Patent ID: 8212525
Filing Date: 2012-07-03
Classification: H02J

Abstract:
1. A battery pack comprising: a secondary battery formed by connecting a plurality of battery cells in series; a control section measuring a voltage at each of the plurality of battery cells and controlling each part according to the result of the measurement; a charge/discharge control circuit temporarily inhibiting charging and discharging of the secondary battery under control exercised by the control section; an interruption circuit interrupting charge and discharge currents of the secondary battery under control exercised by the control section to inhibit charging and discharging of the secondary battery permanently; a discharge circuit discharging a predetermined battery cell among the plurality of battery cells under control exercised by the control section; a capacity measuring section measuring the amount of electricity discharged from the battery cell at the discharge circuit; and a storage section storing total discharge amount information indicating a total amount of discharged electricity measured by the capacity measuring section and a charge/discharge inhibition record indicating a count of temporary charge/discharge inhibitions imposed on the secondary battery by the charge/discharge control circuit, wherein first and second thresholds for determining the safety of the secondary battery are set in association with the value of the total amount of discharged electricity indicated by the total discharge amount information and the count of temporary charge/discharge inhibitions indicated by the charge/discharge inhibition record; the control section determines the state of cell balance between the plurality of battery cells based on the result of the measurement, performs a leveling process to achieve a proper cell balance by controlling the discharge circuit to discharge a battery cell having a high voltage among the plurality of battery cells when it is determined that the cell balance has been lost, and updates the total discharge amount information based on the amount of discharged electricity measured by the capacity measuring section, the control section compares the total amount of discharged electricity indicated by the total discharge amount information stored in the storage section with the first threshold, controls the charge/discharge control circuit to inhibit charging and discharging of the secondary battery temporarily when it is determined that the total amount of discharged electricity is in the excess of the first threshold as a result of the comparison, and updates the charge/discharge inhibition record; and the control section compares the count of temporary charge/discharge inhibitions indicated by the charge/discharge inhibition record stored in the storage section with the second threshold and controls the interruption circuit to inhibit charging and discharging of the secondary battery permanently when it is determined that the count of temporary charge/discharge inhibitions is in the excess of the second threshold as a result of the comparison.