Relay device including a restriction unit

A relay device converting a control signal related to charging from one format to another and relaying a converted control signal between a first communication unit that is provided on a vehicle having a battery and that sends and receives a control signal related to charging in a first format and a second communication unit that is provided on a charging station for supplying DC power to charge the battery and that sends and receives a control signal related to charging in a second format, comprising:

• a restriction unit that restricts energization between the charging station and the battery regardless of control performed by the vehicle based on the control signal;
• an acquisition unit that acquires a voltage value of the DC power supplied from the charging station and a voltage value of the battery;
• a determination unit that determines whether or not a voltage difference between the voltage values acquired by the acquisition unit is less than a threshold;
• and
• a release unit that releases restriction by the restriction unit if the determination unit determines that the voltage difference is less than the threshold, wherein
• the vehicle is provided with a DC cutoff relay that cuts off DC power supplied from the charging station to the battery and a signal line that transmits a signal for opening or closing the DC cutoff relay,
• the relay device comprises a signal cutoff relay that cuts off the signal, and
• the restriction unit restricts the energization by changing a state of the signal cutoff relay to an interrupted state, and the release unit releases the restriction by changing a state of the signal cutoff relay to an energized state.