Charging abuse-how well can a VRLA battery cope?

It is shown that the resistance of a valve regulated lead acid (VRLA) battery to overcharging can be quantified to a large degree. Two aspects are examined: measurement of the Tafel relationship of a cell, and thermal runaway testing. Practical implications of the tests results are seen in applications involving constant potential charging, and also those in which constant current charging is used. Another aspect of overcharging that is seldom examined is seen during normal float operation. If the recommended float voltage is higher than necessary, the float current will be elevated, thus accelerating positive grid corrosion, and possibly causing premature battery failure. The Tafel curve data are used to support ongoing work to optimize the float characteristics of VRLA batteries, most notably with respect to the correct choice of float voltage