DIY Volt Hybrid - Open ReVolt style

[bennelson]

Well my friends, I love my electric car....

But it does only run on just a few, used, batteries, and doesn't have phenomenal range. There are times where I really wish I could just go a bit farther.

Since it's already an electric car, and gets its power from the wall, through the charger, it's already efficient and can run on renewable energy. I like that and want to keep it that way.

What makes sense to me is a "Chevy Volt"-style DIY Plug-In Hybrid.

A friend of mine is an RV mechanic. A while back, he gave me a propane generator. (Generac NP-40, 30 amp 120V) It didn't run, needed some troubleshooting and TLC, but still quite a score!

My idea is to mount the generator on the back outside of the car, along with its propane bottle. AC power from the generator would run to the cars charger, which would continuously "top off" the batteries as long as it's running.

The generator is out of an RV, so it's already DOT approved for use in vehicles. It runs on propane, so emissions are no worse than cooking burgers on your home gas grill.

The car uses about 7Kwatts while cruising at 35 mph. The generator is rated for 3Kwatts, so, if I am driving 35mph half the time, and at stop lights, going down hill, and off the accelerator the other half of the time, the battery level should stay pretty even.

Real world tests will show how well it actually works or not in the end, but it's off to a good start. I just got the engine to run on it's own (using scrap parts from a gas grill!)

[Dr. Jerryrigger]

I like it! Even if you are using more juice than the generator puts out, you could dramatically improve your range when needed. And you could leave it running in a parking lot for a return trip. It's likely not a very efficient system, but makes a plug-in car far more versatile.

[RobertSmalls]

I think a DIY hybrid is a great idea, and this implementation makes sense since you've already got the generator.

How are you going to convert 30A of 120VAC to... well, what voltage does your car run at? How large is this generator? Is it electric start? What will happen to the generator and its propane tank in a severe rear-end collision? Any idea how many lbs of propane it holds and how far that might take you?

Using a small engine to drive a rear wheel via a chain is the approach I'd like to take, but the generator is probably much easier to implement.

[dcb]

ben, I have a request for data.

for every trip, could you:
log tank starting weight
log tank ending weight
log starting state of charge
log ending state of charge
log miles traveled

? maybe?

[NeilBlanchard]

May I suggest using the FVT eVaro implementation of a serial hybrid instead? It runs the generator at a constant speed until the batteries are charged. You should remove the AC inverter, I think, and rig a DC-DC connection?

[Daox]

Very cool Ben!

[bennelson]

The generator is a variable speed AC unit. It makes AC, not DC, by default, so I may as well use that.

The plan is to just plug the car's charger into the generator. The charger varies the DC voltage and amperage to the batteries, depending on their state of charge. While driving, it would most likely mean that the charger would just go all out. The charger does have user adjustable maximums for amperage and voltage, so I could tell it how hard to work.
By just using the charger, it also means that the generator could be adapted to different electric vehicles easily, even if they are different system voltages. (Electric motorcycle sidecar range extender?)

I have thought about weighing the propane before and after for a measure of how much fuel is used. It uses any standard propane tank. I would think it would run all day on a BBQ tank.

I believe that as far as generators go, this one is fairly compact and efficient. It has a ring of permanent magnets on the OUTSIDE (rotor) and an electromagnet stator on the inside. Sort of like an inside out permanent magnet motor, but with no brushes or commutator. The computer control manages the speed of the generator (it's variable speed) and adjusts the speed depending on the load.

I don't expect that a propane tank is any more dangerous that having a gas tank on a car. People pull camping trailers all the time that have a propane bottle or two strapped right to them. I was also thinking that the generator, propane tank, and anything else that ends up as part of the "Hybrid pack" would all go together in some sort of box/covering/pod thing.

The generator has electric start, and there was even a remote panel available for it. A four pin cable is built into the unit to run to that. It should be pretty easy to put a big red START button on my dashboard.

I got the engine to run a little bit tonight. (I don't think I have quite the right regulator.) When I ran a volt meter to the power output, voltage was all over the board. It may have been just because of only having the engine run so briefly, or it might be an issue with the voltage regulator.

I won't have any more time to work on it until next week, buy it looks really promising.

[vinny1989]

Sounds like a fun project, and getting the genny' free is great!

Have you thought about building a small trailer to mount the whole generator assembly in? Then its easily removable, easily transferred to another EV, and (if designed with aerodynamics in mind,) shouldn't make too much difference in wind resistance..

[RobertSmalls]

Originally Posted by bennelson

Electric motorcycle sidecar range extender

Is building a 30A charger cheaper and easier than hacking the generator to produce DC as Neil suggests?

I don't think a one-off needs to be any safer than a motorcycle, but at least consider what will happen to the tank in a crash when mounting it. It will either be sandwiched between the bumpers of the two cars (Boom!), or it will be driven through your rear hatch or glass. Maybe placement above your bumper but below your glass would work out.

[DonR]

When people convert Jeeps to run on propane they generally use a heavier duty tank, like one off of a fork lift. I don't know if the fittings in the tank are the same as home tanks or not. They also mount them laying down instead of vertical.

I assume the efficency of an ICE running on propane increases with load, just like gasoline. Is there some electronic magic to make sure the generator only runs when it can run at max load?