The ONLY thing I have ever seen that actually works is Hawkers (The old KW, Westinghouse battery co.) Life Plus series chargers. The reason they do work is they use a hi frequency PWM type charge. This causes far less heat generation during the charge cycle. In the long run, this helps the battery last longer and, when cycled to 80% discharge properly, will significantly increase battery life well beyond the 8yr. mfg. design spec. The Life Plus also uses about 40% LESS A/C power to operate. The Mfg. is confident enough to extend the warranty of its batteries to a full 6 years. In the late 80's they actually went to 7yrs. for a short time.