Battery pack, charging control method, and application device

A battery pack having a secondary battery (1) and a circuit (16) that controls charging and discharging of the secondary battery is disclosed. The battery pack has a computer (10) that communicates with another computer (31) disposed in a charging device (30), authenticate the charging device, and calculates remaining capacity information of the secondary battery. When the computer has not successfully authenticated the charging device and has detected that the secondary battery has been charged in a predetermined manner, the computer forcibly sets the remaining capacity information to "no remaining capacity".