Quantifying secondary reactions in VRLA batteries. What purity standards and other factors are necessary to prevent negative plate discharge?
In a VRLA cell with a fully developed oxygen cycle, the negative plates will suffer discharge during float service if their self-discharge rate is too high to be balanced by the corrosion rate of the positive grids. Positive grids have been developed with very low corrosion rates. However, there is little quantitative data available on negative plate self-discharge rates that are required to balance such low corrosion rates. This paper presents values measured from several different battery brands, American and European. The data shows clearly that some production batteries have high negative self-discharge rates that account for the observed tendency for self-discharge in service. Surprisingly, the data also shows that other brands have achieved extremely low self-discharge rates-low enough to be compatible with the best positive grids that the authors have tested. These results are very encouraging for VRLA technology and confirm that the principle can be realized. The focus now shifts to the practical issues: finding the source of the impurities that increase hydrogen evolution and weighing the cost and practicality of reducing them.
Correcting Inherent Imbalance And Consequent Failure Of Vrla Cells By The Use Of Catalysts
VRLA cells have been very successful in replacing flooded cells in long-life telecom and UPS applications. Much of this success is due to assumptions that VRLA cells will provide 20 years of service without the addition of water. However, despite the fact that these cells are often built to superior quality standards, their actual performance in service has been problematic, with persistent reports of early failures.
Hydrogen evolution on lead-tin alloys
Abstract The cathodic evolution of hydrogen from a series of lead-tin alloys (below 1.7% Sn) has been studied with a range of concentrations of aqueous sulphuri