Long lifetime large-sized VRLA batteries for telecommunications

This paper describes large-capacity, long-life valve regulated lead acid (VRLA) batteries which were introduced in March 1997. NTT has mainly installed these VRLA batteries as back-up energy sources in telecommunications systems in central office buildings. The nominal voltage these VRLA batteries is 2 V, and the 10-hour discharge rate capacity ranges from 200 Ah to 3000 Ah. Their lifetime is more than 15 years at an average ambient temperature of 25/spl deg/C, and at a neat charge voltage of 2.23 V. As these VRLA batteries require less space than the present flooded lead acid batteries, it is better to replace these other batteries with the new ones. Failure does not occur even if the installed battery is vibrated horizontally at 1.2 G, or vertically at 0.6 G. These batteries can function in places where earthquakes frequently occur. As the VRLA batteries are produced in an automated factory, they are cheaper, and it is possible to reduce the investment in facilities.