One battery cell voltage can't get higher, is it bad?

[Vanessa998]

Just like the picture show, the voltage of the BMS is measured. Cell 13 remains at a maximum of 3.4V I can't get it any higher. I tried charging it individually to 3.45V, but after disconnecting it it drops quickly in voltage. The other cells remained stable on their voltage for a while. why did this happen? what should I do?
Thank you for your attention. Any suggestions or advice would be very appreciated

 

[sunshine_eggo]

Have you confirmed the readings with a separate meter?

Have you checked all connections for torque and crimps for quality?

If all that checks out, it's likely just simple imbalance. Did you top balance using the guide immediately prior to deployment?

Without additional data, the only conclusion that can be drawn is that cells 9 and 13 lag the others.

Charging to 3.45V may not get you there anyway. You may need to go to 3.45V and hold it there for 2-4 hours.

 

[time2roll]

The real tell will be if the suspect cells prematurely trigger low voltage protection.

 

[Vanessa998]

Have you confirmed the readings with a separate meter?

Have you checked all connections for torque and crimps for quality?

If all that checks out, it's likely just simple imbalance. Did you top balance using the guide immediately prior to deployment?

Thank you so much for your response
I did a top balance before using the batteries and did a second top balance after noticing the cells that drift apart. Cell #13 always was lower than the rest. I even individually charged it and the voltage dropped to under 3.4v in 15 minutes.

I have a balancer but need to install it so I can try that. But given that the voltage of cell 13 dropped this quickly I'm not sure if it will have an effect.

 

[FinalJudgment]

Had same issue with one cell that wouldn't hold charge at 3.4v, charge it to 3.65v but it will immediately race down to 3.37v while it's comrades are holding fine at 3.4+v. During discharge it's also causes LVD.
My conclusion: the self discharge at 3.4+v was high, I swapped out the bad cell with a new one and that pack is now happily churning in/out energy efficiently.

 

[sunshine_eggo]

Thank you so much for your response
I did a top balance before using the batteries and did a second top balance after noticing the cells that drift apart. Cell #13 always was lower than the rest. I even individually charged it and the voltage dropped to under 3.4v in 15 minutes.

I have a balancer but need to install it so I can try that. But given that the voltage of cell 13 dropped this quickly I'm not sure if it will have an effect.

You didn't comment about confirming measurements with a separate meter or checking connections. MANY instances of your exact issue is resolved with discovery and correction of a connection issue.

If the issue is real, you likely have a bad cell.