Battery not fully charging

[pears_91]

I have a bike with 36v battery. When it was new I'm sure it used to charge to 42v. But now it charges only to 36v.

I made the battery pack myself, and will take apart and measure voltage over each cell etc.. I don't have any equipment for reviving battery cells or charging them other than my ebike charger.. so probably if I want to fix anything I guess I'll have to buy some equipment.. also I installed standard BMS not smart so I can't see any info on an app etc.

Does anyone have any ideas as to what itay be.. and any advice best way to test and fix?

 

[saneagle]

First step is to measure the individual cells, then you will know what the problem is.

 

[Nealh]

One can take the ten cell readings directly via the cells by alternating the meter probes to the correct cell group or via the BMS sense wire connector.

A pic of the battery build might also be helpful.

One needs to register ten individual cell readings and the result should pin point where the issue is. At 36v though it sounds like a dead cell group or a verrrry low one.

 

[Nealh]

I made the battery pack myself, and will take apart and measure voltage over each cell etc..

Were they new cells or cobbled together from various used cells ?

 

[pears_91]

Were they new cells or cobbled together from various used cells ?

New cells

 

[pears_91]

It's probably had around 40 charge cycles 18 months old. Unused for about 6 months at 1 point.

 

[Nealh]

Likely BMS has drained a cell group low but until one can take the ten cell readings it is a guessing game.

 

[Nealh]

The cell /battery issue is most likely an exact replica of this current thread.
Battery Cell Autopsy? | Pedelecs - Electric Bike Community