Discharge behaviour of lead-acid batteries with high cycle life

摘要

Two different types of batteries were studied: (i) cells with tubular lead dioxide electrodes and (ii) compressed cells with flat pasted electrodes. The work comprised experimental determination of input parameters for mathematical models, numerical solutions of derived model equations and experimental validation. It has been found that the discharge behaviour of lead-acid batteries with tubular positive electrodes can be well described by a one-dimensional model with the lead dioxide electrode concentrically placed in a cylindrical lead electrode. The effects of the tube envelope have to be considered in the model in such a way that the discharge process of the lead dioxide in the pores of the envelope can be included. This can be achieved by a macrohomogeneous approach for the envelope region, an intrinsic Peukert equation that takes into account the current constriction in the envelope pores and electrode kinetics with a volumetric exchange current density that varies exponentially with the local acid concentration. A more accurate description of the current density distribution in cells with tubular lead dioxide electrodes was achieved by a two-dimensional model for a cell with tubular positive plates between flat pasted negatives. The utilization of the lead dioxide is, to a large extent, governed by the tube envelope and it is more accurate to apply a one-dimensional model on a cell with positive tube envelopes compared to a cell with lead dioxide electrodes without envelope. A mathematical model was derived and applied on a compressed lead-acid cell. The model can be used as a valuable tool for optimizing the design of compressed lead-acid cells to meet high requirements on combined high cycle life and discharge capacity. Features that together with a relatively low production cost make this battery concept more feasible for applications in electric cars compared to cells with tubular electrodes. 80 refs, 32 figs