Life and capacity improvements in lead acid batteries through metal control additives

Metal impurities can be particularly detrimental in valve regulated lead acid batteries (VRLA) operating on the oxygen recombination principal. A number of metal impurities can exert a deleterious effect on the performance of VRLA batteries by affecting one of more of the performance requirements of the VRLA batteries such as by increasing oxygen evolution at the positive electrode, increasing hydrogen evolution at the negative electrode, inhibiting full recharge of the negative electrode, increasing negative plate self discharge and increasing the amount of water lost by the battery in this electrolyte limited system. The control of these adverse effects has been approached through the use of metal control additives in the negative plate and in polymeric separators. Results are presented in both the negative active material and in different polymeric separators for the ES-A4 metal control additive which is capable of 99%+weight percent uptake of certain metals at both 8 and 38 weight percent sulfuric acid concentrations with less than 1% release. Results are presented showing the additive's low binding efficiency for trace amounts of soluble lead ion and it's superiority over other metal control approaches. Further results with metal control additives used in concert with porosity additive in the negative active material are reviewed to show enhanced electrolyte diffusion to the metal control additive resulting in a shift of equilibrium and rate to improved binding efficiency.