The Lead Calcium Battery. Part 4. Comparison of Lead Calcium and Lead Antimony Cells in Float

摘要

Four small portable lead acid cells were tested in a float cycle routine. Three of these cells had lead calcium alloy and one had lead antimony alloy in the positive grids. Cells with the lead calcium alloy positive grids failed early in the test accompanied by excessive softening of the positive active material. The presence of antimony in the positive grid caused depolarization of the positive plate in the floating cell, as well as the usual depolarization of the negative on overcharge. The active material of the antimonial cell remained firm for the duration of the tests. X-ray diffraction showed that the antimonial cell's positive plate contained more alpha PbO2 than the calcium cells, both before and after testing. Electron microscopic examination of the positive active material showed that the antimonial cell contained much prismatic material with many intricate clusters of complex crystals. The failed calcium cells showed only nondescript nodular PbO2 particles. The stability of the paste is believed to be related to the morphology of these particles. The presence of antimony in the positive grid caused the prismatic crystallization of the active material and promoted formation of alpha PbO2 because this was the only known difference in the two kinds of cell.