Patent ID: 7683580

Claim:
A remaining-battery-capacity estimating apparatus for estimating a remaining capacity of a battery to be measured, comprising: a rectifier that is connected in parallel to the battery to be measured, and supplies electric power to an actual load; an actual load connected in parallel to the rectifier, wherein the rectifier supplies electric power to the actual load; a rectifier-voltage control section that reduces an output voltage of the rectifier; a dummy load device provided separately from the actual load and connected in parallel to the rectifier; a load-current measurement section that measures current that flows through the actual load and the dummy load device from the rectifier and the battery; a control section that controls a load of the dummy load device such that the current measured by the load-current measurement section is a predetermined value; a battery-data storage section that stores battery data indicating relationship among a discharging time of the battery, a terminal voltage of the battery, and remaining capacity of the battery, at a predetermined current of the battery; and an arithmetic section that calculates the remaining capacity of the battery based on the discharging time of a discharging current flowing through the dummy load and the actual load, and the terminal voltage of the battery corresponding to the discharging current at the discharging time by referring to the battery data stored in the battery-data storage section.