METHOD AND APPARATUS FOR DETECTING VOLTAGE-CURRENT CHARACTERISTIC FOR ON-VEHICLE BATTERY, METHOD AND APPARATUS FOR CALCULATING INTERNAL RESISTANCE OF ON- VEHICLE BATTERY, AND METHOD AND APPARATUS FOR DETECTING DEGREE OF DETERIORATION OF ON-VEHICLE BATTERY

摘要

PROBLEM TO BE SOLVED: To accurately detect and calculate the degree of deterioration of a battery from a charge/discharge current and the terminal voltage of an on-vehicle battery repeating charging and discharging. SOLUTION: The increasing charge and discharge current of a battery 13 is periodically measured after one of the charging and the discharging states made transition to the other state. The terminal voltage of the battery 13 changes depending on the increase of the charge/ discharge current. When the voltage-current characteristic showing the relation between the current and the voltage is detected, a gradient value calculating means 23A finds for each prescribed unit of time the gradient value of the ratio of the variation of the terminal voltage to the increment of the charge/discharge current represented as the absolute value. From the charge/discharge current and the terminal voltage of the battery 13 measured periodically by a reduction discrimination means 23B after the means 23B discriminated that the gradient value is reduced to a prescribed value, the voltage-current characteristic is detected. The inner resistance of the battery 13 calculated from the gradient determined by on approximate expression deriving means 23C. The degree of the deterioration of the battery 13 is found by comparing the above-calculated inner resistance with the inner resistance of the battery 13 when it was new by a comparing means 23D.