Went to the boat last week and found the house bank dead - I'd left something on (obviously). Bank of 2x Group 31s was down to 4 volts! Clipped on the charger, but it wouldn't pick up the charge. Brought the batteries home and managed to get them to charge individually, but the capacity is way down on both of them. They're rated for 110 Ah, but are only delivering about 60-70 to my tester. Tester draws 6 amps and times how long it takes to pull them down to 11 volts. I'm open to suggestions, but am suspecting I'll be shopping for new batteries in the Spring.