BMS heating up, how to diagnose BMS/Battery

[mscir]

Thanks, I never thought to check that, there's a surprising difference, granted it's a cheap power supply.

Ipsu 0.5A
Vpsu 0.1V
Vmeter 0.002V

I psu 2.0A
Vpsu 0.4V
Vmeter 0.3V

Any suggestions?

 

[meetyg]

So if I understand correctly, you have PSU set at 0.1v or 0.4v ?

I think you can go a bit higher... like 2.0v, but with low amps (0.5a). See if that helps.

 

[mscir]

I have no evidence that the BMS is faulty, I thought it was bad because it was getting warm, but I didn't know they warmed up while balancing the cells, all of the cells are charged almost identically except for this one bad cell. Are you saying that since this cell is not working the BMS is faulty? This is my first battery teardown so I'm still learning this stuff. Thanks.

 

[mscir]

So if I understand correctly, you have PSU set at 0.1v or 0.4v ?

I think you can go a bit higher... like 2.0v, but with low amps (0.5a). See if that helps.

Sorry I wasn't clear, those are two different settings of the power supply and the actual voltage reported by the voltmeter for each one. It shows the voltage displayed on the power supply is significantly different from the voltage measured by the voltmeter. When I bought the supply I checked the voltage accuracy with no load and it was very good, but under loads it is a bit different. I am going to do a mod to remove a lot of the switching noise on it but I don't think it will help this.

 

[Supervstech]

I bought a CC CV pwr supply and turned up the current until I could register voltage, at .5A I saw 0.1V, so I left it that way for 2 days, no observable change, so now I'm trying 2A which gets up to 0.4V. So far no detectable heat from the cell, doing it outside in case it blows up. Is it safe to say this cell is permanently dead?

What temp is it outside?

 

[mscir]

What temp is it outside?

California so worst case about 40F at night but seldom.