Insulation resistance detection. During the use of electric vehicles, conditions such as collision and aging of parts will occur, which will make the insulation between the high-voltage electrical system of the vehicle and the vehicle chassis abnormal. When the situation is serious, the heat accumulation effect generated by the leakage circuit will occur. It will cause the vehicle to burn and catch fire. Therefore, the insulation detection between the high-voltage electrical system and the vehicle chassis has become one of the key functions of the BMS. Power components with a maximum working voltage greater than 60V are defined as B-level voltage levels in personnel electric shock protection, and B-level power components must have sufficient insulation resistance.