Making Your Own Solar Powered Motorhome

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Editor’s Note: This post is another entry in the Prepper Writing Contest from Kurt Shafer.  If you have information for Preppers that you would like to share and possibly win a $300 Amazon Gift Card to purchase your own prepping supplies, enter today!


What if you could design a completely independent motor home that uses solar power or grid power to charge batteries to provide engine power, a dehydration system for water and hydroponics for food? Do you think that would enhance your ability to be mobile and offset many bad effects resulting from the most common emergency scenarios you could conceivably be faced with? Dehydration systems and hydroponics are well-known so they are not discussed in this article. The purpose of this article is to describe how you can build your own solar-powered motor home.

Tesla and other electric vehicle sources are showing us how good the latest technology is in battery-powered vehicles. As you will see later in this article, Tesla’s latest powerhouse, the P90, offers over 700 horsepower and a range of nearly 300 miles using a battery that is small enough to hide in their car.

Design goals for the solar powered motorhome

  1. Range – this is determined by the battery pack. Goal is to maximize it.
  2. Power – I expect to replace the gas engine with about the same horsepower as it had.
  3. Recharge time – this is a challenge due to the limited space for solar panels.

Range

To understand the possibilities that exist one needs only to look at the latest Tesla P90. It has 762 HP and a range of 253 miles. So, In theory, if we just want 300 HP then using the same battery we should get a range of 642 miles, and at 60 MPH that should be over 10 hours! We know that this Tesla battery is small enough to hide in their luxury sedan body so with the amount of volume in a motor home our range is only limited by our pocketbook.

Powering your motorhome

 

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Solar panels are coming down in price and can easily be mounted out of the way on top of your motorhome.

Research shows that many motor homes have gas engines that are rated at or about 300 horsepower . It turns out that a 3 phase 460 volt AC motor  is readily available from many suppliers. An example is a simple search on EBay. RPM varies but 1800 RPM is quite common and, as you know, is nearly the same as the RPM of a gas engine at cruising speed. A valuable property of electric motors is that it is likely that the electric motor will have so much torque that the use of the motor home transmission might not be needed.

The next challenge is to cope with the power in amps needed to produce 300 horse power. Electric motors draw 750 watts per HP so the number of watts needed is ¾ times 300 or 225,000 watts. At 460 volts that will result in a current of almost exactly 490 amps. That current must be connected between the battery bank and the VFD by heavy copper bus bars.  Bus bar tables on-line show that if one wants to limit the increase in the temperature of the bar to 30 degrees C (86 F) then a bar of copper that is 3/8 thick and 1 inch wide is recommended. One source for these is invisco.com/rv.

Solar Panel Starter Kit 400W
Solar Panel Starter Kit 400W

When replacing a gas engine with an electric motor it is necessary to replace the mounting hardware and the connection to the transmission shaft and the gas pedal. The frame used for 300 HP motors is technically termed a 449T and it is almost exactly 2 feet high and 2 feet long. The gas engine is larger than that and likely has 2 mounting points at the front of the engine and none at the rear because most vehicles depend on the transmission for the rear mount. It will be necessary to add a mounting brace to the front of  the transmission and then add a platform for the motor. Invisco.com/rv is a source for this hardware.

Another detail is the speed control design. 3 phase speed controllers are easy to find. They are known as VFD or variable frequency drives and they are available from many sources. One source is vfds.com and another is EBay. The challenge is to adapt the speed control input signal to a gas pedal like pedal. One source for a speed control vehicle pedal is invisco.com/rv. Then there is the issue of solar panels. As you  know,  they are becoming easier to get. All of the electronics needed to wire them to a battery bank are available. The trick is to design the high power bus bars needed to power the inverter. Another challenge is to install enough batteries to run the huge motor for a time long enough to travel a useful distance.

Next is the time needed to charge the battery.  Again, Tesla offers a glimpse into the future. If we rely only on solar power  it will take some time. More on that later. Tesla gets a full charge in the P90 in just 1 hour and 15 minutes using 440 VAC! That makes a transcontinental motor home realizable. With New York about 2500 miles from Los Angeles, one could imagine traveling 642 miles at a time, stopping for a meal and a charge, then another 642 miles, etc.

