BATTERY STATE DETECTING DEVICE

PURPOSE:To detect the rest capacity and rest life of a battery accurately by storing the relation between the life and rest capacity of the battery corresponding to battery characteristics at the time of large-current discharging and small- current discharging. CONSTITUTION:The CPU 8 of a microprocessor 7 inputs the terminal voltage of the battery 1 and a discharging or discharging current through an interface 10 to calculate battery characteristics (electromotive force, maximum output, internal resistance, dead short current, etc.) at the time of large-current discharging and battery characteristics (internal resistance) at small-current charging and discharging. A memory 9 is stored with the relation between the life and rest capacity of the battery corresponding to the battery characteristics at the time of the large-current discharging and the battery characteristics at the time of the small-current charging and discharging. Then, the life and rest capacity of the battery are detected on the basis of the arithmetic result of the CPU 8 and stored information in the memory 9.