?ll keep trying, and maybe this is a better forum to do it.

MPPT controllers can be adjusted to current limit at amperage values below their rating, but if you do that, you are also limiting the output of the array in general, and the amount of PV power available to run the loads directly from the array (through the inverter). Not the best use of available PV power.

Say you have an 80A controller and a 200AH battery. With current technology, you have two choices:

Let the controller operate at 80A. If you have loads to draw off some of the current (or sell to the grid), great, but if not you could be seeing a charge rate of C/2.5, which would be pretty hard on a sealed 200AH battery, to say the least. Granted, the battery voltage would rise pretty quickly, and the controller would start to taper off, but it would still see high currents especially if the absorption time is set long. Not a happy scenario.

Or, you can set the current limiting on the controller to 20A for a C/10 charge rate. But if you had loads drawing 60A, you would be pulling that additional 40A from the battery and not using the array?s full power. Also not a happy scenario.

What we need is a controller that can read the signal from a shunt at the battery, and use that as the basis of current limiting control.

For example, if we have an array that can produce 80A of current, but we want to limit the battery to 20A of charge, there would be 60A of potential current there to run loads without drawing on the battery. If there are no loads running, the controller should current limit at 20A (reading from a shunt), but if loads are turned on, the controller should be able to let more current through while still limiting the battery to 20A. When loads are shut off, the controller should go back to a 20A limit.

This doesn?t all have to happen very quickly as a battery can take a heavier charge for a short period of time, but I think that this would be a major improvement of controller function.

Of course, if you are grid-tied you can sell all the excess power, but if the grid goes down, or you are off-grid?.?

Because of the low cost of PV and the high cost of batteries these days, I?m seeing more and more requests for large arrays with smaller batteries. I also think that PV is now cheap enough to allow for oversizing of arrays for better battery charging on cloudy days, which can reduce generator run times. We need smarter controllers.

What say ye, charge controller gurus?

Brian Teitelbaum
AEE Solar



From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Drake
Sent: Thursday, July 19, 2012 2:21 PM
To: RE-wrenches
Subject: [RE-wrenches] Small battery bank vs too large array

Hello Wrenches,

Where can I get a device that will measure current through a shunt and create a signal to trigger a relay?

We want to be able to use a 2 kW array with four, 200 AH sealed batteries on an Outback system. 2 kW of PV would be too much amperage for the batteries. The idea is to open relays to disengage strings in conditions of high current to the batteries.

The reason for this is to create backup systems where power will be abundantly available when the sun shines. The system will normally connect to the grid, except during outages. In normal charging conditions the power will go straight to the grid. When the grid is down, power will be available for loads and battery charging, but batteries will be protected from overcharge?

Any suggestions on ways to accomplish this are welcome!

Thanks

Drake


Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
[http://athens-electric.com/] http://athens-electric.com/


Sent from Finest Planet WebMail.
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maverick
2012-07-20 02:34:24 UTC
Permalink
I say it is waste of time.

1. AGM batteries can take the high current and you are right, the absorb voltage is reached and the absorb current is tapered rather quickly. Current generation charge controllers are rather fast at the transitions. I have a bunch of data from a system with a PentaMetric that shows the battery bank going to absorb voltage at grid tie, during cloud events, but only for a few seconds at a time.

2. A properly designed GTBB system should cover the connected loads for 24 hours of each sunny day, at a minimum. Keep in mind, off grid systems are designed for that, and 3 days + of backup, etc.

3. I would say, based on my experience, the minimum battery bank should be 400Ah. I personally try to set it at 600Ah (48V). It is a backup system after all. But the key is the customer's expectations...who are they going to call after the lights go out?


