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Concieve the electric RV

43K views 77 replies 38 participants last post by  brian_ 
#1 ·
The electric RV.

Instead of buying a $75,000 -$100,000 brand new RV, what if I bought a used one for $10,000 as a conversion project? The technology has changed very little on the inside so it can be a few years old as long as it is clean and in working order (fridge, sofa/bed, tv, generator, toilet/bath, carpets, etc.).

I don't like driving all day long, so traveling 200 miles at 55mph in one day is great. Besides this leaves more time for camp set up. Some mountain grades can be very steep so the ability to go at least 5% grade at times is a must.

What motor/controller/battery set up will work? Some cities use electric buses so I know its possible to find some heavy duty parts.

Hmmm. Imagine removing the primary ICE and transmission. Could a powerful ac motor(s) be attached straight to the drive shaft and still meet the torque and rpm requirements? Perhaps a gear ruduction assembly would be required. Perhaps a change in the ratio in the diff would be needed.

The existing generator will be left as is to assist in its normal functions (air conditioning, and other ac power) but it will also be able to help slow the main battery packs from depleting. Obviously it would require a much larger generator to keep the batteries from ever depleting but the goal would be to assist in the range bump it from lets say 100 miles electric only to 200 miles using generator. Re-gen braking would be used on all the grade decents and braking during traffic. Obviously this is a minimal amount but every bit helps for range extension.

The long flat roof is ideal for solar panels. If my RV is sitting out doors all the time, then it makes sense to have solar panels. The extra weight and cost is a draw back at first, but the savings over time (and thats what solar is all about) would be great. 99% of the time an RV is sitting around at your storage lot or your house or even the camp ground. I would love to have the sun recharge the batteries for me, sort of like a full tank of gas a week, only not paying $250 and worrying if the gas is getting old as the RV sits through winter. And if my RV is parked in my side yard, then perhaps it's solar energy can be fed back to the utility company's grid, another cost savings plus over time.

When I get to the camp site and pay my $25, I could re-charge the batteries...big gas savings especially the more I use the RV over the years.

Another savings could be the yearly registration. Maybe there is a loop hole for a electric RV and could save hundreds each year.

Most RVs are desinged for their weight and also to pull something like another car or boat. Plenty of room along the frame for all of those batteries. Even if some of the storage compartments have to be sacraficed for batteries that would be just fine. I think lead batteries would be much cheaper at first, but then when you consider that the generator had to be used most of the time during operation, and too much increased weight, in the long run it would be worth while to have higher energy density batteries right from the get go.



Or just not mess with and have a regular motor home with it's factory warrenties and shell out $2000 for gas each trip. Plus all the maint cost.

I've read a lot of these posts and a I'm interested in how this concept can be improved. Good day.
 
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#2 ·
I'm not saying it's impossible, but fairly improbable to meet your goals.

The Top-Two killers of EV range are weight and drag, something an RV has in abundance.

If it were purpose built from lightweight aluminum and composite materials with a focus on ultra-lightweight materials and the bulk of the vehicle weight made up from lithium batteries, it may be possible to get 200 miles range out of it for $300k+ in EV and vehicle construction costs alone (i.e. a "shell" with nothing inside.)

If someone can make an ERV for a reasonable price, I'll be interested. I've thought for years that considering you can get 50 amp service at most RV parks, it would be simple to roll up, plug in, and recharge while you're camped.

However, an ERV would be really rough to go boondocking, which is my favorite sort of RVing.
 
#3 ·
It's way cheaper to buy electricity than do it with solar cells. It'll take longer than you'll live to pay for them likely at todays prices. Wait for Nano Solar's products to hit the market at 1/10 today's cost and you'll be much better off. I think you'll be able to buy them in a year or so. I can't wait!

And wanting an RV to go 100 miles without a recharge is going to be REALLY expensive, a lithium pack surely!

But you never know the answers until you investigate your ideas. Some work out and some don't. Those never attempted never make it!
 
#4 ·
Thank you for the responses. Since the closest vechicle to a RV is a bus, I did a search on hybrid buses, and this company illustrates the feasability. Thought it was interesting so I posted it here.

http://www.advancedenergy.org/corporate/initiatives/heb/hybrid_tech.php

And I agree that the use of nano solar is ideal, it's so thin that you wouldn't even know that they were up on the roof unless you climbed up the ladder. I wonder if it could be somehow fashioned on the awning for increased solar surface area.

