I bought a boat in April. It has 3 batteries, split into 2 banks. From reading other posts I realized boat batteries weren't the "no maintenance" variety that are used in cars (hey, I'm a rookie!). They're EverStart Deep Cycle "Trolling" batteries.Since the boat was for sale since last July, nobody's done anything to the batteries for a year. I just had to add 1 pint of distilled water to each battery. Amazingly, they've worked pretty well for me for the last 3 months.Is there anything I can do other than just topping up the water?