I have a 12kw 3-phase Sunsynk with 3 x UP5000 Pyltontechs - the Sunsynk and Pylontechs are running the latest firmware.

I'm currently experiencing an issue where one or two of the Pylontechs will go into an overvoltage error state and stop. I then need to turn off the batteries and restart them to bring them back. The error state seems to occur after my batteries have reached 100% SOC from the sun during the day - this seems to happen at least once a week. I allow my batteries to drain down to 35% over night and then use only the sun to charge them up - they are typically charged by 110h00 to 12h00 in the day and the error tends to happen around 13h00 on the day that it happens. When looking at the Inverter voltage graph - the graph shows a voltage of 55.5V at 12h35 which is around when the alarm started.

Screenshots of the Battery Voltage, SOC and Current on the most recent day this happened. The drop off in the SOC and Voltage is where the batteries were turned off and left off before they were turned on again.

The system is relatively new inverter and batteries have been in for about 2 months and panels for a month.

Has anyone seen this or has advice on what to do to prevent this from happening?

Edited July 25, 20224 yr by BryanM
added more information

55.5v is very high and may damage the BMS. see attached

pylontech-official-statement-for-us2000c-us3000c.pdf

Thanks Tinbum - very concerning read.

One thing mentioned in the notice you attached is that I should check if my cable Pins 1/2/3 are NULL (not connected). I'll do that tonight.

I might also try a different Battery as the Master 

@BryanM

Please ensure that your newest battery as the master, if you did not buy them at the same time. Alternatively use the one with the highest SOH as the master.