Status and results of ANL life evaluation of valve-regulated lead-acid load-leveling batteries

Argonne National Laboratory has developed and initiated a three-year life evaluation of both gelled-electrolyte and absorbed-electrolyte valve-regulated lead-acid (VRLA) battery technologies for deep-discharge applications. The objectives are (1) to use accelerated testing techniques to obtain data within 6 months on VRLA battery life expectancy, and (2) to determine VRLA battery life within a 2-3 year time period under temperature and depth-of-discharge (DOD) conditions that simulate those encountered in a utility load-leveling environment. The accelerated life test uses a matrix of operating conditions designed to increase the stress of known failure modes, thereby accelerating the mechanisms that cause battery end-of-life. The primary failure mode is expected to be active material changes caused by charge-discharge cycling (i.e., microstructural and morphological changes, sulfation, mass isolation, loss of surface area, loss of porosity, etc). The test matrix consists of four sets of operating conditions (80% and 100% DOD and 30{degree}C and 50{degree}C temperature), which include the stress factors to accelerate failure.