EG4 Lifepower4 BMS repair

[AntronX]

So thanks to @Sharing Society I got my hands on couple of fried BMS boards from EG4 Lifepower4 48v batteries. One of the mosfets labeled SVG104R0NS (120A 100V) got so hot it scorched the pcb. I desoldered it and amazingly this mosfet still works! Next I tried to power up the board but I could not figure out how to make it wake up. So I bruteforced it by applying 27V directly to input of dc-dc converter that feeds the micro controller. It woke up and did its LED light dance which ended with red fault LED staying on. I ordered USB to RS485 dongle to try to connect it to PC for further testing.

 

[Sharing Society]

Here's how that board connects inside an EG4 Lifepower4 battery

 

[AntronX]

Thanks. Applying 50V to B- and B+ and shorting those white wires together that go to the breaker did not wake up the board. So either I am missing something or power up circuit that applies power to dc-dc has failed. But the brains are still alive. More circuit tracing is needed but that hard conformal coating is a pita to deal with.

 

[AntronX]

MCU: FM33G048, BMS IC: SH367309

 

[Sharing Society]

Thanks. Applying 50V to B- and B+ and shorting those white wires together that go to the breaker did not wake up the board. So either I am missing something or power up circuit that applies power to dc-dc has failed. But the brains are still alive. More circuit tracing is needed but that hard conformal coating is a pita to deal with.

are you getting red fault light?

 

[AntronX]

are you getting red fault light?

yes but probably is expected with batteries missing

 

[AntronX]

Got it talking with BMSTest software. So It looks like you can't edit voltage setpoints with these BMS boards. Kinda lame but understandable since these batteries supposed to be safe from user tampering.