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Tiny cargo trailer to camper/sleeper conversion

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    Tiny cargo trailer to camper/sleeper conversion

    This is something I’ve been wanting to do for a couple of years but I just never had the time to devote to a project like this. Well, be careful what you wish for because you might just get it!

    Now that I’m medically retired from work, I needed something to keep my mind and body busy for a couple of hours a day. Low and behold, a small cargo trailer happened to fall in my lap for a price that I couldn’t pass up! So let me introduce you guys to this project!




    The trailer is an older retired Uhaul trailer that is 5’X8’ with an interior height of 52”. Yes, it is tiny! But I’m only 5’6” and Mrs 91CavGT is only an inch taller than me so we don’t need anything huge. Since it is a former Uhaul cargo trailer, it is overbuilt! It has a single axle with 6 lug 15” rims riding on 205/75/15 tires. With the size of the axle and the 6 lug hubs, I’m thinking this has a 3,500 pound axle. It has a small drivers side door in front of the axle and barn doors in the back. The frame is steel with strong fenders that you can stand on and an aluminum box for the sides and top. The floor appears to be 3/4” pressure treated plywood and looks to have been replaced a couple of years ago.



    So what are we going to use this trailer for?


    Primarily, we have been using it and will continue to use it to pick up supplies from hardware stores, move items while keeping things dry, and to take it camping. I have to preface the last word, camping, with this. My wife does not camp, she glamps. We do have a 5th wheel RV that we can take camping, but it is a 40’ RV and there are some places we just can’t take it. We have tent camped for a few years and my wife still likes to do that, but she wants a better area to cook, a comfortable place to sit down or lay down in the shade, and I want to ensure we have a dry place to sleep in case a storm comes through. I also want the ability to be able to take this boondocking or hunting without needing a generator.



    So here is the intro video to this trailer:


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    BTW, towing this behind my wife’s VW Atlas SUV is quit nice! With it empty and keeping the speed at about 65 mph and locking the car in 6th gear(it is an 8 speed auto), the car got 23 and 25 mpg from 2 different fill ups! Since then I’ve used this trailer to help us move. Over a period of 300 miles, half of those miles were with the trailer loaded, the VW Atlas averaged 20 mpg with about 80% highway and 20% city driving! The Atlas has a turbocharged 2.0L 4 cylinder and an 8 speed automatic.

    #2
    So what are my plans for the interior?


    First thing is to insulate it! Nothing huge, just 1/2” foam board insulation. Cedar planks will be installed on top of the foam board insulation so it’s only going to have an R factor of about 4, but with how small it is, that should be enough to hold the heat in come the winter and to keep some of the heat out in the summer.


    I want an AM/FM/Bluetooth radio along with a pair of car speakers. There will be lights, an exhaust fan(but different than anything that is out there), USB outlets, a 12v power outlet, a water tank, a water pump, a lithium battery bank(home built), a big solar panel that covers the entire roof, an MPPT solar charge controller, a sink, a single burner stove(with the ability to swap it out for a dual burner Coleman stove), a twin(ish) size bed that can convert into a padded bench, and a decent size power inverter.


    My goal is to have the bed where it can fold up out of the way, the water tank be removable, the kitchenette be able to fold out of the way, and possibly the battery bank be removable as well so we can still use this as a cargo trailer.


    As of right now, there are no plans for an air conditioner(although one could potentially be added in the future) and the toilet will be a 5 gallon bucket with a toilet seat on top(only for boondocking).

    Comment


      #3
      On this video I go over some progress. Got the weather stripping replaced on the back doors, except for the bottom. Later I will be putting weather stripping at the bottom of the doors to help keep out creepy crawlys.

      I found a solar panel that fits the roof PERFECTLY!!! It is about 4’ wide and 7’ long and less than 1/4” thick. It is also flexible with no glass on it so no worries about hail damaging it. Found this panel on eBay as a NOS model. It is a VERY high voltage but low amperage model. It puts out a little over 74 volts and a hair over 3 amps. This makes it around a 230 watt model. After going through the MPPT charge controller, it will end up putting around 15 amps of current into the battery.


      The battery, this is a part that’s taking a while. I’m building a lithium battery bank. It is made of 76 lithium pouch cells that are rated at 8 amp/hr each at a nominal voltage of 3.6 volts each. There will be 19 of these cells wired in parallel to make a “brick”. There will be 4 bricks that will then be wired in series to build the battery. It will end up being a 152 amp/hr battery that will have a maximum voltage set to 14.8-14.9 volts and a minimum voltage of 10.0 volts. If the battery is discharged down to 10 volts, then charged to 14.8-14.9 volts, that is 1 cycle. These cells are rated for 2,000 cycles! If I don’t let the battery run all the way down then these cells can go for at least 4,000 cycles! To control the battery bank, there is a 200 amp Daly BMS(battery management system). This BMS will prevent the battery voltage from going too low or too high. The MPPT charge controller also has a temp sensor that will be set to stop charging if the battery bank temperature drops below freezing. Charging a frozen lithium battery can destroy it.

