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

[Jason Szumlanski]

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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