The present invention provides a power
source system that increases the power supply capacity of a power source device and continuously supplies the power necessary for a load device when a power source device stops. A
control unit has a state quantity setting unit that sets a first target state quantity indicating a
state of charge of the
power storage device that is to be a target value when
charge and discharge of the
power storage device are controlled. When the power source device stops, the state quantity setting unit can change the first target state quantity to a second target state quantity that is to be a target value exceeding the first target state quantity and can increase the target state quantity of the
power storage device. As a result, when the power source device stops,
charge and discharge of the power storage device are controlled on the basis of the target state quantity exceeding that during the operation of the power source device. Therefore, the
state of charge of the power storage device can be improved over that during the operation of the power source device. As a result, the power supply capacity of the power source device can be increased and the power necessary for the load device can be continuously supplied, in place of the power source device.