A not so often used 24v 15AH battery (LiFePo4)on a bike i sold to an elderly guy has 5 cells with below 2 v could it be that the C rating of the batteries was not high enough for the BMS attacthed to it --this is a guess as to why this has happened , i have another battery same as this one which I expect the same might happen,these are the small cells so its good reason to stick to the big screw in ones so easy to replace . ----learning we all are.