[Destroyer]

Originally Posted by THEFERMANATOR

Just because you can, does not meen you SHOULD. Deep cycles can give high amperage loads when needed for starting, but any good deep cycle battery is designed to put out low to moderate amperage amounts for longer periods of time. Using true deep cycle batteries for cranking WILL shorten the batteries life, that's an undisputable fact. The thing is there is very few TRUE deep cycle batteries in the group 24/27 range because they know people are going to abuse them as starting batteries. True deep cycle batteries will not have a cranking amp rating, only amp/hour ratings which is what is important to a deep cycle battery.

X2. A regular car battery, either traditional lead/acid or AGM (Absorbed Glass Matt) is more than sufficient for most boats. If you're running an electric trolling motor from a small skiff or rowboat then a deep cycle battery comes into play. But for regular day to day usage just a straight car battery is fine (And usually costs less) By way of further explanation, allow me to copy/paste a quick article about the types of batteries. (Keep in mind this does not include Lithium-Ion batteries which are very expensive and not really practical for boat use unless you have an electric powered car or boat)

Types of batteries:
1) Wet/Flooded Battery: The wet/flooded battery is one of the most popular types of batteries. It is so popular because the battery price is very low. The battery design uses plates that are freely suspended. These plates are insulated from each other as the negative plate is completely sealed in a separator bag. These are maintenance free and sealed so no gases are replaced. The fluid in the battery will last until the battery dies and you do not have to keep topping it off. These batteries can range from $50 to several hundreds of dollars depending on the brand.
2) Calcium-Calcium Battery: This battery has a calcium alloy that is on the different charged plates. This calcium reduces the amount of fluid loss and the rate of self discharge is much slower. The main disadvantage is that you can seriously damage the battery if you overcharge it. The bubbles that move through the fluid are important, as they are responsible for mixing the different acid densities. You can find a calcium-calcium battery for under $100.
3) VRLA: The VRLA stands for a valve regulated lead acid battery. This name really describes the safety valves that are on the battery box. The safety valves are all pressurized. By containing the gas in the battery it will mix and form water so you stop any fluid loss. There are two main designs of this VRLA battery: AGM or GEL. A GEL battery uses silicon to make the acid more solid and like a gel. This type of battery is very good but is not the best for a starter battery. This type of battery costs between $100 to $250.The AGM battery uses absorbed glass matt. The matts are very thin, which keeps internal resistance very low. This makes it a perfect battery for starting a car, as you can get a lot of power out of very small volume. AGM batteries price range anywhere from $50 to $300 depending on the brand.
4) Deep Cycle: A deep cycle battery will provide power for a very long time. These are typically used on small boats, golf carts, or electric vehicles. You will also find these used to collect and store solar and wind power. These batteries have thicker plates inside the battery as this increases the capacity charge. They are typically not used for cars or boats because they have a high discharge rate, so the battery will run down very quickly. If you do not drive your vehicle for a long time, then you will not sufficiently recharge the battery. Deep cycle batteries are expensive and starting prices are about $200.

Hope this helps clear up what kinds and how these batteries work.