Performance measurement and reliability of VRLA batteries

This paper provides a brief review and the level of understanding of some of the aspects of VRLA battery technology which determine performance and are potentially life limiting. It underlines the complex interrelationships involved and highlights their impact in narrowing the optimal “window” for VRLA cell design, process, and application. It describes how the search for a suitable technology to allow determination of the “state of health” of VRLA cells and batteries has resulted in the largest published capacity performance data base ever created for any type of industrial stationary lead acid battery. It then presents the results of actual discharge capacity tests on more than 24000 VRLA cells, describes the extent of premature failures discovered, the obvious implications on VRLA battery reliability, and the success of conductance and impedance techniques in detecting cell failure. Finally it urges aggressive pursuit of teardown diagnostics, which will be needed for proper understanding of failure modes in order to develop appropriate correctives in cell design and application