I picked up this one in the fall
I used a much smaller cheap one I bought at Princess Auto last year for $27.99, worked not too bad for just the lights
, but if I ran the fan I built all night, along with lights for an hour or so, it really drained the battery, then used my 13Watt solar
to charge it. It worked until I left it one time connected to the fridge
running on 12volt (oops), and it pretty much killed the battery. I would guess at best it was a 7amp hour battery, but i have a feeling it was a 3.5amp hour battery.
The new setup works real well, the lights are much brighter, and I should be able to leave the fan on at nights without worry.
I have also seen this one for about $80 or $90 when on sale, would give you lots of power as well. Your trailer sounds just like ours, and it is surprising how much juice those little bulbs use.