Newbie Questions

I have been fortunate enough to gather several E-bike batteries. i have a couple of them that are 36v and the battery stops charging at 38.1v and a 48v stopping at 50.1V what are some things i should look for.. bad connection? dead cells? faulty bms?

Feraldave said:

I have been fortunate enough to gather several E-bike batteries. i have a couple of them that are 36v and the battery stops charging at 38.1v and a 48v stopping at 50.1V what are some things i should look for.. bad connection? dead cells? faulty bms?

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First-off i'd check the voltages of the p-groups via the balance leads. Have you already checked the individual p-group voltages with your DMM (via the balance leads) of these three battery packs (2-36v & 1-48v). Check for significant imbalance between one or more of the p-groups in each of the three battery packs.

Is it 13S or 14S? A so-called 13S 48V li-ion battery with full charge is 54.6v and 14S li ion 58.8v. If 13S then 50.1 ÷ 13 = 3.85v to 4.21 difference resulting in shut-down which is close to 10S voltage of 3.81v to 4.21v resulting in shut-down.

If the charger is AOK one might assume there's at least a difference of 0.40v between the ten 10s p-groups (3.81v + 0.40v = 4.21v) or a difference of at least 0.63v between the fourteen 14s p-groups (3.58v + 0.63v = 4.21v). That's assuming the BMS is doing what it's suppose to do when p-groups are out-of-order which is protection ... the primary function of a BMS.