There are different metals in a lead battery than just lead. The lead “mixture” found in the plates consists of either Antimony-Antimony, Antimony-Calcium or Calcium-Calcium, depending on what best suits its purpose. The difference between Antimony and Calcium is that Antimony has a higher degree of water consumption. Calcium-Calcium batteries lose fluid at a rate of approximately 80% lower than Antimony batteries and have an even lower self-discharge rate.