VW wagon EV with charging trailer...thoughts?

[ai4kk]

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?

[Piwoslaw]

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.

[luvit]

i'm lost for words.

[ai4kk]

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.

[MetroMPG]

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:



AC Propulsion generator trailer for its Tzero electric car:

AC Propulsion also produced a portable internal combustion powered generator mounted on a trailer known as the Long Ranger that could be towed behind the car and feed power to the batteries during travel. The trailer used a 500 cc Kawasaki engine with a 9.5 U.S. gallon (40 liter) fuel tank and achieved 30 to 35 mpg over at least 20,000 highway miles. It is rated at 20 kW DC output and can maintain 60 to 80 mph. Video footage of the backtracking feature, which allows drivers to easily back a trailer through a set of slalom cones.

AC Propulsion tzero - Wikipedia, the free encyclopedia

Example of a "pusher" trailer:



EV Pusher Trailer

The idea of the pusher trailer and/or generator trailer is to give the normal EV long-range capability with fast fuel stops without permanantly installing an IC hybrid system in the vehicle. This saves the weight, and complexity, of having the IC engine with you (in the EV) for the 80+% of driving that is done within the EV's normal range. For long-range operation, the IC engine will take over all of the load and battery drain will cease or slowly reverse.

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

[gone-ot]

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

[discovery]

Originally Posted by Old Tele man

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

i guess you get a gas engine...

[hamsterpower]

Originally Posted by Piwoslaw

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.

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.

[alohaspirit]

why have a charging trailer in the first place

just use those small portable Honda generators



and use this to mount on the back if you dont want to put it inside

[ai4kk]

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?