Thank you,

Maverick


Maverick Brown
BSEET, NABCEP Certified Solar PV Installer ?
President & CEO
Maverick Solar Enterprises, Inc.
Office: 512-919-4493
Cell: 512-460-9825

Sent from my HondaJet!
Post by Brian Teitelbaum
Drake,
I?ve been hounding a couple of the charge controller manufactures about this issue, but so far I just haven?t seen a light bulb go off in their heads, but I?ll keep trying, and maybe this is a better forum to do it.
MPPT controllers can be adjusted to current limit at amperage values below their rating, but if you do that, you are also limiting the output of the array in general, and the amount of PV power available to run the loads directly from the array (through the inverter). Not the best use of available PV power.
Let the controller operate at 80A. If you have loads to draw off some of the current (or sell to the grid), great, but if not you could be seeing a charge rate of C/2.5, which would be pretty hard on a sealed 200AH battery, to say the least. Granted, the battery voltage would rise pretty quickly, and the controller would start to taper off, but it would still see high currents especially if the absorption time is set long. Not a happy scenario.
Or, you can set the current limiting on the controller to 20A for a C/10 charge rate. But if you had loads drawing 60A, you would be pulling that additional 40A from the battery and not using the array?s full power. Also not a happy scenario.
What we need is a controller that can read the signal from a shunt at the battery, and use that as the basis of current limiting control.
For example, if we have an array that can produce 80A of current, but we want to limit the battery to 20A of charge, there would be 60A of potential current there to run loads without drawing on the battery. If there are no loads running, the controller should current limit at 20A (reading from a shunt), but if loads are turned on, the controller should be able to let more current through while still limiting the battery to 20A. When loads are shut off, the controller should go back to a 20A limit.
This doesn?t all have to happen very quickly as a battery can take a heavier charge for a short period of time, but I think that this would be a major improvement of controller function.
Of course, if you are grid-tied you can sell all the excess power, but if the grid goes down, or you are off-grid?.?
Because of the low cost of PV and the high cost of batteries these days, I?m seeing more and more requests for large arrays with smaller batteries. I also think that PV is now cheap enough to allow for oversizing of arrays for better battery charging on cloudy days, which can reduce generator run times. We need smarter controllers.
What say ye, charge controller gurus?
Brian Teitelbaum
AEE Solar
From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Drake
Sent: Thursday, July 19, 2012 2:21 PM
To: RE-wrenches
Subject: [RE-wrenches] Small battery bank vs too large array
Hello Wrenches,
Where can I get a device that will measure current through a shunt and create a signal to trigger a relay?
We want to be able to use a 2 kW array with four, 200 AH sealed batteries on an Outback system. 2 kW of PV would be too much amperage for the batteries. The idea is to open relays to disengage strings in conditions of high current to the batteries.
The reason for this is to create backup systems where power will be abundantly available when the sun shines. The system will normally connect to the grid, except during outages. In normal charging conditions the power will go straight to the grid. When the grid is down, power will be available for loads and battery charging, but batteries will be protected from overcharge?
Any suggestions on ways to accomplish this are welcome!
Thanks
Drake
Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
http://athens-electric.com/
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
www.re-wrenches.org/etiquette.htm
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Drake
2012-07-20 02:52:49 UTC
Permalink
Brian: Thanks for the clarification, it saved a
phone call to Outback. That is how I think it
works also. It seems that a current activated
relay to disconnect strings, to bring the charge
rate into line with the battery bank, could be
an answer. I don't know what equipment is
available. A device that could read the current
from a shunt and generate a signal could be a solution.

Jason: The regulation of the CC might take care
of things but I'm concerned that the C/2.5 would
occur for too long before the voltage got high
enough to activate the charge control. AC
coupling could be a problem, since the full
output of a direct grid-tie inverter goes
straight to the batter without any controls
(unless dump or other loads are present). A
coordinated system of dump loads, using a Morningstar Relay driver could work.

Todd: We just got done with an extended power
outage here, and people with direct grid tie PV
are looking for ways to have power when the sun
shines. Many people ran their generators for a
couple of hours at a time to cool their
refrigerators and freezers, then lent them to
their neighbors to do the same. Having power
during the day would have been a great help. A
bank of 4, 220 AH AGM batteries would allow for
CF lights, music and computers after dark.
Batteries are expensive and have a shelf
life. They also take up a lot of space. We are
trying to minimize these issues.

