Battery charge difference calculation system

A power supply device comprising:

• a power generator;
• a drive source that drives the power generator;
• a plurality of power supply lines that supply electric power generated by the power generator to a plurality of electric loads;
• a plurality of batteries that are connected to the corresponding power supply lines upstream from the corresponding electric loads in an electric power supply direction;
• a diode that is provided upstream from the battery in the corresponding power supply line and allows electric power to flow in only one direction from upstream to downstream of the power supply line;
• a difference calculating unit configured to calculate a difference between target electric power set for each battery and measured electric power;
• a difference summing unit configured to sum the difference in electric power of the batteries of the power supply lines calculated by the difference calculating unit;
• and
• an electric power summing unit configured to sum electric power calculated by the difference summing unit and electric power required for the electric loads,
• wherein the drive source is controlled such that electric power calculated by the electric power summing unit is generated by the power generator.