VW wagon EV with charging trailer...thoughts?
 

Looking at various vehicles for conversion I thought about taking a diesel VW wagon and using a forklift to convert it to EV a la forkenswift. That part's pretty straightforward. I chose the wagon because of storage room for the batteries and possibly a stiffer suspension.

Where this starts getting freaky is: use the removed ICE to power a generator on a trailer.

I noticed that Forkenswift's donor forklift provided 2 (or was that 3?) small motors and 1 big one. They used one of the small ones for around town poking around. If I'm correct, a DC motor will also act as a generator.

My thought is to build a trailer (that could also double as an aero-boattail for the wagon) that would hold the ICE-big motor combo as a generator, and the other small motor would drive the trailer wheels (or at least one of them...maybe make it a single-wheel trailer) as a helper motor. The trailer could also be used to carry an additional battery pack or luggage as needed and allowed under the weight ratings.

The idea would be to use it as a plug-in EV under normal use, then hook the trailer up for longer trips, like to other towns. The motor would only be started when a charge was needed, and for that time would only run at the most efficient RPM until the batteries were topped off, then would shut down until needed again. This would overcome the biggest single practical issue with using EVs as DD cars: range.

Am I totally crazy?

The idea isn't bad, but I think the ICE from the donor car would be too big. Instead of a heavy 50-60kW engine, you may want to find a much smaller 10-20kW diesel engine. The reason you want a diesel is efficiency. There is no need to use a gasser if it's going to rev only at a single rpm.

Putting extra batteries into the trailer with the engine-generator isn't a good idea: either the engine or the batteries.

i'm lost for words.

Part of the reason I would use that particular ICE is because it would be available. It also would not run all the time, only when needed and would be tuned for peak efficiency. Not knowing what size the generator motor will be or it's output, or how fast it should spin when used as a generator, I can only guess at what gearing might be needed (via chain drive perhaps?) to drive it to it's max reliable output.

Yes, trading it for a small industrial diesel would be a great idea if one became available, assuming that I could find such a critter.....I was working with what was handy and left over after gutting the car and the forklift.

Perhaps what I should do is set up my performance parameters and then work backwards from there to determine what type of motor and power is needed rather than base it on resources available.

Generator trailers have been done before, as Piwoslaw mentioned. As have "pusher" trailers. So the options are out there for you to study:

A few links:

http://upload.wikimedia.org/wikipedi...o_DSC00467.jpg

AC Propulsion generator trailer for its Tzero electric car:

AC Propulsion tzero - Wikipedia, the free encyclopedia

Example of a "pusher" trailer:

http://www.jstraubel.com/EVpusher/trailersideview.jpg

EV Pusher Trailer

On that page, the builder also lays out the pros & cons of pushers and generators.

...but, what happens when you need to tow a real trailer too?

i guess you get a gas engine...

Even better, salvage an APU from a small corporate jet. Small and light weight, APUs are designed to charge batteries and could run on bio-diesel. Problem is even a salvaged APU would be a budget buster.

why have a charging trailer in the first place

just use those small portable Honda generators

http://www.happyproductions.com/imag...0Generator.jpg

and use this to mount on the back if you dont want to put it inside
http://ucanhealth.com/local/image_pr...941045Ljpg.jpg

I don't think 1 or 2 KW would do it for a car on the open road.

If the car can do 40 or so around town, I would hope to push that up to highway speed with the extra juice and the extra push from the trailer.

Question is, would that large motor from the forklift put out enough juice to drive the two smaller motors at highway speed (>-55MPH) and charge the batteries at least a little when driven by the factory diesel ICE?

you dont?

then get a bigger generator :thumbup:

I like aloha's idea. So maybe it's too small to meet the on-the-go needs. Pull over, have a burger, let her charge up while you relax.

Remember that the generator doesn't have to charge the batteries in 30 minutes. If the 2kW gennie is on for the whole trip, plus stops, then it will let the batteries discharge more slowly.

BTW: How much power is needed to keep a vehicle with reasonably small CdA at 50mph?

That was kind of the point behind using the ICE from the donor car and the bigger motor from the forklift :)

Seriously, roughly how many KWs does it take to maintain 65 in a reasonably slippery car? What would that equate to in HP? I realize that we have to factor in efficiency losses but that is a starting point.

