ELECTRIC POWER SUPPLY SYSTEM AND CONTROL METHOD THEREFOR

An electric power supply system comprises a fuel cell system including an FC auxiliary machine that operates to causes fuel cells to generate an electric power, and a battery that generates heat through discharging and charging. The electric power supply system supplies the electric power to an electric load device . The electric power supply system determines an operation state of the battery , and supplies the electric power discharged from the battery to the FC auxiliary machine of the fuel cell system when it is determined that the battery is a predetermined temperature or less. When it is determined that the battery is in a charging state, the electric power supply system reduces or stops the electric power supplied to the FC auxiliary machine