Patent ID: 7675291

Claim:
A battery characteristic detecting method for a battery of an electric or hybrid vehicle, comprising: (i) mounting the battery in an electric or hybrid vehicle; (ii) performing constant current discharge from a battery that is not fully charged at a predetermined current value, and measuring a voltage in the battery during the constant current discharge, wherein the predetermined current value is selected as follows: in the battery where a characteristic change has not occurred, determining a relationship between overpotential of a cathode and a logarithm of the current density in the battery, determining a select current density at which the overpotential of the cathode and the logarithm of the current density in the battery changes between a linear relationship and a non-linear relationship, and selecting the predetermined current value to be a current value at which the current density in the battery is 5 to 90% of the select current density; (iii) calculating overpotential for mass transfer control in the battery based on the measured voltage; and (iv) determining that a characteristic change has occurred in the battery, when the calculated overpotential for the mass transfer control in the battery is larger than a predetermined threshold value, wherein, in step (ii), both a first voltage, E1, in the battery immediately after a staff of the constant current discharge from the battery, and a second voltage, E2, in the battery when a predetermined time has elapsed since the staff of the constant current discharge, are measured during the constant current discharge, and, in step (iii), overpotential, E, for the mass transfer control is calculated based on the first voltage and the second voltage measured in step (ii) according to a following equation: E=E1 − E2.