A detection circuit includes a switch conversion unit and a collection control unit. The switch conversion unit is configured to: enable a first end of the switch conversion unit to connect to a third end of the switch conversion unit within first duration, and enable a second end of the switch conversion unit to connect to the third end of the switch conversion unit within second duration. The collection control unit is configured to: collect a voltage (V1) between a first end of a relay and a second end of a battery pack within the first duration, collect a voltage (V2) between a second end of the relay and the second end of the battery pack within the second duration, and determine, based on V1 and V2, whether the relay is faulty.