Cheers,

Drake
Content-Language: en-US
Content-Type: multipart/alternative;
boundary="_000_8961DF9D3453CF41A4A5B6E6BECA4C770B17874813VSSJEXCH01rec_"
Drake,
I?ve been hounding a couple of the charge
controller manufactures about this issue, but so
far I just haven?t seen a light bulb go off in
their heads, but I?ll keep trying, and maybe this is a better forum to do it.
MPPT controllers can be adjusted to current
limit at amperage values below their rating, but
if you do that, you are also limiting the output
of the array in general, and the amount of PV
power available to run the loads directly from
the array (through the inverter). Not the best use of available PV power.
Say you have an 80A controller and a 200AH
Let the controller operate at 80A. If you have
loads to draw off some of the current (or sell
to the grid), great, but if not you could be
seeing a charge rate of C/2.5, which would be
pretty hard on a sealed 200AH battery, to say
the least. Granted, the battery voltage would
rise pretty quickly, and the controller would
start to taper off, but it would still see high
currents especially if the absorption time is set long. Not a happy scenario.
Or, you can set the current limiting on the
controller to 20A for a C/10 charge rate. But if
you had loads drawing 60A, you would be pulling
that additional 40A from the battery and not
using the array?s full power. Also not a happy scenario.
What we need is a controller that can read the
signal from a shunt at the battery, and use that
as the basis of current limiting control.
For example, if we have an array that can
produce 80A of current, but we want to limit the
battery to 20A of charge, there would be 60A of
potential current there to run loads without
drawing on the battery. If there are no loads
running, the controller should current limit at
20A (reading from a shunt), but if loads are
turned on, the controller should be able to let
more current through while still limiting the
battery to 20A. When loads are shut off, the
controller should go back to a 20A limit.
This doesn?t all have to happen very quickly as
a battery can take a heavier charge for a short
period of time, but I think that this would be a
major improvement of controller function.
Of course, if you are grid-tied you can sell all
the excess power, but if the grid goes down, or you are off-grid
.?
Because of the low cost of PV and the high cost
of batteries these days, I?m seeing more and
more requests for large arrays with smaller
batteries. I also think that PV is now cheap
enough to allow for oversizing of arrays for
better battery charging on cloudy days, which
can reduce generator run times. We need smarter controllers.
What say ye, charge controller gurus?
Brian Teitelbaum
AEE Solar
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Drake
Sent: Thursday, July 19, 2012 2:21 PM
To: RE-wrenches
Subject: [RE-wrenches] Small battery bank vs too large array
Hello Wrenches,
Where can I get a device that will measure
current through a shunt and create a signal to trigger a relay?
We want to be able to use a 2 kW array with
four, 200 AH sealed batteries on an Outback
system. 2 kW of PV would be too much amperage
for the batteries. The idea is to open relays
to disengage strings in conditions of high current to the batteries.
The reason for this is to create backup systems
where power will be abundantly available when
the sun shines. The system will normally connect
to the grid, except during outages. In normal
charging conditions the power will go straight
to the grid. When the grid is down, power will
be available for loads and battery charging, but
batteries will be protected from overcharge?
Any suggestions on ways to accomplish this are welcome!
Thanks
Drake
Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
<http://athens-electric.com/>http://athens-electric.com/
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
www.re-wrenches.org/etiquette.htm
www.members.re-wrenches.org
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Chris Mason
2012-07-20 11:06:37 UTC
Permalink
I did a similar system for a client, in a place where grid connections were
not very legal. We powered s sub-panel but the power exported was used in
the rest of the house.
If you use 4 x 250Ah batteries, a 60A controller is not going to over
charge the batteries as they have a 65A charging limit so you don't need to
get into homegrown solutions.
2KW PV will only give you 40A @ 50V
The system will send the excess to the grid (We did grid tie).
The grid will take over if you have an outage.
The system will revert to grid once the battery level falls below a setting
- we used 44V.
It works well and is inexpensive to do.



