Tapping into 7 pin trailer plug outlet in bed for 12v power

[SFAngus]

I read a few different posts on people using the Curt 7 pin splitters for different purposes, but I couldn't find a relevant answer to my question:

I want to have a 12v constant power supply in the bed of my truck, and I'm trying to figure out if I should use the blunt cut wire from the tailgate, or if I should buy a spare 7 pin wiring harness, and just splice into the constant 12v lead.

I'm thinking something like this:

Amazon.com

I will be using the 12v power to run a small 12v bus bar, which will in turn power 12v led lights, a 12v power outlet, and USB charging ports.

Any advice is appreciated, as always.

For reference, this was the 12v power station that I installed in my last bed, but I want something a little larger:

 

[SFAngus]

So... this is a bit random, but while searching online for something unrelated, I stumbled across this "Stow n charge" device on topperezlift.com.

It seems to basically be a slightly overpriced version of what I was trying to accomplish. I think I'm still going to make my own version using a Curt replacement 7 pin harness, but the fact that they sell something specifically designed to use the 7 pin as a 12v power source in the bed makes me think that my idea will work.

Stow-In-Charge - TopperLift

Truck camping with TopperLift. Live on the road, setup camp at the touch of the button.

topperezlift.com

 

[Razzman]

On my last truck I wanted power for the factory LED bed lights I installed, didn't want the factory wiring method. Installed a Curt harness inline with the 7 pin factory harness that adds a flat four connector. Cut off the connector and had power for the lights, worked perfect. However a year or so later I had issues with trailer lights blowing fuses, tracked it back to the Curt, removed it and problem solved. Sold the truck before I figure out why.

https://www.amazon.com/CURT-55384-Custom-Wiring-Connector/dp/B0009FJ38Q

 

[SFAngus]

On my last truck I wanted power for the factory LED bed lights I installed, didn't want the factory wiring method. Installed a Curt harness inline with the 7 pin factory harness that adds a flat four connector. Cut off the connector and had power for the lights, worked perfect. However a year or so later I had issues with trailer lights blowing fuses, tracked it back to the Curt, removed it and problem solved. Sold the truck before I figure out why.

https://www.amazon.com/CURT-55384-Custom-Wiring-Connector/dp/B0009FJ38Q

View attachment 19946

Hmm. Good to know, thanks for the heads up. My application would be a little different, because instead of adding the 4 pin off of the 7 pin, I would just plug a 7 pin into the bed just for this purpose, and the trailer would still use the 7 pin on the bumper.

Perhaps that would make enough of a difference to not create issues, since the trailer and the aux power would be coming from different outlets?

 

[Fishnerd]

I'm thinking something like this:
I will be using the 12v power to run a small 12v bus bar, which will in turn power 12v led lights, a 12v power outlet, and USB charging ports.

Any advice is appreciated, as always.

Do you know what you will be powering with the 12v power outlet? One thing to consider is the wire size of the trailer wiring harness. I recall the wires being fairly small. You will have to take into account the amp draw on whatever you plug in. Lets assume that the trailer wire 12ga and the oem harness is less than 13ft (and assuming the wire is pure copper vs copper clad aluminum), you would be limited to 20amps. Note portable air compressor usually draw 30amps.

 

[SFAngus]

Do you know what you will be powering with the 12v power outlet? One thing to consider is the wire size of the trailer wiring harness. I recall the wires being fairly small. You will have to take into account the amp draw on whatever you plug in. Lets assume that the trailer wire 12ga and the oem harness is less than 13ft (and assuming the wire is pure copper vs copper clad aluminum), you would be limited to 20amps. Note portable air compressor usually draw 30amps.

Yeah, that's basically what I was wondering... my plan is to run the 12v power to a bus bar, which in turn will power 12v led lights for the camper shell, as well as USB charging outlets, and a 12V DC outlet.

Do you think the blunt cut wire at the tailgate would provide more amperage? Or, I guess I could also use both to maximize my available amperage... use the 7 pin for the lights and USB chargers, and use the blunt cut for the 12v DC outlet.

 

[Fishnerd]

Yeah, that's basically what I was wondering... my plan is to run the 12v power to a bus bar, which in turn will power 12v led lights for the camper shell, as well as USB charging outlets, and a 12V DC outlet.

Do you think the blunt cut wire at the tailgate would provide more amperage? Or, I guess I could also use both to maximize my available amperage... use the 7 pin for the lights and USB chargers, and use the blunt cut for the 12v DC outlet.

Yeah, that's basically what I was wondering... my plan is to run the 12v power to a bus bar, which in turn will power 12v led lights for the camper shell, as well as USB charging outlets, and a 12V DC outlet.

Do you think the blunt cut wire at the tailgate would provide more amperage? Or, I guess I could also use both to maximize my available amperage... use the 7 pin for the lights and USB chargers, and use the blunt cut for the 12v DC outlet.

Sorry im not familiar with the the blunt cut that you are referring to. It all comes down to the wire size and the what you want to power. The “blunt cut” wont necessarily “provide more amperage” in theory it can supply as much amperage you need but at the expense of heat and risk of fire, which is something to consider. Led lights and usb charging are fairly small loads and wouldnt be overly concerned with. If you are planning to plug in something that draws significant amperage i.e. compressors, tools, etc i would consider running a dedicated fused larger 12v wire to the rear vs utilizing the trailer wire.

 

[SFAngus]

Sorry im not familiar with the the blunt cut that you are referring to. It all comes down to the wire size and the what you want to power. The “blunt cut” wont necessarily “provide more amperage” in theory it can supply as much amperage you need but at the expense of heat and risk of fire, which is something to consider. Led lights and usb charging are fairly small loads and wouldnt be overly concerned with. If you are planning to plug in something that draws significant amperage i.e. compressors, tools, etc i would consider running a dedicated fused larger 12v wire to the rear vs utilizing the trailer wire.

Thanks for the advice. The blunt cut wires are wires that Ram runs to the rear of the truck for accessories. They sit just above the spare tire, and there are three of them: CHSML (3rd brake light, mostly for toppers/shells), constant 12v, and switched 12v. They are decent sized, so I'm thinking maybe they would handle a little more draw.

The blunt cut wires are described briefly here, around the 1 minute mark:

 

[Gondul]

Thanks for the advice. The blunt cut wires are wires that Ram runs to the rear of the truck for accessories. They sit just above the spare tire, and there are three of them: CHSML (3rd brake light, mostly for toppers/shells), constant 12v, and switched 12v. They are decent sized, so I'm thinking maybe they would handle a little more draw.

The blunt cut wires are described briefly here, around the 1 minute mark:

Conversation here about just that...

https://hdrams.com/forum/index.php?threads/blunt-cut-wires-rear-of-truck.6222/