48v 7.5ah ebike Lithium Ion Battery from China Fail and Dismantle Part 1

So I bought this 48v battery 3 years ago from China off eBay for $110 and it only charges to 52 volts now vs. the 54 Volts it used to when it was new. I tore it apart to diagnose to fix. Battery groups were not evenly charging, new BMS is in order.