      Even though these cells are rated for being able to supply a LOT of current(200 amps per cell continuous and 400 amps for a 3 second burst), the entire battery will be fused with a 150 amp fuse to help prevent a meltdown!


      The last thing that I got done on this update was to install the foam board insulation in the ceiling. Between the solar panel being on the roof and the foam board insulation, interior temps have dropped tremendously! I’m confident once the insulation on the walls goes up and the cedar planks get installed, it is going to stay pretty comfortable inside.


      [ame="https://www.youtube.com/watch?v=0AP3vifp2yk"]https://www.youtube.com/watch?v=0AP3vifp2yk[/ame]

      Comment


        #4
        Interesting project. I've been thinking along similar lines. And need something narrow to get in and out of my back yard.


        For some reason, I was think-n you were around 6'-6'.2" tall! Bet I could fit in that trailer too. As I've lost another inch in the last two years, according to my rheumatologist. I'm down to 5'-5". I was 5'-8" twenty years ago. Lost a total of 2 over the last 7 years. Furthermore, I'll prob make the incredible shrinking man look big when I'm done.

        Comment


          #5
          Interesting project!

          Check out this trailer build: Adventure Trailer Build Thread

          This one is smaller than yours, but packs all the stuff you mention wanting in yours. Hope it gives you some good ideas.

          Good luck with the build!

          Comment


            #6
            Originally posted by kmack View Post
            Interesting project!

            Check out this trailer build: Adventure Trailer Build Thread

            This one is smaller than yours, but packs all the stuff you mention wanting in yours. Hope it gives you some good ideas.

            Good luck with the build!

            Wow!!! Yeah mine is not going to be anything like that. I’m not as talented nor am I much of a carpenter. No, scratch that. I’m not a carpenter at all!!!


            One of the things that I want is for it to look 100% like a normal cargo trailer from the outside. This way if I need to stop for the night somewhere, nothing on the outside will scream “SOMEONE IS SLEEPING IN THERE”. Except for the solar panel, that is the only exterior part that you can see.

            Comment


              #7
              Got some more work done.


              The solar panel wires are now ran inside the trailer. But before I ran them to where they need to go, I realized the rest of the wires had to be ran too. So I got the wires ran inside 3/4” PVC pipe for the fan, for the speakers, for the water pump, for the kitchen light as well as the ceiling lights.




              Had to stop working as I could tell I was getting tired. My words kept getting mixed up in the video.



              So next I’ll be working on securing the PVC pipes so they won’t move around at all, gotta rivet the sheet metal back in place, finish running the wires to their end destination, and then seal things up with expanding foam. After that I’ll need to clean up the expanding foam and probably start putting the battery together.

              [ame="https://m.youtube.com/watch?v=u9Z6kVhn_qQ"]https://m.youtube.com/watch?v=u9Z6kVhn_qQ[/ame]

              Comment


                #8
                Short update today. I’m exhausted!


                Got the ceiling sprayed with expanding foam to help insulate the roof more. Also got the wires ran to where they need to go along with ran inside PVC pipe to keep them protected.

                The biggest thing I got done today is the battery is built, mostly! I still need to build the end plates and finish installing the insulation inside the battery, but the battery is assembled, the BMS is hooked up, and got an internal fuse hooked up to protect the battery. The sides and bottom of the battery box are assembled with brad nails, but the top of the battery box is screwed down. This way, if I need to get inside the battery to replace a blown fuse or to work on the wiring then I can do that.


                [ame="https://www.youtube.com/watch?v=FuXPoGlwPGI"]https://www.youtube.com/watch?v=FuXPoGlwPGI[/ame]

                Comment


                  #9
                  So yesterday evening I had gotten the voltage of the battery down to 14.9 volts. But I want to setup and test the MPPT charge controller after I get the battery finished. So I put a 12 volt fan on the battery pack yesterday and turned it on. 24 hours later and the voltage has only dropped down to 14.6 volts!! It’s not going down quick enough. So I added a second 12 volt fan along with two fluorescent 12v work lights. I’ll check back in tomorrow evening to see what the voltage has dropped down to. I’m hoping it’s down to 13 volts.

                  Comment


                    #10
                    Can you tell me more about your battery and type? Looks large.

