S250 Military Shelter Camper conversion on military trailer

[coultergeist]

I've built out a couple of camper vans. They did a great job, but I purchased an LSSV (essentially a militarized Chevy Silverado set up to be an ambulance) and decided I wanted a good off-road setup. Originally, I was going to build out the ambulance body on the LSSV, but I decided it would make more sense to have a trailer camper to pull behind it. That way, the camper can be setup and the vehicle would be free for other stuff. Plus, having a dedicated camping trailer and tow vehicle means I would have a lot more storage capability and wouldn't have everything crammed into one space. I found a HMMWV trailer (M1102) to use for the base of the build. They are strong and relatively light as military trailers go. They also have great ground clearance. I was going to build a camper shell on top of the trailer, but I ended up finding an S250 communications shelter that a trucking company had bought at a surplus sale and never used for anything. I made them an offer and they accepted. I loaded it up on the trailer, tied it down and towed it the fifty miles back home.

 

[coultergeist]

As you can see from the first post, the shelter had a number of panels missing. The first order was to seal all of those up and clean up the inside. It had been sitting outside for a while, so it was very dusty and dirty on the inside. I cut pieces from pressure treated 3/4 plywood. After they were primed and painted and had about a million holes drilled, the panel pieces were mounted with rubber gaskets. She has been waterproof since. I haven't had a single leak so far. This picture is of the inside after it was sealed and most of the cleaning out was done. Originally, there were tons of straps everywhere and mounting holes spaced periodically throughout the interior walls.

 

[coultergeist]

After cleanup and sealing came figuring out how to setup the interior. I had a good general idea of what I wanted based on previous designs. I've seen a fair number of S250 shelter conversions, but I didn't like most of them. Most of them were really just a bed and a few things on the floor. I wanted to pack a whole lot more into the shelter. My challenge was figuring out how to mount everything inside. The shelter has anchor points spaced irregularly on the walls, floor and ceiling, but they weren't really where I needed them to be and I didn't feel I could trust them to hold much weight. I bounced a bunch of ideas around and ultimately came up with a unique solution. The floor and shelves of the shelter are meant to support the weight of the military installed racks and equipment. I went the same route, but with a twist. I built an inner framework with unistrut. The framework is supported by the floors and side shelves, but also extends floor to ceiling on all corners. The beauty is it can't move and all of the shelves and items that I would mount can be connected directly to this inner frame. It allows me to put things exactly where I want without having to worry about where the existing anchor locations are. Wherever possible to inner frame was attached to previously existing anchor points to make it even stronger. The next few pictures show the inner frame when it was first getting started on each side.

 

[coultergeist]

After the basic inner frame structure went in, the next phase was to work on the electrical system. The goal was to run most of the wiring prior to having the cabinetry in when the fewest things would be in the way. The electrical system actually took a good bit of time. The setup is a hybrid system. It is capable of being powered from shore power, but it also has a solar setup with a large battery bank and a 3000W inverter. I worked on the shore power inlet and AC outlets first. It is set up with a 30amp input. The input goes to a source selector switch which then feeds a standard house breaker panel. Every outlet is switched individually so I can conserve energy when running on battery reserve.

 

[coultergeist]

The AC side of the camper wiring was actually pretty straight forward. The DC side was much more complicated. Whereas the AC side was really just a breaker panel, wiring and outlets, the DC side was batteries, battery charger, solar charge controller, inverter, switches, fuse panel and solar panels. The first big issue was the batteries themselves. I started to go with six 6V golf cart batteries. I didn't like the idea of 6V batteries. They would have to be wired in pairs and if one battery dies, it takes the whole pair down. If all are 12V batteries, then a failure affects just that battery. I looked at a bunch of different 12V batteries. Space comes at a premium inside an S250 shelter. I ultimately decided on four deep cycle scrubber batteries. They are taller than standard batteries, but have very large reserves. Each battery has a rating of 238amp hours at 12V. The four batteries give me nearly 1000 amp hours of battery storage. Even with only drawing down to 50%, I'd still have nearly 500 amp hours of usable power. The catch is that they each weigh 125 pounds. Altogether, that's roughly 500 pounds of just batteries. That was too much to put all in one place. To keep the trailer relatively balanced, two batteries are at the front under the bed and the other two are at the rear of the trailer on the shelf near all of the DC components. All batteries were wired with inline disconnects so they can be individually disconnected if there is an issue.

 

[coultergeist]

After battery placement was worked out the real fun began. The great thing about an S250 is that it is an aluminum skin on the inside and out, with insulation sandwiched in between. It is very strong, but lightweight for its size. The down side, from an electrical standpoint, is that is all aluminum. I was somewhat concerned about potential shorts and accidental grounding. Not a big deal for a small load, but 1000 amp hours of battery discharging due to a short could be very, very bad. As such, I went for ultra safety. All positive battery cables are sheathed to minimize the possibility of cable rub. All batteries have individual Anderson connectors so they can be unplugged if needed. Each pair of batteries goes through a battery selector, so they can be individually switched off. Each battery has its own circuit breaker. The common connection points for the battery positives and negatives each go to a heavy bus bar, which is sealed inside a nonconductive box.

