The Problem

When I'm dry camping without an electric hookup, I'm limited to only the 12v system that runs off the battery. The only things that really run on this system are the lights, water pump, and the motors for the slide out room and tongue jack. This means I can't use any of the outlets to charge my phone or laptop, can't use my second monitor, can't watch TV, etc. Up until now I've gotten by just running the generator whenever I needed to do any of these things, but now that I have a solar panel I wanted to be able to do more off my batteries.

The Solution

I decided I wanted to install a large power inverter that would connect to the batteries and convert the 12v DC battery power into 120v AC power. Then, in order to get power to the whole camper I would install a 30 amp outlet on the outside and run that to the inverter. This way I could plug the main camper power cord into the outlet and it would be like I was connected to shore power. Furthermore, I wanted to install a battery monitor so that I could see the charge level of my batteries. And while I was at it, I also decided to install a battery disconnect switch so that I could cut the power to my RV for times when I need to store it or work on the electrical system.

One problem with my inverter solution was that the camper has a converter built in that charges the batteries when the camper is hooked up to shore power. So running the inverter this way would basically be using battery power to charge the batteries. It would just be wasted energy. So I knew I needed a way to turn the converter off.

The obvious solution was to just flip the breaker that the converter is on, however, I realized that my outlets were all on the same circuit as my converter. Fortunately the breaker box had an empty slot and I was able to move the converter to a new breaker.

Moving the black converter wire into a new breaker

Now that I was able to turn off the converter, it was time to get started installing the inverter, battery monitor, and power switch. I had been planning this install for several months, so I had plenty of time to work up some plans and wiring diagrams. At this point I basically just started wiring according to the diagrams I had drawn previously.

One of the most important parts of this setup is the battery monitor. The monitor came with a device called a shunt which connects to the negative terminal on the battery. Then, any device that you want to add to your system that will either pull a load or charge the battery needs to be connected to this shunt, rather than directly to the battery. So in my planning I decided to only have two wires come into the camper from the batteries. The negative would connect to the shunt, which would then connect to a bus bar (which just gives me 4 extra terminals to connect things to). Then, anything that was connected to the bus bar would be going through the shunt. The positive wire coming in would also connect to a bus bar, and then all positive wires would also connect to it.

Once I had the wiring figured out, I measured the inside of my front pass-through storage area and cut out a piece of plywood that would fit. I then started screwing the components into the plywood and wiring them together. Before mounting it all inside the storage area, I decided to test it outside to make sure everything worked correctly.

Testing the components before installing.

After verifying everything was working, it was time to mount the plywood inside the storage compartment. From there I planned to run two large, 0 gauge battery cables from the battery box outside up through the floor into the pass-through storage area to connect to the two bus bars I mounted on the plywood. This was probably the most difficult part of the whole install. My camper has a sealed underbelly so I had to open that up first.

Of course Earl had to jump in as soon as I got it open

After opening the bottom plastic layer, there was another layer that was full of insulation that I had to go through as well. I eventually managed to get the holes drilled and ran the cable through to connect to the bus bars.

Everything installed in the pass-through storage area. Annotated image here.

In the image above, you can see the shunt on far left side. The wire coming up through the floor is the battery cable, which connects to the shunt. Then another wire connects the shunt to the black bus bar. Above the shunt is the battery disconnect switch (you can also see the camper wires coming up through the floor), and on the far right is the 1200w inverter. To the left of the inverter, two additional wires are coming up through the floor. These wires connect to exterior terminals that I installed in the top of the battery box.

Exterior terminals installed in the battery box.

These exterior terminals will allow me to connect my solar panel, and also devices like my water pump, without having to open up the battery box. The reason I had to run these cables back into the camper, rather than connecting right to the battery, is so that they could connect to the battery monitor shunt.

I only had to run two wires into the main living area of the camper, and those were the wires for the inverter remote and the battery monitor display.

Battery monitor display (top) and inverter remote (bottom).

These are mounted in the night stand area to the left of my bed. The inverter remote allows me to turn the inverter on without having to go outside and reach in the pass-through storage area. The battery monitor display will show me voltage, current, estimated time remaining, and a bunch of other useful information. The monitor I got also came with a bluetooth module and an app so I can view all of this information on my phone.

Interface of the bluetooth battery monitor app (iPhone).

Now with everything installed, the last thing to do was run the outlet that would let me connect the main camper power cord to the inverter.

I bought a metal outdoor box, a 30amp female outlet, and a cover plate to protect the outlet.

30 amp outlet, cover, and box

Then I bought a standard 15 amp extension cord to use for the wiring of the outlet. I cut the female end off of it, as this would get wired into the 30 amp outlet. The male end would get plugged into the inverter. I also drilled a hole in the floor next to the inverter so that i could run this cable to the outlet.

15 amp extension cord with female end cut off.

I then mounted the box onto the front of the camper frame. Fortunately there was already a hole drilled into the frame where I could run the extension cord wire. Then I wired the extension cord to the outlet, adding a ground wire that connected to the screw in the box.

Installed outlet box and wired outlet.

Now it was just a matter of closing everything up and testing it out. I pulled out main power cord from the back of the camper and pulled it all the way around to the front and plugged it into the new outlet.

Finished outlet with main camper wire plugged in

Then I went inside and flipped the power switch on the inverter remote. Sure enough, the microwave and refrigerator turned right on and I could see the power light on the TV kick on. I also looked at the power it was using and noticed that turning off the converter lowered it by about 250 watts, so I was glad to have found an easy way of disabling that. Overall, everything worked out exactly as I had planned.

Conclusion

With this new setup I should be able to camp off-grid for long periods of time without having to constantly run my generator. Now I can charge my laptop and phone and run other 120v devices off my batteries while my solar panel keeps the batteries charged.

Moving forward, I know the weakest point in my setup is my battery capacity. Since I only have two group 24 deep cycle batteries, I only have about 125 amp hours. With this small of a capacity, running something large like a microwave or a toaster would be possible, but it would significantly drain my batteries. Eventually I would like to get a bank of 6v golf cart batteries which could get me to more like 400 amp hours, but for now I'm happy with what I've got. It should allow me to work while I'm off-grid and for larger things like the microwave I can still run the generator.

Parts List

The following are the main components I purchased for this install:

Additionally I had to purchase smaller battery wire, ring terminals, cable clips and zip ties, several different tools I didn't have, etc.