An EV Main Contactor Relay is a high-voltage, high-current relay used in electric vehicles to connect and disconnect the battery pack from the rest of the powertrain. It operates as a switch, ensuring that the electrical current only flows when needed. The MCR is crucial in maintaining the vehicle’s energy flow, helping to regulate the charging and discharging processes of the battery, as well as preventing electrical faults that could lead to catastrophic damage.

    The relay is controlled by the vehicle’s Battery Management System (BMS) or Electronic Control Unit (ECU), which monitors the battery's state of charge, temperature, and voltage. When the system determines it is safe for the battery to provide power to the electric motor or be charged, it sends a signal to close the contactor, allowing current to flow. Conversely, if any abnormalities are detected—such as overvoltage, undervoltage, or excessive temperature—the system will send a signal to open the contactor, disconnecting the battery to prevent damage or safety hazards.