I got a mystery A123 battery pack for free...

[NiHaoMike]

Someone on a Facebook solar group (who happens to be fairly close to my area) gave away a mystery A123 battery pack since he couldn't figure out how to repurpose it. He did mention that all the modules have the normal voltage (which I later confirmed was in fact the case), so I thought it was well worth getting. 188V and 25Ah is 4.7kWh, quite substantial and worth a lot if it works.

The pack is made up of 7x 8S modules that separate easily. Each one has its own BMS board although I'm not sure if the board can be easily reused. I plan to build my own BMS based on a string of RISC-V microcontrollers but reusing the boards would be much less effort if practical. Note that unlike a standalone BMS, those boards do not interrupt the current flow in a fault condition, that part is handled in the control system.

There's a CR0303 PLC taking care of the central control. No idea if the program is protected against readout.

There's also a built in charger apparently based around a modified motor inverter design. A complex arrangement of HVDC relays is used to switch between boost and buck mode for 120V and 240V mains input. Surprisingly, there's no PFC, which means it would only be able to get the about 70% of the maximum charge rate possible from the mains circuit. Maybe they tried to implement it but ran into issues (EMI?) and just decided to do a quick respin of the rectifier board without PFC and release it to market.