Pulse charging of lead-acid traction cells. [300 Ah

Abstract

Pulse charging was investigated as a method of rapidly and efficiently charging 300-Ah lead-acid traction cells for an electric vehicle application. A wide range of charge pulse current square waveforms were investigated, and the results were compared to constant current charging at the time-averaged pulse current values. In addition, experiments were undertaken to define the effect of peak charge pulse current, peak discharge pulse current, duty cycle, and pulse frequency for a Romanov-type waveform. For each of the above methods the charge was terminated when either 10% of the charge pulse current produced gas or the cell temperature reached 120/sup 0/F. In order to explore ways to improve the energy and ampere-hour (amp-hour) efficiency of pulse charging in a limited study, two alternate methods of charging were compared. In method 1 the cell was pulsed throughout the entire charge. In method 2 the cell was initially charged at a constant current, and after the onset of gassing was switched to pulse charging. Experimental results indicate that, on the basis of amp-hour efficiency, pulse charging offered no significant advantage as a method of rapidly charging 300-Ah lead-acid traction cells when compared to constant-current charging at the time-average pulse current value. There were, however, some disadvantages of pulse charging, in particular, a decrease in charge amp-hour and energy efficiencies and an increase in cell electrolyte temperature. The constant-current charge method resulted in the best energy efficiency with no significant sacrifice of charge time or amp-hour output. 4 figures, 4 tables.