Marine Batteries

In this modern world you have more and more choices when you go out to purchase items for your boat. There was a time when the only battery in a boat was the “wet cell” type. Now, there are “dry cell” and “gel cell” batteries, just to name a few. The wet cell battery is still the most common battery on a boat.

There are a few things that you should know about your wet cell battery. First, the battery in your engine compartment gives off hydrogen gas. The good news is that the amount of hydrogen gas given off by your boat's battery under "normal" circumstances is minimal.

Hydrogen gas is lighter than air and highly flammable (explosive). Usually, the low levels of hydrogen gas escaping from your battery are dissipated before there is enough accumulation to present a danger. However, in the event of a "low water" level and/or "excessive current flow" through the battery, the volume of hydrogen gas may increase. Therein lies a potential problem.

Low water is an avoidable problem solved by performing routine maintenance. Excessive current flow can come from a malfunctioning battery charger or from an exceptionally heavy electrical load on the battery. In either case, when one of those things occurs, the level of hydrogen gas emitted may exceed a safe level.

A heavy electrical load can be the result of a few different things. The most common thing is known as “hard cranking.” That’s when your engine won’t start and you keep the starter engaged for a long period of time. The high current for extended periods can cause your battery to emit more hydrogen than normal.

If the water level in the battery is low during “hard cranking,” the amount of hydrogen is increased even more. All it takes is a spark or an open flame to ignite that hydrogen. Arcing and sparking can result as your wiring heats up.

A short circuit is another source of a “heavy electrical load” on your battery. A current as a result of a short circuit produces the highest current that your battery will ever experience. In this case, the “hot” (+) and the “ground” (-) terminals (battery posts) are connected by a cable or a piece of “gear adrift” in your engine compartment. That’s why keeping your battery covered is so important.

The next thing to know is what "locked rotor" current means. The term "locked rotor" refers to an electric motor that is energized with electricity, but is prevented from turning due to a malfunction. The current flowing through an electric motor in a "locked rotor" situation is some multiple of its maximum rated current. The excessive rate of current causes a lot of heat.

The last thing is what a "neutral safety switch" is. On most cars, there is a switch that prevents starting your engine in any position but "park" or "neutral." The switch is connected to the gear shift lever and prevents starting your car while it is in gear. Most boats have a "neutral safety switch" also. That prevents the “locked rotor” situation.

Did you know about all of these battery issues? The more you know, the safer you’ll be!

Until next time, I wish you clear skies, fair winds, and calm seas!