Discussion:
Thirsty batteries: Daily absorb cycles on top of grid powered float
(too old to reply)
Mick Abraham
2014-10-06 14:16:29 UTC
Permalink
Greetings, Mechanics~

My client's (flooded lead acid) battery is in Float almost all the time,
courtesy of an XW inverter stack plus public utility power while the system
waits in standby. "Selling to grid" is not enabled for complicated reasons,
so here's the problem.

Each day at sunup, the Midnite charge controls implement a new 3 stage
charge cycle including a lengthy absorption interval. The batteries require
frequent water additions and there may be other deleterious effects from
running a complete bulk/absorb charge every day on a battery that's already
highly charged.

Possible solutions:

(1) We could tweak the Midnite settings for a short absorption interval
with less gassing...but if a prolonged grid outage should develop we would
wish the absorption interval had not been shortened.

(2) Your suggestions here, please. The client would be willing to update
and/or reconfigure their Midnite software if that would help or the client
would even consider hardware revisions. We chose the Midnite controllers in
2011 largely because of their 250 volt input ceiling, btw.

++++++++++++++++++++++++++++++++++++

Thinking ahead to my future but similar projects:

Does any DC charge controller know that a new absorb cycle is not needed
each day provided that the battery never dropped below Float the night
before? A full cycle would still be wanted every 30 days or so just to stir
things up, so that's almost like a 30 day equalization trigger only it
would be a bulk trigger instead.

OR: would "selling to grid" avert this problem since the "battery backup
with grid tie" type inverter is aware that the battery never left the Float
stage?

OR: would AC coupling also avert this problem even if "sell to grid" is not
enabled, for the same reason cited above?

OR: Your suggestions here, please.

Thanks & Jolliness, Mechanix. The Wrench List is the Bomb!

Mick Abraham, Proprietor
www.abrahamsolar.com

Voice: 970-731-4675
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Roy Butler
2014-10-06 14:49:53 UTC
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Rebekah Hren
2014-10-06 14:58:18 UTC
Permalink
I'm just wondering if anyone could tell me if I have programmed this right
on my own off-grid cabin system with an Outback FX80 -
If I set the re-bulk fairly low (like 24.5 volts for a 24 volt system) I
should avoid bulk/absorb charging on days when the batteries are not being
cycled? There are no loads at all when I am not there, which is most of the
time,
Thanks!
Rebekah

On Mon, Oct 6, 2014 at 10:49 AM, Roy Butler <roy at four-winds-energy.com>
Mick,
You are in luck!
The Classic controller can be programmed to skip up to 32 days of bulk
charging.
Look for this in the Main menu under Charge/ Advanced/ Skip....and select
the # of days you want to skip.
Not sure what firmware version this goes back to but the current one
(1849) has it.
Roy Butler
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a large number of electrons were terribly inconvenienced.
Greetings, Mechanics~
My client's (flooded lead acid) battery is in Float almost all the time,
courtesy of an XW inverter stack plus public utility power while the system
waits in standby. "Selling to grid" is not enabled for complicated reasons,
so here's the problem.
Each day at sunup, the Midnite charge controls implement a new 3 stage
charge cycle including a lengthy absorption interval. The batteries require
frequent water additions and there may be other deleterious effects from
running a complete bulk/absorb charge every day on a battery that's already
highly charged.
(1) We could tweak the Midnite settings for a short absorption interval
with less gassing...but if a prolonged grid outage should develop we would
wish the absorption interval had not been shortened.
(2) Your suggestions here, please. The client would be willing to update
and/or reconfigure their Midnite software if that would help or the client
would even consider hardware revisions. We chose the Midnite controllers in
2011 largely because of their 250 volt input ceiling, btw.
++++++++++++++++++++++++++++++++++++
Does any DC charge controller know that a new absorb cycle is not needed
each day provided that the battery never dropped below Float the night
before? A full cycle would still be wanted every 30 days or so just to stir
things up, so that's almost like a 30 day equalization trigger only it
would be a bulk trigger instead.
OR: would "selling to grid" avert this problem since the "battery backup
with grid tie" type inverter is aware that the battery never left the Float
stage?
OR: would AC coupling also avert this problem even if "sell to grid" is
not enabled, for the same reason cited above?
OR: Your suggestions here, please.
Thanks & Jolliness, Mechanix. The Wrench List is the Bomb!
Mick Abraham, Proprietor
www.abrahamsolar.com
Voice: 970-731-4675
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jay peltz
2014-10-06 14:36:47 UTC
Permalink
Hi mick,

The more current classic firmware has a VMX mode which is adjustable for absorb time based on how quickly it got there, plus you can set it to skip days etc. Also. The new wiz bang jr allows better return amp monitoring
So if you are running old firmware, good time to upgrade.

Jay

Peltz power.
Post by Mick Abraham
Greetings, Mechanics~
My client's (flooded lead acid) battery is in Float almost all the time, courtesy of an XW inverter stack plus public utility power while the system waits in standby. "Selling to grid" is not enabled for complicated reasons, so here's the problem.
Each day at sunup, the Midnite charge controls implement a new 3 stage charge cycle including a lengthy absorption interval. The batteries require frequent water additions and there may be other deleterious effects from running a complete bulk/absorb charge every day on a battery that's already highly charged.
(1) We could tweak the Midnite settings for a short absorption interval with less gassing...but if a prolonged grid outage should develop we would wish the absorption interval had not been shortened.
(2) Your suggestions here, please. The client would be willing to update and/or reconfigure their Midnite software if that would help or the client would even consider hardware revisions. We chose the Midnite controllers in 2011 largely because of their 250 volt input ceiling, btw.
++++++++++++++++++++++++++++++++++++
Does any DC charge controller know that a new absorb cycle is not needed each day provided that the battery never dropped below Float the night before? A full cycle would still be wanted every 30 days or so just to stir things up, so that's almost like a 30 day equalization trigger only it would be a bulk trigger instead.
OR: would "selling to grid" avert this problem since the "battery backup with grid tie" type inverter is aware that the battery never left the Float stage?
OR: would AC coupling also avert this problem even if "sell to grid" is not enabled, for the same reason cited above?
OR: Your suggestions here, please.
Thanks & Jolliness, Mechanix. The Wrench List is the Bomb!
Mick Abraham, Proprietor
www.abrahamsolar.com
Voice: 970-731-4675
_______________________________________________
List sponsored by Redwood Alliance
List Address: RE-wrenches at lists.re-wrenches.org
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://www.mail-archive.com/re-wrenches at lists.re-wrenches.org/maillist.html
www.re-wrenches.org/etiquette.htm
www.members.re-wrenches.org
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