DIY 6x12 Cargo Camper with Solar

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Joined
May 25, 2017
Messages
392
Hey folks! Here is one of my most ambitious projects for a long time. Converting a cargo trailer into a camping trailer. This will be semi off grid, so both solar and grid power. Oh, for my metric friends, this is a build in the US, so it's a 6 feet by 12 feet trailer and 120VAC at 60Hz grid connection. I've got reasons for wanting to do this instead of just buying a camper.

- Customization
- Lower cost
- Sounds like fun

So here is a floor plan and wiring diagram. Keep in mind these are works in progress, and will probably change over time. Gotta start somewhere though.
FloorPlan1.jpg

CargoCamperElectrical.jpg


Anyway, I thought you all might be interested. :)
 

OffGridInTheCity

Active member
Joined
Dec 15, 2018
Messages
1,706
Nice drawing - it really does help to lay things out before doing the actual hookup.

One thing that jumps out at me is the green boxes at the top-left that say "Solar Panel 40a12v". I don't know of any panel that produces 40a, so I'm curious as to what you intend :)
 

cak

Member
Joined
Mar 14, 2021
Messages
52
Looks like a big project :) Nice detailed plan. I like your plan to have the core of the system 24vdc. I made the same choice for my off grid cabin. Some thoughts relating to the 24v pieces. It might be a typo but why would you use 12vdc panels to charge a 24v battery? It is easy to get higher voltage panels and many mppt charge controllers can accept 1-3 standard 44 short circuit voltage panels in series and can charge 24v. On the other side of the system most of the appliances you list have 24v versions which would help with wire voltage drop energy loss and simplify the system. For my cabin I have all the dc wires with 24vdc and for the few uses that need other voltages I have usb c power delivery that runs off the 24v and can make many lower voltages with cheap sink boards. For most connections I don't want to be wired in I have Anderson PP 45A connectors. You can also get dc(12v or 24v) fridges which would reduce energy loss from the inverter. In my cabin I have an inverter 6kw that also works as the charge controller when I need to top the batteries off in winter.

On a different note you may want a switch that only has the alternator charge when you need it. Ideally most charging will be done by the solar and might as well not waste the engine resistance using the alternator to charge when you don't need it. By my math 180A 8s battery would be about 5kwh not 1229wh. depending on how much sun you get and how long you want to be unplugged that seams like enough for everything except the air conditioner. In my cabin we are currently using about 5kwh per day without an air conditioner but using my high powered desktop computer and electric induction cooking.

Have fun and I am sure we would all love to hear how the project progresses.
 
Joined
May 25, 2017
Messages
392
Thanks guys!
The two solar panel banks would be 5 parallel 100W panels, so 41.7A. I just rounded down to 40A. I figure I'm not likely to get 100% power from the panels anyway. And I found some that will fit 10 on my roof. My solar charge controllers are boost converters and can only do 600W each, so putting them in two groups will keep each controller well below it's limit.

All the DC appliances I've seen are way to expensive for me. But I will keep things accessible for future upgrades and repairs.

The manual off switch from the truck is a good idea. In fact, I've already designed how the power will come from the truck:
CargoCamperAlternator.jpg

Still a work in progress. I don't know the length of wire I'll need or what gauge to help limit voltage drop. But the power will only be available if the truck is running, and if I have the switch (which will be on the dashboard) turned on. I also don't know how many Amps I want. Right now I'm guessing 5A wouldn't be too hard on the alternator. Probably won't charge the battery at all, but will send a little power to help run the fridge.

The cells I'm looking at are 60Ah, LiFePO4, but the spec sheet recommends only discharging to 80%. Or maybe they mean 80% discharge would be the bottom voltage of 2.5v. I'm not sure, so I'm assuming only 48Ah to be safe. At 3.2V nominal they would be 153.6Wh each, and 8 of them in any configuration would be 1228.8Wh. These cells are cheap enough that I could buy another 8 in the future and make an 8s2p battery and double the Wh, if I find I need it.

One guy just made a trailer with a 600Wh battery, and runs his A/C and a fridge and a stereo. I have no idea how much power stereos use. He says his solar powers most everything, and the battery only discharges very slowly. He's in Florida though, and I seriously doubt I'll get that much sun here in Washington, LOL.

A lot of the time, we should have access to grid power, but I'd like the option to have a day or 2 without it so we're not totally dependent. In that case, I'd probably use the A/C very sparingly, and we'd have a small generator if things got desperate.