 

[coultergeist]

After the main battery wiring was complete, solar system wiring was next up. The compartment above the rear battery pair houses a 100amp MPPT charge controller. There is a main power disconnect switch below the charge controller for emergency shutdown. The main DC switch panel controller is also located there, along with its circuit breaker.

 

[coultergeist]

Mounting the solar panels was a bit of a challenge. I wanted to maximize the amount of solar power for times when the camper would be completely off-grid. Six 100W panels covered the roof almost exactly. I didn't want to drill into the roof, so I made an external unistrut framework to mount the panels and rear equipment to. The panels mount to the frame on top. They then go to a solar combining box at the right rear of the panel. Each panel can be individually switched off by its circuit breaker. There is a master breaker and short circuit disconnect. The picture on top was taken with the first two panels in place. All six are mounted now. Also the Charge controller remote panel was mounted near the bed in order to easily verify power and battery level.

 

[coultergeist]

I didn't take any pictures of it, but the inverter and battery charger are located to the left of the rear batteries in a compartment under the refrigerator area. The inverter provides power to the AC circuitry when shore power is unavailable. The battery charger is there to charge the batteries from shore power when needed.

 

[coultergeist]

I wanted to have as many controls centralized as possible. The main panel is on the left, rear wall of the shelter. All AC circuits are individually switched. Most DC circuits are switched from the black panel. The inverter remote panel is there, along with the main power select switch.

 

[coultergeist]

My original plan was to use a portable air conditioner that vented out of the rear of the shelter. As things progressed, I realized that it would take up alot of room that could be better used for other things. The front of the shelter had a cutout for the original military air conditioner. I sealed it when I first got it to keep out rain. I found a military air conditioner designed for the cutout, but it was over a thousand dollars, with no guarantee it was good. That didn't seem like a good option to me. I decided to use a regular window mounted air conditioner/heater instead. This required me to cut out some of the original mounting points and fabricate a way to securely mount the civilian air conditioner/heater. Once all that was sorted out, it was mounted and then painted to match the shelter. I must have done okay. Haven't had any rain leaks yet.

 

[coultergeist]

Once the air conditioner was in place, I focused on cabinetry. All the cabinets have the same door latch assembly. They are all lockable and use the same key. I have grandkids that may be inside the shelter at some point and I wanted to be able to lock up the cabinets that contain the batteries and DC components. The refrigerator was also mounted in its location. The orange straps are used to secure the refrigerator doors when the shelter is being moved.

 

[coultergeist]

The TV and related components were next. The TV itself attaches to a very flexible mount so it can be oriented just about any direction. The cabinet above it holds all of the other equipment. Within the space is a DVD player, Roku media player, source selector and HDMI switch. The TV antenna is mounted to an extendable pole on the right rear of the shelter. The source selector allows any content to be played on the TV inside as well as outputs for two other TVs. That way I can play to a TV outside for the grandkids (thinking movie night) or in a tent if there are a bunch of us.

 

[coultergeist]

The microwave is mounted in the cabinet above the bed to the left of the refrigerator. I don't have a stove mounted inside. One will be carried in a storage container under the bed for when it is needed.

 

[coultergeist]

I wasn't happy with the ratchet straps being used to secure the shelter to the trailer. I replaced those with turnbuckles and chains. The outside of the trailer got a little more paint as well. Still have some more outside work to do, but it's coming along pretty good.

 

[coultergeist]

I repurposed the area where the portable air conditioner would have went and made it a closet instead. Worked out pretty well, I think.

 

[BinDerSmokDat]

Nice build, very rugged and heavy-duty!
Being 6'6" tall I flinch when I see all that steel and exposed bolt heads over the bed, I'd whack my head on that for sure.
I flinch when I see that.

Will you rig a cover for the AC unit on the trailer?
I'd be worried about picking up dirt, debris and bugs when rolling down the road, clogging or damaging the fins.

How much does that trailer weigh?
I aim for the lightest builds possible, but I can see how you'd want that rugged for off-road.

 

[Sky]

Great ! work you do ! very impressive !

 

[coultergeist]

Nice build, very rugged and heavy-duty!
Being 6'6" tall I flinch when I see all that steel and exposed bolt heads over the bed, I'd whack my head on that for sure.
I flinch when I see that.

Will you rig a cover for the AC unit on the trailer?
I'd be worried about picking up dirt, debris and bugs when rolling down the road, clogging or damaging the fins.

How much does that trailer weigh?
I aim for the lightest builds possible, but I can see how you'd want that rugged for off-road.

The trailer itself is 1420 pounds. Shelter and everything else likely adds about 1600 more pounds. My estimate is a little over 3000 pounds total. Inside height is just under six feet, so I do have to bend my neck a little bit to stand up. I will probably put some padding on the cabinet rails above the bed. That’s in the make it better phase. LOL.

I did add a hard cover for the air conditioner that folds down when not in use. Didn’t want rocks and debris flying into the cooling fins.

 

[user 32232]

Great build, great write-up. Just curious as to the interior height of the ambulance itself?