Analysis of the partial charge reactions within a standby VRLA battery leading to an understanding of intermittent charging techniques

Constant potential charging, either with a single voltage or with two voltage levels, is by far the most common float charging strategy. It is, however, a compromise since the voltage levels must be selected in order to both recharge and compensate for any self-discharge reactions and also to minimise the degree of positive grid corrosion, the usual failure mode of the battery under stationary operating conditions. Intermittent charging reduces overcharge and offers advantages for high temperature operation; however, the major risk is undercharge of the battery particularly of the negative electrode. This paper, by qualitative and quantitative consideration of the main electrochemical and chemical reactions in a valve-regulated lead-acid battery, attempts to estimate the gains and also the risks that could be expected by employing an intermittent charging technique that minimises the overcharge whilst maintaining the battery in a full state of charge.