OPERATIONAL EXPERIENCE WITH VALVE-REGULATED LEAD-ACID-BATTERIES

Valve-regulated lead/acid (VRLA) batteries provide the very high level s of reliability required for standby service. Various types are avail able, in particular cells with lead-calcium-tin alloy grids and absorp tive glass-mat (AGM) separators; cells with pure lead grids and AGM se parators; cells with tubular plates and gelled electrolyte, These cell types are subject to a number of factors that affect durability in fl oat service. These factors are reviewed and it is shown that grid corr osion is the usual failure mode. As a result, practical cell and batte ry designs need to ensure all other potential causes of failure are ei ther eliminated or occur at a slower rate. Test results based on therm al acceleration are presented and have been correlated with real-time tests. The attainment of satisfactory product life under practical con ditions is fully demonstrated. Techniques for battery monitoring and s urveillance also have a strong impact on reliability and can be used t o define the best strategy for replacement. The overall result is bett er levels of protection which, together with precise specification and careful consideration of the service conditions, enable user requirem ents to be met in full.