Patent ID: 7098625

Claim:
A charge rate estimating apparatus for a secondary cell, comprising: a current detecting section capable of measuring a current flowing through the secondary cell; a terminal voltage detecting section capable of measuring a voltage across terminals of the secondary cell; a parameter estimating section that calculates an adaptive digital filtering using a cell model in a continuous time series shown in an equation (1) and estimates all parameters at one time, the parameters corresponding to an open-circuit voltage V 0 which is an offset term of the equation (1) and coefficients of A(s), B(s), and C(s), which are transient terms; and a charge rate estimating section that estimates the charge rate from a previously derived relationship between an open-circuit voltage and a charge rate of the secondary cell and the open-circuit voltage V 0 , V = B ⁡ ( s ) A ⁡ ( s ) · I + 1 C ⁡ ( s ) · V 0 , ( 1 ) wherein s denotes a Laplace transform operator, A(s), B(s), and C(s) denote poly-nominal functions of s, wherein the open-circuit voltage V 0 of the cell model in the continuous time series shown in the equation (1) is approximated by means of an equation (2) to provide an equation (3) and the adaptive digital filter calculation is carried out using the equation (3) and equivalent equation (4), h is estimated in at least equation (4), the estimated h is substituted into equation (2) to derive an open-circuit voltage V 0 , and the charge rate is estimated from the previously derived relationship between an open-circuit voltage and a charge rate of the secondary cell and the open-circuit voltage V 0 V 0 = h s · I ( 2 ) V = ( B ⁡ ( s ) A ⁡ ( s ) + 1 C ⁡ ( s ) · h s ) · I = s · B ⁡ ( s ) · C ⁡ ( s ) + h · A ⁡ ( s ) s · A ⁡ ( s ) · C ⁡ ( s ) · I ( 3 ) s · A ⁡ ( s ) · C ⁡ ( s ) G 1 ⁡ ( s ) · V = s · B ⁡ ( s ) · C ⁡ ( s ) + h · A ⁡ ( s ) G 1 ⁡ ( s ) · I , ( 4 ) wherein s denotes the Laplace transform operator, A(s), B(s), and C(s) denote poly-nominal equation functions, h denotes a variable, and 1/G 1 (s) denotes a transfer function having a low pass filter characteristic.