Can I Charge My Trailer Battery Using 7-Way Trailer Connector on Truck

Question

Question:

My truck is equiped with a 7 way plug. Is there any way I can use one of the leads to charge a battery in my trailer? Currently, the trailer has a flat four plug that I connect to the truck using an adapter. Any help is appreciated. Thanks,

asked by: Dennis P

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Expert Reply:

You would not be able to charge your battery through the wiring on your 4-way trailer connector. Since your truck has a 7-way connector, you could maintain the power to the battery but not charge it.

To begin, you would need to cut off your 4-way trailer connector and install a 7-way connector on the trailer like the Optronics 7-way, part # A7WCB. You would need to connect the appropriate wires. White is ground, Yellow is left turn and brake, Green is right turn and brake, and Black is the hot lead that you will tap into later. If your trailer does not have brakes or reverse lights you would not connect these pins (see picture).

To maintain power to the battery, you would need to run a wire from the positive terminal on the trailer battery to the power wire on the 7-way. I would recommend using 10 gauge wire, part # 10-1-1, and connecting to the Black wire on the trailer 7-way, or the pin in the 11 oclock position when looking at the front of the connector to the positive battery terminal (see FAQ). You would then connect the negative terminal to a clean metal surface on the trailer frame for a ground connection.

I have linked an FAQ on wiring and a diagram showing the wiring pin out for the trailer side 7-way.

expert reply by: Reno H

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Sean D.

6/19/2020

i want to do the same. my trailer has a 7 pin and a brake box. i want to use battery for lights and usb charging at the track. i just want the TV to charge the trailer battery while we are traveling and not drain the tv battery while we are parked

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Chris R.

6/23/2020

The above method will do a nice job of maintaining the trailer battery charge but the 12V circuit won't provide quite enough power to actually charge the battery up during travel. If you'll actually need to charge the battery your best option will be to add a DC to DC charger like the Redarc # 331-BCDC1225D, which will boost that charge and includes an isolator to cut off power when the truck is off.

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Jason B.

2/27/2024

@ChrisR would this connect to 7 pin/ 7pin fuse box?

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Mike L.

2/28/2024

@JasonB The Redarc DC to DC charger would not use the trailer connector. We'll link you to an excellent install video that will explain the process for you. Just let us know if you have any questions.

Helpful Links

tv-install-redarc-in-vehicle-battery-charger-331-bcdc1225d.aspx

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Rich B.

7/8/2020

On a 2011 Pilot does the 7 Way also control the trailer brakes on a 2020 RP-190 travel trailer?

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Chris R.

7/13/2020

The 7-Way connector on your Pilot will have the brake output pin that carries this circuit, but you will still need to add a brake controller to actually send the power. Since you already have a 7-Way I recommend the Curt Echo # C51180, which will plug right into the 7-Way itself and pair to your smart phone.

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Answer 1

You can put a maintenance charge on your trailer battery with the 12 volt accessory circuit of the 7-way. The 1:00 position of your 7-way carries this circuit. You would just need to run a length of 10 gauge wire like part #10-1-1 (sold by the foot),…

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Answer 2

You are correct in your description of how to wire in a new auxiliary battery in your enclosed trailer. You will take the 7-Way's 12V power feed and route this to the positive terminal on the auxiliary battery, and you will ground the second…

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Answer 3

Yes, in order to set your trailer up for use with shore power you will first need an AC distribution panel. For this, I recommend a Progressive Dynamics Series AC Distribution Panel. In order to bring power into the panel you will also need a power…

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Answer 4

On an 4 foot long section of E-track #EM19147 and 2 screws every 16 inches that is a total of 6 screws in the aluminum frame. This most likely will not get you near the capacity of the E-track. I recommend bolting through the aluminum frame so that…

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Answer 5

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Answer 6

The auxiliary 12-volt wire that runs from the 7-way connection to 7-way trailer plug will supply 12-volt power from the vehicle to the trailer. The 12 -volt power will allow interior or exterior lights to run that are not wired in to the…

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Answer 7

Typically, the 5th circuit of a 5-way is for a reverse light circuit. I have a solution for you, but you will not be able to use the Adapter 7 Pole to 5 Pole Flat #A75TB to activate your trailer brakes as it has an empty port where the brake output…

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Answer 8

E-tracks are typically the stronger of the two, but X-track is more versatile since you can mount them horizontally or vertically. Choosing between the two really depends upon how you plan to use them. If you are installing something in a truck bed,…

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Answer 9

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Answer 10

In order to charge an on-board trailer battery you'd need to have a seven way connection on both the vehicle and trailer, this would contain the necessary circuits to pass a charge from the vehicle battery to the trailer battery. If you don't…

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Answer 11

The best way to power the interior lights in your trailer is with its own independent battery. You will not want to use the breakaway battery. The breakaway battery is only designed to operate the breakaway and will drain extremely quickly,…

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Answer 12

We do have a 7-way blade wiring harness available for your 2023 Toyota Highlander. What you need is the Tekonsha OEM Replacement Vehicle Wiring Harness #TK57VR. This plugs into the connection in your rear cargo area for installation. You can use the…

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Can I Charge My Trailer Battery Using 7-Way Trailer Connector on Truck

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