Capacity predictions for lead/acid battery plates having conductive additives

In this paper, we predict the capacity of positive plates having conductive particles mixed into its paste. Computer models previously reported are used to make these predictions. The models use a few physical parameters to predict capacity. The most important of these parameters is the critical volume fraction. This parameter provides the maximum amount of active material that can be discharged before the pasteʹs conductivity limits the reaction. We estimate the critical volume fraction for plates containing different size conductive particles using the conductivity model. These results are then used in the capacity model to predict cell performance. Conductive particles improve low rate capacity and, on a per weight basis, can improve cell capacity at higher rates. The model predicts that the addition of 34% by volume of a conductive particle 20 μm in diameter will increase the capacity from 25 to over 60% of the stoichiometric capacity at 1 h rate. We compare the predicted performance of plates with conductive particles to other plates having no additives or non-conductive additives. A number of conductive particles were tested in an attempt to validate the model, but all proved to be unstable in the positive plateʹs oxidizing environment.