Progress in lead–acid automotive batteries and their separators in Japan
The types and features of automotive lead–acid batteries are shown in Table 1. The specifications for the battery have been modified in accordance with the trend towards MF batteries. For example, the grid alloy has been changed progressively from an antimony alloy to a low-antimony alloy, to a hybrid and, presently, to a calcium alloy in order to reduce water losses during charging. The grid-manufacturing process for calcium alloys has also been changed from the conventional casting method to the expanding method. With expanded grids, the positive active-material can fall out more readily than with the cast-type. Thus, a pocket-type separator is required (Fig. 1).