The beginning of the end of oil?

[Rondar]

I always wondered on the electric cars, if charging them up is a problem, can't say a 5-10 hp or so  briggs and stratton engine be hooked up to a good 12v generator or alternator and keep itself charged up?  Or charge it up while parked somewhere and there is not a plug in handy?

[lazs2]

You could probly build a fun little electric sportscar for a lot less than that lotus.   I think the price will come down.  we are now talking a range of over 200 miles and a 3.5 hour recharge time..  they are getting more practical and.. more important.. fun.

the liberal socialists are wrong.. you can't shame people into doing what you like.  You have to make it work for them.

lazs

[Nashwan]

That was not the point I was trying to make.  The public has never taken it seriously enough in the past for it to really go anywhere.  Things will improve at a faster rate now.

The point I was making is it doesn't matter how seriously the public have taken electric cars. Electric cars are easy, after all it's just the integration of two existing technologies, cars and electric motors.

The problem is the batteries. But batteries have been big business for a long time, and there's no reason to expect that increased interest in using them in cars is going to lead to any breakthroughs.

You could probly build a fun little electric sportscar for a lot less than that lotus.

Not with any range. Petrol stores about 47 million joules per kilogram. A 50 litre fuel tank stores getting on for 2000 million joules.

Lithium ion batteries, which is what the Tesla uses, store about 250,000 joules per kilo. Electricity is more efficient for car use, but to equal even a small 50 litre tank requires about 2.8 tons of batteries.

That means electric cars have to be built very light to offset the weight of the batteries. That pushes up cost, even before allowing for the price of the batteries. The Tesla roadster uses over 6,800 cells that cost about $4 each.

The end result is an electric car weighs more, has less range, and costs a lot more, than a comparable petrol or diesel car. And that's going to remain the case until there is a major breakthrough in battery technology.

I think the price will come down.  we are now talking a range of over 200 miles and a 3.5 hour recharge time

I'd take the range with a pinch of salt. It doesn't include things like air conditioning or heating which have a major effect on electric vehicles. It also doesn't allow for much "fun". The Tesla has a motor that produces a max of just under 250 hp, and that consumes about 220 kw/h at max power. The battery pack stores about 53 kw/h, which means you can use maximum power for about 14 minutes (somewhat less because the battery cannot be totally "emptied")

[Hornet33]

I'm still wondering why they can't figure out a way to hook a small electric generator up to the drive wheels that will allow the vehicle to recharge while it's being driven. I know that you can't fully recharge as fast as you drain a battery pack but if you could charge at a rate of even 30% over the current draw needed to move the vehicle that would amount to a rather large increase in available battery power and range. Maybe add some solar cells as well and the range and available power would increase even further.

[Nashwan]

I'm still wondering why they can't figure out a way to hook a small electric generator up to the drive wheels that will allow the vehicle to recharge while it's being driven. I know that you can't fully recharge as fast as you drain a battery pack but if you could charge at a rate of even 30% over the current draw needed to move the vehicle that would amount to a rather large increase in available battery power and range.

It would increase range, but you then have the extra weight of the generator and its fuel.

Maybe add some solar cells as well and the range and available power would increase even further.

Forget solar cells. A square metre receives about 1 kw/h on a sunny day close to the equator at noon. Solar panels have about 15% efficiency, meaning in ideal conditions a square metre of solar cells will add about 150 watts to the battery pack per hour around noon, somewhat less in the afternoon and morning, little in the evening, and nothing at night.

In a day you'd be lucky to get a kw/h out of a 1 square metre solar panel. When you consider that a Tesla roadster has a 53 kw/h battery pack, the extra thousand dollars for solar cells would make little difference.

[john9001]

""The Tesla has a motor that produces a max of just under 250 hp, and that consumes about 220 kw/h at max power.""

you do not need 250HP to move a small car.

[Hornet33]

It would increase range, but you then have the extra weight of the generator and its fuel.

I wasn't talking about a gas generator. I was thinking alternator, like what is already used in gas cars to charge the battery. I'm sure they could make one that would generate at least 50% of the power used by the drive motor and put that back into the battery. The weight is nothing. Hell my truck has a 136amp alternator in it and it only weighs 9 pounds, so says Auto Zones website.

With that installed if I'm cruising down the interstate at 65mph and drawing say 300amps an hour with a 150amp alternator hooked directly to the drive motor I would be recharging at half the rate of battery consumption and increasing my range.

You would think that they could build an alternator that recharges faster than the drive motor uses power that would allow you run almost indefinately. You would use more battery energy starting and stopping but on long drives if you could produce more electricity than your using, the alternator itself would be supplying 100% of the drive power with the rest going to the batteries and charging them.

Of course I'm not an electrical engineer so I don't know how feasible an idea that is, but it kinda makes sense doesn't it?

[john9001]

You would think that they could build an alternator that recharges faster than the drive motor uses power that would allow you run almost indefinately. You would use more battery energy starting and stopping but on long drives if you could produce more electricity than your using, the alternator itself would be supplying 100% of the drive power with the rest going to the batteries and charging them.

Of course I'm not an electrical engineer so I don't know how feasible an idea that is, but it kinda makes sense doesn't it?

thats called diesel electric locomotive, they have been in use since the 1950's.

[Hornet33]

What part of, not a gas generator, did you not get??

Electric car, hook alternator up to the drive motor, recharge batteries at the same time your using power from them. Build alternator efficient enough to provide 100% of drive power at speed and charge batteries at same time. No fossil fuels used at all. That's what I'm wondering if they can do.

[dmf]

What part of, not a gas generator, did you not get??

Electric car, hook alternator up to the drive motor, recharge batteries at the same time your using power from them. Build alternator efficient enough to provide 100% of drive power at speed and charge batteries at same time. No fossil fuels used at all. That's what I'm wondering if they can do.