--Bill
 
#5 ·
I certainly don't think it would be impossible. In fact I think it is a pretty good idea. With the combination of a generator, solar panels, a slowish top speed and a huge battery capacity you could certainly get a decent range. If you could go 100 miles then stop for an hour or two for lunch (with the generator and panels going) then drive the other 100 then it would probably be a lot easier/cheaper. What sort of HP do RV's have and what sort of budget do you have for the conversion?
 
#6 ·
Just a thought experiment here:

My RV gets about 8-mpg. Using the VERY ROUGH model for EV mileage (36.6kWhr/gal-of-gasoline and about 25% efficiency) my RV should consume about 1150Whr-per-mile. For a 100-mile range at relatively low speed that would require about 140kWhr (to 80% dod). If I ran my 6kW generator and drove 50mph that would knock 10 or 12 kWhr off of the battery requirement.

Based on this, my GUESTIMATE for my RV would be a 100 to 150kWhr battery.

Using 225-AHr 6-Volt lead batteries (e.g. Trojan T105), that would be about 94 units (126,900Whr) for a weight load of about 5734-lbs.

Now, how long would it take you to recharge assuming you had 120-Volt 50-Amp service at a campground? And how long would it take to check and top-off the batteries!:eek:?

It is certainly feasible, but is it worth doing?

Joe
 
#7 ·
I like your GUESS ESTIMATE example!

I agree that using Lead batteries just isn't a good idea. This drives the build cost way up. Its easier to get a loan for a new RV, vs an unsecured loan to do this project.

A lot of gas RV's use Ford Trition V-10 which I think is around 300hp 360ft/lb of torque. That's an incredible amount of hp to match with an electric motor... probablly 700 volt or more system would be required. Expensive and dangerous.

Its ok if the charge time takes a long time, say 14 hours. If I roll into the campsite at 6 pm and leave at 8 am the next day, that isn't really interfering with travel time.
 
#8 ·
I think a 144v system can produce far more than 360 ft/lbs torque. Heck, Crazyhorse makes over 1200 ft-lbs, and I think it's a 300-ish volt system (with gobs and gobs of amps). However, 300 HP = 223 kW... which can be generated by 111 volts @ 2000 amps... or 223 volts at 1000 amps, or 446 volts at 500 amps...

The problem isn't making the power so much as finding something that can handle that power...

Additionally... that 300 horsepower V10 probably only needs about 60-80 HP to push that RV down the road at freeway speeds. Sounds like a job for a large AC drive to me, something, oh, I dunno, in the 440 volt RMS range?

It's do-able... but how much would you want to spend? If you buy a nice RV for 100k, and put 400k into the drive/battery/charger systems, who would you ever resell it to when you no longer need it? :)
 
#10 ·
I think a 144v system can produce far more than 360 ft/lbs torque. Heck, Crazyhorse makes over 1200 ft-lbs, and I think it's a 300-ish volt system (with gobs and gobs of amps). However, 300 HP = 223 kW... which can be generated by 111 volts @ 2000 amps... or 223 volts at 1000 amps, or 446 volts at 500 amps...

:)
Actually, I found a 3 phase 150hp AC motor a few years ago through a Canadian electric motor company for $1,000 new. I think a 150 hp motor would easily run an RV down the road. It was rated at 3650 rpm.
I can't remember the name of the company since it was a while ago, but you could probably dig around and find something similar.

I believe its possible without spending a life savings on it.
 
#9 ·
Pretty cool idea. I would use the nice tractor (commerical) 12 volt 800amp lead acid batteries myself for starters. I use them to run part of my house with my solar system and they are great. Can get them at Napa for $189.00 and they have a 72 month replacement warrantee. Worth checking out. Each weighs about 75-80 pounds.

I would love to see an EVRV on the road.
 
#11 ·
Correct me if I'm wrong, but if a high volt system is used than I won't need as thick gauge wire.
Sort of like why the power company uses high voltage to transmit power because the resistance is so great. But what are the other inherent drawbacks from using highvolt/low amp system compared to low volt/high amp?

If I use a really high torque rated motor than I think that would require at least a four speed transmission and I would have to shift a lot just to get going, but when it comes to hills all the torque will be there!

I hope it is possible to not use a transmission. I think that goal really determines what type of volt/amp ratio and motor required.
 
#13 ·
But what are the other inherent drawbacks from using highvolt/low amp system compared to low volt/high amp?
Cost. The higher the voltage, the harder to build a controller that can handle it. Zilla 1k, for example, came in a "low" voltage flavour (I think it was up to 200 Volt) and a high voltage flavour (375 Volt) and the price tag was noticeably more painful on the HV-version.
 
