Patent ID: 8285501

Claim:
A battery pack, comprising: a plurality of batteries; a detection section to measure a voltage of each of the plurality of batteries to obtain a voltage variation of each of the plurality of batteries at different lapse times and compare the obtained voltage variations to thus detect whether at least one of the plurality of batteries has been replaced, the detection section sampling voltages of each of the plurality of batteries in a time-axis direction during discharge of the plurality of batteries after being charged, the detection section obtaining a square sum of a deviation of the sampled voltages for each of the samples, the detection section obtaining the voltage variation by adding up the obtained square sums of the deviations, and the detection section determining that at least one of the plurality of batteries has been replaced if a present voltage variation is less than or equal to a previously measured voltage variation; and a controller to disable, when a result of the detection by the detection section indicates that at least one of the plurality of batteries has been replaced, a use of the plurality of batteries.