Can I use a GENERATOR to power an Electric car directly?

[LeanBurninating]

So on a theoretical level, basic physics tells us that the energy created by any generator, which is then stored in bateries and used by an electric motor to power the car... at the end of the day you will end up with less energy than if you just used the same style generator motor as a regular engine.

The only advantage to setting up a car this way is to get a combustion engine to run at a fixed rpm, that way you can fine tune the intake and exhaust runner lengths and stuff like that to make the engine run optimally at a very specific speed.

The question is, if that advantage is significant enough to offset the energy lost by using an electric motor to power the car.

Am I missing something?

[Nerys]

Actually on a theoretical level that is not correct. Theoretically if you had a proper generator and a battery pack to handle the acceleration loads you would use FAR LESS energy end up net plus at the end of the day (compared to just using the engine to move the car)

This is because using electricity to move a car is far far far more efficient than using gasoline.

A generator is in theory far more efficient than an engine because the gen only has to run at one speed. OUR problem is strong enough generators are crazy expensive and integration electronics don't exist on the consumer level yet.

for example my Genset is a 6000watt generator. thats only 41amps. Barely enough (maybe) for level highway cruise maybe.

In reality I would need a 80amp generator (12,000 watts continuous) since gensets are LEAST efficient at full load and most efficient at 50% load.

Thats a very big very expensive generator :-)

then you need integration electronics to be able to "MANAGE" the battery charge and discharge Generator output and how this power is all sent to the controller.

Also our generators are not all that efficient really. Remember these things are designed for power stuff at a campsite powering your home essentials during an outage or equipment at a work site.

Mediocre efficiency is "good enough" for all these applications so thats what they design for.

but it would still be more efficient than a gasoline engine directly powering the car.

worth the hassle? probably not. Keeping a 2000 watt HONDA generator in your BEV might not be a bad idea though since you can slow charge from a 110 outlet. If you ever run out of go juice you can plug it in go find something to eat or see a movie for 2-3 hours and come back to maybe enough charge to at least get home.

[dcb]

Originally Posted by Nerys

but it would still be more efficient than a gasoline engine directly powering the car.

I don't believe so, at least not when you choose the engine and gearing wisely and use it just for maintaining a fixed speed on the hiway (and use your batteries around town and to get up to speed). Engine to wheels is a much more direct route than engine to generator to motor (and some in and out of the batteries) then finally to the wheels.

That is kinda why I like the motorcycle pusher ev range extender idea

[LeanBurninating]

hmm.. so perhaps the best option is to supplement with a nuclear reactor.

doesnt make sense that electric motors use far less energy.. you cannot "create" energy, some of it is always lost to friction, heat, sound, ect.

The way I see it, if you use a generator to power an EV, you just have more opportunities for energy to be lost. Using a regular car, energy is lost in the heat and sound created by the engine, as well as all of the friction in the engine itself and the whole drive train. Using a generator to power an EV has all of those opportunities for energy loss in addition to the amount of energy lost while generating electricity, storing it, transferring it, ect.

Theoretically if you had a proper generator and a battery pack to handle the acceleration loads you would use FAR LESS energy end up net plus at the end of the day (compared to just using the engine to move the car)

This is because using electricity to move a car is far far far more efficient than using gasoline.

I'd be interested to know how the potential evergy of gallons of gas compares to that of, say, watts in an EVs battery pack. How else can you accurately compare efficiencies?

I would agree that using electricity to move a car is far more FUEL efficient.. haha.

[Nerys]

Well lets see. Gasoline engine 2% efficient Electric engine over 90% efficient.

makes perfect sense that electric motors use far less energy they are far more efficient.

Only about 20% of the energy from gasoline is extracted and about 90% of that is HEAT and some of whats left is lost in friction.

So what you end up with TO THE WHEELS is single digits efficiency and LOW single digits.

The most efficient gasoline engine is 50% efficient at converting energy to motion and its a diesel engine larger than your house :-)

Potential energy in gasoline is irrelevant. how MUCH of that energy your able to put to work moving your car is relevant. With gasoline very very little of it goes to moving your car. Most of it goes right out the tail pipe the rest goes into heat and some goes into friction. Whats left moves your wheels.

