Marina put in 3 brand new marine batteries just before end of season last year. They have disconnected the positive sides but left negatives connected and the batteries in their holders over winter on the boat. Boat was shrink wrapped and kept outdoors. What should I do, if anything, to the batteries so whe she goes in the water, they fire the engines up?
If they are maintenance batteries, you should pull the top caps off and make sure they have enough water in them. If they are low, add distilled water only to them. Also in the winter I never leave my batteries in the boat outside. You should bring them into the basement and set them on a block of wood or something. You never leave a battery sitting directly on the concrete, this will kill the battery fast. Then in spring I trickle charge my batteries to get the surface charge back to the 12.3-12.5 volt range so I know they are charged.