I have a 2010 Ram TRX which included the factory tow package.

I also have an 18' tandem axle car hauler that has electric brakes.

When I got the truck I added an aftermarket electric brake controller through the harness under the dash as the truck did not come equipped with the factory controller. It works perfect with my trailer.

My trailer has a battery back up for the electric brakes that supplies power to the brakes should the trailer disconnect from the truck. This small 12v battery is charged by the truck when the trailer is plugged into the 7 pin harness.

What I would like to do is add a full size 12v battery in a seperate box that will power my trailer's winch, electric jack, and evenually some deck lights since I load my enduro car in the dark after racing. Adding the battery and wiring it up to my accessories is easy enough.

BUT.... what I would like is for this standard 12v automotive battery to be charged by my truck when it is running.

My original electric brake controller was in a box that had a circuit board in it, and the new one (had to replace the original) had a special wire with some electronics in it and it is my belief that these electronics were for charging the battery when connected to the truck.

So how do I go about charging the new battery from the truck? I don't imagine that it is as simple as having the battery connected to the 7pin harness positive connection?

Could the new trailer battery also feed back power into the truck when it is not running but the trailer is still connected?

Any suggestions? Looking to work on this project once I get my hauler out from being buried in five feet of snow (nothern Ontario!).

Thanks.

 

Adding a battery isn't a problem. The problem is when you decide to use your winch. You MUST unplug your trailer 7pin harness whenever you use your winch or the winch will draw evenly from both batteries. This is a problem because the trailer line is a fused 30A line going to your trailer and that cannot handle the massive draw a winch places on it. I would not trust yourself to remember to unplug each time you use.

You can install a battery isolator, but this will still not solve the problem of drawing excess current from that line while truck is running. If you go isolator route, your truck will need to be turned off anytime your winch is in use. Just make sure the truck is off when in use.

You could run welding wire 1/0 from your engine compartment all way back to your bumper and install quick releases. This is what I plan on doing so it's completely isolated and can be used while truck is running or not, trailer hooked up or not. Completely removesd anything to do with factory issue's! What's one more connector to plug in for the peace of mind? Price should be about $120 for the wiring and quick disconnects(150-300A) one's. Forklift style one's and you'll need an inline fuse as well. I have resettable circuit breaker style fuses that I uses for my stereo equip and I plan to use same for winch line.

 

the fused +12vDC in the 7 pin connector is hot all the time, even when the truck is not running. I'm not crazy about this set up as the second battery could potentially discharge the truck battery. I've never had an issue though but I disconnect the trailer when I get to my destination. The wire from you bake controller could be a wire to drive an isolator for the second battery in generic applications.

 

I don't mind running new line and a connector.

Would I simply tap off the trucks battery terminals and run it to the new trailer battery (with fuse and connecter in between of course)?

Assuming then that the alternator would charge both the truck and trailer batteries when running?

With that set up would the winch also not draw from both batteries?

I am not too worried about drawing from both batteries... the two ways I would end up using the winch would be with the trailer disconnected completely or, if it is connected to my truck I would have the truck running.

Would that acceptable? I do like the seperate connector idea so that if someone else hooks up my trailer they do not burn up their wiring if they use the winch. Its rare that I loan my trailer but you never know I guess.

 

Yea... my Enduro car matches my truck....

 

Straight off the under hood battery into a battery isolator. Keep all that under your hood. Then run the line from the isolator to the back of your truck and attach your quick disconnect. Dont forget to put in an inline fuse under the hood as well.

This will allow you to run your winch without draining your battery when the truck is off and will allow the alternator to charge both batteries while the truck is running.
Make sure you get an isolator capable of sustaining the current your winch draws. 300A or so.