Thanks for all,the replies guys. I appreciate it. Dennis do you mean to wire it to my 5 battery and run wires back? What if I were to mount a battery box to the hitch and do it that way?
If I ignore the '5'...yes run a 6 gauge wire from positive battery terminal to a 30 amp fuse (If your winch looks like a Brave Little Toaster with a hooks coming out).
Of course you will need a battery terminal configuration which will allow connecting a new additional wire to it.
Batteries with side terminals only are a problem.
My fuse is a single holder inside a plastic container under the hood near battery.
Then from the fuse down under and to the back of tow rig.
Use wire plastic wire covers. Secure the wire from chafing
Connect to the Anderson Power Products Connector of the appropriate size (requires soldering and you may need a torch instead of a solder gun).
For negative, I cleaned off a portion of my truck frame and connected a black wire there, no need to run back to battery.
(Check your existing negative connection from battery to frame and engine block, if they look like skinny wires, you should double them up or replace with 6 gauge.
If you put a battery box on the 'hitch', what part of it, tow vehicle side, or trailer side?
What would you put in it?
If you put a battery in there on the trailer, (and I see this often on land based trailers with winches at the local race track) you still need some heavy gauge wire to charge it up, or some additional electronics to allow low current charging (to prevent melting the trailer connector wires using them instead of 6 gauge)
This is certainly doable (battery on trailer, use trailer connector wiring), can you guarantee you won't put saltwater in the battery box
Can you describe or post pics of your battery and your winch?