Video: Marine Battery Care & Feeding

In the accompanying video, New England Boating’s Tom Richardson walks you through the steps of making sure your batteries are in top shape for the boating season. If you don’t feel like watching, the steps are below in written form.



1.) Clean terminal posts and housing

Use some spray cleaner or WD40 to remove dust and dirt from the battery housing. Also apply cleaner to the terminal posts and use a wire brush or terminal post cleaner to remove rust and corrosion from the threads.


2.) Check electrolyte level (lead-acid batteries only)

Add distilled water to cover the battery’s internal plates if necessary. Replace port covers securely.


3.) Charge battery

Charge the battery overnight using a 3-stage charger.


4.) Test battery

Use a volt multimeter to test the voltage of the battery at rest (open circuit). When fully charged it should register above 12.4 volts. (You should also test the battery later under load to be sure it is functioning properly). Re-test the battery after 24 hours to see if it holds the charge. If your battery fails to hold a charge of around 12.4 volts, you may need to replace it. In general, marine batteries should be replaced every 4 or 5 years.


5.) Use nylon insert locknuts on your battery posts.

Do not rely on wingnuts, which can loosen over time.

Use nylon insert locknuts on your battery posts.

6.) Install properly

Install the battery in the boat, making sure it’s secured with straps or bands to limit motion. Attach the leads and use a socket wrench to tighten the terminal post nuts (use nylon-insert locknuts). Coat the posts and leads with dialectric grease and slip protective covers over the posts.

Test battery under load: Use only distilled water to top off the electrolyte level.

Use a volt multimeter to test the battery under load. With the engine in the water or hooked up to a water source, turn the ignition key. The meter should register no less than 9.6 volts as the engine turns over then return to resting charge of 12.4 or higher.