My battery was fried for sitting and wouldn't take a charge. I wanted one of the sealed gel battery with lots of power. I called a battery recycle center in Denver and they had two marine batteries one ten inch long and another thirteen inch. I had room for a 13 inch and bought it. They put it on a testing machine and it pinned the meter. It was very clean and it came with a two year warantee. Cost with tax, now hold on to you hats--$32.00.
Sure beets $150 plus. I don't care if its lasts one year, with small solar charger and plugged in to the tow vehicle it is more than enough for 3 to 4 days at a time.

I usually go this route too, and have had good lifespan from these batteries, usually over five years.

Since my vehicles are older pre-computer types, I used marine batteries in them. Then, instead of having a dedicated battery for the trailer, I just remove one from whichever vehicle is to be left home when needed.

In addition to saving the expense of another battery, another level of theft resistance is added to the vehicle left behind. That is in addition to the fact that it is usually an old, shall we say, 'work truck' that is fairly theft resistant by virtue of its appearance.