Help Troubleshooting 100AH 48v Overvoltage Issue

[jjphat]

Howdy solar gurus. I seem to be having a problem with my system shooting out a surge of high voltage every 30 seconds or so when the system is simultaneously charging and also powering its little area of the house.

This causes the inverter to shut off and the power to cut off and on in a loop until I go downstairs and just switch everything back over to the grid. It ONLY happens during the day when the battery is receiving a charge and simultaneously trying to provide power. At night this is not an issue. I plugged in a 1500w vacuum cleaner (Inverter is 3000w) just to see if it would correct the problem, and it did, but obviously I don't want to keep a continuous high draw on the system just to catch the spike.

I actually have 3 identical systems running, so I was able to swap out charge controllers, batteries, inverters, and transfer switches, and believe I have isolated it down to this one battery. Transfer switch points are 51.2 and 54.4. Charge controller is set to charge the batteries to 56.1. I have played with all those numbers a little bit but nothing seems to fix the problem. So that's what's going on...it seems to be that this one battery does not like to charge and provide power at the same time. The other 2 systems have the same settings and no problems. Is there a fix for this? Any help is greatly appreciated!

 

[jjphat]

Messing with this a little more today. I ran the battery completely down last night, and just happened to be standing there as it very quickly went through the last few volts (down from like 47, to 46.9, 46.8, 46.7 etc. I think the inverter cut off at about 44, but it was neat to watch those last few seconds as the display counted down those last few 10ths of a volt.

I noticed that the charge controller displayed "fault" as it reached the end. This morning, I flipped the breaker back on from the panels (~1600w 2s2p setup) and jumped the charge controller back into action using one of the other batteries and noticed that the "fault" was still there. It did begin charging the dead battery and the fault error went away once it reached about 50v. I don't know why it was there or what it means, but it's not there now.

My plan is to charge the battery up all the way to 58.4, and then plug a 10w lamp into it and let that sit for about a week. Maybe that will get things back into equilibrium? I honestly have no idea if this is the right approach, but I did come across this thread where the guy seems to have been having a similar problem:

Signature Solar EG4 48v 100ah Batteries Alarming Out

Hey Everyone, I hope I can get some advice on my current situation. Equipment: Growatt 3000w 48 All-in-One Inverter Charger (Rounded corner model) 2x EG4 48v 100ah Lithium Batteries (non LCD version) 3,300w Solar Array Problem: Batteries go into Alarm state and disconnect power to inverter...

diysolarforum.com

It doesn't look like his problem was ever resolved, but they do talk about getting it all the way charged up and letting the cells "balance". Other than that, I can't think of any other ways to troubleshoot this issue. I would hate to think that the battery is just junk/toast.