Very rapid recharging of large VRLA cells

The high rate charge behavior of 2V 1000 Ah VRLA cells, subsequent to a full 12 minute rate discharge, is described. Charging rates with current equal to I/sub 10/, 3I/sub 10/ and 7I/sub 10/ were evaluated for their influence on cell and connector temperatures and gas evolution. The result show that high rate charging, at the 3I/sub 10/ rate, can restore the UPS autonomy time within 1 hour without excessive cell heating and gas emission. The thermal imaging of the cells during the discharge and charge event allowed to detect the sites of maximum heating and heat transfer effects.