Battery only charging to 79%

[ZeroEmissions]

My Kingsong 18L only charges up to 79%... Any ideas how I can repair this? 

Thanks 

[Meserias]

you will need to provide more details how this started to happen ....
battery-packs DYI repairs are somehow dangerous.

[Chriull]

1 hour ago, ZeroEmissions said:

My Kingsong 18L only charges up to 79%... Any ideas how I can repair this? 

Thanks 

First the charger should be checked if it delivers full (84V) voltage.

If not, it's easy to replace.

If the prob is not the charger one (or both) of the battery packs have to be replaced.

[Philip W]

I found out how BMS boards work with my own battery packs' problem.  They will only be charged up to 63.5v, versus the supposed 67.2v.

The BMS in my battery pack detects one battery that's malfunction, probably no voltage difference between positive and negative, so the board decides to lower the cut-off charging voltage to 63.5v. This way it can prevent the malfunctioning battery from busting in flames, but also makes the battery lost quite a lot of charge.

I don't know how you calculate the 21% lost. Did you calculate it by the loss of the range, or by the loss of voltage? They are very different measures.

I think if you calculated by the loss of range, then probably one cell is dead; if you calculated by the loss of voltage, then 4 cells in a series are dead, which is very awful.

To fix it, you need to open the EUC, cut open the battery pack and do a lot of testing and soldering. It's not easy for regular people.

[Chriull]

52 minutes ago, Philip W said:

To fix it, you need to open the EUC, cut open the battery pack and do a lot of testing and soldering. It's not easy for regular people.

So checking the charger is the easier first step