So recently I decided to check the balances on my 12s3p battery and noticed the balances were a little off for the first cell. These were the readings and the corresponding volts:
I messaged the builder of the battery and he mentioned letting the battery hit green for a bit when charging to make sure the BMS balances out all of em, I did so and I think it was green for about 30 mins, BMS was hot so I disconnected the charger and plugged it into my board. My built in voltmeter on the board read at 50.8 volts which is .4 over the rated 50.4 volts for my battery. I was concerned and got out on the road pretty quickly after that and bled it down to 48.6 volts with minimal braking. I thought all was good and done but I am paranoid now about the safety of my battery. I took new readings and got these values:
Are these readings alright now for the recent over voltage? If it helps the pack is built with Samsung 30q’s and this BMS:
Is this pack safe? Is there something else I should check to verify the integrity of my pack or is 50.8 volts within safety parameters for samsung 30q batteries. If anyone can help shed some light I’d appreciate it since I’ve already bothered my builder enough haha. I’m just curious whether keeping it in a metal box is overkill right now safety wise.
BMS getting warm is it doing its job. Usually. It needs to bleed the extra energy off as heat.
Im not the most experienced battery builder by any means, but
your cells look ok. the one at 3.97 is just within what I would consider acceptable. 100mV variation if my personal limit. I would cycle it again to make sure its behaving properly.
If there are issues its a bad BMS.
You can either just go ahead and replace it. or cycle a few more times to see.
I would also check cell voltages at full charge to see.
Going to leave it on a long charge today to see what happens, and if the cells arent balanced then I suppose I’ll need a new BMS. Ill make sure to check with my actual voltmeter when it hits green this time
Just checked, it is coming out to 50.4 on my multimeter but will jump between 50.4 and 50.5 occaisonally which im guessing is a small voltage difference that the meter cant resolve. Going to charge the battery back up next week to see if it balances out.
Alright so I’m pretty sure the mini direct voltmeter I was running on my board was giving the wrong reading. I just charged it from 45V up till the charger hit green and unplugged it. My proper voltmeter gave me a reading of 50.3 and after 20 mins a reading of 50. I checked all the balances and got:
My voltmeter is only accurate to 2 decimal places up to 16V and 1 decimal palce after than, but it looks like theyre all withing 100mV of each other. Rode the board and its just as good as ever.
That being said this has made me do some research and I’ve definitley put more effort into making sure this battery is stored safely when not in use (sand and steel baby).
