Wiring up a trailer winch
 

I bought a small marine battery box, a small car battery (no vent) and
some std cable connectors (see attached picture). It was something
like $75 for everything.

The way I'm thinking about hooking everything up is as follows:

Directly wire the winch to the trailer battery using the existing cables and
spade connectors. Easy.

Run a wire from the positive aux power (#4 black wire) to the trailer
power panel (below the front of the trailer) then to the battery.
Run a wire from the ground (#1 white wire) to the trailer power panel
(below the front of the trailer) then to the battery.

For the two wires above I would just match the existing gauge and
verify the amp (size of fuse - I believe 40amps).

I'm leaning towards this variation because it seems very simple and
you don't have to depend on your truck's power to light the interior
or run the winch. While towing the trailer battery would be getting
charged up. If the trailer battery dies, it will draw from the truck's
battery.

Does this solution fly? What if the trailer battery dies and the winch is getting powered by the truck's battery? Would that cause a problem?

Trailer Wiring Diagrams - http://www.etrailer.com/faq-wiring.aspx

Attachment 22413

It sounds like it should work. Pos to Pos and Neg to Neg, in parallel. Then the truck should be able to charge both batteries. And I believe in some states the trailer brake battery must be wired dedicated to the trailer brakes.

As far as running the winch when the battery's dead on the trailer, then you likely also have no power on the brake's battery, too, which is a problem. You could simply use a volt meter to check status periodically. And if you're concerned about running the winch off the truck's battery, then simply unplug the electric to the trailer, and the truck will be isolated.

Electrical gurus might know, but wonder if there's a way to charge both batteries in tandem when connected to the truck's running alternator, but have the trailer batteries isolated from each other. So the brake battery doesn't power the winch. I suppose a simple solution might be a switch in the 2nd batteries charge wire somewhere, so that "ON" it would receive a charge when driving down the road. But when "OFF", the winch is only drawing power from the 2nd battery (and saves the brake battery).

mine too.

Youre asking for trouble. What happens when you plug a large winch battery thats partly discharged from sitting out in the cold disconnected for months into the wiring harness of a freshly charged (and likely running) truck battery. 100s of amps inrush and lots of sustained current too. Jumper cables are A LOT bigger than a trailer wire harness.

You need to determine a way to prevent the inrush w/ a limiting resistor of some sort. AFAIK, Thats how the brake battery charger boxes do it. (A large 12V PTC might be ideal here since the battery is much larger.) There are also things called 'battery isolators' for RVs that are basically two huge schottky diodes in a block. Allow you to charge two batteries but not have one back feed the other.

We make a solar charger (SSPPT-15A) that can be used to rapidly charge one batt from a slightly higher voltage one (even 24 or 48v -> 12V) but is prob overkill for your needs. And $200+.

Screw the battery and box, just run a feed off your truck. That's what I did. Use this:

http://ecx.images-amazon.com/images/...500_AA300_.jpg

I'm trying to emulate what trailex offers as an option.

I have the exact same winch/ stand etc.

Trailex are smart people, so I'm sure it can be done safely.

http://www.trailex.com/options2.cfm?id=93

Yeah, they're running a current limiting charger off the trailer harness. To do it safely you need to do the same.

Sorry, I read that as rewiring the trailer wench. . . About to offer an inane suggestion. . .

Fxd