On Thu, Jul 19, 2012 at 5:20 PM, Drake <drake.chamberlin at redwoodalliance.org
Post by Drake
Hello Wrenches,
Where can I get a device that will measure current through a shunt and
create a signal to trigger a relay?
We want to be able to use a 2 kW array with four, 200 AH sealed batteries
on an Outback system. 2 kW of PV would be too much amperage for the
batteries. The idea is to open relays to disengage strings in conditions
of high current to the batteries.
The reason for this is to create backup systems where power will be
abundantly available when the sun shines. The system will normally connect
to the grid, except during outages. In normal charging conditions the
power will go straight to the grid. When the grid is down, power will be
available for loads and battery charging, but batteries will be protected
from overcharge?
Any suggestions on ways to accomplish this are welcome!
Thanks
Drake
Drake Chamberlin
*Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
*http://athens-electric.com/
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
www.re-wrenches.org/etiquette.htm
www.members.re-wrenches.org
--
Chris Mason
President, Comet Systems Ltd
www.cometenergysystems.com
Cell: 264.235.5670
Skype: netconcepts
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Drake
2012-07-19 21:20:45 UTC
Permalink
Hello Wrenches,

Where can I get a device that will measure current through a shunt
and create a signal to trigger a relay?

We want to be able to use a 2 kW array with four, 200 AH sealed
batteries on an Outback system. 2 kW of PV would be too much
amperage for the batteries. The idea is to open relays to disengage
strings in conditions of high current to the batteries.

The reason for this is to create backup systems where power will be
abundantly available when the sun shines. The system will normally
connect to the grid, except during outages. In normal charging
conditions the power will go straight to the grid. When the grid is
down, power will be available for loads and battery charging, but
batteries will be protected from overcharge?

Any suggestions on ways to accomplish this are welcome!

Thanks

Drake


Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
<http://athens-electric.com/>http://athens-electric.com/
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Jason Szumlanski
2012-07-19 21:53:04 UTC
Permalink
I could be wrong, but I thought the FM60 and FM80 charge controllers have
adjustable current limits that apply to battery charging, and I think when
integrated with GVFX inverters in sell mode and a Mate controller, you will
be able to accomplish what you need to do without a relay. I always thought
when the charge controller indicated GT Mode and was in bulk charging mode
that the current limit would be essentially ignored because the battery
voltage is above the sell voltage and any available DC current would be
inverted and sold to the grid. In other words, the batteries are full, so
they are not being charged - the FM60 and GVFX communicate and balance the
current available for selling.

You may want to talk to Outback about that, because I don't think it is
documented all that well, and again, I could be wrong. I've never installed
that much solar on a small battery, so it never came up! Incidentally, I
have someone that came in today looking for a 5kW grid-interactive system
and a small battery to handle critical loads. I was leaning to an AC
coupled system to get away from the issue you describe, but now I am
second-guessing that theory. I'd be interested to learn what you discover.

Most inverter manufacturer's have a minimum battery size, but that
seemingly is there to address the maximum possible current out of the
battery, not the charging rate because that can be limited, too.

Jason Szumlanski
Fafco Solar


On Thu, Jul 19, 2012 at 5:20 PM, Drake <drake.chamberlin at redwoodalliance.org
Post by Drake
Hello Wrenches,
Where can I get a device that will measure current through a shunt and
create a signal to trigger a relay?
We want to be able to use a 2 kW array with four, 200 AH sealed batteries
on an Outback system. 2 kW of PV would be too much amperage for the
batteries. The idea is to open relays to disengage strings in conditions
of high current to the batteries.
The reason for this is to create backup systems where power will be
abundantly available when the sun shines. The system will normally connect
to the grid, except during outages. In normal charging conditions the
power will go straight to the grid. When the grid is down, power will be
available for loads and battery charging, but batteries will be protected
from overcharge?
Any suggestions on ways to accomplish this are welcome!
Thanks
Drake
Drake Chamberlin
*Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
*http://athens-electric.com/
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
www.re-wrenches.org/etiquette.htm
www.members.re-wrenches.org
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Brian Teitelbaum
2012-07-19 23:35:14 UTC
Permalink
Drake,

I've been hounding a couple of the charge controller manufactures about this issue, but so far I just haven't seen a light bulb go off in their heads, but I'll keep trying, and maybe this is a better forum to do it.

MPPT controllers can be adjusted to current limit at amperage values below their rating, but if you do that, you are also limiting the output of the array in general, and the amount of PV power available to run the loads directly from the array (through the inverter). Not the best use of available PV power.

