[RE-wrenches] Strange battery overvoltage issue (Midnite AIO / Lithionics Battery)

[Jason Szumlanski]

The specs for this particular battery list a charging voltage up to 58.4V.
I believe the BMS protection level is set at 60V, but I need to confirm
with the manufacturer when they open on Monday.

I just noticed that the AIOs responded to a relatively high load and
entered a re-bulk type of behavior. But the voltage stayed withing an
acceptable range. I'm not clear on how the AIO handles re-bulk and also why
the float voltage setpoint isn't being respected (or how absorb time is
determined).


Jason Szumlanski
Principal Solar Designer | Florida Solar Design Group
NABCEP Certified Solar Professional (PVIP)
Florida State Certified Solar Contractor CVC56956
Florida Certified Electrical Contractor EC13013208

On Sun, Jan 25, 2026, 12:48 PM Zeke Yewdall via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> I see on the Lithionics spec sheet it says a charged voltage of 57.6
> volts   This seems very high for a 16 cell LFP battery.  I am used to using
> 55 to 56 volts, maybe 56.5 volts at most on a 16 cell LFP.  I suspect that
> the 57.6 is the protection voltage of the BMS, not the appropriate absorb
> voltage setting.  I have seen this error a lot on lithium battery spec
> sheets, where they give the overvoltage protection level, which is not an
> appropriate absorb setting for typical solar equipment.
>
> Not everyone will agree with me, but the way I set up absorb voltages when
> doing open loop lithium battery systems is to NEVER let the BMS do
> anything.  if the BMS shuts off charging, that means that I already
> failed... the charge controller or inverter should have stopped charging
> before the BMS feels the need to protect the cells.  Same with low voltage
> disconnect... if the BMS shuts off due to low voltage, I already failed --
> I should have shut the load off before the BMS felt the need to turn of
> discharge to protect the cells.  The BMS is like an airbag...only to react
> in cases of emergency when the rest of the system doesn't work properly.
>
> Open loop equipment (all of the traditional outback/magnum/schneider, etc
> stuff, plus any AIO's in open loop setup) is designed to always have a
> battery in the system to stabilize the DC bus voltage.  Without the
> stabilizing effect of the battery, voltage spikes can occur.  I find that
> many charge controllers, especially the midnite classic and victron ones,
> can actually keep the system fairly stable without batteries, but charging
> from inverters is more questionable, and especially charging from any DC
> generators can cause severe spikes if the battery disconnects. I have fried
> equipment when a lithium battery disconnected from a large kohler DC
> generator and the generator couldn't react fast enough to keep it from
> spiking to 75 volts or more.  This is why you never want the BMS to
> disconnect... which means setting absorb at a level where the BMS never
> feels threatened.  Lithium battery manufactures giving the voltage at which
> the BMS disconnects as the "charge to" voltage does not help the
> situation.  That may work when charging it with a dedicated lithium battery
> charger, without anything else connected to the battery while it's
> charging.  But in a functioning solar system with charging from multiple
> sources and loads all occurring at the same time, we need to be smarter
> than the battery, IMO.
>
> Zeke
>
> _______________________________________________
> List sponsored by Redwood Alliance
>
> Pay optional member dues here: http://re-wrenches.org
>
> List Address: RE-wrenches at lists.re-wrenches.org
>
> Change listserver email address & settings:
> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>
> There are two list archives for searching. When one doesn't work, try the
> other:
> https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/
> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>
> List rules & etiquette:
> http://www.re-wrenches.org/etiquette.htm
>
> Check out or update participant bios:
> http://www.members.re-wrenches.org
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20260125/67055036/attachment-0001.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 51V110A-8D-MODULE-REV2 (1).pdf
Type: application/pdf
Size: 247811 bytes
Desc: not available
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20260125/67055036/attachment-0001.pdf>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Screenshot_20260125_155512_Chrome.jpg
Type: image/jpeg
Size: 590151 bytes
Desc: not available
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20260125/67055036/attachment-0004.jpg>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Screenshot_20260125_155550_Chrome.jpg
Type: image/jpeg
Size: 657542 bytes
Desc: not available
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20260125/67055036/attachment-0005.jpg>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Screenshot_20260125_155623_Chrome.jpg
Type: image/jpeg
Size: 553292 bytes
Desc: not available
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20260125/67055036/attachment-0006.jpg>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Screenshot_20260125_155722_Chrome.jpg
Type: image/jpeg
Size: 845588 bytes
Desc: not available
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20260125/67055036/attachment-0007.jpg>