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

[dcb]

Nonetheless, If you go to home depot and get an $800 generator, and plug your charger into it so you can recharge your batteries while driving your EV, you have a formula for a very inefficient hybrid.

[jamesqf]

Originally Posted by dcb

...and you have extra weight (motor + generator) to carry all the time.

But that doesn't have to be a lot of extra weight, since the IC engine doesn't have to be all that big. Same logic as regular hybrids, but carried further: you can make the engine smaller, with battery & electric motor providing power for acceleration. Instead of a couple of hundred horsepower from the IC engine, most of it only used when starting or hill climbing, you only need maybe 10-20 hp to run at highway speed on level ground.

[dcb]

Here is a typical generator, if you want to add 10kw continuous power to your traction motor. It weighs 283lbs, converts 18hp to 10kw(13.4hp), for an efficiency of %75 maybe. If the traction motor is %90 efficient then you are looking at %67 efficiency at getting the output of the ICE to the wheels (ignoring any conditioning of the generator output which would drag it down much farther and transmission from the motor to the wheels).

Even if you add selectable gears to the ICE to drive a wheel it will still be in the %90 efficient range from the output shaft to the wheels and be able to be kept at or near peak ICE efficiency even when not on the hiway.

So in this example, assuming a continuous 12 hp at the wheels is sufficient (can be augmented by battery/motor in both cases where needed), you need a 18hp engine for the serial and a 13.4hp for the parallel versions.

[dhymers]

It's called a "Series Hybrid"

Its better also if you have a battery pack at least as a buffer between generator and motor controller, this will also reduce the power needed from the generator. Balance both power sources and you get the benifit of both.

[Allch Chcar]

Nerys, An EV RAV4 will take a lot more than 10kw-hrs to go 100 miles. If you were driving an EV1 your math might make logical sense. And the average ICE gets more than 20% of the available energy in gasoline. The 80% is approximate but not all of it is energy some is unburnt hydrocarbon.

dcb, You're forgetting to add in the loss of burning the gasoline. It makes a large difference how efficiently the fuel is burnt. Improving the efficiency of a gasoline engine by 1% improves the power to the crank by 4%. Power efficiency isn't always the same as fuel efficiency. If it was we'd all be driving at WOT. Instead the best fuel efficiency is usually around 62.5%-75% before you get into the high fuel:air mixtures. The typical generator might be cheaper upfront but a purpose built generator for the series hybrid will be much more efficient overall. Mechanical drivetrains are approx 85% efficient through a manual tranny and differential. You might get 90% if you ran it in 1:1 but you'd be sacrificing acceleration. Ev motors get away with 1:1 to the differential because they create more from 0rpm even though they eventually run out of power and torque the faster they turn.

Where the series hybrid or the range extended electric vehicle shines is it allows an electric vehicle to still be driven when battery power reaches a certain point. Electric vehicles are far more efficient at using energy and even less polluting using power from a coal power plant than a comparable gasoline ICE driven vehicle. But batteries are very heavy for the amount of energy they contain. A generator that operates at a fixed rpm can be built to be far more efficient than a variable RPM engine and provide acceptable fuel economy should you deplete the batteries to lowest recommended %SOC. So the range is improved.

Most of the hybrids gain fuel economy in the mid to high speed range by minimizing drag and maintaining a better" ideal specific power to speed ratio." I believe it's called BSFC. If you just skipped on the hybrid system and used the ICE you would get better mid to high speed fuel economy only if you kept the low gearing. Your acceleration would be dangerously low. I understand 0-60mph in 30 seconds isn't unreasonably safe but beyond that you'll have to use flashers to get onto the Interstate or even onto a Highway or busy street. Hopefully you would stick to backroads and drive smarter in that scenario.

[dcb]

Originally Posted by Allch Chcar

dcb, You're forgetting to add in the loss of burning the gasoline.

I'm not, I've been advocating that folks should at least look at a bsfc chart and drive and shift accordingly (and select an engine that allows you to cruise within %10 of peak bsfc). I absolutely not forgetting that, not one iota.

[chelochavez]

You are not better of using the generator instead of batters. using the generator you will need to have investor plus the speed controller (PWM) to control the DC motor. Or if you use a AC motor you will need a frequency control to control the speed. It is throw that energy is not lost but transform, you will have to coll of the electronics that are getting hot because of the wiring and the constant convention of AC to DC, or AC to DC and AC(new frequency). So batteries will be more efficient if you plan to use the car in small trips.

[Allch Chcar]

DCB, a steady output generator will be more efficient than a variable output generator, period. The 75% is the power efficiency not the energy efficiency. The generator will use a different amount of energy from the gasoline not just 18hp. Power doesn't equal energy. You're not counting the fuel efficiency.

25hp is the standard number repeated for getting 55mph steady. The JourneytoForever hybrid went 45mph on a 7hp generator. 60mpg at 45mph on the generator's power alone. A good example of a homebrew serial hybrid. Diesel engine, but at least someone tried.