Patent ID: 8129996
Filing Date: 2012-03-06
Classification: G01R

Abstract:
1. A method for determining SOH of a secondary battery according to an internal impedance or an internal resistance of the secondary battery supplying power to a load, comprising: preparing in advance a specified temperature characteristic function which contains at least one exponential terms and one adjustment parameter and expresses a temperature dependency of the internal impedance or the internal resistance; calculating the internal impedance or the internal resistance based on a measured current value or a measured voltage value at the time when the secondary battery is charged or discharged with a specified current; determining a value of the adjustment parameter by substituting a measured temperature at the time when the secondary battery is charged or discharged with the specified current and the calculated internal impedance or the internal resistance to the temperature characteristic function; calculating a reference internal impedance or a reference internal resistance by substituting the determined adjustment parameter value and a specified reference temperature into the temperature characteristic function; and determining, using a controller circuit, the SOH of the secondary battery based on the calculated reference internal impedance or the calculated reference internal resistance if the calculated reference internal impedance or the calculated reference internal resistance exceeds a threshold, and determining that the SOH is acceptable if the calculated reference internal impedance and the calculated reference internal resistance do not exceed the threshold.