Low-temperature charging behaviour of lead-acid cells

Abstract

The effect of temperature on the charging behaviour of lead-acid cells was studied at a depth of discharge of ∼20% of their reserve capacity. As expected the charge acceptance rates dropped markedly at temperatures below 0°C. The ability to charge at these temperatures was limited by a precipitous increase in polarization at the negative plates which occurred immediately upon starting the charge. At −18°C the charge acceptance rates fell within a range of 20 to 40% of that observed at 25°C. The highest rates at −18°C were favoured where the charge followed a high-rate, low-temperature discharge, with a minimum time and temperature for the open circuit stand. We speculate that this is due to factors such as a small PbSO₄ crystal size and a non-equilibrium electrolyte concentration in the pores of the plates. Direct evidence for this is lacking, however, because of the need forin situ determination of the physical structure of the plates in the discharged condition.