My 48 volt lipo4 battery shows 50.7 Volts but the output of the BMS is 39.2 Volts. I have tried three different boards and they all read 39.2V. Can the battery show 50 Volts and still have a weak cell?
Old batteries can, seem OK after a charge. They seem to take the charge and show the "right" amount of volts... But, when you put a load on them they collapse/fail and the voltage drops... this is my opinion, I am NOT a battery expert, just saying what my experience has been with some older batteries like 6+ years old.