trailer wiring question - need battery to charge while driving

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mountainsean

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Joined
May 22, 2007
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Hi-

I own a 2002 Toyota Tacoma TRD Doublecab with tow package.  For whatever reason the hitch wiring didn't include the standard 6- or 7-pin plug to allow for charging the trailer battery while driving - instead there was just a basic flat 4-pin receptacle.  I bought and installed an adapter to mate it with a little Viking 1906 pop-up which had the round 6-pin plug, and that works great for brake lights and turn signals, but it doesn't charge the battery (the trailer doesn't have brakes, but that's another matter - I'm not too concerned since it only weighs about 1500 lbs.). 

So my question is what I need to do to get power to the trailer battery to charge while driving.  I *think* it should be fairly straightforward to run a wire (w/fuse) from the truck's battery back to the pigtail that comes off the 6-pin adapter I installed.  I realize that without a battery isolator this means the trailer would always be drawing power from the truck whenever connected, but since I'll disconnect it for anything longer than a pit stop I don't see that being a big problem.  Is there anything else I'm missing here?  I've done similar sort of wiring when I did a car amplifier install, so it's not entirely foreign to me, but didn't know if there are some other concerns that would drive me to having a professional do it.

Thanks,
Sean
 
Running the wire should be easy for you. I would suggest you add an automotive horn relay (they'll handle about 50A) in the line, and turn it on and off with a small toggle switch. That way you could disconnect from the truck battery without having to remove any wires or connectors for those brief stops when you don't disconnect completely. And don't forget a fuse!
 
Or don't bother with the relay and switch and just unplug the electrical connector from the tow vehicle when you stop for the night.
 
If you would like a regulated charge for the trailer battery, you can add a device called the Toad Charge to the tow vehicle. Toad Charge is designed for towing cars & trucks, but should work equally well on trailers. It only puts out 5 amps, but that should be adequate to keep a small trailer battery charged up.

But I don't see any problem with a direct wire either, as long as you remember to disconnect it when you arrive.  Remember to fuse it, though, and to use adequate gauge wire. A depleted battery can suck a lot of amps, at least initially. I would allow for at least 20 and 30 might be a safer bet. And an auto-reset circuit breaker (such as it used for headlights) might be more convenient than a fuse - you won't have to replace it if the battery pulls a bit too much.
 
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