Your boat battery is one of the most important safety items aboard. Yes, I said “safety items”. That’s because it not only starts your engine, but also powers your VHF radio, pumps, and navigational gear. So you want—need—to make sure it’s rigged properly. And quite often, competent do-it-yourselfers make a mistake or two when rigging a boat battery that can be down-right dangerous.
Take the above picture, for example. This installation looks just fine on the surface, but in one way it’s incredibly unsafe. Can you spot the issue? The battery box is mounted in such a way that one side of the top is ever so slightly below deck level. If this boat eats a wave, when the water runs aft it could swamp the battery and over-top the terminals. That’ll short out the entire system, and shut you down cold. Now, let’s remember, in this situation (considering the boat just took a wave over the bow) it’s probably very rough and nasty. This is exactly the worst time to lose power. If the next wave turns your boat broadside, the third could completely swamp or roll you. Meanwhile, since you’ve lost all juice, you can’t call for help on the radio. Bad stuff.
Batteries should always be located above deck level, so that even if your bilges become flooded, you have plenty of time to call for help. Another major error people make when installing a battery? They put in far aft, against the transom, off the center-line, without taking weight into consideration. Located high (above deck level) and all the way aft, the weight of a boat battery can have a huge impact on how your boat sits and runs on the water. So be sure to compensate for the weight; place it on the opposite side of the boat across from the fuel tank, if the tank is off-center, for example. Or locate other weighty gear on the other side of the boat.
Some other common examples of boat battery installation fails include not securing the box to the deck, not putting a top on the box, or forgetting about the box entirely; failing to cover the terminals; installing a battery box before measuring to be sure the cables reach; and installing the battery in a compartment that isn’t vented. Then, of course, there are maintenance issues that also need to be kept in mind. Be sure the terminals and connections remain clean (a thin coat of petroleum jelly helps), make sure fluids are at proper levels, and put the battery on a trickle-charge during long lay-ups between uses. Remember: that battery is a safety device. Make sure it’s installed and maintained properly, or you and your boat could be at risk.