FishBMS forum

DO outputs can be load up to 500mA, but it must respect the internal power supply unless the BMS comes from external 12V. Total power consumption should be up to 300-400mA at 12V including BMS consumption. If this is exceeded, the BMS restarts (the power is turned off). If it balances somewhere on the edge, then the BMS shuts down seemingly at random time (which happened to us when using a GSM module that was powered directly from 12V BMS)

Setting up your relay should be simple:
bit0 DO0 main contactor (on)

thus 4035 = 1

DO0 = output HV_EN (this is given historically, so it may not be clear from the documentation at first sight)

output CHG_EN on connector X4 works by default without any settings.

Since firmware version 17, this output turns off when one of the following conditions is met: (previously turned off only on high voltage error)
(DATALAYER.warning.cellVoltHigh || DATALAYER.error.communication || DATALAYER.error.cellTempHigh | DATALAYER.error.switchTempOver || DATALAYER.error.cellTempLow)
- when a warning is reached
- interruption of communication with slaves
- high cell temperature (setting 4017)
- low charging temperature (setting 4017)
- high temperature semiconductor switch (X4 temp_sw) setting 4050