When I purchased my trailer a few years ago it had 2 fans installed over the rear two horse stalls.  The person that had put them in spliced a wire from the cord that connects the trailer to the pick up and ran it the length of the trailer to switch in the rear tack, it was then run from this switch to the mid tack where there was an inverter and then back to the horse compartment fans.  I could never get both fans to work and it was rare to get a single fan to work well so I haven't used them. 

Last night a friend and I did some experimenting and took the battery from the front of the trailer and connected it directly to the inverter which in turn ran both fans with no issues for an extended period.  As I had thought the multiple runs of wire and the roundabout way they reached the fans was my issue.  What I would like to do is to remove the majority of wire and make a short run from both fans to the rear tack where a battery would fit nicely...this would eliminate lots of wire and based on my experiement the fans will both work well with this configuration.

My issue in doing this is that there is no easy way to charge the battery that I would use for the fans so I would need to remove it to do so.  Most of the shows we go to require less than an hour ride in the trailer so if I only ran the fans 2 or 3 hours on a weekend do you think I could go several weeks without a charge?  The fans are probably 8 to 10 inch fans. 

I don't understand what you are referring to as the inverter. Stall fans I've seen are regular 12V units. I mention this because if you mount the battery in the rear tackroom, you can access the 12V accessory wire in the rear end of your Exiss (usually in the post where the switches are located), and connect it to the new battery you are installing and charge the batt off of the truck.

After re-reading your post- are you using 110V household fans? If so, change over to the 12V and wire as I described. I think it will simplify things for you.

The fans that are in the trailer are 110v fans.

The fans are already installed by the previous owner, not sure why I would purchase new fans if there are already existing fans.....an invertor turn 12v into 110v.