The USB ports could run on as high as 30V, so they could be run directly off the battery like my CPAP will be. Depends on how I do the switching. I designed this console thing to go above the bed. A couple of reading lights, USBs for phones and whatever, 12V socket for my wife because she has this tablet thing for work that doesn't work on normal USB ports. It has to have its own proprietary thing. And a 24V socket for my CPAP.
ConveniencePanel.JPG


I'm also trying to keep as much of the electrical stuff centralized as I can. A lot of it will fit in this cabinet:
FloorPlan4.jpg


All the AC stuff will be in the cabinet except for an outlet in the kitchen for the microwave. Everything is still estimated though, and anything could change. I need to get hold of an actual trailer before I can start to be sure of anything. I'm hoping to hear from a company tomorrow...
 
Joined
May 25, 2017
Messages
392
Company says it can get one built in 8-12 weeks. And I've got 2/3 of the money saved up already! Looks like this project may actually happen. :)
Here's some detail I made of the front and back.
FloorPlan2.jpg

Nothing is to scale yet, except the microwave.

I've also started thinking about how to install the air conditioner.
AirCon.JPG

Since the unit will be in a cabinet instead of hanging out a window, it will need air flow, and drainage for condensation. Still guessing on the actual cabinet size, but what other people have done is separate the hot exhaust from the cool air intake on the sides and top. I figure I'll paint and caulk the inside of the cabinet with outdoor rated stuff, and install a drain in the a/c pan, and one on the bottom of the cabinet, and route those down to the floor. The vent I have in mind is one that can be opened, so I'm thinking of putting in an insert to block the vent when the a/c is not in use to help keep weather out.
 
Joined
May 25, 2017
Messages
392
Slightly related to the trailer project is a custom panel I'm building for my truck, to replace the old AM/FM Cassette player. When it's done, I'll have a switch to manually shut off accessory power to the trailer. Also, it will only work if the ignition switch is on. So it can't drain my battery if I walk away with the keys and forget to shut it off.

I found a small Blue Tooth amplifier so I can get audio from my cell phone to the truck's speakers, and divided up the various wires from the old player to use for the new stuff.
a829103e5f1b6b5f59500f4202bdce73.jpg


I made a cardboard mock-up of the panel so I could see how all the things would fit. Or if they would fit. Then I started making permanent connectors.
20210816_082007.jpg


Today I made the actual wood panel and fit all the parts on it, and got it fit to the bezel.
P8180002.JPG

P8190003.JPG


The clock runs on a circuit directly to the battery for timekeeping, and the display lights up when the dashboard lights are on. The only hygrometer I could find runs on its own battery, but everything else will run on the circuit that used to send power to the old player. I wanted a hygrometer because I have humidity issues inside the cab in the winter.
P8190004.JPG

P8190008.JPG


I wanted everything in green to match the rest of the dashboard, but it seems that's a hard color to find. Also wanted switches that light up when they're on, so they have their own ground pins. The first switch turns on the amplifier, and the last switch will be for the trailer circuit. The middle one will be for a backup camera that I haven't installed yet. I added a volume control for the amplifier, as its lowest volume is still too loud if I'm not driving. And the startup sound is really annoying, LOL.

Rather than run the trailer directly from the switch and circuit, I'm going to put in a relay, and add a fused circuit specifically for the trailer. I don't know yet exactly how I want to put that in. No hurry though, since I don't have the trailer yet.
 
Joined
May 25, 2017
Messages
392
Well, I've actually ordered the trailer! Should be here in a couple months. Also, total weigh, and weight distribution in the trailer is important. I've started building a list of stuff that will go in the trailer, and added a tongue and axle weight calculator at the bottom.
Weight3.JPG

Thins in yellow are only estimates. As you can see, it's a total WIP, and everything is either yellow or not there yet, LOL. Also, it's pretty hard to know exactly everything that goes into the project, so I've found a way to make real life weight measurements as I go, without needing a commercial scale.
Weight2.jpg

Who knew physics has real world applications, LOL.
 

OffGridInTheCity

Active member
Joined
Dec 15, 2018
Messages
1,706
I just finished a 7 x 14 cargo trailer -> camper. The base was 2000lb and it wound up 3800lb - e.g. 1800lb of build-out. It has 4 x 300w panels, 14s88p 18650 battery, PIP 3048, 9000BTU heat-pump, 2 x 30# propane, 40gal water tank, 9 cabinets, and eu3000is generator among the heavier things.

You've got your work cut out for you! I'll be interested to follow your progress :)
 
Joined
May 25, 2017
Messages
392
Mine is pretty simple. No propane or water heaters. No water tanks. Just a couple jugs. Generator will be in the truck. No bathroom or shower, though I do plan to have an emergency toilet. The trailer is supposed to weigh 1,100 lbs stock, and I'm taking out about 240 lbs of OSB as soon as I get it. I may leave off a couple solar cells. 10 is the max I can fit, but I'll have to see what I can use through a charge controller. I'm a total solar noob, so I'm learning this as I go. :)
 
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