                    Comment


                      #11
                      Originally posted by Texas Grown View Post
                      Can you tell me more about your battery and type? Looks large.
                      Sure. These are lithium pouch cells. Here is some information on each individual cell;


                      Specs:

                      Max Charge Rate 120A
                      Recommend Continuous Discharge Rate 200A
                      Pulse Discharge Rate(3 seconds) 400A
                      Fully Charged voltage 4.2V
                      Discharge cut off voltage 2.5V
                      Working Charge Temp 0~50°C
                      Working Discharge Temp –20°C~50°C
                      Storage Temperature –20°C~50°C

                      Each cell weighs about 2/3 of a pound.


                      There are a total of 76 of these cells that make up the entire battery. There are 4 of these bricks that make up the battery. Each brick consists of 19 of these cells, all wired in parallel via all thread, nuts, and washers. The 4 bricks of cells are then wired in series to then build the 12 volt battery.


                      So each cell is capable of delivering 200 amps of current constantly with a 3 second peak of 400 amps. So each brick of 19 cells is capable of 3,800 amps of current continuous and 7,600 amps surge! But that is only at the brick voltage of 2.5-4.2 volts. The entire battery has 4 of these bricks. So, the entire battery is capable of 15,200 amps constant and 30,400 amps surge!! However, the hardware connecting the cells is not capable of handling that kind of amperage. I’m sure the all thread would melt!!

                      However, I’ve got the battery internally fused with a 150 amp fuse. To connect the bricks together I have 4 gauge wire along with dual 8 gauge wire. For the cargo trailer, the most amps that could potentially be pulled is going to be around 130 amps. That would be the 1,000 watt Dewalt power inverter running along with lights, the fan, the radio, the water pump, and whatever else could be running at the same time.


                      Ohh, I almost forgot. These cells are also rated at 2,000 cycles. This means if the cells were charged fully to 4.2 volts per cell, then discharged to 2.5 volts per cell, that is one cycle. So if the cells were cycled once per day, they would be about 80% capacity at the end of 5 1/2 years!!! So at the end of that time, instead of the battery being at 152 amp/hr capacity that it is at now, it would be at 121 amp/hr.

                      However, if you don’t fully charge the cells and if you don’t fully discharge the cells then you GREATLY increase their lifespan. In my case, the Dewalt inverter shuts off if the voltage is over 15 volts. So, I can’t charge the cells up beyond 3.75 volts. The low voltage alarm on the inverter goes off when the input voltage dips down to 11 volts which is 2.75 volts per cell. So if I keep the battery voltage between 11 to 15 volts, the battery should have a lifespan of around 4,000-5,000 cycles!! That is over a 10 year lifespan being used every day.


                      So how much did this cost?

                      I bought these cells used. They came out of a test mule all electric bus that had a couple of cycles before they removed them. They were purchased at $4 each for a total cost preshipping of $304! The BMS(battery management system) was purchased new a few years ago for around $65. Now, you can’t find BMS modules for less than $100 that have specs similar to mine(charge and discharge ratings of 100-150 amps). So all total, the battery cells, the BMS, the all thread, nuts, washers, wood, and wire is about $400-$425.

                      Comment


                        #12
                        Thanks for the info . I thought those might be Liths. But needed confirmation. I can barley keep up with what your talking about. But have a basic understanding . I just started taking an interest in Lithium batteries not to long ago. And have been doing a lot of reading on systems. Got a BattleBorn with built in blanket in my boat now, for trolling motor. And added a Vectron Bluetooth 500a shunt to it to monitor it with. Had to engineer a case for the shunt to make it waterproof. Got it all mounted on/in a battery box with external poles for hooking up the power cables so that if I need to disconnect it, I can take it out as a unit, kinda like what you did. But smaller scale.


                        I like your idea about power supply for the trailer.

                        Comment


                          #13
                          Battle Born batteries are pretty much the cream of the crop right now! They are some amazing batteries!


                          I thought about getting a shunt setup for the cargo trailer but for right now, I’m gonna pass. It won’t be used often enough for me to have to monitor the battery level that closely.


                          I too am relatively new to lithium batteries. When the lockdowns started last year I had to stay at home(was a school bus driver) but still got paid. So I bought a bunch of used 18650 batteries and started experimenting. I’ve learned a lot but still have a lot to go.



                          One thing that completely confused me this afternoon is I just got back from testing the battery voltage. So last night at this time, the battery was at 14.6 volts. So I turned on 2 fans along with two 12 volt work lights. The battery voltage right now is 14.5 volts!!!! Maybe the battery had a surface charge of 14.9 volts and then settled to 14.6 volts once that surface charge was used up? I’m not sure.


                          So I left the fans and lights on. Tomorrow at this same time we will see where the battery is at.

                          Comment


                            #14
                            brain is smoking form trying to decipher the batteries geragan, but, a cool build

                            Comment


                              #15
                              Very cool build.......even more interesting is your battery setup. We have camp house that is setup on partial solar since getting shore power to it isn't an option. We have been looking at upgrading batteries and I think this just might be the solution

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