fj12ryder wrote:
If you're hooked up to shore power all the time, go to Wally World with the measurements of your battery box and buy a deep cycle battery that will fit. Not a starter/deep cycle battery. A deep cycle marine battery will work fine, and probably run you under $100. If that battery you have is the original, I think you got all the good out of it. :)
Not to confuse the OP but true 12v deep cycle lead-acid batteries are almost unheard of. There are a few ultra expensive ones but nothing the OP would find or should consider.
The combo-marine batteries mostly provide the convienence of a wingnut connection to make it easy to attach cables but the internals are no different from starting batteries.
If you want true deep cycle lead-acid, you are looking at 6v golf cart batteries wired together to produce 12v.
But as has been said a few times, if the OP is on shore power any basic 12v battery will be fine. He just needs enough power to operate the jack while hooking and unhooking before getting plugged into the truck and then the truck will take over providing for the trailer 12v needs.