Temperature-dependent formation of vertical concentration gradients in lead-acid-batteries under pSoC operation - Part 2: Sulfate analysis

Flooded lead acid batteries that had been cycled under micro-hybrid conditions at −5 °C, 3 °C, 27 °C and 60 °C were torn down and investigated by scanning electron microscopy (SEM) and sulfate analysis, both on the surface and in the bulk. The results are correlated with acid density measurements that have been published earlier [10]. As a result, it is confirmed that the extent of concentration gradients in flooded lead-acid batteries (i.e. acid stratification) is strongly dependent from temperature. Locally higher acid concentrations at stratification will be consumed by local sulfation of negative active mass during partial state of charge cycling causing premature aging of these plate areas.