An electric motor IIRC is about 95% efficient at converting its input power into motion and that can be further improved upon.

GRID to WHEELS EV's are about 86% efficient. (compared to 24% for hydrogen fuel cells)

Even motorcycles are NOT very efficient. the only reason they get such high mileage is that drag to a small degree and mass to a massive degree are dramatically reduced allowing you to use a much much smaller engine.

my 82 Goldwing only gets about 30-35mpg then again its 25 years old and has a giant 1.1liter 4 cylinder engine and masses 900 pounds :-)

Compared to a 200 pound 250cc scooter which can nab 70+mpg

One of the reasons GM's EV1 got such amazing range NIMH or not (even the lead acid version got 60-80 miles to a charge sometimes 90miles) was that is was very CLEAN aerodynamically and it was VERY light (aluminum chassis plastic body etc..)

If you make your engine to run at one speed its not an engine anymore persay its a generator either way it won't work. Except in Arizona nevada and kansas etc.. there are no FLAT roads on this planet. they all have gradings up and down turns curves hills etc..

Next time your driving get on a flat and notice how you can keep the gas in one spot to maintain speed. NOW keep the gas pedal in that spot no matter what. see what happens when you hit even a small incline. you will lose 5-10-15mph or more if you do not compensate with "more gas"

this would not effect a genset arrangement. It never touches the hill. you would simply use more watts from the battery pack when you hit that incline.

Your motorcycle pusher would be very efficient but no where near as efficient as a serial hybrid setup. (that is what using a generator to keep a battery charged is)

It takes about 8000 watts to go 100 miles in a lightweight EV like the EV1

about 10,000 watts in something like say the Rav4EV

do the math from there. My generator can run 11 hours at 50% load that means I can generate 27,500 watts for 5 gallons of fuel. (thats conservative mine has gone over 12 hours at 60% load but lets use the manufacture rating just to be easy with the math)

that means IF I had a battery pack and IF I had a way of integrating it with the genset to keep the battery charged up while driving in theory I could go 340 miles on 5 gallons of gasoline

That's 68mpg and thats not even counting using the power in the batteries after the genset is out of fuel. if they can get me say 40 miles (average lead acid EV range) thats 380miles or 76mpg

Not bad ehh. and in theory you would only need to use the genset if you know your going further than the range of your battery pack.

this would be pretty harsh on the batteries though I would imagine. Not sure how well leads would take being charged and discharged at the same time rapidly.

Now you may have noticed a problem with these numbers. the 27,500 watts is over 11 hours. going 340 miles on the highway will used 27,500 watts in 3.4 hours. Wee problem there :-)

Depends on how many watts you use CRUISING and if there is enough surplus watts to replenish the battery pack while cruising. I am guessing you would really need at least a 10,000 watt generator to make this work and probably end up around 60-65mpg

The point of a genset arrangement is not to be your final car. its to allow you to have an EV if you need MORE than the 40 mile range a lead ev can currently give you. Later on down the road once the patent expires and they start making NIMH's or when a cheaper alternative comes along you UPGRADE the battery pack and eliminate the Genset.

alas its a lot more complicated than I thought. I have NO idea how to integrate the 3 systems to make them behave with each other. Somehow I don't think you can just plug the generator into a bunch of chargers and connect them to the batteries.

[Allch Chcar]

What's great about putting the electricity in the batteries is the batteries can store that energy for quite some time. And when you do use the electricity the motors are very efficient about using it.

Gasoline ICE engines produce 20%(varies) mechanical energy and 80% heat energy from friction or escapes as heat. It uses all of the gasoline you put in it(except for the stuff that evaporates) but only 20% of the energy is in the form of mechanical energy. The driveline on a manual transmission vehicle is approx 85% efficient which is on par with electric motors after you run the electricity from the batteries through the controller to the motor. So best case, an average of 17% of the energy from the gasoline is used for movement and 72%(varies but 85%x85% is average) of the electricity from the battery becomes movement. If you run a generator you're going to lose energy from the charging process. In the end an electric vehicle uses about 1/3 the energy of an equivalent gasoline car would get with similar power outputs and energy usage. Most generators are 2 cycle for the power and light weight. They get half to one-third the fuel economy of 4 cycle engines.