#12 ·
So do you have a ballpark budget? If you are serious about it we can put together something on paper. It would be an awesome project.

Higher than about 156V generally means you need to go AC, (or twin motors) which is more expensive. But you probably should anyway. Higher voltage means less energy lost as heat in your cables and batteries, we just need to find you a system that will let you run that high. It would also probably be worth getting a professional electrician to help at the higher (more dangerous) voltages.
 
#14 ·
Some thoughts (though I have never converted) ....

1) Go AC, as the higher voltage can work. Look into the systems used by city buses, as you have already, as they can handle the weight and torque.

2) Life4Po are just about the only choice of batteries for weight and capacity. This will be your biggest cost.

3) Your choice of RV is going to be a HUGE decision. I suggest you go with the lightest weight one you can find (and as aerodynamic as possible). Then go inside and gut as much out of it as you possibly can. After that start to work on the outside and adapt it's look and design to smooth the flow of air. These changes will make you "free" miles off your battery pack.

4) Think of the use of solar (and also wind) as an assist for the charging or a bonus, but their cost won't pay for itself for a many years, but if you want the independence and have the cash, they can help.

5) With the investment of such a great amount of battery power, you could take your house off the grid and run it off solar and wind using your RV battery pack as the power reserve. Far out thought, but interesting idea.

6) Look into the idea of having the RV system simalr to the Chevy Volt, where you have some generators help or make all the power needed to run the car. It will give you more range. Make it biodiesel and you can just pull into the local truck stop, ask for the old cooking oil, spend the afternoon converting it and bam, you have your day to go.

An interesting engine I came across when watching Mythbusters the other day was this aircraft engine.
http://www.rotax-aircraft-engines.com/a_engine_582.htm
It can produce up to 48kw of energy and weights only around 90lbs! now that is some power to weight ... they were using it for a personal hovercraft idea, so it's got the ablity to put out the power, but finding the fuel for it might be a problem. It won't get you all the power you need, but it can get you farther(or emergency power).

7)Look to the boating industry (and airplane) for ideas of how to make the RV more self-sufficient, efficient and lighter

8) Be prepared to have two important things, time and money. If you have these ANYTHING of this sort is possible. If you get this right consider turning this into a commercial enterprise. The tax credit for battery packs would make a 140kw pack a large discount on the cost...

I wish you all the best ...
 
#15 ·
I think it is a great idea. I can imagine you can get old RV's dirt cheap with the slow economy and the fear of gas prices rising again.

I have a 92 Isuzu Trek A-class RV. It has a small 4 cyl diesel and gets a solid 15 mpg. It is probably about 110HP.

Really how much would it cost? Find an RV with a blown motor-under $10K. Maybe 80 t-105's - $10K, Motor for $1k. The electronics, no idea? $5k? Scrounge for parts, find used stuff.

I too think the panels are probably a waste. It is a good idea, but it would probably not be cost effective. You could probably fit 8 x 200 watt panels on the roof of a typical A class. The best you can get in the US is about 6 sun hours a day so that would make (8x200=1.6kwx6hrs)=9.6 Kwhr. If we use the previous estimate of 1150whr/mile, those panels would give it 8.3 miles of charge everyday. This is under good conditions, not taking any losses into account. Those panels would cost about $5K, then a charge controller $1k, then installation.

Actually, I guess the key to making the panels practical is using them as much as possible. As was suggested, using them to run your house would be a good idea. You can do net metering in most parts of North America these days.
 
#16 ·
I had this same idea, especially the charge from the campground J
You have gotten some good responses.
Some of the numbers here don’t look good for us.
I was looking at the electric busses too.
How about a parallel system that can just use the electric to keep you going once up to speed as someone mentioned.
I wonder what that would take?
Also, have you seen the latest on Lithium batteries that they came up with a way to charge in minutes?
 
#19 ·
OK, the idea of the electric RV appeals to me as I just purchased an RV, and converting it to electric is interesting. One advantage I have is that, as an earlier poster suggested, this particular RV has a very lightweight aluminum frame (1990 Holiday Rambler Aluma Lite XL 31') which makes it significantly lighter than some other units of comparable age, price and size.

It is currently equipped with a GM 454cid V8 and three speed automatic. I currently own some bateries I was expecting to install as additional coach batteries, but I doubt they would be anywhere near adequate for this purpose (25 pieces Hawker SBS60 12v 50ah).

The original intent was to put solar on the roof and use the extra batteries with a large capacity inverter (5000-8000 watt) to run some 120vac appliances/computers inside, but converting the primary drive seems more interesting. How would one begin to aproach this?
 
