Effects of Pulsed—Current Discharge Waveforms on Lead—Acid Traction Cell Performance

Chopper-type controllers commonly used in electric vehicle propulsion systems impose pulsed-current discharge conditions on the battery that influence both its internal power losses and available energy. In order to optimize propulsion system design, those discharge parameters that affect battery performance must be understood and characterized. In a series of tests performed on Exide EV-106 and EE-IV lead-acid traction batteries, a range of operating values were examined for current pulse frequency, average current discharge rate and pulse-to-average current level ratio. For each test, one parameter was selected as the variable while the other two parameters were maintained at fixed levels. Constant-current discharges were periodically performed during each test to relate battery performance for equivalent pulsed and constant current discharge conditions. The results show that battery performance was independent of current pulse frequency and battery internal power losses varied directly with both the average current discharge rate and the pulse-to-average current ratio. The amp-hour capacity obtained with pulsed-current discharges was greater than that obtained with equivalent constant-current discharges due to the increase in battery temperature produced by the higher pulsed-current internal power losses. However, with pulsed-current discharging, battery output power and available energy were always less than that obtained with equivalent constant-current discharging.