How to easily add 12V outlets into your RV slide

Installing 12V Outlets in our Slide Out

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Adding 12V outlets in our slide to make our dinette area even more usable.

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Introduction

One of our favorite features about our Outdoors 21RBS is the slide with its huge dinette. With the wrap around windows and skylight above, the area is really bright and sunny. Plus the dinette itself is large and sturdy enough that Diana and I can sit opposite one another and work comfortably on our laptops.

We often work at the large dinette, but the lack of 12V power means trailing wires across the floor.
We often work at the large dinette, but the lack of 12V power means trailing wires across the floor.

Except, there's no power.

Well, slight correction: there is a 110V AC socket under the dinette seat on one side, but we keep the inverter turned off when we're not using it since it has a fairly high background draw (around 3A @ 12V DC or 35W). So to charge our laptops (which are powered by USB-C), we run a USB-C cable from an adapter in a 12V outlet we installed in the end of the bed. Although trailing a cable across the floor isn't ideal, it's worked OK so far.

This 110V AC outlet is the only source of power we have in the slide - and it only works when we have the inverter turned on.
This 110V AC outlet is the only source of power we have in the slide - and it only works when we have the inverter turned on.

But, we recently bought an AeroGarden. If you've not heard of these before, they're self-contained hydroponics system for growing flowers or herbs (the legal type!). We had two of them in our house before we hit the road, and loved growing fresh basil, dill, mint, thyme, etc. Unfortunately the AeroGardens both ran off 110V AC and there is no easy way to modify them to run off 12V DC - trust me, I've spent a lot of time researching it!

Recently however, we came across the AeroGarden Harvest line, and it turns out that these run on 12V DC - perfect! We bought an AeroGarden Harvest Elite that we can keep on our dinette and have fresh herbs whenever we want them. Except this would mean having a 12V cable trailing across the middle of the RV - not a good idea.

The solution? Install some 12V outlets in the slide itself.

The Plan

Every RV is different - maybe you're lucky and already have 12V outlets in your slide. Our slide has 12V going to it, but only to power a ceiling light. This light doesn't even have a switch on the wall - the switch is on the light itself. With no easy way to trace where the wiring runs, tapping into that was a no-go for us.

If in your RV you can get to the 12V wire, you might want to consider tapping into that. Maybe there's a light switch on the wall, or you can see 12V wires under the dinette bench. Sadly not so for us.

In our RV, both the 110V AC and the 12V DC power is supplied via two coiled wires that run under the slide and disappear up the wall. Looking more closely, I found that there is a wire splice on the 12V wires at the bottom of the slide wall - I can cut out this splice, then install a new splice with an additional pair of wires for the outlets. I would then be able to run this wire alongside the 110V AC wire up into the slide, and install the 12V outlets right next to the existing 110V AC outlet.

Both 12V and 110V power is delivered to the slide via these coiled wires underneath the trailer.
Both 12V and 110V power is delivered to the slide via these coiled wires underneath the trailer.

We chose to install a 3-outlet panel. This would give us a dedicated 12V outlet for the AeroGarden Harvest Elite, plus have 2 additional outlets for charging laptops, etc.

Tools & Supplies

Disclaimer: As always, electricity can be dangerous and if you are not completely confident in what you're doing then hire a qualified professional to do the job for you.

Whether you're working with 12V DC or 110V AC, remember to disconnect power by using shutoff switches and / or removing fuses - and make sure the power is off by checking with a multimeter.

The installation on our RV is pretty straightforward - depending on your layout it may be easier or more complex, but the general approach is the same. All you'll need is basic tools and simple supplies. Below I've listed the specific items you'll need, but I'm assuming you also have tools such as a screwdriver and pliers available too since you may come across cable clips that need loosening, or similar.

Tools

Here are the tools we used - I've linked to specific products in case you're looking to buy them, but if you have something similar then that's fine.

Supplies

The triple-outlet that we bought came with some spade terminals, but I chose to use my own since they were higher quality and slightly larger to accommodate the thicker wire I chose to use.