#20 ·
start with current MPG rating which can back into HP/ BTU per mile which can back into KW per mile.

since you now know what the energy requirements are to run it 1 mile, then figure out how far you need to go in a day at say 80% battery capacity.

now look at motors that will work and related controllers.

have fun
 
#22 ·
The electric RV.

Instead of buying a $75,000 -$100,000 brand new RV, what if I bought a used one for $10,000 as a conversion project? The technology has changed very little on the inside so it can be a few years old as long as it is clean and in working order (fridge, sofa/bed, tv, generator, toilet/bath, carpets, etc.).

The long flat roof is ideal for solar panels. If my RV is sitting out doors all the time, then it makes sense to have solar panels. The extra weight and cost is a draw back at first, but the savings over time

Or just not mess with and have a regular motor home with it's factory warrenties and shell out $2000 for gas each trip. Plus all the maint cost.

I've read a lot of these posts and a I'm interested in how this concept can be improved. Good day.
* Most or all of what you describe can be found in a smaller package (Class B) Used for around 10K (or less, if you start out looking for one with blown motor..... but rest of RV, clean and in working order.. with bed, fridge, microwave, generator ect........ A nice Class B with a slide or two can be very comfortable, large enough roof for some solar panels (I thought I heard of a printable solar Ink some time back, that would be great on awnings and such..... supposedly generated more power than conventional panels as well)

I was thinking along those lines - small Class B ERV or at the very least conventional Class B with electric upgrade.... trailer towed behind with small electric vehicle or scooter or both along with some or all of batteries and or generator and or more solar panels.... (wind turbine would be a must too, so batteries could be charged quietly at night while I was sleeping, when power hook up wasn't available and I didn't want to or couldn't run generator....)
 
#23 ·
This is a really interesting thread. One day maybe I might tackle something like an electric RV.

A 40 seater bus uses about 100hp at 60mph cruising so you're looking for an industrial induction motor of about the same continuous rating. Buses actually have a very low coefficient of (wind) drag from its long narrow shape which is a good thing. However, when you multiply that by the 10m2 frontal area and also factor the 9 ton weight and higher rolling resistance compared to a car, the energy required would be around 260kWh for 180mi range at 55mph. You were pretty much spot on with the energy per mile at 55mph of 1120Wh/mi.

A little ambitious? Well, you're converting a luxury motorhome. You're probably going to spend US$50k on refitting on top of the US$90k for batteries.
 
#24 ·
How about if you only needed enough batteries to run a compressor and the rest of the electrical devices in the Electrically propelled RV? Instead of batteries providing the power for the drive train, use a generator that runs off compressed air to power the electric drive system. It would be similar to a turbine generator but instead of jet fuel burning through it, compressed air would be forced through it.

The electric compressor i mentioned would run and fill at least three tanks that the generator would syphon it's air supply from. I say three so you have a reserve tank but two might be sufficient if space became an issue.

This solves some of the weight issue with the batteries as the tanks can be carbon fiber and the generator could be very lightweight also, depending on the materials needed and the size requirement to generate enough kwh's.

If you doubt the compressed air generator is feasible, then look at this link: http://www.mdi.lu/english/

This is a car company that make a compressed air engine for a passenger car. Surely I could even connect an ac motor to the drive shaft and get enough electricity off that motor. Be cooler with a compressed air turbine though ;)
 
#25 ·
So, you're proposing using the electricity that is stored in batteries to run an air compressor, to run a turbine, to generate electricity for the motor?

Errr, why not just use the electricity in the batteries? Converting one form of energy to another always incurs a loss due to inefficiencies. Converting electricity, to air, to electricity is a phenomenal waste of energy. You'll never get more electricity out of the compressed air driven generator than you put in to create the compressed air... by a long shot.

Maybe I'm just confused here...
 
#29 ·
So, you're proposing using the electricity that is stored in batteries to run an air compressor, to run a turbine, to generate electricity for the motor?
That is the proposal.
Errr, why not just use the electricity in the batteries? Converting one form of energy to another always incurs a loss due to inefficiencies. Converting electricity, to air, to electricity is a phenomenal waste of energy. You'll never get more electricity out of the compressed air driven generator than you put in to create the compressed air... by a long shot.

Maybe I'm just confused here...
No confusion. OCRVGUY was trying to get around issue of having either tons or a mint's worth of batteries in the vehicle. The problem is that the energy density of compressed air makes it just as impractical.

A more realistic possibility is liquid nitrogen. It has the same profile as compressed air, but the phase change to liquid and back can store much more energy than compressed air. Also storage does not require pressurized tanks.

