JK BMS SOC - what happened?

[RCinFLA]

The JK bms requires a cell overvoltage to reset its Colomb counter to 100%.

It will readjust the battery AH size entry when it reaches an undervoltage cell setting based on its Colomb count when undervoltage trip occurs.

 

[cityel.uk]

Charge to full, tippy top.
It's not full when the meter says 100% full. It's full when the battery will take no more amps. Then the meter should reset to 100% and then you can determine where you're at with your battery. Those state of charge indicators require regular recalibration. Recalibration is accomplished by FULLY charging the battery.

Thabks for your reply. Unfortunately, this does not explain the random UCP/ODCP.

 

[TomC4306]

The JK bms requires a cell overvoltage to reset its Colomb counter to 100%.

Andy's doesn't.

 

[RCinFLA]

Andy's doesn't.

You need to rewatch his videos. He continuously complains about the stupidity of so many BMS's requiring an overvoltage trip to reset Columb counter.

I happen to agree with him on this.

 

[J_Iu]

My JK bms is reading 54.36v
Measuring with multimeter, individual cells read 3.202v.
I tested the wiring by measurements , the last one gave 51.26v but when I plug the cables into the Jk bms and start the bms, the app display in my phone is showing 54.36v.
What could be the problem?

 

[TomC4306]

You need to rewatch his videos. He continuously complains about the stupidity of so many BMS's requiring an overvoltage trip to reset Columb counter.

I happen to agree with him on this.

And I agree with you on this point.
Why would someone design a BMS that has to go offline. Definitely not a generic requirement because many bmss do not do that.
Yes, Seplos, Pace, et al. Many of the so called commercial ones.
I don't recall him ever complaining about that when doing all his separate testing with the JK, JBD, or Heltec that are the BMSs currently attached to his big battery.

 

[TomC4306]

My JK bms is reading 54.36v
Measuring with multimeter, individual cells read 3.202v.
I tested the wiring by measurements , the last one gave 51.26v but when I plug the cables into the Jk bms and start the bms, the app display in my phone is showing 54.36v.
What could be the problem?

Hmm.
BMS reads higher than multimeter?
Replace batteries in multimeter.

As you are using your dvm, be aware of where you are touching the probes. Are you measuring the cell terminal or are you measuring from the bolt on one side to the lug on the other.

Eliminate variables.

 

[RCinFLA]

Why would someone design a BMS that has to go offline.

Doesn't totally go offline, just stops charging. Discharge is still possible.

But having the BMS block charging results in charger terminating absorb cycle early due to MOSFET body diode voltage that the charger sees as a battery voltage rise while it is trying to charge battery, along with a current drop that some chargers use as additional criteria to terminate absorb cycle.

Once BMS bleeds off overvoltage cell and resets charging, the charger may have already dropped to float voltage so no further battery pack balancing will occur.