Solar Powered Air Conditioner in a Sprinter Van

One of the reasons I have such a huge solar array (945 watts) and a huge battery bank (780 amphours) is so I can run an air conditioner. I went with a portable air conditioner called the Haier 8,000 BTU Portable Air Conditioner. I have the HPRB08XCM model. I selected this air conditioner because it was listed as using about 700 watts and it seemed to be sufficient to cool a well insulated van. In reality, it uses around 750 watts when the compressor is on with a peak startup power of about 2,760 watts. There is some loss when inverting from DC to AC. So you’ll actually need closer to 850 watts DC (70 amps at 12 volts). This means if you go with this air conditioner, you’ll need an inverter that can handle this peak current such as the Xantrex ProWatt 2000. It can handle 2,000 watts continuous and a 3,000 watt peak.

Installation: 

Installation was simple. I cut a well planned hole for the exhaust hose and one for the drain hose.

I slid this duct extension through the floor and used some adhesive on the outside.

On the outside of the van, I secured some metal mesh to act as a bug screen on the exhaust hose and the drain hose.

Any sort of tubing will work fine for the drain hose because it only drips out occasionally.

I left the wheels on because it wouldn’t sit flat without them. The AC is just strapped in place between two pieces of plywood.

The downside of the portable air conditioners is the exhaust hose. They can’t compete with the efficiency of the window units or the roof top units because the exhaust hose is always giving off heat. However, I did my best to mediate this by wrapping the hose with as much reflectix duct wrap insulation as I could. My exhaust goes through the floor, but placing the hose through the wall or through the ceiling would certainly work much better to remove the hot air. The less of the hose you have inside the van, the better it will work. I didn’t want to have a hole on the side of the van so I settled on the floor for the exhaust.

But Joe, how long can you run the AC?

If you don’t feel like reading all the information below, just watch this 10 minute video:

This will be a complicated answer with different scenarios. I think anywhere from 75-80 degrees is a good compromise while living the van life. The higher the temperature that you can comfortably tolerate, the longer the AC will be able to maintain it. In my experience, I’ve been able to lower the temperature approximately 5 degrees within a few minutes, then slower after that. So if it’s 90 degrees outside, I’ll compromise at 80.

Here are some different scenarios. Keep in mind the times listed below are compressor run times, not how long the AC is on. Once an AC reaches a set point, it only runs the fan and uses very little power. In other words, “how long I can run the compressor” is a typically a shorter time than “how long I can keep the van cool.” How often the AC cycles on and off will depend on how well insulated the van is. I’m ignoring all the other loads such as the fridge just to keep the numbers simple and minimize variables. I’d never actually run the AC long enough to the point where I couldn’t used any other loads.

1. Afternoon parked under direct sun: 9.5 hours

This is when it’s the hottest, but also the most common scenario. The current from the solar panels will carry some of the load, and the batteries will pick up the rest. So if the batteries are fully charged, and you’re still getting plenty of energy from the sun you might as well divert the extra energy into the AC. Most of the time, my batteries are fully charged before I even reach peak power from the sun. For example, 850 (maybe a few clouds) watts coming from the solar panels for 3 hours would be able to run the AC without ever depleting the batteries. Then the sun starts to set and perhaps I only take in 400 watts from the sun. Now 33 amps from the solar panels, and 37 amps from the batteries would be powering the AC. My battery bank is 780 amp hours (390 useable amp hours). This state of discharge may last for 2 hours and using up around 74 amp hours. Then the sun goes down completely. Way before this even happens, I would just open the door to cool off with the fantastic fan. For the sake of worst case scenario, I’ll keep going with this. So I’d have 316 amp hours left. I could run the AC for an additional 4.5 hours before my batteries get to 50%. In this scenario, The AC would be running full blast with the compressor on for 9.5 hours. Of course, Once the set temperature is reached, the compressor turns on intermittently to maintain that temperature.

2. Driving, then stopping: much greater than 9.5 hours

If I know it will be very hot at my next destination, I’ll have the AC running from the dash full blast while driving to cool off the whole van. It does a great job. I can park, and turn on the portable AC to maintain that temperature. So imagine the above scenario, but much longer because It will be using less energy to maintain a temperature rather than trying to lower a temperature.

