1 cell is draining faster than the others

[Chris_g]

I have a 12v diy battery with a bms. After using for a year all of a sudden the battery turns off and when I test each cell 3 are still close to 3.2v but 1 is at 2.8. Bad cell or faulty BMS?

 

[TomC4306]

Or loose connection causing it to not charge the same as the others.
Easy to check. Free.

Do you have a torque wrench?

 

[sunshine_eggo]

I have a 12v diy battery with a bms. After using for a year all of a sudden the battery turns off and when I test each cell 3 are still close to 3.2v but 1 is at 2.8. Bad cell or faulty BMS?

If it's not a connection issue, it could be that the cells are imbalanced. Do you regularly charge to 14.2-14.V?

Note that 2.8 to 3.2V/cell is likely only about 10% difference.

 

[Chris_g]

The battery chargers to 13.2v then the charger shuts off. At this point the first 3 cells measure at 3.3v and the cell in question is 3.25v. once the battery gets to around 12.2 it shuts off and that's when there is a bigger difference in cell voltage.

 

[Zapper77]

The battery chargers to 13.2v then the charger shuts off. At this point the first 3 cells measure at 3.3v and the cell in question is 3.25v. once the battery gets to around 12.2 it shuts off and that's when there is a bigger difference in cell voltage.

What can you tell us about your bms and charger?
Did the battery ever charge to 14.2v?
Can your charger support 14.2?
Please check your word usage (chargers or charges)? Can you update your bms settings?
What kind of battery cell?
Why does the battery stop charging? (Insufficient charger, bms shuts of)
How long is the wire that goes from the charger to the battery?

 

[Chris_g]

The BMS is a Jiabaida sp04so20A 4s 120A. The charger is an Expert Power 12.5v 5amp and says an output of 14.4vdc 5.0A.
I don't know about updating the BMS settings.
All wires are less than a foot and relatively equal length.
The green light on the charger comes on noting "charge ok" as opposed to the red light on while charging.

 

[TomC4306]

The battery chargers to 13.2v then the charger shuts off.

This is not high enough. Minimum is to charge to 13.8v and hold for at least an hour.
Better to charge to 14v.
Your battery has never balanced because your battery has never been fully charged

 

[SparkyJJO]

This is not high enough. Minimum is to charge to 13.8v and hold for at least an hour.
Better to charge to 14v.
Your battery has never balanced because your battery has never been fully charged

This.