What is going on with my BMS??

[WillAK]

I have 16x 280ah REPT cells wired 8S2P with 2x 200a JK BMS, one on each 8S but they are constantly throwing up wrong data.

For instance, I'm getting Battery Fully Charged message and it's showing 100% when the voltage is showing 27.4v. I also know its not fully charged because this morning the batteries were showing 50% and the solar has only put in 6kw today into a 15kwh battery pack.

But if I go to settings and change the battery capacity to say 200ah then change it back to 280ah it drops from 100% to a more realistic 79% and allows more power.

Are these cheap JK BMS useless? Or is 27.4v actually full?

I've attached some images for reference.

 

[PotusGobbleBottom]

Useless? Nope, it's doing its job so you don't burn your house down.

I see the problem. And yes, it currently is preventing you from doing irreversible damage to your battery.

That bms is saving your ass right now.


Perhaps you should read about what a bms is supposed to do

 

[PotusGobbleBottom]

You have a cell that is very unbalanced. It is pushing the pack SOC to 100.

The bms halts charging and sets soc 100 because you will overcharge that one cell if it doesn't.

Is this a new pack or an old one?

 

[Bob B]

Yep .... You had one cell at 3.657 V. If the BMS allowed the charging to continue you could have a major problem.

After sitting for a bit, that cell voltage settled and the BMS would allow further charging.

Perfectly normal and desirable behavior. If you held it at a little lower charge voltage it would give it time to balance.

 

[Quattrohead]

You have a couple of horribly balanced cells possibly due to setting your balance start voltage way too low, it should be 3.4 volts not 3.2 volts.