Schedule a demo to enter to win free SeaKits Essentials


Batteries: Keep On Charging


It’s that little box that keeps the whole show running. Show it the respect it deserves with these tips.

Load Testing Your Batteries

On a boat, the easiest way to apply enough load to a battery for a meaningful test is to use the starter motor on the engine as the load. Disconnect the ignition coil, if yours is a gas engine, so the engine won’t start up, connect your voltmeter to the battery, and have a friend crank the engine. If the voltage falls below 9.6 volts, you need a new battery.

— Ed Sherman (The 12-Volt Bible For Boats)

It Won’t Stop Your Heart, But …

Direct current (DC) might be less likely to shock you than alternating current (AC), but there’s a lot more to safety than not getting shocked. DC sparks around charging batteries can cause an explosion. Battery electrolyte is made from sulfuric acid, which can cause severe burns or blindness. DC systems are relatively safe, but still demand your respect and caution.

— E.S.

Just Add Water … Carefully!

When topping off lead-acid batteries (wet cells), use a turkey baster to put the right amount of water perfectly into the holes on top of each cell. The acid may ruin the baster but they are cheap.

— John & Susan Roberts (Why Didn’t I Think Of That?)

Charged Up!

A charged battery can’t freeze, and a frozen battery won’t hold a charge. Keep your battery working over the winter with a marine, properly regulated charger.

— Chris Landers

Battery Grease

Battery terminals and connections need to maintain a good contact for trouble-free operation. Disconnect and clean each contact point, then apply silicone grease, which seals out moisture and helps prevent corrosion on your reconnected terminals, cables, and wires, ensuring a more reliable battery bank.

— Jim Favors

Don’t Let Your Batteries Go Boom

Batteries do go boom from time to time. Explosions involve two things: hydrogen gas and a spark. Hydrogen is the lightest of the elements, so it will disperse quickly if released into a ventilated space. But an explosion could still happen if the electrolyte levels get so low that the plates are no longer covered or, if the vent is clogged, allowing hydrogen to build up. So, be sure your deep-cycle batteries are in a well-ventilated space, check the electrolyte levels regularly, charge it using a marine charger with a regulator, keep grease and other contaminants away from the vents, and watch out for bulges in the battery case, which indicate a buildup of hydrogen gas.

— BoatUS Seaworthy Editors

Bake Those Battery Boxes

Spread a layer of baking soda in your battery boxes before installing the batteries. If the electrolyte spills, the baking soda will help neutralize the sulfuric acid.

— J. & S. Roberts

BoatUS Editors

Contributor, BoatUS Magazine