Very easy to add optional backup (rear facing) lights on a trailer that contains its own onboard 12V battery. Simply:
- Purchase low profile 12V autommotive clear lens fog lights. Ensure they are 12V 55W - as seen at: http://i178.photobucket.com/albums/w...oFogLights.jpg
- Mount under the trailer's rear bumper - facking backwards.
- Ensure its "-" wire is self grounding - on the bumper's rear steel frame.
- Run a single 12V live wire to the trailer's onboard 12V battery. Due to long distance, use 12V - 12 guage wire for best results.
- Install inline fuse approx 6-8" from the battery's "+" post. Fuse size = (55x2)/12 (rounded up) = 10 Amp Fuse.
- Between battery and rear fog lights, simply install a 12V rated manual off/on switch. Mount this switch in a location away from water and easy to access. For example, inside an outside access storage compartment.
When you want to light up the rear of the trailer, simply turn the manual OFF/ON switch to ON. And when you want to backup in the dark (re: 3:00 AM in a crowded CG site) and want lights OFF, simply leave the manual switch to OFF. And, for greater safety, remove the fuse during long haul travels. Only install the fuse at the last gas/fuel station you visit.
By installing a manual off/on switch on the trailer (TT, 5er), you don't need to re-wire the truck's 7-pin connector either. The optional trailer reverse lights will work with any Tow Vehicle pulling it.