This article presents a shrinking core model for the discharge of porous lead particle at the negative electrode of a lead-acid battery by considering the reaction in a separate particle of the solid matrix. The model relates the shrinking unreacted lead core with the maximum amount of active material that can be reacted before termination of the discharge process due to poorly soluble low-conducting product. The developed model equations also incorporate the effect of double-layer capacitance and a dissolution-precipitation mechanism on the discharge process. The expressions for evaluating concentration and potential distributions as functions of time and distance are presented in three different models of a porous lead particle. For the simple case, equations are solved to achieve analytical expressions and where the coupled potential and concentration gradients with dissolution-precipitation mechanism are taken into account; the numerical method of lines is utilized to study the discharge behavior. The simulation outcomes are in good agreement when compared with the experimental data for discharge. (c) 2005 Elsevier B.V. All rights reserved.