Impact of grid corrosion in valve regulated lead-acid battery on standby float service

Grid corrosion and dry out are among the main failure modes in valve regulated lead-acid (VRLA) secondary cells. This paper deals with grid growth resulting from corrosion and its effect on the failure of lead-acid cells. Accelerated test data at elevated temperatures are presented and compared for both valve regulated and flooded lead-acid cells. The data is primarily for pasted plates made from the lead-calcium family of grid alloys, with or without tin as the additional alloying element. Effect of acid gravity higher than equivalent flooded cells, a key design feature in VRLA cells, is quantified for the first time. Grid growth, a direct result of grid corrosion, affects capacity and service life. Within the applicable temperature range an Arrhenius relationship between grid growth and temperature enables prediction of service life at room temperature. Effect of positive plate polarization and acid concentration have been quantified; both affect grid growth and hence the relative life. Similarity in the growth characteristics is found for the alloy containing tin as the ternary component when compared to the binary lead-calcium alloy. For VRLA products, tight retention of the cell element improves longevity on float and endurance in cycle service