Patent ID: 8874393

Claim:
A battery pack attachable to and detachable from an electronic device main body, said battery pack comprising: a chargeable and dischargeable battery; and a microcomputer that acquires information on a voltage drop across the battery in a condition equivalent to no load and stores the information therein, the condition equivalent to no load is a condition in which the battery pack is detached from the electronic device main body, the acquired information includes (i) an initial first voltage acquired at a first time in the condition equivalent to no load, said first time being approximately 10 minutes after the battery pack is detached from the electronic device main body, (ii) an updated first voltage acquired every 10 minutes after the first time while the battery pack remains detached from the electronic device main body, and (iii) a second voltage acquired at a second time which occurs after the first time and after the battery pack is re-attached to the electronic device main body, and the microcomputer calculates a value pertaining to the voltage drop (i) from the second voltage and the initial first voltage when the battery pack was detached from the electronic device main body for less than 10 minutes after said first time or (ii) from the second voltage and a latest updated first voltage when the battery pack was detached from the electronic device main body for 10 minutes or more after said first time.