Development of long-life small-capacity VRLA battery without dry-out failure in telecommunication application under high temperature environment

The authors have developed a long float service life small-capacity VRLA battery without dry-out failure for telecommunication applications. They previously reported the development of medium size (12 V 15-65 Ah at 20 hours rate), life expectancy of 13 years at 25 degree C, VRLA batteries in 1997 (1998). The batteries employed a new lead alloy grid and grid design which improved the corrosion resistance of a positive grid, while at same time they could reduce their float current at high temperature by the effect of new additives into the negative active mass. The authors have developed the advanced technologies, especially in the point of the suppression of dry-out failure, and applied them to small-capacity VRLA batteries, because dry-out failure is the most prominent for these small-capacity VRLA batteries. They studied the inhibition of increase of internal resistance even if much water was lost, and reported that AGM separator easily shrunk and lost compression to the plates after some amount of water loss, which caused the premature capacity loss in 1995. They employed both the new AGM separator and the new manufacturing method reported previously so as not to lose the initial high compression during operation in the small-capacity VRLA batteries. Furthermore the prevention of water loss in itself could be achieved by employing a new container plastic material with a low moisture permeability ratio. They provided 12 V 7 Ah (at 20 hours rate), 10 years expected life at 25 degree C, VRLA battery with these newly developed technologies