The use of lead-tin alloys in VRLA batteries for extreme telecommunication applications

Pure lead VRLA technology has for many years provided long life and reliability in traditional telecommunication DC power systems. These systems are usually centrally located with the batteries housed under environmentally controlled conditions with rectifiers providing thermally compensated float voltage. As telecommunication technology evolves, the requirement for the traditional centralized facility is decreasing and the need for decentralized, street level, locations is increasing. Consequently the demands on the battery system have become more onerous. The design of the VRLA battery has had to be modified in order to cope with the changing performance requirements. In, particular the ability to withstand temperature extremes, regular deep cycling and periods of deep discharge has become a necessity for a successful telecommunication battery. This paper demonstrates that the inclusion of a small percentage of tin into the positive grid of pure lead VRLA products greatly enhances the products capability of meeting these increasingly demanding requirements. A reduction in float life by an increased rate of positive grid corrosion, however, has to be compensated for by modifying the grid design in order to achieve design life