Pasted positive plate of lead–acid battery: General analysis of discharge process

A general analysis of the discharge process of pasted positive plates of lead–acid batteries is presented. Two models are explored in order to understand qualitatively the phenomenon: a solid-state reaction model and a dissolution–precipitation reaction model. The two models are presented and related to two important phenomena: the existence, always during the discharge, of a reaction zone going from the surface to the bulk of the plate active material and the possibility, for low H2SO4 concentrations and high rates of discharge, of H2SO4 depletion, producing the reduction of the used active material. The influence of the rate of discharge and sulfuric acid concentration on potential versus charge curves during the discharge, on capacity and on plate resistance during the discharge transient, especially for very low discharge rate conditions are analyzed. Two equivalent plates from two different manufacturing technologies are tested. Both models, sometimes with the introduction of some modifications from traditional formulations, explain the different results found.