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Auxillary trailer battery wiring

Discussion in 'Towing' started by mesmeralda, Feb 17, 2010.

  1. Feb 17, 2010 at 2:39 PM
    #1
    mesmeralda

    mesmeralda [OP] Member

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    I have an 06 Tacoma with a tow package. I currently tow an enclosed Haulmark 6X10. I want to run an auxillary battery in the trailer for lights and I want the Tacoma to charge it while I'm driving. Has anyone had any experience in wiring this? Pictures and explanation would be grateful.
     
  2. Feb 18, 2010 at 9:04 PM
    #2
    CtryBoyInMT

    CtryBoyInMT Lifetime Member

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    Since you have the tow package it's 5% done!!!:D

    It takes some work, but it can be done. It's hard to describe in a forum and some good electrical knowledge goes a long way.

    Since wire color varies from trailer manufacturer to manufacturer, I can't suggest wire color.
    Your trailer should already utilize the 12v+ source to charge the surge brake battery. If you follow the trailer wiring from the connector to the junction box (if so equipped). Use a test light to determine which wire to splice into. With the connector connected to the vehicle with the key and lights off, there will only be one hot wire. You can also locate this wire (to determine the color) from the micro charger located inside the surge brake battery compartment.
    Run a splice from that wire and a ground wire to your "DC to DC" battery charger and then from the charger to your aux battery.
    [​IMG]


    You must be aware that whenever the trailer connector is connected and the Aux battery is discharged, you will draw power from your truck even when it's not running. Unless you wire a switch to the supply wire to the charger.
    ^--Dis-regard that:
    The 12+ trailer charging port on the connector is keyed to the ignition.


    Note: I do not endorse or have I ever used the Powerstream brand charger. I just supplied a link for you to research.
     
  3. Feb 21, 2010 at 1:31 PM
    #3
    RX2RIDE

    RX2RIDE Well-Known Member

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    I am looking for this same info and posted it today on another fourm. What if you do not have brakes? I simply have the 4 way plug on the trialer and a 7 way on my Tacoma
     
  4. Feb 22, 2010 at 2:55 PM
    #4
    CtryBoyInMT

    CtryBoyInMT Lifetime Member

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    You will need to replace the 4 flat on the trailer to a 7 RV plug. Run the extra wire from the 12+ constant.

    If you hold the trailer end of the connector and look at it (as if you were going to plug it in your mouth:D), it will be the #4 Black terminal.
    [​IMG]
     
  5. Mar 1, 2010 at 4:15 PM
    #5
    mesmeralda

    mesmeralda [OP] Member

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    So in essence if I have trailer brakes I can tap into the hot wire for charging purposes?
     
  6. Mar 2, 2010 at 11:34 AM
    #6
    CtryBoyInMT

    CtryBoyInMT Lifetime Member

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    Not sure if I understand your question.
    If I get into too much detail you already know, I'm sorry. Just want to make sure all basis are covered.:D

    Electric trailer brakes utilize both the Blue and Black wires for proper operation.
    The Blue wire goes directly to the brake magnets and is of a variable voltage depending on braking requirements.

    The Black wire is a constant 12+ source for charging the little on-board battery for the brake system.

    As long as you use the constant 12+ source for your 12v to 12v charger, your good to go.
     
  7. Apr 2, 2010 at 6:00 PM
    #7
    flawless

    flawless Member

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    I just checked with a light indicator and there are NO hot wires running to the 7-way plug with the truck off and the lights off. This is a 2005 with tow package. I only get one constant hot lead if I turn on my running lights.

    I am trying to use a hot wire so that i can run my dome light in my trailer off of the truck without starting or turning on the running lights which is how it works now.

    Will there be a hot wire on the trailer after I plug it in, maybe at the break-away break battery? I assumed nothing would be hot on the trailer if there was nothing hot at the plug. Thanks for the help.
     
  8. Apr 3, 2010 at 8:28 PM
    #8
    CtryBoyInMT

    CtryBoyInMT Lifetime Member

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    I stand corrected. The charging port on the connector is keyed to the ignition switch. Fixed original post.
     
  9. May 9, 2010 at 7:45 AM
    #9
    Dr Rocken

    Dr Rocken New Member

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    Tow Mods: Air Bags, E-Bracks, 4 & 7 pin plug.
    The Tacoma with the stock tow pac has a relay to turn the hot wire on and off with the key.
     
  10. May 14, 2010 at 5:37 AM
    #10
    71roadrunner

    71roadrunner Active Member

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    .

    I own an FJ Cruiser (5,000# tow capacity) and they only come with the harness for the 4-way flat plug. I'm not sure what the factory provides on the Taco, but I needed the 7-way plug for my 3200#camping trailer as I had to have the electric brakes functioning as well as the trailer battery charging while I drive. So I went ahead and utilized the 4 wire harness for lights and then wired an additional harness front to rear on my FJ.
    Do yourself a big favor and buy good wiring (for the extra harness) to run from front to rear on the truck. I ordered 20' of: Jacketed 2 Wire, 10 Gauge, Brake Wire (from etrailer.com) @ $.89/foot. It's two (2) insulated 10 gauge wires (red & white) inside of another jacket. One wire for the electric brake and the other for the trailer battery charging circuit. You want the 1st 10 gauge wire for the trailer brakes because they operate by magnets and are current dependent (I don't like unnecessary voltage drops before you reach the trailer). The 2nd wire is the battery charge circuit. I merged the factory 4 wire and my 2 wire into the 7 way plug I bought. This set-up works like a charm.

    .
     
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