03-701-Solar-panels-on-motorhome-RV-camping-in-Quartzsite-Arizona

Now, the reality of purely solar recharge is that a motor home is about 8 feet wide and 40 feet long and about 8 feet high. If we use just one side and the top for solar panels we get 640 square feet of panels. Best case if the panels were all facing the sun we would get 300 watts per panel. One panel is just about 18 square feet so we can get just over 35 panels on. That would get us 10,666 watts best case. In one hour we could expect 10.6 KWatts. We need 225 kilowatts and if we are going to use it for 10 hours we need 2250 kilowatt hours. So at 10.6 KW per hour we need to charge for about 225 hours. At 10 hours of charging per day in the summer that is less than a month. It is clear that using solar power alone for battery charging is the least efficient but it is possible.

Now a rough cut at the cost of this autonomous solar powered motorhome. First, a look at an average motorhome on the market today. A quick search for 40 foot motor homes shows there are many listed for sale at under $100,000 and some under $50,000. This is, of course, the major expense. The second largest expense is  the solar panels at about $300 each or $10,500. Then the battery pack – I cannot find a good estimate on one but we know the Tesla P90 sells for about $90,000 so I imagine the pack might be $10,000. The AC motor is advertised on EBay for around $9000. Other miscellaneous parts might add up to $5000.

Combine solar power with rugged off-road capability for the best of both worlds.

In summary, here are the costs if we start with a $50,000 motor home

  • $50,000 for motor home
  • $10,500 for solar panels
  • $10,000 for battery
  •  $9,000 for the motor
  •  $8,000 variable frequency drive
  •  $5,000 misc parts
  • $92,400 Total

The single most important advance in technology that makes this all viable is the advance in battery design. Without the latest batteries made by Tesla and others we would be forced to install huge lead acid batteries and the whole design might be undesirable. For more information and to follow the progress on this project email kurt@invisco.com

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19 Comments on "Making Your Own Solar Powered Motorhome"

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christopher
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I would really interested to see if this would work, but I dont have 100 grand lying around to try it though:)

christopher
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i would be curious about scrounging the batteries from these hybrid vehicle if they were still usuable… may need a engine lift to remove the battery at 1000lbs or just tow the broke down car to your property.. i dont know anybody that has a tesla or hybrid vehicle, but would be a good batt source if you can connect them to solar panel if vehilcs are broke down along road in SHTF scenerio.

BobW
Guest

I’d be curious if the batteries would survive. They are heavily controlled by computers, so good chance an EMP would wipe them out too.

Last time I read about early hybrids and battery replacement, it was very expensive to replace them, and a lot of work to get them out. Something about disassembling most of the body/interior to get them out, but its been a while, and maybe the tech of the batteries has improved size and ease of access.

Dolt Hunter
Guest

its very doable if you are not a power glutten IE always driving alot and running high wattage devices.

christopher
Guest

just saying “its doable” doesnt present any facts that it would be(i’d be intersted in hearing them though) .. .. just the weight of the rig alone would kill the batteries , add on all those solar panels. even if you just used it to propel the vehicle, you wouldnt get 5 miles.. what good is a large box iloaded down with gear if you’t can get from point a to b without having to stop every 5 miles.. once you hit a hill, your batts would be dead and your a sitting duck.

Jon
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I agree with Christopher. The weight of the motorhome is going to drain the batteries quicker than on the Tesla. Your theory of increased range would only apply if you were making the HP adjustment to the Tesla P90. Otherwise, the range for motorhome would drop to about 75 mile or 100 mile if your lucky and driving only downhill!!! Wonder if the author watched “The Ark 2” on Saturday mornings back in the 70s. Who remembers that? There motorhome/lab I think was solar powered!

