1. Field of the Invention
The present invention is concerned with improvements in or relating to a lead storage battery.
2. Prior Art
Lead storage batteries are placed in an unchargeable state upon permitted to stand for an extended prior of time or after overdischarging. In order to avoid this, various designs have heretofore been conceived for grid alloys for lead batteries or grid/active substance interfaces. For instance, it has been proposed to reduce or limit self discharge by reducing the content of Sb in their grid plates or use Pb/Ca base alloys as Sb-free alloys.
In order to improve the performance of lead storage batteries upon left overdischarged, it has also been known in the art to add alkali ions to electrolytes, increase the Sn content of grid alloys or apply Sn or Pb/Sn plating to the surfaces of grids.
However, some difficulties are involved in increasing the Sn content of grid alloys or applying Sn or Pb/Sn plating to the surfaces of grids, thereby improving the performance of lead storage batteries upon left overdischarged. That is, an increase in the Sn content of grid alloys leads to a remarkable rise in the cost. Problems with plating are that during formation or charging, deposits liberate Sn and disintegrate, thus producing an adverse influecne upon the performance of lead storage batteries upon left overdischarged, or the liberated Sn is dendritically deposited on cathodic plates, thus causing a through short circuit with respect to anodic plates. This is also true of the formation of alloy layers on the surfaces of collectors by dipping.
Lead storage batteries are made unchargeable especially when the specific gravity of sulfuric acid in electrolytes is 1.050 or less while they are permitted to stand. This may be avoided by increasing the concentration or weight of sulfuric acid. However, an increase in the concentration of sulfuric acid has an adverse influence upon the performance of cathodes and, particularly, reduces the service life of the batteries. An increase in the weight of sulfuric acid, on the other hand, entails an increase in the weight of the batteries. In any case, there is a limitation as to industrial practicality.