Update on UPS battery life characteristics

A 1991 paper from C&D had reviewed the problem of large scale premature failure facing many UPS batteries at the time. It analyzed the failure modes and the causes for the premature failure of early designs. It also discussed the improvements to the design, already in place, to overcome the problems. Improved performance was predicted on the basis of accelerated tests that had progressed only partially forward. Completed data from the accelerated tests and more than ten years' field experience with these improved designs are reported here, vindicating the change. Also discussed are five years' field experience with a utility battery for frequency regulation-the PREPA battery, which is a massive and heavily cycled UPS battery. Valve regulated batteries, which had relatively less exposure at the time of the earlier paper, have since had a build up of experience; the authors' experience is discussed.