EV Pusher
EV Pusher Trailer
Some Background:
Electric vehicles are great for around-town driving. Clean, quiet, and up to the task of keeping up with urban traffic. Longer trips can be difficult. The problem is that they do need to be recharged. Mine has a range of approximately 40 miles, so a trip to, say, Portland (100 miles) would require two stops to charge, at about 8 hours per stop. Obviously, this is unworkable in terms of convenient traveling. I could drive my internal combustion engined pickup, but it's kind of worn out, and gets only "OK" mileage.
What's needed is a way to convert the EV into a hybrid for longer distances. Enter the EV pusher trailer, which allows me to have an internal combustion engine to drive the EV forward longer distances when needed, but is detachable for around town use when I want to drive as a pure electric vehicle.
How It Works:
The EV pusher is constructed out of the front end of a 1978 Volkswagen Rabbit, powered by a 52 horsepower diesel engine. It has a stock three-speed automatic transmission, axles, and CV joints, all connected to the front wheels as a front-wheel-drive vehicle. It is constructed as a trailer that is towed behind the EV, just like an ordinary utility trailer. Through the use of electronic controls, I am able to operate the ignition, starter, and throttle in the trailer from the driver's position in my electric car. To use the trailer, I start the engine, open the throttle, and the diesel engine in the trailer drives the EV forward through ground traction provided by the front-wheel-drive train in the trailer. Usually, the electric drive system in the EV is used to help the EV/pusher combination up to speed. Once highway speed is attained, I have several operating modes, some of which are capable of either preventing the batteries from being discharged during driving, or even recharged as the trip progresses.
Using the pusher trailer, I can cruise at 65 MPH continuously, and have kicked the speed up to 75 MPH briefly for passing. Further tests may show that higher speeds are possible. Range is limited only by the availability of diesel fuel, which is pretty common these days.
Operating Modes:
It's possible to operate the pusher trailer in several configurations, as follows:
Parallel Mode/Electric Assist: This describes using the electric and diesel drives together. After attaining cruising speed, I can use partial electric and diesel power. This results in the highest fuel mileage, but does put a variable drain on the batteries. By calculating driving time and current used from the batteries, I could arrive at my destination with a partially or fully discharged battery pack. This would be a good option for saving fuel for the times when I know I'll have the time and availability of charging facilities.
Parallel Mode/No Electric Assist: In this mode, the diesel engine is driving the car forward, and the EV throttle is backed off until the E-meter shows 0 amps, no current entering or leaving the batteries. The electric motor does consume a small amount of battery current, but this is returned through gentle regenerative braking, consuming a little bit of power provided by the diesel pushing the car forward. The electric motor is on-line, with the clutch engaged and transmission in gear. In this manner the electric drive is in "hot standby", ready to assist the diesel in providing power for passing, or conversely, available to provide powerful regenerative braking to slow the car to adjust for changes in traffic speed.
Parallel Mode/Regenerative Braking: This is the mode I operate in frequently, particularly on short trips. The principle is the same as described above, but the electric throttle is backed off even further, so that the diesel driving the car forward provides a charging current to the EV battery pack. This requires that the diesel throttle is opened up enough to account for the additional power that the EV is consuming to charge the batteries. Generally, I keep the charging current to 10-15 amps, which isn't very much power, and doesn't seem to load the diesel overly. It is possible to produce charging currents of 200+ amps in this manner, but this really strains the pusher, and results in loss of speed due to the load.
Diesel Stand Alone: Basically, this is cruise control, with the electric drive shut down and the EV transmission placed in neutral. On a long, straight stretch, with consistent traffic speeds, this mode is the least effort on the driver's part. Although this mode doesn't provide charging current, It can be useful when the batteries have only been used a small amount and charging facilities are available at the destination.
Series Mode: There is one last feature of this trailer, which is that it has a 3,000 watt AC generator installed, driven by a pulley from the crankshaft. This is mostly meant to be used to charge the batteries in the EV when the car is stationary, although it could be used to offset the current consumption when the car is running. Since the EV and pusher combination requires about 20,000 watts to power down the road, this mode isn\'t very useful while the car is in motion.
A true series hybrid vehicle would need a whopping big generator, something along the lines of a 30-40,000 watt unit to produce sufficient current to drive the car, have peak power for hill climbing and passing, and to make up for the losses incurred when changing energy from chemical to heat, then to mechanical, then to electrical, sending it forward to the EV, controlling the current, converting it back into mechanical energy, and then sending it to the road to drive the car forward.
Additional problems with series hybrid operation is that the electric motor in my EV is still only 24 horsepower, and won\'t develop more no matter how large the generator on the ICE engine is. Added to this is the full-load capacity of the motor, and it\'s ability to be cooled fast enough to keep up with heat production, etc. In all, the parallel modes work out best for me.
