High rate recharge of stationary VRLA batteries

The high rate charge behavior of 6 V 155 A h lead acid monoblocs of the VRLA type for stationary service, subsequent to a full discharge in 1 h to 1.60 Vpc, is described. Charging rates with an initial constant current equal to I10, 3I10, 7I10 and with constant voltage of 2.25 Vpc, resulting in a peak current of 22I10, were evaluated for their influence on the sites and magnitude of internal heating, speed of recharge and gas emission phenomena. The results indicate that recharge with an initial current in the 3I10 to 7I10 range and the maximum voltage limited to 2.25 Vpc appears to be a viable charging strategy. Full recharge can be achieved in 4–6 h with the temperature rise limited to 12°C above ambient and the gas evolution to an equivalent of 0.4 l per cell of a hydrogen–33% oxygen mixture. The thermal video imaging revealed that the loci of maximum internal heating reflect the IR drop and the heat loss through top lead and monobloc walls.