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Understanding Marine Batteries

By Rich Johnson

In boating, one of the most important and least understood systems of your vessel has to be the electrical power source systems. Marine batteries! Marine batteries are the "heart" so to speak, of any sea-worthy platform as it pumps life giving electricity and current though the vessel. Obviously this is needed as the many electronics and other comforts of home on a boat need power to make them run. As usual, if the heart of any machine is not in tip-top shape and working to perfection, then things don’t get done. Marine batteries come in several kinds and sizes and as with most items associated with our recreational activity, you get what you pay for.

I called on a couple of my battery "experts," namely Wally Werner of Sea Coast Distributors (516-842-2338) and Frank Regan of Sea-Curity Systems (516-226-1616) of Lindenhurst. Both of these gentlemen made appearances on my television show for exactly this subject, marine batteries and here’s what I concluded from my conversations with them

CAR vs. BOAT. One of the most commonly asked questions I receive is, "can I use my car battery in my boat?" Well, this is one of the oldest misconceptions in the boating game and the truth is you can use a car battery for your boating needs, but it certainly won’t last very long!! Probably not even several trips!

The real truth of the matter? There is a big difference in the two with the first, being the location of the lead plates within the batteries. In a marine battery, they have taken the plates that cause electricity and elevated them so as the boat and battery bounce around, they don’t short out. Secondly, they use a special bonding process, so as things bounce and fall around inside the battery, things stay put. If you use a car battery, with the bouncing a boat and battery, take it would soon die out on you and the last thing we want is a call to Sea Tow.

WHAT KINDS? There are three different kinds of marine batteries for you to choose from. Cranking Amp, Deep Cycle and Gel Cell batteries. First is the Cranking Amp battery. This battery is used mainly for starting. The cranking amp battery uses many plates, close together within the battery, to allow current to flow very quickly through the battery for quick, powerful starting power and quicker battery recharging too.

Next is the Deep Cycle battery. The deep cycle is used for running your accessories or allowing the electronics to remain on while the engine is shut down, for example when on the drift while fishing. The plates within the Deep Cycle battery are spaced further apart and are larger in surface area, which in turn allows the battery to discharge at a much slower rate and consequently it will recharge much slower as well. You can run lights and all other assorted gizmo’s off this battery.

Gel Cell is the remaining battery type and uses the same type of technology, that is lead/acid, but only with gel inside. The main advantage to the gel cell is with the sailor in mind. While most of us have experienced the thrill of sailing, you also notice the tilt of the boat when sailing. Gel Cells, since they contain gel and are closed are perfect for this use, because they will not leak water or acid when off center as on a sailboat. When anything containing a liquid is on its side and takes the punishing effect bouncing on the high seas gives, you want a battery that will not leak, such as the gel cell battery. Gel Cell batteries are a closed system of battery, that is inaccessible to us with no need to check water or in this case gel levels.

RATINGS. All batteries, car or marine come rated for the job they are supposed to do, namely starting engines & supplying power. Cranking amps is the term used for "power output," or the amount of power needed for turning over the engine. Another term, cranking amps, are rated on temperature. Cold cranking and marine cranking. In cars, or cold cranking, it’s 0 degrees and in marine batteries it’s 32 degrees. An amp is a measure of current. The cranking amps needed to start engines in marine batteries, is less than that required for cars, for obvious reasons. Not too many of us have to start our outboard or inboard engines in temperatures of 30 degrees or less, never mind 0 degrees. In marine batteries, the cranking amps needed to start an outboard engine is greater than that needed to start stern drives or inboards.

There’s also reserve capacity ratings on batteries. Reserve capacity is the amount of power, rated in minutes, a battery has before draining to a point where the battery can no longer do its job. A marine starting battery for example may have a cranking amp rating of 650 amps, but a reserve of only 85 minutes in which you can use accessories (depends on drain) before the battery is drained of the power needed to do the job, starting an engine. A deep cycle marine battery may have cranking amps rated at 550 amps, but a reserve of 130 minutes, which translates into less starting power on cold days, but more reserve time for running accessories with the engine shut down. Next week, we’ll cover open or closed batteries, setting up your battery system and safety in Part Two.

OPEN OR CLOSED. When it comes to batteries, you have "open" and "closed" batteries. Open means just that, it is open and you have accessibility to check water levels. Closed batteries do not give you this option and usually come with a little light or "eye" that reads green when good and red or black when no good.

Remember though, when batteries are recharged via an alternator or other charging device, they heat up a little and will bubble off (evaporate) some of the water within the battery, which you can replace (check weekly). With a closed system, when recharging and heat & bubbling occurs, pressure increases and can cause a problem if over charging comes into play. I prefer to use batteries with an open system and I think it advisable when using Cranking Amp or Deep Cycle batteries to use an open battery system. One in which you can check and add distilled water when levels are low. This way you get added life from a battery.

Also remember, a gel Cell battery is a totally closed system and while it may charge better in the long run, but the biggest problem with them is over charging. Gel cells can only be charged to 14.3 volts and anything over this can cause a rapid breakdown within the battery. However, gel cells big advantage is quick discharge and very quick recharging capabilities, and when hooked with a high charge power alternator, can recharge in as little as a half-hour to an hour.

SETTING UP A SYSTEM. When it comes to setting up a battery system, there is good, better and best. Smaller boats that only run on one battery, should opt for a deep cycle as the better choice. You’ll still have enough cranking power for starting and the reserve is longer for running accessories with the engine shut down.

The better system involves two batteries and a battery switch, that allows you to run on both batteries, or either one individually. On this switch are the words or numbers for 1, 2 or both. In this system, the best scenario is the cranking battery as the starting battery and the deep cycle battery as the accessory battery. You would start the engine on the cranking battery, #1 on the switch and when drifting or running accessories with the engine off, the deep cycle battery, or #2 on the switch. You would then restart the engine on 1 and continue this pattern until it’s time to head home. Now start the engine on the Both (all) switch, which then recharges both batteries at the same time while underway home.

The best system includes this dual battery system, however we now take it one step further and install an isolator on board. An isolator is a diode that allows both batteries to be charged simultaneously without one battery affecting the other. A diode also prevents overcharging of either or both batteries. An isolator acts as a "T" valve, in that electricity can flow in only one direction. As "juice" flows into the batteries upon recharging, when one battery is fully charged, the "T" valve closes and prevents further charges from entering the battery, thus preventing an overcharge.

SAFETY. Whenever you install batteries or do any installation of battery systems yourself, safety is the number one concern. Batteries have pressure and are explosive materials when not handled correctly. You must always wear some sort of eye protection, such as safety goggles. For a battery system to work correctly, polarity must be correct. That is, positive (red) to positive and negative (black) to negative. When connecting your battery wires to the terminals, always connect the positive (red) last! Just as in a car battery, connecting the negative wire last, can cause a spark and this spark may ignite any escaping gaseous fumes from the battery, causing an exploding battery.


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