Why A Diesel?
Lots of reasons. They get great fuel mileage, about 48 MPG for the 1.6 liter VW diesel when it was installed in the stock VW vehicle. They are also rugged, with a life expectancy of 150,000+ miles between major repairs.
In this application, I can't hear or feel the engine, as it is contained in the trailer behind the car, so using an engine that is not harmed by sustained high RPM's, heavy loads or being lugged in high gears is a definite plus.
Also of some attraction to me is the possibility of brewing up some Biodiesel, which is vegetable oil motor fuel. Then I can continue to drive my EV over extended distances with my nose planted firmly in the air, as I won't be polluting or supporting petroleum companies.
Most VW enthusiasts I consulted with universally hate the CIS fuel injection system on the 1.6 liter gas engines, and finding a gas power plant with low mileage and at an affordable price was getting to be too much of a chore.
Modern gasoline engines are a rat's nest of emission control devices, all of which require maintenance and steal away power. Diesel engines are an emissions control device, in spite of the black smoke that many emit.
(All Too) F.A.Q:
Here's the list of the questions I get asked most, beginning with #1.
Q: How do you control the trailer with a single-point hitch? Doesn't it get all squirrelly and make the car jackknife?
A: The trailer tracks behind the car perfectly. You can't even tell that it's there. You can't hear it and you can't feel it. The EV outweighs the trailer 3-to-1 and the hitch point is very close to the rear axle. Having 1,000 pounds of batteries in the back of the car helps a lot too, I'd guess.
Q: What do the police think about it?
A: I don't know, I didn't ask them.
Q: Couldn't you put a generator on the engine to charge the batteries while you drive?
A: Yes, I did have a 3000 watt generator mounted on the engine, but was having problems keeping the mounting hardware from failing due to vibration. After installing a new engine, I haven't had time to re-install the AC power plant, and so far, haven't missed it. Perhaps this will be a future project.
Q: How do you shift the transmission?
A: The trailer uses a stock VW three-speed automatic transmission. Operation is pretty much, uh, "automatic".
The Archives:
So, now that you know what an EV Pusher is, I'll explain how my construction of one is coming along;
First, you may want to visit Archive Page One, which tells all about the first two months of this project, the acquisition of the donor car, the repair of the engine, and all of those groady details.
Next, chronologically, is Archive Page Two, which gives the low-down on converting the car to a pusher, cutting it in two, adding the towing tongue, and all of the fiddly-bits associated with getting it ready to test.
The project grinds on with road tests, more fabrication, problem solving, and vaporous ponderings in Archive Page Three.
Beginnings of body work, long distance test drives, and A whole vacation's worth of no progress can be found in Archive Page Four.
The most current stuff is here, Archive Page Five, getting the trailer and car ready for an extended trip over the mountains and into the desert (in July!).
Sharkey's Big Adventure On the Road is played out in the best serial form, with exciting cliff hanger chapter transitions, heroes and villains and good versus evil (well, at least not-so-very-nice).
The seemingly never-ending "Big Adventure" is still being written to it's conclusion, but there's been some progress to report on in the realm of Pusher construction, so Archive Page Six has been posted, and includes a surprise for All Hallow's Eve (October 31st.).
Apart from many hours of engine rebuilding and installing, the pusher is still sitting in wait of it's rebirth to the open road. Perhaps before Archive Page Seven is filled, I'll get this thing running again! For now, consider this Pusher Project Year Two.
Some people never learn. Here's the story of my 2002 trip back to SolWest Renewable Energy Fair, and yet another attempt to cross the high desert with my cobbled-together contraption.
"I thought you were going to take the EV and Pusher to SolWest 2003". As it turns out, another adventure awaits the homemade hybrid combo. Read all about it in the continuing saga of EV Pusher Meets the Eco-Trekker
Additional uses for the pusher: Old motor home power enhancement.
Of course, if you haven't been there yet, you'll want to visit the page describing my EV, 1981 Electric Rabbit.
A page to answer all of those nagging questions about LPG Fumigation of diesel engines.
And finally, you can view or download a PDF copy of this page that was edited and published in issue #97 (Oct - Nov 2003) of Home Power magazine (1Mb file size).
I'd like to thank JB Straubel for the inspiration for this project. Follow this link: <http://www.jstraubel.com/EVpusher/EVpusher.htm> (which will open a new window in your browser), to view the original pusher trailer that gave me the idea for mine. Don't forget to come back and see the rest of the archive pages!
Original material ©1996-2024 Mr. Sharkey | All rights reserved