Trust me if you have it you will use it alot more than you think. To me it would be a pain in the rear to have to go get a battery off of a tractor or something and then hook it up before you could go to get your new tractor you just bought!
Here is my set up. I would think for the cost of a deep cycle battery you could do it this way. I am not sure, the wire was gave to me, i just bought the quick connects (if i can remember were about $25 to $30 a set) I have also found them on E-bay