by brian_bp » Wed Jan 31, 2007 7:48 pm
What you want is a "deep cycle" battery, which means you can discharge it more before recharging than other batteries, but it can't take the high current demand of a "starting" battery like the one in your car.
"Marine" batteries can be starting, deep-cycle, or a compromise, but when a store carries only one kind of marine battery it is usually a compromise, and may be sold as the one choice for all "marine" and "RV" purposes. Given only "automotive" and "marine" you would want to pick marine... but really look for that "deep cycle" description.
Ken's right: you want capacity as measured by "amp-hours", not the starting-type current ratings such as "cranking amps".