Electric-powered vehicle, charging system, and charging-discharging system

An electric-powered vehicle including a power supply for vehicle driving, a first system-control power supply, and an inlet electrically connected to the power supply for vehicle driving, wherein

• the electric-powered vehicle is connected to a charger or charger/discharger including a second system-control power supply through a cable that is provided at one end with a connector connectable to the inlet, the cable including a first signal line and a second signal line,
• the electric-powered vehicle comprises:
• a first voltage detecting circuit to detect that a voltage is applied to the second signal line by the second system-control power supply;
• a first relay to open/close an electric path between the first system-control power supply and the first signal line;
• and a vehicle controlling circuit to control the first relay, and
• when the vehicle controlling circuit detects from the first voltage detecting circuit that a voltage is not applied to the second signal line by the second system-control power supply, the vehicle controlling circuit causes the first relay to open the electric path between the first system-control power supply and the first signal line.