Skeeter Smith
Guest
I remember The Ark and didn’t they have a guy with a rocket pack, to survey all those post-nuclear communities of savages? To do this properly, you need to determine the drag and power needed to move a large RV at a reasonable speed – 60 MPH for pre-collapse (otherwise people will be shooting at you with road-rage) or perhaps 30 MPH post-collapse (and people will still be shooting at you for your food). Then calculate what range you desire, and how much battery pack weight you need. Then subtract the tons of supplies you are bringing along, and come… Read more »
paul crosley
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It seems that it would be better to modify the fuel source instead of trying to reinvent the wheel, so to speak. Why spend incredible amounts of money on very high tech stuff when you can take existing gas powered engines and convert them (comparably easy) to run on wood gas using Bio solids. It was done in WW II during petroleum shortages and used on tractors, passenger cars and large trucks. The systems have been refined in the 70 + years since.

Skeeter Smith
Guest

Every dead car or truck you come across is potentially 2 gallons of diesel fuel.

Mix three parts well filtered motor / tranny oil to one part old gas. Presto! you’ve just made ersatz diesel.

Even a dead car has a little gas left in the tank.

paul crosley
Guest

Very good advice!

jr023
Guest
weight of the motor home more like 60 to 75 miles on charge possably a little more if the panels get sun while driving.and at 60 to 70 mph the wind drags heavy, the medium deliver trucks are mainly aimed at urban delivery are rated at 100 miles. and like epa gas ratings are useally optimistic at best. and remember tesla batteries can not be run below a certain charge level. they also have complicated electronics to keep the batteries cool as well as warning on charge level and you cannot put 5 gal of gas or diesel if you… Read more »
BobW
Guest
I agree with the running theory that the author’s computations of extending mileage would only apply to a similarly sized/weighted vehicle. Pushing that mass over hills and mountain passes would sap batteries fast. Also, maybe we can get an electrical engineer to jump in on the idea that reducing HP extends mileage appreciably. I recall that not really being the case, but I’m just a lay person. I would like to entertain the idea of converting an old pickup into a propane or natural gas burner. You can buy trucks new fully converted to propane, so the systems exist. There’ll… Read more »
BobW
Guest

To the author: Years ago, the Army (probably DARPA) experimented with converting a HMMWV into an electric all-terrain vehicle. They used four independent 100hp electric motors (one on each wheel), and a small diesel generator to recharge the battery system.

With advances in diesel technology, battery tech, and computer control of vehicles, this previously dead research project is probably extremely viable now.

BobW
Guest

Interesting article on how an all electric drive train HMMWV works from SAE.

http://articles.sae.org/11940/

Danny B
Guest
It’s great that you took the time to work out the calculations. BUT, cruise mode in a Tesla car uses very low amperage. A model S will run at full power for just 12 minutes. The motorhome has CONSIDERABLY more drag than a Tesla car. You’ve cut the range in half but, I don’t see that as being realistic. Don’t let me rain on your parade. I suggest that you find the cruise horsepower necessary for the motorhome and convert that into watt-hours. The Ultra-Coach was very aerodynamic and light. It was powered by a Corvair engine. Best of luck.
Tom
Guest

I think the only practical use of this tech is to replace generators for RV power. You don’t need massive battery size, just enough to get you through a couple of days in a campground. Even the quiet generators aren’t completely silent. Charge while driving with some solar to help when possible. I think that is the low hanging fruit.

Skeeter Smith
Guest

A better idea. Buy the solar panels and battery. Ditch the rest and save $22,000.

Use the $22K to buy diesel fuel – enough for 50,000 or more miles of travel.

Tovy
Guest

I guess one won’t replace the engine, so why not try more efficient variant due to the smaller size? Like this:comment image costs 5 times cheaper.

Mindbreaker
Guest
Pie in the sky figures. You only get the rated wattage out of a panel about 1 hour a day, if everything is exactly lined up, and you are where the sun is shining. And then there are the losses with the electronics, and the battery. And that ridiculous calculation telling you, you can go double as far with half the horsepower? Rubbish. The Tesla is not using all that horsepower to move the car along at a constant speed on a flat highway. It probably only uses 40hp to do that. The energy necessary to move the vehicle is… Read more »
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