The reason is that some batteries have been discarded.
The reason is that some batteries have been discarded, but they play a role in the chronic discharge of the battery pack. The checking method is: after full charging, unplug the serial connection point and wait. one to two days. Measure the voltage changes of each group. If the voltage of a certain group drops below 4V, check the defective battery and dispose of it.
This shows that the consistency of the two battery strings is not good. One has high capacity and the other has low capacity. Although the self-discharge of the lithium battery is small, it does exist. -discharge after all. After two months the low capacity battery will be damaged due to over discharge, if a few months pass the other one will also have zero voltage. It's a matter of time, the difference. is it early orlate.