Wiring a Battery to my trailer?

[WHYT LIE]

Ok, so I just mounted a Yellow top Optima in a battery box inside my trailer box and want to keep it charged up. My trailer (Diamond C Charger/Challanger/car hauler) trailer has a 7 pin round connector and up under the rails there is a blue and red wire (look to be 10 or 12 gauge wires. They are capped off and I called the trailer company. Blue is "Battery charge" and the red is "back up lights when reverse is selected"...

So since I have a Superwinch 4,000lb winch for the trailer wired up through quick dissconects to the battery I'd like the tow rig to "charge" the battery while in tow.

So, do I just connect the blue wire directly to the positive side of the battery (trailer place recomended a 30 amp circuit breaker) or do I need to ground the battery? Do I just ground the battery to the frame of the trailer? Or does it need to get grounded to the truck somehow?

I'm no nOOb to wiring, but this two vehicle/trailer thing has be confused a bit.

Thanks for any help you can provide.

[KWTMECH]

I would double check with a test lamp, blue on trailers most of the time is the wire for the trailer brakes themselves. Red may be direct from the batt. and should come from a 20a to 30a self resetting breaker.

[WHYT LIE]

I would double check with a test lamp, blue on trailers most of the time is the wire for the trailer brakes themselves. Red may be direct from the batt. and should come from a 20a to 30a self resetting breaker.

Well this weekend at an Auto-X I ran into a guy with a nearly identical trailer (same style/brand) and he had a battery and a winch and had wired up his blue wire to the battery too. But I forgot to ask him about the grounding issue.

Then I called the trailer company and they told me the same thing about the blue wire and the battery...

I will check with a test light or a multimeter first, but how about the grounding issue?

The breakaway brake switch has a small gauge blue wire going from it... This is a "sealed/modular" wiring harness as well if that matters.

[MattyL13]

if you ground to the trailer, youre grounding to the truck as well I would think. the hitch ball and receiver and the hitch itself is all metal right, which gets boltded to the truck frame......i dont see why it would really matter. im thinking of doing something similair with my bumperpull camper, id liek to get an optima or jsut a reg car battery and hook up two batteries in parrallel for longer weekends without electric hookup. however im unsure of how the battery on teh camper gets charged, this is not the brake-away battery, this is the 12v battery for all the lights, water pump etc etc for the camper. I am pretty sure it gets charged while being towed but im not sure. sorry for the hi-jack

[ChiXJeff]

Uh, no. DO *NOT* assume that the trailer is grounded through the ball. That's a poor ground.

One of the leads in a 7 wire round RV type connector is a ground connection. You probably already have a decent ground in place. A fuse is a good idea, carry spares. I don't think I'd get clever and use an auto-reset circuit breaker like I would on a brake circuit.

My pop-up trailer has a deep cycle on it, and it's also got a 12V constant draw from the tow rig. And a ground through the trailer pigtail.

[pmurf1]

I personally would use the center pin on the 7 prong connector to steal power from the battery. Chances are, there's already a blue stub or wire coming out of the back of it on the truck end of the connector just waiting for something to do. It's usually the auxilary circuit for stuff like winches, dump bed pumps, etc.. Just hook your trucks battery to that wire with some decent gauge wire (at least as big as the stub coming out of the connector). You already know you need to fuse it, but the resettable circuit breaker is a good idea too. On the trailer end, just use the center pin to go to positive on the battery. You may want to put a heavy duty switch or disconnect in between the pin and the battery wire otherwise you will be drawing from your truck's battery too while winching. It may even pop the fuse depending on how hard you winch, won't know until you try it. I'd just ground the battery's neagative to the frame of the trailer. I've never had a trailer that didn't ground itself nicely through the ball. I have a slide-in camper that I've done the same thing you're talking about doing. My PSD has two batteries and the camper has it's own. I ran a 10 AWG wire back from one truck battery with a fuse to the connector on the trailer that goes to the 12 v hot all the time. It charges as I drive, and when I stop I have three batteries to pull from not one. I used to worry about leaving stuff on all night like the heater fan, but not any more. It still starts easy even in 25 degree cold.

Your other option would be to just buy a quick disconnect like Warn has for their multimounts and just run it back to the rear bumper and hook it into the trucks battery. Plug the winch in when you need it and run the truck while winching. Then you don't even need a battery and all the associated stuff on the trailer. Either way will work, it's probably about a wash monetarily either way.

[saprobe]

I personally would use the center pin on the 7 prong connector to steal power from the battery.

um,yeah,thats a great idea,if you want to limit yourself to only being able to pull your trailer with your truck and know that no one else(who has their 7 pin connector wired correctly) will ever need to pull your trailer.

the center pin is normally used for reverse lights. not such a big deal,except that the trailer is only going to recieve power when youve got the truck in reverse if your using a different truck to pull your rig. if youve got someone elses trailer hooked to your truck,youll be driving down the road with the reverse lights on.

i can see why youd want to use that center pole for constant 12v(it looks beefier than the other connections) but there is a reason that diagrams are available and there is an accepted way to do certain things. youd never purposely wire the turn signals backwards,or hook the brake wire up to a different terminal would you?

my 2 cents,anyway.

couplel inks if you havent seen em:
7 pin wiring: http://www.pirate4x4.com/tech/billavista/Towing/7%20way%20wiring%20diagram.mht

billavistas towing info:
http://www.pirate4x4.com/tech/billavista/Towing/index.html

[pcorssmit]

Ground the battery to the trailer. Your trailer should already have a ground wire going from the frame to the connector. However you should check to make sure that this wire is large enough, I would say it should be at least one or two sizes bigger than the charge wire (since it carrys power for the lights and brakes as well).

Pete

[Albin]

You should always ground a trailer through the appropriate pin on the connector (white - #1 position on the 7 round) and never depend on the ball/hitch as the ground connection.

Also, Black - #4 position is the battery charging pin - use it to charge the battery, that's what's it's there for.

Good luck.

Al