Battery charging device

A battery charging device comprising:

• a rectification unit configured to output DC electric power which is obtained by rectifying three-phase AC electric power output from a power generator as charging electric power of a battery through turning-on of a switch element connected to an output signal line of each phase of the three-phase AC electric power with rotation of a rotor;
• a power supply sustaining switch that is able to be sustained in a state in which control electric power of the switch element from the battery is able to be supplied when a main switch for supplying the control electric power of the switch element from the battery to a power supply line is switched to a cutoff state in which supply of the control electric power to the power supply line is stopped;
• and
• a control unit configured to control turning-on of the switch element, the control unit sustaining the power supply sustaining switch in a state in which the control electric power of the switch element is able to be supplied when the main switch is switched to the cutoff state and performing control such that the switch element on a negative electrode side connected to a negative electrode terminal of the battery is switched to a turned-on state when the rotor is rotating.