Install

Since I was confident that the wiring would be fairly straightforward, I chose to start by mounting the outlets. This would make it easier when wiring to get the wires the exact length.

Mounting the outlets

We chose to mount the 12V outlets alongside the existing 110V AC outlet on the bench under the dinette. This will keep the outlets out of the way, but still easily accessible when we want to plug things in. Furthermore, it would simplify the wiring later on as I'd be able to follow the existing 110V AC wiring run.

We used this triple 12V outlet from Carviya. Although it came with screws and terminals, we didn't use these in the end. The outlets seems sturdy though.
We used this triple 12V outlet from Carviya. Although it came with screws and terminals, we didn't use these in the end. The outlets seems sturdy though.

We started by removing the dinette seat and emptying everything out of that end of the dinette storage area. It's worth noting that the back side of the outlets is unprotected - that's not an issue for us as we can be careful with what we store there, but if you're concerned, I'd recommend covering the back of the outlets with a protective box or cover.

Using a piece of scrap 1x4 cut to a few inches longer than the 12V front panel, I marked the locations of the holes and drilled them out. Our dinette seat front panel is just thin hardboard, and the 1x4 behind would give it extra strength and rigidity.

This piece of scrap 1x4 was perfect to use as a backing board for the outlets to make the mount a little stronger.
This piece of scrap 1x4 was perfect to use as a backing board for the outlets to make the mount a little stronger.

I lined up the 1x4 on the back side of the dinette bench and drilled a small hole through the center hole. I covered the front side with blue painters' tape - the thin hardboard always blows out on the back side, and the tape will help create a clean hole on the front side. Using the 1x4 as a template, I drilled out the three holes. Since the holes are slightly larger than the threaded barrels on the outlets, it doesn't need to be perfect, but get them as close as you can.

A few stripes of blue painters' tape really helps to stop the hardboard from blowing out when drilling holes in it.
A few stripes of blue painters' tape really helps to stop the hardboard from blowing out when drilling holes in it.

I placed the front panel on the front of the dinette bench, the 1x4 on the back side, and pushed the 3 outlets through. I tightened down the screw rings as tight as I could by hand, making sure to align the 3 outlets as I did so.

We chose not to install the 4 screws in the front plate - with the rings on the back, the panel isn't going anywhere. If I change my mind in future, it'll be easy enough to install the screws, but it didn't seem necessary for now.

And that's it - the outlets are now securely mounted in position. Time to wire them up!

Wiring

Adventurous Tip: Now's not the time to be adventurous - make sure all the power is off on these 12V and 110V wires. Turn off switches and / or pull fuses - then check the power is really off!

The coils of wire leading over to the slide made this next stage really simple because there was loads of slack! I loosened a cable clamp at the bottom, and marked with a Sharpie pen where the cable passed through the clamp. Diana then pulled the 110V AC wire up from inside the RV while I pushed it up through from underneath.

Once she could see my Sharpie mark, we stopped feeding the wire through. From inside the RV, I used electrical tape to secure a length of my new 12V wire to the 110V wire, then Diana pushed both back down while I pulled from outside again. Once the wire appeared, I was able to remove the electrical tape, realign the 110V wire in the cable clamp and tighten it up. We now had our new 12V wire running from underneath the slide, up into the slide inside the trailer.

Running the wire for the 12V outlets was easy - we just taped it to the existing 110V AC wire and pulled it through.
Running the wire for the 12V outlets was easy - we just taped it to the existing 110V AC wire and pulled it through.

The next part was by far the hardest - not that it's complex, but at least on our trailer there was very little slack on the wires and there are sharp metal edges around. I managed to cut my knuckles a couple times, so be warned!

The 12V coiled wire was joined with butt splices to the existing 12V wiring as it disappeared up into the slide - and then this was all wrapped in electrical tape. I removed the electrical tape, cut off the existing butt splices, then stripped the 4 wire ends.

