EMI improvement suggestions

[Candide1976]

I'm using the DIY BMS V4.0 for half a year now, impressed! I'm using the ESP8266 controller.

If EMI is still an issue:
To improve UART EMI I would suggest to place the optocouplers on the other ends: LED current running through the connecting wires, optocoupler output near to the ESP. (As this is the most likely path to pick up disturbance)
Buffering as done by MOSFET probably better done with BJT as this is a current fed device.

I greatly improved UART noise in my own board by placing 100pF across the ESP Rx to 3V3.