3. Park in shade, or Night time: 5.5 hours

This is the least likely scenario. I can sleep comfortably with the fantastic fan on. If it’s a little warm I’ll also turn the AC on in fan mode only. However, If I do need to run the AC on battery power alone, I can do it for 5.5 hours. Again that’s 5.5 hours of the compressor trying to reach a set temperature. This number is the most accurate because it contains the least number of variables.

4. Night time and I need more than 5.5 hours: As long as I need to

If I was absolutely desperate and about to have a heat stroke in the middle of the dessert somewhere, I would crank the engine, turn on the dash AC, while charging the house batteries with my 200 amp alternator. The alternator will also pick up the load for the portable air conditioner. In reality, I’d probably just drive somewhere colder.

Also, this AC has a dehumidify mode. It uses a little less energy. I’ve experimented with it a little. It has a made a huge difference. A dry 85 degrees really doesn’t feel too bad at all.

How well does it cool the van?

It depends on the outside temperature and where I’m parked. The biggest challenge I’ve encountered was about 105 degrees outside while parking under direct sunlight. I was able to cool the van down to 85. On a typical day when it is around 90 degrees outside, it has no problem going down to 75 degrees inside. Living this lifestyle is all about making compromises. Keeping the van at 72 degrees all the time is a waste of my energy. You’d be surprised how fast you can acclimate to hot weather.

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  • Daniel

    Awesome post. I think if I make the move for a portable AC, I will try a two hose system through the ceiling. Not having an AC is a deal breaker in the hot humid south. I wonder how big of a factor your insulation is to making the temperature control efficient.

    • Joe

      I think insulation is one of the biggest factors in determining how much energy the AC will use to maintain a low temperature.

      • Frank Furtive

        Correct. R10 minimum. Radiant barrier with 3/4″ air space is also beneficial.

    • Richard Hauser

      This is my biggest fault with this design, the inefficiency of single hose AC systems. It means that it is taking air from the interior to cool the condenser. This means that it is constantly sucking in hot air from the outside to replace that interior air. I think I will be installing a standard window air conditioner into an insulated box with two ducts running through the floor. This should increase efficiency significantly, as it would lower the air exchange and the insulated box should limit the heat transfer from the condenser air. Ideally I’d like to find a small unit that does both heating and cooling, but that has eluded me so far. I think the key in any system like this is to maximize efficiency.

  • AntiGrndhogDay

    Hi Joe, a few questions… Has A/C been more of a “need” vs “want” on your trip? A lot of folks talk about traveling with the good weather, but come the end of July that’s pretty tough: https://www.youtube.com/watch?v=W8GmL8BEtPU , thus I’m considering a solar install like yourself. Also, how loud is your A/C when running? Might you be interested in filming and walking around your van some time to show noise/stealth levels?

    • Joe

      There have been times where it felt like a need. Sometimes you accidentally end up in very hot weather. I could definitely live without it, but it wouldn’t be very fun. The AC isn’t loud at all. It sounds the same as the fantastic fan. I’ll make a video about it.

      • Daniel

        I am very curious about how loud the system is as well, both inside and outside the van. I am seeing some roof DC units, but I am afraid they will make too much noise since the unit is outside. Blows your cover haha

        • Joe

          You can’t hear mine at all from outside. Inside it isn’t too loud. There are three fan speed settings. Even on the highest setting, I can easily sleep.

    • Frank Furtive

      There’s a map out there showing where to go for 70 degree temperatures year round, but I’m not inclined to head for Alaska in July.

      • Richard Hauser

        Yeah, don’t head for Alaska till September so they have a chance to fix the frost heaves in the road. Also you will miss the northern lights. 🙂

  • sprint2freedom

    What’s the diameter of the vent opening for your A/C? I’m thinking about adding A/C to my build but I keep going back and forth between a two-hose portable vs. trying to build something around a $100 window unit.

    Diggin’ your build and your adventures, thanks for the writeup.

    • Joe

      The hose is 6 inches. The hole is 4 inches. There wasn’t enough room the floor for a 6 inch hole so i had to reduce the end of the hose from 6″ to 4″.

