The reason why does Battery was charged to swelling status :
A. Measure the voltage of each cell of the battery pack and make a record.

B. Check whether the charger voltage is normal. If the battery cells are well balanced, it is impossible for the battery to be charged to swollen status

C. Check whether the C- wire welding position is correct or not. If the B- and C-wires are welded reversely, the protection board has no charge and discharge protection function; if the C- wire is welded to the P-pad, there is no charge protection function.

D. Check whether the battery cell has mechanical damage or assembly errors.

E. Check whether the charging MOS tube on the BMS is good or not. (please measure the resistance between C- and P- after disconnecting the BMS from the Battery , it is normal if resistance value with unit of M is above ,it means the Mosfet work normally OK , otherwise BMS has been broken with value unit of Ω and K)