Super backup lights

[KYAvion]

Thanks for explaining this. Would you happen to have a link to a relay that allows power from two separate sources for an application such as this?

[pbsled]

My old Navy nuke ET training (which is little more than intuition these days) would say as long as the two vehicles are properly grounded and only running off one charging source (alternator or converter) it’s just a simple parallel circuit with two possible ways to route current into the latching coil. Once the relay is latched that just closes the circuit to power the lights from the 12v source from the trailer fuse panel, which is its own circuit by virtue of being a relay. What current loop latches the relay should be inconsequential.

So in reading your question I am saying (I think) that both the switched hot and the feed hot from the truck are electrically the same node that meet at the hot side of the coil of the relay, so a standard single pole / single throw should suffice.

I would be happy to do a smoke test of this and share results if you like with some voltmeter and current readings, which might ease my mind a bit as well . Electricity has generally always been my friend, but a good diagram and meter readings would be good to have anyway.

[KYAvion]

So are you saying that if I run directly off the battery via a switch and also from the 7 way, that I won’t backfeed to the tow vehicle?

I don’t quite understand how I can independently feed the lights from the 7 way and the batteries via a switch without a traveler in between.

I’m comfortable with 120v/220v circuits, but I’m just learning with DC. Does this wire appear ok if run underneath the trailer inside conduit? Price is right. https://www.amazon.com/dp/B000E7D394/?c ... _lig_dp_it