Say you have an 80A controller and a 200AH battery. With current technology, you have two choices:

Let the controller operate at 80A. If you have loads to draw off some of the current (or sell to the grid), great, but if not you could be seeing a charge rate of C/2.5, which would be pretty hard on a sealed 200AH battery, to say the least. Granted, the battery voltage would rise pretty quickly, and the controller would start to taper off, but it would still see high currents especially if the absorption time is set long. Not a happy scenario.

Or, you can set the current limiting on the controller to 20A for a C/10 charge rate. But if you had loads drawing 60A, you would be pulling that additional 40A from the battery and not using the array's full power. Also not a happy scenario.

What we need is a controller that can read the signal from a shunt at the battery, and use that as the basis of current limiting control.

For example, if we have an array that can produce 80A of current, but we want to limit the battery to 20A of charge, there would be 60A of potential current there to run loads without drawing on the battery. If there are no loads running, the controller should current limit at 20A (reading from a shunt), but if loads are turned on, the controller should be able to let more current through while still limiting the battery to 20A. When loads are shut off, the controller should go back to a 20A limit.

This doesn't all have to happen very quickly as a battery can take a heavier charge for a short period of time, but I think that this would be a major improvement of controller function.

Of course, if you are grid-tied you can sell all the excess power, but if the grid goes down, or you are off-grid....?

Because of the low cost of PV and the high cost of batteries these days, I'm seeing more and more requests for large arrays with smaller batteries. I also think that PV is now cheap enough to allow for oversizing of arrays for better battery charging on cloudy days, which can reduce generator run times. We need smarter controllers.

What say ye, charge controller gurus?

Brian Teitelbaum
AEE Solar

From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Drake
Sent: Thursday, July 19, 2012 2:21 PM
To: RE-wrenches
Subject: [RE-wrenches] Small battery bank vs too large array

Hello Wrenches,

Where can I get a device that will measure current through a shunt and create a signal to trigger a relay?

We want to be able to use a 2 kW array with four, 200 AH sealed batteries on an Outback system. 2 kW of PV would be too much amperage for the batteries. The idea is to open relays to disengage strings in conditions of high current to the batteries.

The reason for this is to create backup systems where power will be abundantly available when the sun shines. The system will normally connect to the grid, except during outages. In normal charging conditions the power will go straight to the grid. When the grid is down, power will be available for loads and battery charging, but batteries will be protected from overcharge?

Any suggestions on ways to accomplish this are welcome!

Thanks

Drake


Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
http://athens-electric.com/
-------------- next part --------------
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Chris Mason
2012-07-20 11:06:37 UTC
Permalink
I did a similar system for a client, in a place where grid connections were
not very legal. We powered s sub-panel but the power exported was used in
the rest of the house.
If you use 4 x 250Ah batteries, a 60A controller is not going to over
charge the batteries as they have a 65A charging limit so you don't need to
get into homegrown solutions.
2KW PV will only give you 40A @ 50V
The system will send the excess to the grid (We did grid tie).
The grid will take over if you have an outage.
The system will revert to grid once the battery level falls below a setting
- we used 44V.
It works well and is inexpensive to do.



On Thu, Jul 19, 2012 at 5:20 PM, Drake <drake.chamberlin at redwoodalliance.org
Post by Drake
Hello Wrenches,
Where can I get a device that will measure current through a shunt and
create a signal to trigger a relay?
We want to be able to use a 2 kW array with four, 200 AH sealed batteries
on an Outback system. 2 kW of PV would be too much amperage for the
batteries. The idea is to open relays to disengage strings in conditions
of high current to the batteries.
The reason for this is to create backup systems where power will be
abundantly available when the sun shines. The system will normally connect
to the grid, except during outages. In normal charging conditions the
power will go straight to the grid. When the grid is down, power will be
available for loads and battery charging, but batteries will be protected
from overcharge?
Any suggestions on ways to accomplish this are welcome!
Thanks
Drake
Drake Chamberlin
*Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
*http://athens-electric.com/
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
www.re-wrenches.org/etiquette.htm
www.members.re-wrenches.org
--
Chris Mason
President, Comet Systems Ltd
www.cometenergysystems.com
Cell: 264.235.5670
Skype: netconcepts
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