Vent Bilge
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Vent Bilge
Tips on Choosing a Marine Battery for Your Boat
The most popular kind of battery in marine use today is the standard lead acid battery. The wet cells can store a large amount of energy in a small package using just sulfuric acid. This energy is stored within lead grids mounted inside the battery. The lead is what makes wet-celled batteries so heavy.
Battery choices are further divided along three methods of construction. These three methods are Wet-celled, Gel and AGM.
Wet Cells are the most popular lead-acid battery-type in use today. They offer the most size options, are the cheapest and can be found almost anyplace.. When used in boats, wet-celled battery compartments are not sealed so the user can replinish the electrolyte and the batteries can be vented. Wet-celled batteies have a grid of lead plates that is used with the acid. The grids in wet-celled batteries are only supported along the edges, hence these are the weakest mechanically. And since these batteries are not sealed, you must be certain to insure you do not touch the acid when filling (chemical burns) or come in contact with sea water (chlorine gas) or create an explosion from the vented gas, hyrdrogen.. Batteries should always be stored in a spill-proof box.
Gel Cells use a thickening agent to immobilize the electrolyte. So if the container is cracked, the cell will continue to perform as normal. In addition, the thickening agent prevents stratification by preventing the electrolyte from sloshing around. As gel cells are sealed and cannot be re-filled with electrolyte, controlling the rate of charge is very important or the battery will be ruined in short order.
Absorbed Glass Mat (AGM) batteries are the latest step in the evolution of batteries. Instead of using a gel, an AGM uses a fiberglass like separator to hold the electrolyte in place. The physical bond between the separator fibers, the lead plates, and the container make AGMs spill-proof and the most vibration and impact resistant lead-acid batteries available today.
Basically, an AGM can do anything a gel-cell can, only better. However they are too sealed and charging must be carefully regulated. I have used them on my personal trawler for three years now without any problems..
Absorbed Glass Mat batteries are relatively new but are quickly gaining acceptance. Here are a few good reasons to consider them:
Absorbed Glass Mat (AGM) batteries can dispense a charge at a higher rate than flooded cells.
Virtually no gassing under normal operating conditions: Unlike wet cells, AGMs are sealed and operate under pressure to recombine the oxygen and hydrogen produced during the charge process back into water. Some of your high-end boat builders use AGMs in their boats like Broward and Viking.
The ability to put AGMs in the bilges (they can even function under water) also lengthens their lives; Remember that for every 15 degrees over 77F, a battery's life will be cut in half
AGMs can operate in any orientation (although you may lose some capacity that way) and even if a container is broken, an AGM will not leak. This should be of particular importance to blue-water cruisers that could find themselves tossed around; you would not want sulfuric acid in your boat. Proper (heavy duty) battery constraints are a must, regardless of battery type.
AGMs require no maintenance once the charging system has been properly set up.
The prices of batteries are an issue:
Let's review prices
- Wet cell 8-D - $150.00
- Gel - 8-D - $250.00
- AGM - 8-D $365.00 (Marine centers have them for $501.00)
So select the battery you feel is best for you and enjoy your boat.
About the Author
Mike Dickens, the author, is a boat owner and owner/Broker of Paradise Yachts. Paradise Yachts is a Yacht Brokerage offering used yachts to customers worldwide. Visit our website to view our selection of Used Trawlers, Used Motor Yachts, and Used Sailboats .
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