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

[Jason Szumlanski]

I imagine the readings are being taken at slightly different intervals. The
sampling is 10 seconds for Solar Assistant.

Speaking of absorb, I noticed that there is an absorb and float setting for
the Midnite AIO, but no absorb time setting. These batteries have never
dropped to float. They just sit at absorb voltage once it's reached each
day. I can't figure out how to get them to drop to float, but there hasn't
been any adverse effects until now.


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 Sat, Jan 24, 2026, 5:22 PM Jay <jay.peltz at gmail.com> wrote:

> I don’t understand how 3 inverters on a single buss could be recording
> such wildly different dc voltage readings. Regardless if the inverters are
> independent or paralleled.
>
> I don’t have those battereis specs but would expect absorb if there is any
> to be less than 90 minutes?
> Or did the issue occur at the exact end of absorb?
>
> What a pain.
>
> Jay
>
>
>
> On Jan 24, 2026, at 1:36 PM, Jason Szumlanski via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
> 
> I have a triple stack of off-grid Midnite AIO connected to a 60 kWh
> lithionics battery bank (51.2V LFP) in open loop. Today the site had BMS
> shutdowns (there are two BMSs, one for each 30 kWh stack of batteries).
> Both BMSs shut down about 90 minutes after the solar got the batteries to
> 100% and were just meeting loads with solar.
>
> I got some data from Solar Assistant (attached) that shows erratic voltage
> readings from each of the three inverters. This has never happened at this
> site before. Some of the voltage readings exceeded 60V, which I am guessing
> caused one or both BMS to shut off and come back on, possibly quickly.
>
> I do see some solar charging spikes, so it looks like the inverters would
> detect a low battery state and start charging, raising the voltage of the
> batteries quickly, and the process repeating itself.
>
> Any ideas on what the source of the problem might be?
>
> Thanks,
>
> Jason Szumlanski
> Florida Solar Design Group
>
>
>
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