electric winches draw a fair current, so you would need either to run the battery supply to the trailer, or fit a battery to the trailer and charge it from the vehicle, either way the connections need to be good and kept out of the salty stuff. if you go down the route of a trailer mounted battery you will need to make sure the charging circuit is switched off before the winch is operated otherwise you will blow the fuse in the charging circuit. Britpart do a good range of electric winches, worth a look