The energy density is still bad. As outlined here:

http://en.wikipedia.org/wiki/Liquid_nitrogen_vehicle#Energy_density_of_liquid_nitrogen

Energy density of liquid nitrogen

Any process that relies on a phase-change of a substance will have much lower energy densities than processes involving a chemical reaction in a substance, which in turn have lower energy densities than nuclear reactions. Liquid nitrogen as an energy store has a low energy density. Liquid hydrocarbon fuels by comparison have a high energy density. A high energy density makes the logistics of transport and storage more convenient. Convenience is an important factor in consumer acceptance. The convenient storage of petroleum fuels combined with its low cost has led to an unrivaled success. In addition, a petroleum fuel is a primary energy source, not just an energy storage and transport medium.
The energy density — derived from nitrogen's isobaric heat of vaporization and specific heat in gaseous state — that can be realised from liquid nitrogen at atmospheric pressure and zero degrees Celsius ambient temperature is about 97 watt-hours per kilogram (W-hr/kg). This compares with about 3,000 W-hr/kg for a gasoline combustion engine running at 28% thermal efficiency, 30 times the density of liquid nitrogen used at the Carnot efficiency [2].
For an isothermal expansion engine to have a range comparable to an internal combustion engine, an 350-litre (92 US gal) insulated onboard storage vessel is required
The bottom line is that a 100 gallon non pressurized tank would be more doable than 50 highly compressed air canisters.


As for the efficiency, it's less of an issue than normal. The OP pointed out that they get "free" access to a 120V 50A outlet for their slip when they pay the $25 to park the RV for the night in the RV park. So essentially they can pull 6 kWh worth of power for however many hours they are there.


So it remains an issue of carrying that energy in a portable fashion. While batteries are efficient, there is a large weight/cost burden to be paid to carry them. Though the liquid nitrogen route is much less efficient it does offer the possibility of generating the range required without weighing a ton or costing a mint.


The other hidden advantage to liquid nitrogen is that in a lot of places you can buy it off the shelf very very cheaply. A log of airgas companies have liquid nitrogen as a byproduct of liquid oxygen generation. In some places it would be possible to fill that 100 gallon LN2 tank for as little as $20.


So it offers quite a bit of flexibility. You can get LN2 from outside sources. You can use your own distiller to produce it yourself just add electricity.


Finally the energy density listed is only to 0 degrees Celcius. Warming the LN2 to normal air temp will release even more energy.


The best bet would be to have a hybrid with as much batter capacity that can be afforded to carry/pay, with a LN2/generator system to charge the batteries.


Just some thoughts. LN2 actually has some measure of hope
whereas compressed air simply won't cut it.

ga2500ev
 
#26 ·
Actually, the power is stored in the air tanks. I know I didn't explain it well but let me try another way.

The original problem was to go 200 miles in a day. If you carry enough tanks on board to run the generator to allow you to travel the 200 miles, then you only need the compressor to refill the tanks at the end of the trip. The batteries are to use the on board electrical devices and the compressor is for refilling the tanks. You can recharge the batteries and refill the tanks when you plug in.

if you want to go further than two hundred miles, then run the compressor off the batteries to re-fill the tanks. Couple this with some quality solar panels and maybe even extend range even further.
 
#27 ·
compressed air doesn't have that good of an energy density. You'd need HUGE tanks to propel an RV 200 miles, pretty much the tanks would the the size of the RV. Further, compressing air is not very efficient of a process. I would venture a guess that, for the very high compression required (1000psi) the efficiency would be in the 50%.

So we're burning gas or coal with about 80% efficiency to get electricity that you'd use to compress air and lose 50% more of that energy. Further, air drive trains aren't the most efficient so say 80% and you get to something like 30% of the energy stored in natural gas/coal is used for propulsion. You might as well buy a 35mpg ICE which will do 25-30% efficiency in burning fossil fuels.

The reason batteries are the standart storage medium is because they are 95%+ efficient in storing and releasing energy. Moreover, electric motors can also be in the 90%+ efficiency and there are far less moving parts.
 
#30 · (Edited)
Personally I wouldn't want to be anywhere near a vehicle with a 100 gallon liquid nitrogen if it gets into an accident, especially in a non-pressurized, strenghtened container.


Although, thinking about it, if you collide with an ICE, it could spill over the engine or gas tank and put out any fires. Either that or explode. You wouldn't need the jaws of life either as all the metal that it comes incontact with would become brittle enough to kick down :) Just hope none of it gets on you. .
 
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