By Don Casey
Revised by BoatUS editors in April 2012
Don't let the "maintenance free" battery in your car lull you into complacency about the battery in your boat. Neglecting a marine battery is certain to shorten its life.
Get the most from your boat's batteries by following these guidelines:
- Keep idle batteries fully charged. Leaving a battery even partially discharged leads to sulfation and loss of capacity.
- Check the water level regularly. Top up as necessary to keep the level about 1/4" above the plates.
- Use only distilled water for topping up; trace minerals and/or chlorine in tap water really do shorten battery life.
- Fill cells after charging. If you fill them before, expansion during charging will pump electrolyte out on top of the battery, causing a corrosive mess and reducing the acid level inside the battery.
- Keep the top of the case clean and dry. Dampness, dirt, and acid on the battery case can create a circuit between the terminals that will drain the battery.
- Keep terminals and cable clamps corrosion-free. Use a wire brush to remove corrosion. Coat both terminal and clamp with petroleum jelly (not grease) to prevent future corrosion.