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    Marine Battery Types & Technologies

    Date Added: June 12, 2011 11:42:12 PM
    Author: Anonymous
    Category: How To: Systems: Electrical


    Marine Battery Types
    Marine Batteries come in all shapes and sizes, and when its time to buy new ones the process can cause some head scratching.  The following is a quick guide to the types of 12-volt marine battery types that are available.
    Deep Cycle
    Deep Cycle marine batteries are used for heavy charge/discharge cycling.  They are best used for powering things like trolling motors, depth finders, bilge pumps and fish locators.  They are meant for power usage that is slow and extended.  These batteries come in different power levels, indicated by the reserve capacity (RC) rating.  The higher the RC number, the longer the battery will be able to power devices.  As the name infers, these batteries are designed to be depleted-- something referred to as a discharge/recharge cycle--and can be replenished at the end of the days use.  Deep Cycle marine batteries are specifically designed to withstand several hundred cycles. 
    Cranking (or Starting) marine batteries are designed to provide a burst of energy to turn over your inboard or outboard motor.   They are meant to be quickly replenished by your running boat engine’s alternator.  It is important to check your engine’s manual for the recommended battery starting strength.  Cranking batteries come in different ratings found on the battery’s label, and will be listed as either marine cranking amp (MCA,) or cranking amp (CA.)
    Dual Purpose
    Dual purpose marine batteries combine the features of the deep cycle and cranking batteries and are able to provide immense starting power while maintaining some cycling capabilities.  Generally dual purpose marine batteries should only be used when there are extreme space restrictions on smaller boats as they are not able to provide as much cranking power, or withstand as many cycles, as their specialized counterparts can.
    Now that you understand the basic purposes behind the types of batteries, you can look more into the types of technologies behind the power, and chose which battery will work best for you.
    Marine Battery Technologies
    Marine batteries have different types of technologies, each with their own advantages and disadvantages.  As you shop for batteries you will find the three most common types of marine batteries available are AGM, Wet Cell, or Gel.  The commonality is that they will all provide your boat with the power it needs.  The variables range from cost, efficiency, maintenance, installation requirements, and recharging factors.  As with most boat oriented decisions, recommendations from fellow boaters about marine batteries are often based more on personal opinion and experience than science.  It doesn’t hurt to understand the basics of the technology while weighing the personal experiences and opinions of others when making your decision.
    AGM (Absorption Glass Mat) battery technology was originally developed in 1985 for military aircraft, and has moved into the marine battery market with great success. They are a sealed battery, with dense filling of absorbent glass matting packed between the battery’s metal plates.   This matt absorbs and immobilizes the acid, allowing for fast reaction between materials, and the ability to deliver and absorb higher amperage during discharge and charging.  The sealing allows oxygen and hydrogen gas to recombine eliminating the need to refill the water contents.  Being sealed allows the battery to be installed at any position which is great for awkward boat storage; makes them shock and vibration resistant; and even makes them submersible.  AGM batteries self discharge at a low rate of around 3% per month.  On the down side they are expensive, and since you cannot replace the water they are damaged if accidentally over charged.  Many boaters find recharging to the manufacturers specifications hard to manage which significantly shortens the battery life.
    Wet Cell battery technology is different from dry cell technology in that the battery operates by means of liquid rather than paste.  Most common is the lead-acid battery, where the battery is filled with battery acid (a combination of distilled water and sulfuric acid.)  This is the most popular battery in marine use, primarily due to their low cost and if properly charged and maintained, their long life cycle.  They are more resistant to overcharging.  The downside is that these batteries are vented and allow access to the interior.  They must be installed right side up, inspected and regularly, and topped of with distilled water when needed.  They also release hydrogen gas necessitating good ventilation, and are sensitive to vibration and heat.  Wet cell batteries tend to discharge at a rate of 6-7% per month, and must be consistently recharged.
    Gel Batteries use a thickening agent, usually silica, to immobilize the liquid inside and are sealed.  This makes them resistant to low temperatures.  Like AGM batteries they take advantage of the recombination of hydrogen and oxygen and do not need to have water added.  Likewise the sealed container makes them maintenance and leak free as well as resistant to shock and vibration, and able to be submersed, which can allow you to consider places like the bilge for storage.  Because gel batteries are not as likely to degrade like wet cell batteries do, which shortens life, they can be a great marine battery for boaters who don’t or can’t recharge the batteries immediately after use.  Likewise they have a discharge rate of less than 1% per month.  Unfortunately marine gel batteries can be expensive.  They also are not as efficient as AGM batteries when recharging, and have specific manufacturer recommended volt levels for recharging that often necessitates buying chargers designed for recharging gel batteries.
    This is just a simple breakdown of the three main types of marine batteries available to boaters.   It is important to do your research when replacing your batteries to ascertain if you have the right batteries and chargers for the job, or if you should change to a different technology.  Remember, not all batteries are manufactured to the same standards.  Price is only one consideration; don’t forget the importance of warranties and customer reviews.  Likewise, research and talking to professionals can help you consider your boats entire electrical system and needs before you take the plunge.  For instance, with the extremely low discharge rates of Gel and AGM batteries, maybe you don’t need solar chargers.  However, if you just invested the money for solar chargers maybe saving the money and enjoying the long life of wet-cell batteries is the best move.  Understanding the technology of your marine batteries, and how best use and maintain them will save you money and hassle in the end.
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