Real time VRLA life test or how a small difference can have big effects

Stationary lead acid batteries can experience temperature differences within a string especially when operated as 110 V or 480 V back-up batteries. In the present study the influence of a /spl sim/3/spl deg/C temperature difference on the corrosion induced capacity loss of VRLA monoblocs during 7 and 9 years of float operation in a 5 tier rack installation is reported. Corrosion sensitive VRLA monoblocs can have residual capacity values ranging all the way from 3% to 110% in the same string due the cumulative influence of such minor temperature differences. VRLA cells and monoblocs in which positive grid corrosion has been designed-out as main failure mode, show a much more robust performance under these adverse conditions.