Adventurous Tip: Keep track of which colored wire goes where. In our RV, the white wires are negative while the black / green wires are positive.

I stripped back some insulation on the red (positive) side of my new wire, twisted it with the green (positive) wire and crimped these into one side of a new butt connector. I crimped the black (positive) wire from the trailer into the other side of this connector.

Adding new butt connectors to splice the various wires together. Keep track of which wire goes where!
Adding new butt connectors to splice the various wires together. Keep track of which wire goes where!

I then did the same thing with the black (negative) side of my new wire and white (negative) wire in the slide, crimping these into one side of another butt connector opposite the white (negative) wire from the trailer. Pay close attention to the colored wires, and if in doubt, check with a multimeter!

When both connectors were crimped in place, I used a heat gun to seal them, then wrapped everything in plenty of electrical tape and pulled the wire up inside the slide to take up the remaining slack. That's all the outside wiring, time to move inside.

Even though the butt connectors should have been strong enough with the heat shrink and adhesive, we wrapped each butt connector in electrical tape, then wrapped all of it together.
Even though the butt connectors should have been strong enough with the heat shrink and adhesive, we wrapped each butt connector in electrical tape, then wrapped all of it together.

The wiring inside is straightforward; essentially it's just a daisy chain. The red (positive) wire attaches to the positive terminal on the first outlet, which connects to the positive terminal on the second outlet, which connects to the positive terminal on the third outlet. Same on the negative side.

Although the wire I used is advertised as 12 AWG, I found it to be more 14 AWG. To accommodate two pieces of wire going into each connector on the first two outlets, I used 10-12 AWG terminals (yellow). On the final outlet there is just a single wire going into each connector, so I used 14-16 AWG connectors. Once all the wires were cut and crimped, I attached them to the outlets, then used the heat gun to seal the connectors.

Adding these terminals with the outlets already in position made measuring the wire lengths really easy.
Adding these terminals with the outlets already in position made measuring the wire lengths really easy.

Adventurous Tip: Sometimes the heat shrink will seal over the ends of the female connectors, which is why I attached them to the outlets before sealing them - just be careful with the heat gun so you don't damage anything!

Lastly, I used electrical tape to secure some split wire loom around the wire on the back of the outlets. This will provide a little more protection to the wires in case anything moves around in the storage space. I'll keep a close eye on this area though, and if it looks like anything is getting knocked around, I'll put a cover over to better protect them.

Depending on what's behind your outlets, you may want to cover them with a box, but for us, the split loom should be fine.
Depending on what's behind your outlets, you may want to cover them with a box, but for us, the split loom should be fine.

So that's it - last thing is to turn on the power and check everything works. We checked all three outlets and they all worked great.

Conclusion

This is a simple mod using only basic tools and supplies. But the end result is well worthwhile - using 12V where possible is much more energy efficient than using the inverter, especially for powering always-on products like our new AeroGarden Harvest Elite.

Not only that, but 12V (or USB) chargers are available for more and more devices these days - including phones, cameras, laptops, and more. Our laptops charge from USB-C, and we've found these USB-C 12V Adapters to work really well - they charge our laptops at up to 45W which, although not quite as fast as the 110V AC charger, is plenty fast enough for us! We have three of them now - two in the trailer and one in the truck.

Our AeroGarden and laptops can now be run directly from the 12V outlets under the dinette - no more wires trailing across the RV!
Our AeroGarden and laptops can now be run directly from the 12V outlets under the dinette - no more wires trailing across the RV!

We have so many devices these days that need charging, and it makes sense to charge these from 12V or USB where possible. We hope that RV manufacturers take note of these consumer trends and we'd love to see RVs coming with more 12V outlets and high-speed USB sockets. Ours came with one 12V outlets and 4 USB sockets - we've since installed four more 12V outlets and several more USB sockets.

Let us know if you have any small devices (laptops, cameras, etc) that need powering from 110V AC and maybe we can help you find a compatible 12V charger!

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