About 10 years have passed since Yuasa began selling 30-3000Ah VRLA storage batteries designed for a life of 10 years. Results of accelerated life tests and field tests on these storage batteries demonstrated that they would attain their designed life spans. They also ascertained that failure in these storage batteries is caused mainly by corrosion of positive plate grids. Recently there has been a demand for smaller and lighter VRLA storage batteries with longer lives, to which we responded by mitigating failure causes to develop batteries with about 20% smaller specific volume and about 20% reduced mass over preexisting storage batteries, and a design life of 15 years. To extend life we used a highly corrosion-resistant grid alloy in the positive plates, and used the expanded method to manufacture grids so that corrosion will occur evenly throughout instead of along grain boundaries. Use of the expanded method for making both positive and negative plates made it possible to reduce both the size and weight of batteries. These storage batteries also permit the use of manufacturing methods and battery structures that raise productivity. There are three storage battery capacities of 200, 300, and 500Ah, and their configuration is such that capacities of over 500Ah can be obtained by connecting these three types in parallel to the desired capacity. This paper discusses these newly developed storage batteries.
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