My only real concerns about the original ICE is that A) it may be heavier than needed.....but not sure if a smaller industrial diesel would really be any lighter. and B) if the engine's most efficient output range can't be matched to the generator's best speed whether through a chain drive or whatever. The weight can be dealt with possibly by looking for the smallest automotive diesel I can find, and the speed rating can at worst case be solved by using a bigger generator that can efficiently use all of the ICE's power at best RPM....and then shut it down when it is not needed.

Considering that unless you're a traveling salesperson most cars spend a fraction of their time on long road trips, I can accept a small trade-off in highway efficiency if it makes the car practical to use in daily driving as a primary / only car.

a honda 2000W is plenty. the charging would use no more than 1800W at 15amp current.

there may be some cars that would require 2500W generators, but that depends if a car's charging cable would need to be 20amp current.

Wow, dude, I think you meant 2000 W, or 2 kW, not 2000 kW!!!. That's more than 2680hp, enough to pull a train. So yeah, 2000 kW is plenty.

I used EcoModder's calculator to see how much power is required to keep a certain speed (not accelerate). I used the default numbers, exept Cd=0.26. 2 kW would keep you rolling at just under 35mph (35mph requires 2,148W), while to go 55mph you'd need 5,982W. That's really not much. Changing to Cd=0.32 gives 6,993W @ 55mph.

So, in the first case (Cd=0.26), exactly 1/3 of your power would come from the 2kW generator, extending your battery life by that much. If you count in "burger&pee" stops, coasting and regenerative braking, subtract acceleration, then you could probably extend your range by 50%-60%. A 5kW gennie would be more than enough if you stay below 50mph.

So ai4kk: once you get your wagon converted and aeromodded, use the calculator to see how big a generator you'd need. You'll see that the engine from the donor car will be way too big.

lol. yeah, i meant 1800W or 1.8KW / 2000W/2.5KW
i edited my post, but forgot to drop the K. *fixed*

So in keeping with the theme of reusing as much as possible from the original donor vehicles (VW Fox diesel and electric forklift), if the combination of the VW 1.6l diesel (tuned perhaps to operate more efficiently at a lower RPM) and the large motor from the Frankenswift forklift, what effect would a lower duty cycle have on overall efficiency? Would keeping the ICE warm enough be a problem? How much power would it take to spin an electric motor like that at max reliable/efficient RPM with a sizable load (charging and propulsion) on it?

It seems that if the generator combo is too big, reducing the duty cycle would solve that....kind of like pulse and coast. Run it till it's charged, then turn it off till the voltage drops a certain amount. I don't think physical size and weight would be too big of an issue considering that an automotive diesel is pretty compact to start with compared to an industrial diesel.....and the 1.6 is about as small as we can easily find over here in a car. If someone knows of a suitable alternative, that would be great, but I bet it won't be as cheap as the engine that came in the car.

See Jerry Halstead's excellent EV calculator

Batteries have a max current for charging, above that you're either wasting energy or destroying the battery. It's better to charge longer with less current. (I hope I'm not lying, any EV owners help if I am.)
The ICE/generator's most efficient rpm may produce more "juice" than the drivetrain+batteries can handle at the moment. All of this will have to be sorted out once you know your battery parameters.

The smallest automotive diesel I know of is in the Smart ForTwo. It's a 0.8 liter, direct injection, commonrail turbodiesel (=very new and high-tech). Its 54hp is more than enough to serve as a gennie, plus it weighs less than 200lbs. Here's more info. I don't think the ForTwo had that engine as an option in North America, but in Europe it can be found in scrapyards (I found two at a local auction for the equivalent of US$700 each). There is also the 1.2 liter TDI from the 3L versions of VW's Lupo and Audi's A2, but that's just more eye candy for America with EPA emissions;)

Also, Christ found a diesel engine. I'm not sure if he's found a use for it, but it's heavy!

the current that charges the batteries is controlled by your charger.
the selection of the generator would be based on the current-draw of the charger.
ideally, this setup will hopefully allow the car to drive off of the generator current as well as charge the batteries. then you can eventually turn off the generator and continue driving.

Actually, it looks like there were a few diesel Smarts sold in Canada. See
smart cdi (diesel) owner from BC, Canada

I'd love to get my hands on one of these...even just to drive without converting it. The heck with the 96ft motorhome, I could see my wife and I retiring to a Smart diesel pulling a lightweight teardrop camper.

As it is, some of these little diesels sound rather interesting. Even a constant-speed diesel would work for this as long as it had glow plugs for ease of starting. I mention that as the industrial version of my Isuzu engine has none.

http://biodiesel.infopop.cc/eve/foru...3/m/3361040812

Now THAT would be interesting...electrify my Trooper with traction motors on all 4 wheels and move the engine to a trailer. Just not sure how it would handle submersion and other muddy conditions....I can see the fireworks now LOL

I have a lot of experience with these generators.

