The influence of fast charging on the performance of VRLA batteries

A valve regulated battery (VRLA) with thin tubular electrodes combines the endurance of robust positive tubular electrodes and the enhanced power properties of very thin electrodes. Fast charging is essential for many applications and it can compensate the lower energy density of lead-acid batteries. Thin tubular electrodes VRLA batteries were cycle life tested and influences of two charging regimes were investigated. A comparison is made between a newly developed fast charging regime with current step-down and a conventional charging regime as regards battery life and performance. The fast charging procedure was beneficial for the cycle life; however, associated beneficial effects were reduced by certain drawbacks. A measuring method was developed for analysing the current distribution over the electrodes at high and low currents and results are presented in this paper. Post-mortem battery analyses were carried out to determine the dominating degradation effects. The differences in the degradation effects caused by the charging regimes are discussed. The paper concentrates on the newly developed fast charging regime and compares the influence of the charging regime on ageing mechanisms of the VRLA batteries with tubular electrodes as opposed to a conventional charging regime.