Processes involved in charging of discharged lead-acid battery electrodes by pulse methods: I. Qualitative analysis for flat negative electrodes

In general, a relatively large part of the PbSO4 of lead-acid battery electrode discharge products can be seen as particles at the end of the discharge and thus their reduction, on the negative electrode, or oxidation, on the positive electrode, must involve the dissolution of the Pb2+. In this paper, the processes occurring on flat negative electrodes during the galvanostatic charge transients are studied in detail, especially in relation to where and how much the PbSO4 and Pb2+ are reduced. The understanding of these processes is fundamental for the understanding of any pulse charging process. Thus, it is shown for a single discharge/charge cycle, that during the charging process a disruption of the PbSO4 film, giving rise to a continuous glued non-disrupted film and to a disrupted film attached by surface tension forces to the electrode surface can occur. Further, it is shown that the amount of disruption depends on the charging current conditions and it decreases with decreasing charging currents. It is also demonstrated that the reduction of the Pb2+ dissolved from the disrupted particles takes place simultaneously to the reduction of the non-disrupted glued part of the film. On the basis of these facts, it is finally shown, for the case of multiple discharge/charge cycles, how the charge associated with the disrupted film changes with cycling and why and how it is possible to determine the amount disrupted PbSO4 film formed.