There is provided a battery pack system that allows an output limit during short-time discharging and long-time discharging of a secondary battery, and limits the output appropriately upon request of a vehicle. An output limiting section 104 is provided for changing a limit value of output electric power from the secondary battery when voltage data V (n) from a voltage measuring section 102 reaches a predetermined discharging termination voltage. The output limiting section 104 has short-time output information (Pp) for allowing short-time discharging of the secondary battery and normal output information (Pn) for allowing long-time discharging of the secondary battery, and sets a first discharging termination voltage (V1) during short-time discharging to be lower than a second discharging termination voltage (V2) during long-time discharging.