Valve-regulated lead/acid batteries: they are not all the same!

It has become popular and widespread, both in symposia and battery magazine articles, to refer to valve-regulated lead/acid (VRLA) batteries as if they are a single entity and generic in nature. Sweeping conclusions have been drawn about the reliability and life of VRLA batteries but, usually, little is published alongside of these conclusions that can give the reader much insight into the nature of the alleged non-reliability, or indeed the failure modes associated with the apparent shortage of life. Consequently, there is a danger that the performance of VRLA batteries will become branded as a serious problem. The purpose of this paper is to present facts which demonstrate that VRLA batteries are most certainly not generic in nature. The batteries are designed differently, and they are manufactured in different ways from different materials. Moreover, the various producers make different claims with respect to the likely service-lives of VRLA batteries. When considered against this background, it should not be surprising that there is considerable variation in the life of VRLA batteries in their many and varied applications and environments. Nor should conclusions be drawn about all VRLA batteries by a consideration of a few.