A firmware update method is provided for use in an information processing system powered by a power system. The power system is powered by an external power source and the power system includes a rechargeable battery and a controller. The method includes checking a power status of the rechargeable battery through the controller in response to a firmware update procedure. A power status of the rechargeable battery is determined to be sufficient to perform the firmware update procedure, and an insufficiency of the external power source to power the power system is determined. Power for the firmware update procedure is limited, through the controller, to the rechargeable battery.