Development of a valve-regulated lead−acid battery with thin tubular positive plates for improved specific energy and optimization for low charge-factor operation

An overview of the design and development of a valve-regulated lead–acid (VRLA) battery with thin tubular plates is presented. Substantially improved specific energy in driving-cycle tests shows how the strategy of increasing the number of plate couples through the production of plates with component thicknesses that are 50% of those for existing technology plates is effective in meeting the requirements of the target application. Exploring the possibilities for removing inactive materials shows how reducing spine material to an extent limited to maintenance of an acceptable metal/active-material surface ratio (‘gamma’ value) by using an elliptical spine is effective, but that further reductions impair cell performance on cycling. Matching recharge characteristics with cell design and controlled initial electrolyte of the cells is discussed in terms of the influence of the oxygen-recombination rate on the recharge response. Changes during stable operation are illustrated in terms of charge response data during long cycle-life with 80% depth-of-discharge and a low, overcharge, viz., 4% C5. With an appropriate alloy, thin spines remain intact after more than 1000 cycles of service. Growth and non-penetrating corrosion rates are low for the optimized operating conditions.