Patent ID: 7633297

Claim:
An internal impedance detecting apparatus for detecting an internal impedance of a secondary battery, comprising: a voltage detector for detecting a voltage of said secondary battery; a voltage change detector for detecting a change in the voltage within each of a plurality of detection times which have respective different time durations and include a common time, based on the voltage detected by said voltage detector; a current detector for detecting a current flowing through said secondary battery; a current change detector for detecting a change in the current within each of said detection times based on the current detected by said current detector; a processor for calculating a plurality of internal impedances by dividing voltage changes detected by said voltage change detector by current changes detected by said current change detector at the same detection times as the voltage changes; a judging unit for judging whether the internal impedances are reliable or not based on variations of the internal impedances calculated by said processor; and a generator for generating an internal impedance to be output based on the internal impedances only if said judging unit judges that said internal impedances are reliable.