Patent ID: 7619386

Claim:
A battery pack having a secondary battery and a circuit that controls charging and discharging of the secondary battery, the battery pack comprising: a computer that communicates with another computer disposed in a charging device and authenticates the charging device; and charging control means, controlled by the computer, for supplying a charging current to the secondary battery when the charging device has been successfully authenticated and shutting off the charging current when the charging device has not been successfully authenticated after the charging state has continued for a predetermined time period during which an authentication process is repeated at a plurality of intervals, wherein the computer of the battery pack and the other computer disposed in the charging device mutually authenticate each other according to a challenge and response system, the challenge and response system including a first step where first challenge data is transmitted from the charging device to the battery pack, and after the battery pack receives the first challenge data, the battery pack generates first response data including both secret information associated with the battery pack and the first challenge data, the battery pack transmits the first response data to the charging device, and if the first response data of the battery pack matches the first challenge data of the charging device, the computer disposed in the charging device determines that the battery pack is authentic and causes an authenticated result to be stored in the charging device, and a second step where second challenge data is transmitted from the battery pack to the charging device, and after the charging device receives the second challenge data, the charging device generates second response data including both the second challenge data received from the battery pack and secret information associated with the charging device, the charging device transmits the second response data to the battery pack, and if the second response data of the charging device matches the second challenge data of the battery pack, the computer disposed in the battery pack determines that the charging device is authentic and causes another authenticated result to be stored in the charging device, thereby completing the mutual authentication between the battery pack and the charging device, and wherein the computer of the battery pack and the other computer disposed in the charging device repeatedly authenticate each other at a predetermined cycle, and wherein the shutoff state of the charging current is cancelled when the battery pack is detached from the charging device.