The Use of an Experimental Design Approach to Investigate the Interactions of Additives used in the Making of the Negative Plate in Lead-acid Batteries
When a conventional starting, lighting and ignition (SLI) lead acid battery is exposed to a high rate partial state of charge (HRPSoC) cycling, it would experience a build-up of irreversible PbSO4 on the negative plate, resulting in capacity loss and electrode damage. The addition of certain graphites to the negative paste mix has proven to be successful in reducing this effect. This study looked at using statistical design of experimental (DoE) principles to observe interactions between two graphite types and a nanocarbon together with other additives, such as BaSO4 and Vanisperse, to a negative paste mixture. The response factors considered were in relation to their effect on the battery’s cold cranking ability (CCA) at –18 °C, the HRPSoC and its active material utilization. Typical flooded nominal 8 Ah test cells were assembled in a reverse ratio build,with three positive and two negative plates, with three types of added carbons (flake graphite, natural graphite and nanocarbon) added to the negative paste mixture at a two-level design. The study showed the usefulness of a statistical DoE approach in the effective use of additives that are included to the negative plate paste mixture, where there are interactions between the amounts of added carbon, BaSO4 and Vanisperse, with respect to the responses of CCA and HRPSoC, that do not necessarily act independently – based on their amounts – on the performance of the active material. The study also showed that there are correlations between certain response factors, such as the number of achievable cycles within a HRPSoC test sequence, and the type of added carbon.
Keywords: Pb-acid battery, Pb-plate, graphite, expanders, design of experiment
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