Battery capacity measuring and remaining capacity calculating system

Abstract

A battery capacity measuring device in accordance with the present invention has a fully-charged state detector ( ), a detected current integrator ( ), a divider ( ), and a corrector ( ) incorporated in a microcomputer ( ). The fully-charged state detector detects that a battery is fully charged. The detected current integrator integrates current values that are detected by a current sensor during a period from the instant the battery is fully charged to the instant it is fully charged next. The divider divides the integrated value of detected current values by the length of the period. The corrector corrects a detected current using the quotient provided by the divider as an offset. Furthermore, a remaining battery capacity calculating system comprises a voltage detecting unit ( ), a current detecting unit ( ), an index calculating unit, a control unit, and a calculating unit. The voltage detecting unit detects the voltage at the terminals of a battery. The current detecting unit detects a current flowing through the battery. The index calculating unit calculates the index of polarization in the battery according to the detected current. The control unit controls the output voltage of an alternator so that the index of polarization will remain within a predetermined range which permits limitation of the effect of polarization on the charged state of the battery. When the index of polarization remains within the predetermined range, the calculating unit calculates the remaining capacity of the battery according to the terminal voltage of the battery, that is, the open-circuit voltage of the battery.