Lifetime extension of valve regulated lead acid (VRLA) batteries under hybrid vehicle duty

This paper presents some of the results of a foresight vehicle link research project, exploring the possibility of lifetime extension of valve regulated lead acid (VRLA) batteries under hybrid-vehicle duty cycles. The work shows that by the addition of a second set of terminals to a commercially available spiral wound cell, during manufacture, it is possible to improve the cells performance to a degree whereby it can meet the needs of a hybrid-electric vehicle. It is then shown that by the periodic application of a simple conditioning routine the lifetime of a pack of these modified cells may be dramatically improved. Results from a long-term test of a pack of modified cells are presented outlining cell-to-cell variation and capacity loss. The paper gives an in depth analysis of the whole test series including comparisons of the VRLA results with those from the standard nickel metal hydride (NiMH) battery pack removed from the test vehicle and installed on the test bench.