27.5kw might get you 100 miles at less than 45mph. Why are you calculating 80 watts-hours/mile? Even if the EV1 consumes 80 watt-hours/mile after you convert the energy from the generator to the motor it's going to use more power than that and you aren't even driving an EV1.

You can't just convert miles + energy = time. You're ignoring speed. 27.5kw-hours will only get you a little over an hour of drive time at 60mph. 27.5kw-hours doesn't equal 340 miles of driving at 100mph for 3.4 hours. Not even in an EV1.

Hooking up a generator to your Electric vehicle is as easy as plugging in the charger. 2.5kw chargers are expensive too, Zivan makes one but they sell for over $1k.

Going the EV route with a home generator would just consume more than your current car does. Except for the short range all electric trips. It really depends on your personal commute, which for you Nerys does not sound like an economical choice.

[Nerys]

I assumed 60mph and I used EV1 data because thats the only usable real world example I have. and I did specify and ev1 like vehicle.

Watts is watts. that generator WILL produce 27,500 watts in 11 hours AFTER losses. Battery charging of NIMH is close to 90% IIRC.

I ignored speed because it varies. I assumed a consistant 60mph.

I used that figure because THATS the figure GM used. $1 in E for 100 miles. $1 in E is about 8000 watts. So thats the figure I use. As I noted the RAV4EV uses something more like 10,000 watts per 100 miles (heavier and draggier)

Conversion of energy from generator output to wheels turning is 89% efficient. (86% for lithium as some of the power is used for COOLING the battery pack)

100mph is not legal and I will never go that fast in my commuter so I don't really care what the power consumption is at 100mph

Your example of 20% mechnical 80% heat has a major flaw.

that total of 100% is NOT 100% of the energy in gasoline. that is 100% of the gasoline that gets converted to usable energy.

OF THAT energy 20% is mechanical 80% is heat.

We only extract maybe 5-10% of the total energy in gasoline. so its 20% of that 5% 80% of that 5% Thats where i came up with my guess of 2% assuming 10% total extraction and 20% efficiency at using that 10% for an actual efficiency of 2%

My time figure again comes from the fact that the generator will evenly generator that much power over 11 hours so IN REALITY it will in fact generate about 2500 usable output watts PER HOUR regardless of my speed.

I assumed 60mph so 1 hours per 60 miles. As you can see this presents a problem for while the generator can produce enough power to go 340 miles it will take 11 hours to DO THAT.

at 60mph I will reach 340 miles in 5.6 hours at 60mph. But in that 5.6 hours I will have only gotten 14,000 watts from the generator so far.

so while the generator has the power it does not have the ON DEMAND power needed. I would need something TWICE as large (ie a 10,000watt generator so I could get 5000 watts at 50% load for best efficiency)

Thats where I came up with my time energy and watt values. I apologize for not making that more clear.

this is why its a problem. IF I COULD AFFORD a 10,000 watt continuous rated generator I would already be able to afford to build an EV :-)

[Frank Lee]

[dcb]

There are a lot of assertions/assumptions/conclusions there that I don't agree with Ner. Serial hybrids are pretty half-baked in themselves, they are the least efficient way to extend your hiway miles. An ICE can stay within %10 of peak efficiency over a wide rpm range. Especially if you add things like dynamic valve timing.

If you were to replace the chain on your bicycle with a generator on the crank and a motor on the wheel, this discussion would come to a screeching halt as you realized first hand how inefficient that serial setup is.

It doesn't really matter if you add batteries, in fact it makes it worse in some ways (battery charge and discharge losses). But this is exactly what chevy is doing with the volt, grr...

[Geebee]

A series hybrid that only uses the motor say 8% of the time its running is a hell of a lot more efficient than say a current Prius.
The genset for a series hybrid does not have to be capable of the entire load as the batteries will buffer it, so it can be smaller, genset location is basically unlimited allowing more efficient design and can be optimised for a singel rpm at absolute max efficiency.
I am more of the opinion that a parallel hybrid is the dead end tech. you are better of just optimising the ICE.
Oh and I forgot the losses through the required transmision to match rpm to a usable ICE range