PURPOSE: To positively estimate remainder capacity even if the change in the discharge current of a battery is small by obtaining a current/voltage characteristic straight line so that it nearly passes through a reference point and a measurement operating point which is measured on battery discharge.
CONSTITUTION: Each current/voltage characteristic straight line (characteristic straight line) corresponding to various kinds of remaining capacities of a battery (lead- accumulation battery etc.) converges at a region where a discharge current value becomes negative. The convergence point is used as a reference point (for example, -100A, 14V). By obtaining a characteristic straight line so that it nearly passes through the measurement operating point and the reference point of the battery which correspond to the measurement values of discharge current and output voltage measured on the discharge of the battery to be measured, an accurate characteristic straight line corresponding to the current remainder can be obtained. In this case, it is desirable that a plurality of sets of discharge current and output voltage should be measured and a characteristic straight line should be obtained so that it passes through the average measurement operating point of the battery corresponding to their average value and the reference point. The remainder capacity of battery is estimated using the maximum output estimation method based on the characteristic straight line.
NAGANO MASAO
TAKEMOTO HIDETOMO
