PURPOSE: To prevent arc upon opening a circuit by setting the projecting length of a pair of auxiliary terminals in the power receiving coupler or power supply coupler in an unmanned vehicle shorter than that of a pair of main terminals.

CONSTITUTION: A power supply coupler 4 connected with a charger 6 is coupled with the power receiving coupler 3 of an unmanned vehicle 1 and power is fed from main terminals 4A', 4B' and auxiliary terminals 4C', 4D'. The auxiliary terminals 4C', 4D' are set shorter than the main terminals 4A', 4B'. Main terminals 3A, 3B of the power receiving coupler 3 are set equal to the length of auxiliary terminals 3C, 3D. Main terminals 4A', 4B' of the power supply coupler 4 are connected with charging power source 61 of the charger 6. The auxiliary terminals 4C', 4D' are connected with a relay coil 6b. When the power receiving coupler 3 and the power supply coupler 4 are uncoupled during charging operation, the auxiliary terminals 4C', 4D' are removed prior to the main terminals 4A', 4B' to open a relay contact 6a, and thereby no arc is produced between the main terminals 4A', 4B'.