3 batteries with JK BMS not even

[terjeloe]

I have 3 JK BMS's with 12 280ah cells.. 3 batteries with 4 cells in each connected. The 3 batteries are in parallel so I have 840ah. One of the packs was low when I connected the charger for some reason. I did manage to short one of the batteries when I was wiring so I am worried that have damaged it? You can see the last one has a lower voltage in each of the cells and total and the resistance is a bit higher. Can I balance each of the batteries somehow? Charge, Discharge and Balance is all on in the control panels for each of the bms's.

 

[sunshine_eggo]

Each BMS measures its own voltage and has it's own error. They are all within 0.1V of each other, so I would conclude that's as accurate as they can be and/or they are a little imbalanced. Note also that they aren't very sensitive, so it's very likely that up to 2A of current is flowing between them, and it won't register on the BMS.

The resistance values are the sense leads, not the cells. When the active balancer is passing current between cells, this will influence the voltage reading, so it uses these values to compensate for the balance current.

A brief short is unlikely to damage anything.

Recommend you set balance to 3.40+ and 15mV. Charge the bank to 13.8V and hold it there to see what the cells do.

 

[terjeloe]

Ah okay, thanks.

New with all this.. 3.40 on the "Start Balance Volt" I am guessing? 0.015 on the "Balance Trig Volt"? Then "Calibrating volt" too 13.8?

 

[terjeloe]

Set it according to my guesses and all the cells are at 3.450 now.. +- 0.001.. so thats some better balance. But the first ones are 99% and the last one still 97% capacity as in the screenshots. Is that just uneven readings? Or does it actually have reduced capacity? Have to hit the pillow, but will check in tomorrow

 

[profesor79]

Set it according to my guesses and all the cells are at 3.450 now.. +- 0.001.. so thats some better balance. But the first ones are 99% and the last one still 97% capacity as in the screenshots. Is that just uneven readings? Or does it actually have reduced capacity? Have to hit the pillow, but will check in tomorrow

those bms'es are reseting to 100% SOC when a cell reach OVP (over voltage protection).

this thread have a bunch tips and knowledge: https://diysolarforum.com/threads/how-to-setup-right-parameters-jk-bms.48075/

 

[sunshine_eggo]

Ah okay, thanks.

New with all this.. 3.40 on the "Start Balance Volt" I am guessing? 0.015 on the "Balance Trig Volt"?

Yes.

Then "Calibrating volt" too 13.8?

No. I was just specifying a charge voltage.