Dual power supply system and electrically driven vehicle

The present disclosure relates to a dual power supply system and an electrically driven vehicle with the capability of inhibiting a sub battery having high internal resistance from deteriorating. The sub battery (22) only discharges electricity. When the vehicle accelerates, output is performed to a driving motor (25). When the vehicle decelerates, the regenerative current is blocked by a diode D2 and all the regenerative current and output of the sub battery (22) are charged to a main battery (21) having lower internal resistance. Consequently, occurrence of power loss due to repetition of transient state (charging and discharging) of the sub battery (22) is avoidable beforehand and resistance increase due to frequent repetition of start and stop of discharge is reduced, and thus temperature rise of the sub battery (22) may be reduced and deterioration of the sub battery (22) may be reduced (avoided).