I have a pair of 4-year old group 31 AGM batteries for my house bank charged by a 3-way smart regulator and 150-amp alternator. I monitor the bank with a Link 10. Up until this year I had no real issues with the health of my batteries. They would show between 12.6 and 12.8 when fully charged and charge between 13.2 and 14.2 V. This year, however, they act totally different. When fully charged, I can only get about 12.2 - 12.4 V (they may be at 12.6 for about 5 mins. before dropping off). The usually charging cycle is that they start out accepting 13.2 V and 45 - 50 Amps. This will last for about 1/2 hour where the amps slowly decrease and volts increase to 14.2. I believe this is normal behavior. However, once the volts reach 14.2 and the amps decrease to 0 I start to get negative amp readings and the volts remain at 14.2. I never seem to go into float mode. Once fully charged, I can only get about 4 hours of useful charge out of the batteries under a "heavy load" (7 - 10 Amps) before the voltage drops down to about 11.6. This load includes autopilot, chartplotter, and refridge. I also notice under no-load conditions (everything turned off), I see about 1 amp discharge. I suspect that I have a shorted cell in one of the batteries, but I would like to get some other opinions. Thanks for the help, Les Murray s/v Ceilidh '86 C-36 #560