To provide a secondary battery device of a simplified structure which can accurately determine the operation life thereof under the stable condition without useless consumption of charged power.
This secondary battery 1 comprises a battery voltage detector 5 for detecting a terminal voltage of the same battery, a full-charge detecting means (-ΔV detecting circuit) 3 for detecting the full-charge condition when the same battery is charged, a switch element 2 which is provided in a charging path of the same secondary battery for cutting off this charging path when the full-charge is detected, a memory 11 for storing a battery voltage Von of the same secondary battery immediately before the charging path is cut off, an internal resistance detecting circuit 14 for obtaining a value corresponding to the internal resistance of the same secondary battery from an open battery voltage Voff after the charging path is cut off, and the battery voltage Von and an operation life indicating means (battery operation life table 15) for evaluating the operation life of the same secondary battery depending on the value corresponding to the internal resistance of the same secondary battery and then outputting an information of the operation life.
SHIOJIMA NOBUO
ISHIZUKA SEIJI
