BATTERY CAPACITY MEASUREMENT CIRCUIT

摘要

An electronic circuit and a method for accurately measuring intermittent current pulses supplied by a storage battery to energize a load. In the preferred embodiment, an analog integrator accumulates current pulses in response to a voltage drop across a sense resistor that is connected in series between the storage battery and the load. The voltage drop is proportional to the flow of current from the battery through the load. The output of the integrator is filtered with a low pass filter to block high frequency noise, and the output of the filter is coupled to an analog to digital (A/D) converter that transforms the filtered analog signal into a corresponding digital signal. The output of the A/D converter is supplied to a port of a processor. The processor provides a signal to actuate a reset switch coupled across the integrator. When closed at the end of each integration time period, this switch zeroes the output of the analog integrator. Additionally, the processor recalibrates the circuit at predefined time intervals to determine for leakage currents for improving the accuracy with which the measurement of the flow of current from the battery is determined. In the preferred embodiment, the processor samples the output of the A/D converter every 100 milliseconds. Typically, the calibration procedure is performed every 15 minutes (while the load is energized from an AC source). This measurement circuit is part of a battery management system that preferably also includes a charge circuit for recharging the battery.