A couple weeks ago, I wrote an article about on-board battery chargers that generated several e-mails to me asking questions about not only chargers but questions about the various types of marine batteries. So this week's article will deal with the various types of marine batteries and their particular marine applications.

Basically there are three types of batteries with specific marine applications. Apply the wrong battery to a particular marine need and you can have big problems. There are two primary types of marine batteries and a third type that that is sold but it can cause problems in certain situations.

The three types of marine batteries are deep-cycle, cranking and dual-purpose. The deep-cycle batteries are intended for applications that take power from the battery at a slow rate over extended periods. That would primarily include the boat's trolling battery and accessories like depth finders. They are generally used throughout the entire day and then are recharged.

The discharging over a day can be hard on battery plates so deep-cycle batteries have fewer but thicker plates and are built specifically to handle deep cycling. They can go from fully charged to almost being discharged to then being fully charged again numerous times without losing battery life. It can generally be charged/discharged/recharged several hundred times.

When purchasing a deep-cycle battery the buyer should check the reserve capacity. The reserve capacity tells you how long the battery can carry a load before needing a recharge. A bad deep-cycle battery can damage or degrade accessories like depth finders so always keep these batteries charged.

The second type of marine battery is the cranking battery. A boat's main engine requires a lot of power from the battery for a short period when being cranked. Cranking batteries have thinner and more lead plates which delivers more power than a battery with fewer plates. The motor's alternator will recharge the battery once the boat's motor is running.

When buying a cranking battery it is best to check your boat motor owner's manual to see what marine cranking amps are required. Then you should purchase a battery with at least that rating or more. One very important thing to remember when purchasing deep-cycle and cranking batteries is you should never substitute one for the other.

A third type of battery is available but not extremely popular and that is the dual-purpose battery. They are generally used when space prevents the boat owner from installing both cranking and a deep-cycle batteries. A dual-purpose battery is meant to be used for both cranking and deep-cycle applications. However, the dual-purpose battery generally does not start an engine as efficiently as a cranking battery and the dual-purpose will not survive charge and recharge cycles like the deed-cycle battery.

The internal design of marine batteries is further classified as to how the electrolytes are configured inside the battery. They are referred to a wet-cell, AGM or Gel batteries.

Most of us are very familiar with the wet-cell batteries which are widely used and have the majority of today's market. There are some disadvantages to the wet-cell battery design. The primary drawback is from the fact they are vented which requires periodic inspection and the adding of distilled water.

The primary advantages to the wet cell battery is it generally weighs less than the other types of batteries and the wet-cell battery can be recharged hundreds of times without damaging the battery. Wet-cell batteries are also cheaper than the other two types of batteries. Wet-cell batteries come in both cranking and deep-cycle designs.

The AGM battery has absorbent glass matting that is tightly packed between the battery's plates and that matting is saturated with electrolyte. That allows oxygen to recombine with hydrogen gas to replenish the battery's water content to avoid refilling. However if the AGM batteries are overcharged, the water cannot be replenished. They AGM batteries also tend to be heavier and more expensive.

Advantages of the AGM battery comes from the fact that they can be installed at any angle, they have a very slow discharge rate when not being used and they can be completely submersed under water without damage.

The third type of battery is the Gel battery. Like the AGM battery, they do not require that the water be replenished. They are resistant to overcharging and have a very low discharge rate when not being used. However like the AGM battery, they are more expensive and most importantly they may require a special charger when recharging.

In over forty years of personal boat ownership, the wet-cell batteries have served me well. However they do require some maintenance but when properly inspected and maintained, they along side an on-board battery charger will be the best ticket for most marine application. See you next week.

Outdoor columnist Bobby Peoples can be reached via e-mail at brpeoples@windstream.net.