  • Scott Mauer

    I *really* appreciate this kind of detailed technical and field experience on the AC issue. I’ve previously believed that AC from solar is unachievable, and that’s true for most RV setups. However, not only does this show *why*, but also *how much*, which is a critical thing to know when trying to solve the problem. You and I have very similar goals for our Sprinter stealth conversions, but I had previously decided not to try for AC because I have only 400 watts of solar and a 418 AH 12V battery pack. This is painful because I live in Austin and it’s above the maximum survivable fan-only temperature for a good portion of the year. My first shakedown cruise to the West Coast is starting in a few weeks, and I’ll be gathering operational data about power use that should help me decide if a small AC unit might be in the cards for later. One thing I’m considering is the ability to airlock portions of the van so I’m not cooling the whole thing. Because I’m intending to try out several different internal layouts before settling on one, I’m making my first trip without insulation. However, one of my goals is for the van to be a mobile audio studio, so eventually I will have substantial sound and thermal insulation once I settle on a final design.

    • Joe

      airlocking portions of the van would be awesome for cooling. Don’t forget about fresh air though!

  • Scott Mauer

    It seems likely that it would be more efficient to use only the dash AC to cool the entire vehicle with the engine running than to also run the portable AC unit through an inverter. Ducting is the big issue here, and ideally I’d like to set up a system where I can pipe the AC anywhere in the vehicle I want, and seal off the parts I’m not using so I’m only cooling down the spot I’m at. I’m thinking at this point of the cab, the office/kitchen area, and the bed being separate areas that can be closed off independently. Having a thermal cover that lowers down over the bed would also help reduce the airspace. That’s worked well for heating in my yurt in the field. I build a tent around the bed, even with thin sheets, and the heat stays in a lot better.

    I’ve heard about potential problems idling the Sprinter turbo diesels for this kind of use, but I’m not sure what to think. Delivery people do it all the time. I also got a simple wood clamp as a low-tech idle adjust, since I’ve heard increasing the idle slightly helps with the oil circulation issues that supposedly lead to problems.

    Here’s a really good article on fan cooling from Low Tech Magazine.

    http://www.lowtechmagazine.com/2014/09/circulating-fans-air-conditioning.html

    The main takeaway is that temperatures below 93-95 o F, fan cooling is way more efficient than AC. For temps above that, the best use of power is to use the AC to bring the ambient temperature back down into the 80s, then use a fan to do the rest. I’m putting my Maxxair Deluxe right in the middle of my RV because I don’t know the final floor plan yet. I’m thinking about making a diverter I can clip onto it that will let me point the air anywhere in the cabin. I also have an 18V Ryobi shop fan that runs off LiION batteries I could use. I’m fairly certain it would run fine at 12V plugged directly into the van.

    • Joe

      I tried to do a lot of research on idling the sprinter van. Everything I could find says that it’s not an issue as long as the EGR valve stays clean.

      • Scott Mauer

        I have a V6, and I’ve heard that it’s possible the default idle may not circulate enough oil to prevent engine damage. I need to do more research if I find myself doing it often. I have the Green Diesel Engineering tune, which disables the EGR, so that part isn’t a problem.

  • Frank Furtive

    I’m in the process of converting a 12 x 6 x 7 box truck with barn doors in the rear and side door behind the cab. No metal except aluminum frame. 5000 BTU window AC will be mounted on a bulkhead situated 3 feet from the rear doors. This will leave a 9 x 6 x 7, super-insulated front area to be cooled with an AC powered by wireless remote generator situated in the utility room. The living area will have R10; 2″ of rigid, closed cell insulation board (floor, walls and ceiling and top hat) with radiant barrier for the ceiling and “top hat”. Top hat is the fiberglass shell above the cab. The utility room will have a ceiling fan to vent AC exhaust and generator fumes, while the bulkhead will have a fan venting into the utility room. In addition to the large fans I am planning a 4″ intake and exhaust fan for fresh air ventilation of the living area, most likely vented through the floor. A 10 ft high stealth RV box truck with a single roof fan should not draw any attention. 4 solar panels can be mounted in the center of the roof and should be difficult to spot. I intend to power a chest fridge 24/7 from the AGM batteries but not the AC.

  • Richard Hauser

    Are you going to see the eclipse? Not sure where you are these days, but the eclipse is two weeks from yesterday 8/21/17, time dependent on location

    • Joe

      I’m on the east coast. I’m going to try to see it..