Patent ID: 7358704

Claim:
A critical state estimation system adapted for estimation of an inputtable power of a secondary cell that defines a limiting boundary of a permissible range for power to be input to the secondary cell and an outputtable power of the secondary cell that defines a limiting boundary of a permissible range for power to be output from the secondary cell, in consideration of an internal resistance of the secondary cell, the system comprising: a current detector detecting a supply current from the secondary cell; a voltage detector detecting a supply voltage from the secondary cell; a variable data provider configured to provide a set of variable data on the secondary cell based on the supply current and the supply voltage, the variable data including an estimated parameter on open-circuit voltaae of the secondary cell, and an estimated parameter on the internal resistance of the secondary cell; a specified data provider configured to provide a set of specified data on the secondary cell, the specified data including a specified data on a minimum voltage to be permissible under a prescribed working condition of the secondary cell, and a specified data on a maximum voltage to be permissible under the prescribed working condition of the secondary cell; and a critical state estimator configured to process the set of variable data and the set of specified data for estimation of the inputtable power of the secondary cell and the outputtable power of the secondary cell, the critical state estimator comprising an internal resistance setter configured to process the estimated parameter on the internal resistance of the secondary cell to set an internal resistance of the secondary cell as a function of a current of the secondary cell, a critical current estimator configured to process the estimated parameter on the open-circuit voltage of the secondary cell, the specified data on the minimum voltage of the secondary cell, the specified data on the maximum voltage of the secondary cell, and the internal resistance of the secondary cell as the function of the current of the secondary cell to estimate an inputtable current of the secondary cell and an outputtable current of the secondary cell within the minimum voltage of the secondary cell and the maximum voltage of the secondary cell, respectively, and a critical power estimator configured to process the specified data on the minimum voltage of the secondary cell, the specified data on the maximum voltage of the secondary cell, the inputtable current of the secondary cell and the outputtable current of the secondary cell to estimate the inputtable power of the secondary cell and the outputtable power of the secondary cell.