A novel microprocessor-based ferroresonant battery charger for electric vehicles

The paper covers the design and testing of a microprocessor-based ferroresonant battery charger. The power delivery section of the charger is a ferroresonant transformer with a rectified output that produces 150 VDC at 30 A. The charger utilizes gassing point detection to determine when to terminate a charge on a set of batteries. The control section of the battery charger periodically places a resistive load across the battery under charge that allows this change in resistance to be detected. A microprocessor controls the timing and executes the gating of the needed switches in the circuit, and then gathers and analyzes data from the monitor circuit. The charger monitor circuit measures the voltage drop across the battery, which is proportional to the battery internal resistance, when the load is introduced. Test results indicate that a ferroresonant transformer makes an excellent base for the power delivery section of a high voltage battery charger.