I own a Huasha HS50QT7 electric scooter with a 1.5kW motor. It was powered by 4 Greensaver 12 v 38ah Silicon Lead acid batteries connected in series, with a household circuit breaker in circuit. The range was poor as two of the four batteries are shot, so I inquired with many manufacturers and bought a 48V 30ah LiFePO4 battery and charger from yxmzone. This was the largest capacity, at the time, that would fit in the battery bay (with a club hammer and cold chisel).
On connecting the charger, it blew up, I did return for repair but bit was not collected and came back again. The battery was charged to 48 v when I fitted it, and as it had a BMS, I removed the Circuit breaker. I got a new charger from VPower and on charging it dropped to -4.5V. The polarity was wrongly connected as it had been with the charger. I fixed that and charged to 52 v and it ran OK. After an MOT, it stopped on the way home and will not charge above 48v since and just runs the scooter.
The question is whether it is the BMS or have some of the 3.2V cells been damaged. I have a multimeter and am ready to remove the duck tape wrapping the battery. So I do not completely wreck it, any advice on how to proceed would be appreciated. Otherwise a one year old LiFePO4 battery will be consigned to waste.