Broken cell? Voltage shooting up when charging at .2C

[HRTKD]

It's based on diybms.

You seem to be doing everything you can to avoid saying what brand the BMS is. Why is that?

 

[robby]

Hello,

so I have a new 16-cell bank (EVE 280), not top-balanced yet, with voltages between 3.3 and 3.37V. Charging at 60A causes one of these cells, previously seen with unremarkable 3.33V, to shoot up to 3.7 within less than a minute – apparently too fast for the change controller to react, as the overvoltage caused the BMS to trip the relay, which can't be good for any of the solar hardware around here, but I digress.

Would you agree that this cell is bad?

I would agree that the cell is probably bad, but I would first move it's location in the pack and if the problem persists charge it separately and see how it behaves. A sudden change in voltage like that is not a good sign and I suspect it will also drop down in voltage just as quickly when even a few amps of load is put on it.

 

[MatthiasU]

You seem to be doing everything you can to avoid saying what brand the BMS is. Why is that?

@HRTKD Because it's not a brand (yet), and whatever design mods I'm doing to diyBMS are certainly very interesting but off-topic here – except for the fact that my balancing pulls 3A while diybms does 0.5 (1A by design, but you need active cooling for that to work out).

Suffice it to say that my version polls the cell voltages twice as often as the original diybms, and that I've verified that the voltages I'm reading are correct and the connections to the battery are sound. (I check that physically, verifying with a multimeter at the battery vs. at the cell module vs. reported cell voltage, and automatically by measuring the voltage while balancing. It's the same wire after all.)

 

[740GLE]

Were you able to swap cell location and verify the problem moves with the cell?

It’d be a sure way to verify it’s the cell vs your diybms that could have a cold solder joint or something.

Also are you able to verify the balance leads are actually pulling 3A when balancing?

 

[Daddy Tanuki]

@HRTKD Because it's not a brand (yet), and whatever design mods I'm doing to diyBMS are certainly very interesting but off-topic here – except for the fact that my balancing pulls 3A while diybms does 0.5 (1A by design, but you need active cooling for that to work out).

Suffice it to say that my version polls the cell voltages twice as often as the original diybms, and that I've verified that the voltages I'm reading are correct and the connections to the battery are sound. (I check that physically, verifying with a multimeter at the battery vs. at the cell module vs. reported cell voltage, and automatically by measuring the voltage while balancing. It's the same wire after all.)

it seems to me that you are several leaps ahead of most of the cretins on this board. keep doing your thing and when you get the new upgraded version of DIY BMS done send me a message with its specs... i like new toys to play with and I support people who use their brains.

(even though mine is rotted and worthless at this point in time.)