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Boat Battery Power

When you need battery power, you just need it. Period. Whether cranking the engine to a start or checking a position off the GPS, battery power is not just the difference between getting back before nightfall when the wind dies. Nowadays, it's a significant component of sailing, providing the juice for everything from the autopilot to the on-board computer to the refrigerator and, even, for the 12-volt blender. Thank goodness for those rectangular blocks residing under the sole or settee.

Here's a quick review of the types of batteries available, as well as a few tips on proper maintenance for today's state-of-the-art battery.

When considering battery power for your boat, you'll need. to determine amount of high cranking amperage required for starting and amount of house power, or other sailboat power needs?

Which battery should I choose?
Determine your

*Use in combination. Consult dealer for more information.
NOTE: Always be sure that replacement battery CA and CCA meet the minimum engine requirements.

Starting batteries need to deliver high cranking amperage in short bursts, time and time again. To start an engine, power is drawn off the surface of the battery plates. So starting batteries with many plates will deliver more power (due to increased plate surface area) than batteries with only a few plates. Once started, the engine's charging system takes over and recharges the battery as the engine runs.

What's happening inside a lead-acid battery to produce the power? The lead grids direct current to the terminals. These grids are pasted with two different kinds of active material, forming plates of positive or negative potential. Either the positive- or negative-pasted plates are inserted into envelope separators (to reduce the risk of internal shorts), and then welded and inserted into the battery case, positive to negative. The case is flooded with electrolyte, and then the cover is sealed to the case. Finally, the battery is charged. When the battery is called upon to deliver power, the electrolyte reacts with the active material on the plates creating an electric current. This current is directed through the grids to the battery terminals.

The popular gel cell battery is constructed much the same way as typical flooded batteries. The difference is that instead of a liquid-acid electrolyte, gel batteries are vacuum-filled with a thixotropic gel electrolyte, which is the consistency of candle wax.

In contrast to the quick surge of power required for engine starting, auxiliary loads for other boat needs are smaller amounts of current delivered over longer periods of time. Deep cycling refers to the a battery's ability to deep discharge and recharge repeatedly. This power comes from deep within the plate, not merely off the surface. A starting battery used for an auxiliary load will fail in short order because it simply doesn't have the reserve capacity to handle deep cycling. For these auxiliary loads, you need a battery that is specifically designed for deep-cycle service.

Deep-cycle batteries have thick, heavy-duty grids and plates, enabling them to draw more power over a longer period of time. They generally produce enough cranking amperage for marine starting.

But do you really need two different batteries? Not always. If your starting requirement is moderate or heavy but your auxiliary power requirements are light, a starting battery may contain all the reserve capacity you need. On the other hand, if your starting requirement is moderate but you need a great deal of reserve power, a deep-cycle battery may be able to handle both jobs.

But don't make your decision just yet. There's a new kid on the block. Many manufacturers have introduced dual-purpose cycling/starting batteries. These batteries have been designed as an alternative solution to the two-battery dilemma. They provide good cranking amperage for starting and also deliver sufficient deep-cycle reserve power for running auxiliary electronics and gear.

Another type which has made quite a name for itself in the 1990s is the gel battery. Gel batteries are gaining popularity because of their safety features and longer life. These batteries are leakproof and spillproof, even if the case is punctured. They are completely sealed, eliminating the need to add water. They can be installed at severe tilt angles, although upside-down installation is not recommended. They can even be used under water. Gel batteries are ideal for both starting and deep-cycle power.

Which battery is right for you? That depends on your power requirements. By determining the starting and cycling usage, you can choose the most dependable and cost-effective battery solution (see sidebar). But remember that replacement battery marine cranking amps (MCA) and cold cranking amps (CCA) must meet the minimum requirements for your engine.

Since 1946, East Penn Manufacturing Co. has produced a range of batteries under the Deka brand name. For more information about Deka batteries, contact the East Penn Manufacturing hotline at (610) 682-4231, or visit their Web site at:

Taking Care of the Battery

Correct battery care can mean a long service life. Most starting batteries and all gel batteries are considered maintenance-free. That means they have no vent caps. They experience minimal gassing and are hermetically sealed. There is never a need to add water. (Never attempt to add water to a sealed battery. Opening the battery will dry out the electrolyte and void the warranty.)

Deep-cycle and dual-purpose batteries will require some maintenance. As the battery provides deep-cycle power, it releases oxygen and hydrogen gases into the atmosphere. This needs to be replaced periodically by uncovering the vents on top of the battery and adding water to the electrolyte reservoir. Be sure to follow the manufacturer's recommended procedures because under- or over-watering can limit your battery's service life.


Charging is critical to the extended life of the battery. Be sure to follow all instructions provided on your battery charger. Gel batteries have special charging requirements and should only be charged with a reliable, temperature-compensating, voltage-regulated charger. Never use a trickle charger to recharge a gel battery.

Be careful to never overcharge a gel battery. Overcharging any battery will cause it to gas and lose moisture. Gel batteries are designed with one-way vents to release gas in case of overcharging. But because gel batteries are sealed, there is no way to replace this water if it is lost into the atmosphere. Follow the manufacturer's charging instructions closely.

Always wear eye protection when working on or near batteries. Be sure to ventilate the battery area. Dangerous hydrogen gas will collect in enclosed spaces around the batteries. The smallest spark could cause a dangerous explosion.

In addition to watering and charging, it's important to keep batteries and cables clean and corrosion-free. Corrosion protection spray, terminal protectors and battery cleaners are available from battery manufacturers.

East Penn Manufr. is offline  
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