They run very quiet and would be a great option for extending range on any EV that can utilize a hitch.

Noel Perrin used one with Solo to try going over the mountains of California. Ultimately, he could not generate enough power to go over the steep grades though. :turtle:

And therein lies the rub. To start with, a big part of the idea here was to re-use as much of the original vehicles as possible, neither of which came with Honda generators. At the same time, while a small generator might produce enough current for charging over time, it will not put out enough for sustained highway travel, especially not if any substantial climbing is involved. That doesn't mean that a larger gen-set might not work, but those aren't cheap.

If I had an EV pickup with only 50 mile range and wanted to go 75 miles...

I see no problem with putting this in the back and plugging in the juice. The gradual charge should keep my batteries topped enough.

Oh and these generators can be paired together for double the output!:thumbup:

And double the cost!

If I'm going to add on anything to extend my range (beyond what I need around town), it's not going to be limited to a mere 75 miles....there's nothing worth visiting within 35 miles of Tallahassee (look at the map and see). It would have to be indefinite...or at least capable of extending the range to a full day's worth of travel so I can get a recharge overnight.

To me, this is what would make an EV feasible as a primary/only car...the ability to function around town or on a trip to Ocala or North Georgia for a weekend of primitive camping.

No solution is going to replace what gasoline gave us because of its high BTU per gallon. At 40 Mpg many cars can now go 500+ miles without a fill up. No pure EV built today is going to offer that with the convenience of a "quick fill up" at the local charging station.

Sorry, but the "it has to be easy argument" is why we are so dependent on foreign oil in the first place.

The topic here is discussing popular opinion of the EV charging trailer. I think that it works and will be a solution that you see many weekend travelers using 20 years from now.:)

Not sure if you realize it, but you and I are reading from the same hymnal so to speak.

Maybe 4K worth of generators can put out enough juice to keep my car charged up at highway speed....at that speed, the car would mostly be running off the output of the generator anyway, not the batteries; anything extra would go to keeping the batteries topped off. For those without pickups, maybe the generators could go on a hitch-mounted cargo rack, although that could easily exceed the weight rating of the car, hence a small trailer being a reasonable answer...with the advantge of being unhooked once you're back home and commuting, thus converting the car back into a pure EV. This is the only way I see EVs replacing ICEs as primary transport.

Refilling a generator or trailer on the road is as convenient as topping off your car at a gas station, the tank is simply in a different location :)

I think we all agree that the ideas have potential, the only thing is how much power should we budget for the generator? Do we use the bare minimum and let it run all the time on a road trip, or use what came with the car (in my case, a diesel running on WVO), possibly putting out more power than needed, and then compensate for the surplus of power by reducing the duty cycle of the ICE?

Of course, in a recent post, I did mention some other small diesels that may have potential, so we're not necessarily stuck with the car's original ICE any more. I may look at some of the powerplants from some of the bigger mowers and off-road vehicles (John Deere Gators etc), I'll just have to see. For my project, I do want to stay with diesel since they are more efficient, my other cars burn that, and I like to use alt fuels in them.

My father (Dangerous_Dan here) and I have done our own research on a switching power supply that powers my 2009 Honda Accord which runs without an alternator (another subject please).

We discovered that a PROPERLY TUNED battery charger will not pull the maximum wattage from the 120VAC source, instead the drain is proportional to both the temperature of the battery and the remaining capacity.

If you put two Honda generators on your EV while driving and monitored their RPMs (yes, they have ECU monitors for that), you will see they increase in load as you drive. The result would be that the generators can sit at low RPM's and conserve your ethanol until the batteries become severely drained.:cool:

just exactly how far are you going to drive before stopping?


1000 miles?

Possibly...I did 1,000 miles once, but my mom was in the hospital in FL and I was in MI.....it's not something I make a habit out of. To give you an idea, it took me a week to drive up when I first got based there, and only 30 hours to come back.

On back roads I usually average about 250-300 miles a day. When I picked my Trooper up in Richmond, it took us 4 days to drive the 900 miles home, but a lot of that was on twisty mountain back roads. On this trip, we stayed with other couchsurfers in Roanoke, Asheville, and Atlant and could have potentially plugged in overnight, but on other trips we may be camping off the grid if we find someplace neat.

