ANALYSIS OF THE CONDITIONS THAT PROMOTE PASSIVATION ON CALCIUM ALLOY GRIDS IN LEAD-ACID-BATTERIES

It is well known that calcium-alloy grids used in positive plates in lead/acid batteries often exhibit passivation phenomena. Such phenomena do not always appear for a given set of conditions. An investigation has been conducted of the conditions giving rise to grid passivation. As a result, it has been concluded that high potential and low acid concentration are the major factors promoting an increase in impedance. In addition, cell design variables such as the acid/active-material ratio and operational conditions such as over-discharge and squeeze discharge with a very low-rate current may also give rise to passivation. It has been found that a new surface-treatment technology involving application of tin-rich and/or an antimony-rich, thin layer on the grid surface is very effective in overcoming this disadvantageous characteristic of calcium-alloy grids.