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Deep Cycle Batteries

I really need to know more about batteries and engines. And this is a good opportunity.

Starting, Marine, and
Deep-Cycle Batteries

Starting (sometimes called SLI, for starting,
lighting, ignition) batteries are commonly used to start and run
engines. Engine starters need a very large starting current for a very
short time. Starting batteries have a large number of thin plates for
maximum surface area. The plates are composed of a Lead "sponge",
similar in appearance to a very fine foam sponge. This gives a very
large surface area, but if deep cycled, this sponge will quickly be
consumed and fall to the bottom of the cells. Automotive batteries will
generally fail after 30-150 deep cycles if deep cycled, while they may
last for thousands of cycles in normal starting use (2-5% discharge).

Deep cycle batteries are designed to be discharged
down as much as 80% time after time, and have much thicker plates. The
major difference between a true deep cycle battery and others is that
the plates are SOLID Lead plates - not sponge. Unfortunately, it is
often impossible to tell what you are really buying in some of the
discount stores or places that specialize in automotive batteries. The
popular golf cart battery is generally a "semi" deep cycle - better than
any starting battery, better than most marine, but not as good as a true
deep cycle solid Lead plate, such the L-16 or industrial type. However,
because the golf cart (T-105, US-2200, GC-4 etc) batteries are so
common, they are usually quite economical for small to medium systems.

Marine batteries are usually actually a "hybrid",
and fall between the starting and deep-cycle batteries,though a few
(Rolls-Surrette and Concorde, for example) are true deep cycle. In the
hybrid, the plates may be composed of Lead sponge, but it is coarser and
heavier than that used in starting batteries. It is often hard to tell
what you are getting in a "marine" battery, but most are a hybrid.
"Hybrid" types should not be discharged more than 50%. Starting
batteries are usually rated at "CCA", or cold cranking amps, or "MCA",
Marine cranking amps - the same as "CA". Any battery with the capacity
shown in CA or MCA may not be a true deep-cycle battery. It is sometimes
hard to tell, as the term deep cycle is
sometimes overused. CA and MCA ratings are at 32 degrees F, while CCA is
at zero degree F. Unfortunately, the only positive way to tell with some
batteries is to buy one and cut it open - not much of an option.