I’m looking to have fans installed in my trailer for the horses.

I emailed two trailer service places and both said it sounds like something they could do. One asked for pictures.

Is this not a common thing???

I have them in my trailer.  I love them.  Mines a 3 horse.  I have 2.  I'd like to add a third.

I bought fans and installed them in my trailer myself.  It was super easy.... and I found them online pretty cheap.

Do they run off your battery? Where did you run the wire? 

I run fans and a lot of other stuff in my trailer. 

So I installed a compact Nuclear reactor in one of the mangers. 

but yes, they run 12 volt and run off your aux circuit. 

I guess I got lucky... My trailer wires run inside above the drop downs right where I mounted the fans.  There's a hot wire there that I just spliced the fan wires into.  Yes, they run off my battery.  They were like 35 each.