We go to Gainesville or Jacksonville quite often to take my kids to visit their mother or to see my sister. Either way is about a 300mi round-trip and we don't usually stay overnight in Gainesville although I wouldn't mind doing so as I grew up there...it's just usually at the end of a weekend and we need to get back...besides, I doubt my ex would let me plug in LOL. Any trip to Orlando or Tampa is going to be 300 miles 1-way and we may or may not be able to plug in while there.

On some longer trips, we have topped 500-600 miles in a stretch by changing drivers...it's all according to how much time we have to get there vs how much we want to see enroute. We obviously aren't typical "get on the interstate and lock in the cruise" travelers, but sometimes you have to get someplace in reasonable amount of time, whether for work or to make the most of limited time off from work.

When we do SCA and Rainbow events out in the National Forest, It's about 200 miles there and we do not have grid power available although we could potentially run our generator a little bit in the evening before bedtime and some again in the morning after most folks are up.

That said, most use of this vehicle would be typical daily commuting, about 10 miles/day, during which it would be a pure plug-in EV.

i gather then the ev trailer wouldnt just be used as a charging station

but also as camping storage as well



basically im trying to find reasons why you cant stop and charge periodically
or the cost difference between a larger generator versus a dedicated (heavy) trailer that would drop your efficiency

You could stop and charge periodically...but for those of us with jobs and using our limited free time to go somewhere or do something with the kids, you may not be ready to stop and do something else beside drive while ou wait for the batteries to be charged. Yes, I agree that we should be willing to make certain lifestyle adjustments for the planet, but taking a 3-hr break in the middle of a trip might be asking more sacrifice than most folks are willing to put up with in order to drive an EV...especiall when by making the trailer powerful enough to eliminate that break, you can do your trip and git 'r dun....then unhook the trailer and go back to being a meek and mild little plug-in EV. I see it as giving an EV a dual personality...something that can lightfoot it around town while still retaining the highway range of a standard ICE car.

Yes, it would be a mobile charging station....with enough output to help the car over those hills or while carrying a load such as us, 2 teenagers, camping gear, and a couple of bicycles. I would want it to put out enough power to drive the vehicle on it's own at a reasonable speed (55 MPH perhaps?) on flat ground even if the batteries were dead, and to climb a hill with a good charge. I would have no problem shifting to first to make it up a hill as long as I could at least keep up with the semi-trucks and their loads.

Of course the original concept was to reuse components off of the original donor vehicles....you know, the whole reduce, reuse, recycle thing rather than buying more new/used stuff. Hence the ICE from the car, driving the big electric motor from the forklift as a generator with the other smaller 2 motors being used to move the car.

So far, I have yet to hear why reducing the duty cycle of the ICE/electric combo to meet reduced overall need is not a good idea; why not just run it only when the voltage falls below a certain level then turn it off again? Of course it might run continuously while climbing a mountain pass but that is why it is there....it'll stay off most of the way down the other side! Your comment about weight being the main reason I've heard to go with a smaller engine. Yes, weight may be an issue when using a diesel engine as the ICE....I'm not sure what's going to weigh less, as I just found some of these smaller diesels and have yet to look them up, but I suspect that a small automotive diesel might be fairly light compared to a similar-sized industrial diesel (see 2815 - Diesel Engines & Components at Government Liquidation )and probably cheaper too....perhaps this may be just one of the compromises to make to make an in-town EV highway-worthy without breaking the budget. Considering how little time most cars will spend on the open road compared to pulling daily commuting duty, some tradeoffs might be worth it. Of course, perhaps the ultimate answer may be to top looking at diesel for this application and we may have to look at that option at some point.

Camping storage is a minor factor...we often backpack, canoe, and bicycle-camp, so we can pack pretty tightly and we don't "take it all" with us. At any rate, if this trailer is also designed as an aerodynamic boattail, storage space should be available in the fairing...and we don't take our microwave, hair dryer, and easy chair with us, so I don't see much weight for camping gear..maybe 100 lbs at the most for 2-4 people.

If taking a road trip in an EV was as simple as strapping your Briggs and Stratton gen-set to the trunk-lid, why aren't more EVers doing it?

This all still comes down to:
Build the Ev conversion and ecomod it. Drive it around for some time so you know how much juice it needs at what speed and then build the trailer and add weight to simulate the engine to test energy consumption. Then start thinking about how powerful the generator should be to meet your needs, depending on whether you are willing to make compromises (lower speed, stops every 4-6 hours, etc.).