Development of long life VRLA for load leveling use

摘要

A load-leveling system is in demand for effective use of electric power supply to preserve the environment in Japan. This system stores up surplus electric power during nighttime and supplies electric power when demanded at daytime. A battery is considered to be suitable for this, but is required to have long cycle life such as 3000 cycles or calendar life of 10 years. We are now developing a new VRLA that has long cycle life for the load-leveling system. So far we have succeeded to realize the life of 1900 cycles with a 35 Ah class VRLA with the following means. 1) Charge acceptance of the negative plate in the VRLA has been improved by addition of carbon fiber additives, because these additives have been found to improve the electronic conductance between each negative active material particle. 2 ) Electrolyte stratification has been prevented by using a horizontal plate group design. 3 ) Excess recharging has been reduced for reduction of the positive grid corrosion from the conventional 15 % to 4 % against the discharge capacity.