Method and device for measuring pure resistance of on-vehicle battery by periodically measuring a discharge current and terminal voltage while a rush current flows into a constant load

A device for measuring a pure resistance of an on-vehicle battery for supplying electric power to loads in the vehicle comprising:

• measuring means for periodically measuring a discharge current and terminal voltage of the battery while a rush current flows into a predetermined constant load of the loads, the rush current first monotonically increasing from zero to a peak value and subsequently monotonically decreasing from the peak value to a steady value;
• first computing means for computing a first approximate expression of a current-voltage characteristic for the increasing discharge current and a second approximate expression of a current-voltage characteristic for the decreasing discharge current, said current-voltage characteristic indicating a correlation between the discharge current and terminal voltage of the battery measured by the measuring means;
• and
• second computing means for computing an intermediate value of two values of the terminal voltage, change per unit current change at points corresponding to the peak values of the first and second approximate expressions excluding a voltage drop caused by a concentration polarization component when the first and second approximate expression include the voltage drop,
• wherein the intermediate value computed by the second computing means is measured as the pure resistance of the battery.