POWER SUPPLY DEVICE

A power supply device includes a power generator, a drive source, a plurality of power supply lines, a plurality of batteries, a diode, a difference calculating unit or and a difference summing unit The difference calculating unit or is configured to calculate a difference between demanded electric power P P P or P in the corresponding power supply line and a charge state of the corresponding battery. The difference summing unit is configured to sum the differences in electric power in the power supply lines calculated by the difference calculating units and In the power supply device, the drive source is controlled such that electric power equal to or higher than the electric power calculated by the difference summing unit is generated by the power generator.