That would be the closest thing to perfection in a car, although as long as theirs oil on the planet, the oil company's would have you killed before they let that hit the open market.

[AquaShrimp]

Lol, where do those dumb idiots think electricity comes from?  Here on the East Coast, we tear up the forests in the mountains to mine for coal.  Then we burn the coal, releasing all kinds of mercury (dont eat too much fish now) and CO2 so we can heat water to turn steam turbines.

[eagl]

I'm still wondering why they can't figure out a way to hook a small electric generator up to the drive wheels that will allow the vehicle to recharge while it's being driven. I know that you can't fully recharge as fast as you drain a battery pack but if you could charge at a rate of even 30% over the current draw needed to move the vehicle that would amount to a rather large increase in available battery power and range. Maybe add some solar cells as well and the range and available power would increase even further.

That violates every law of physics we know.  That's why it's not done.  The electric motors CAN be used for "regenerative braking" when the car is slowing down, but let's do a simple exercise...

Let's say the car requires 5 watts to propel down the road.  The battery must expend 6 watts because 1 watt is converted to heat in the motors and circuitry, and wasted.

Now let's hook up a generator to the wheels that generate 5 watts of power.  It takes, you guessed it, 6 watts of energy input to output 5 watts of power, because of waste heat, mechanical losses, etc.

So, you have either a car running down the road sucking 6 watts and getting 5 watts worth of work, or a car running down the road sucking 12 watts of power, getting 5 watts of work, and putting 5 watts back into the batteries.  12 minus the 5 you get back is 7 watts expended in the second case, vs. 6 watts expended in the first case.

It's simple thermodynamics.  You simply can't try to take any more energy out of the system than you put in, and it's doubly inefficient to simultaneously stand on the brakes and the gas (run a generator and the motors at the same time) because you double the heat and mechanical losses.  The ONLY mechanical way you can recapture the energy in a conventional electric car is to either use the motors as generators when it's time to slow down, and even then you will only get out a portion of the kinetic energy the car has at the instant you start braking (basically it's mass times the square of the velocity, minus losses for inefficiency and factors like rolling resistance).  You could theoretically capture some of the waste heat either via the principle that runs the sterling engine or some of the newer technology coming out right now, but those options are either very heavy, don't recapture enough energy to be worth it, or are cost prohibitive (around a few million bucks to capture a couple of watts).

A more efficient way to do this is to run a large flywheel, using the rotating mass as a big capacitor.  You only pump in enough energy to keep the flywheel spinning, and the mass of the flywheel absorbs instantaneous loads which really helps with the efficiency of the whole system since you can trickle in energy to the flywheel at the most efficient rate using cheaper components, and let the flywheel handle loads greater than the energy transfer rate from the battery.  This can be fairly efficient especially in stop and go situations, however to be effective it must be VERY heavy, it makes turning somewhat interesting due to gyroscopic precession, and when heavy flywheels break they can explode or at the very least go tearing around smashing things until the energy is expended.

[Nashwan]

I wasn't talking about a gas generator. I was thinking alternator, like what is already used in gas cars to charge the battery. I'm sure they could make one that would generate at least 50% of the power used by the drive motor and put that back into the battery. The weight is nothing. Hell my truck has a 136amp alternator in it and it only weighs 9 pounds, so says Auto Zones website.

With that installed if I'm cruising down the interstate at 65mph and drawing say 300amps an hour with a 150amp alternator hooked directly to the drive motor I would be recharging at half the rate of battery consumption and increasing my range.

You want to drive an alternator with an electric motor? So you have one motor drawing power from the battery pack to power another motor that's charging the battery pack?

You would think that they could build an alternator that recharges faster than the drive motor uses power that would allow you run almost indefinately. You would use more battery energy starting and stopping but on long drives if you could produce more electricity than your using, the alternator itself would be supplying 100% of the drive power with the rest going to the batteries and charging them.

Of course I'm not an electrical engineer so I don't know how feasible an idea that is, but it kinda makes sense doesn't it?

You can't make an electric motor 100% efficient. For your idea to work you would have to make it more than 100% efficient.

Imagine you have an electric motor that's 90% efficient. You are going fast in your electric car, so you need 90 kw of power to maintain your speed. The electric motor is using 100 kw from the battery pack. Net drain on the battery pack is 100 kw.

Where does the spare power come from to power the alternator? If you couple up an alternator to the motor, either the amount of power going to drive the car drops, or you have to draw more power to run the alternator.

Let's say you draw more power to run the alternator. The motor is now putting out 180 kw, and drawing 200. The alternator is being driven by 90 kw, and if the alternator is also 90% efficient, it will be putting 81 kw back in to the battery. That means net power drain has gone up to 119 kw.

There's no such thing as a free lunch. The power to run the alternator has to come from somewhere, and in an electric car it has to come from the battery. A motor that turns an alternator ending up with a net gain in energy is called a perpetual motion machine. People have tried to make one of those for centuries, no one ever has, and unless there is something fundamentally wrong with basic scientific theory, no one ever will.

you do not need 250HP to move a small car.

No, you don't. But note that the same principles apply whether you are talking about a sports car or a small runabout. The electric car will be more expensive, heavier, have less range and will cost more overall than the petrol powered car.

Consider the fact that in Europe petrol/diesel is taxed to around $7 - $8 a gallon. Electric cars usually have subsidies to encourage people to buy them. Yet even in Europe there are only a handful of electric cars on the road.

[vorticon]

so...how much power would a small gas engine driven generator capable of recharging the batteries at a decent rate need...and how much would it weigh?

[eagl]

Vort,

Now you're talking about a hybrid, and we already have that answer.  There are several smallish cars that get around on anywhere from 1 to 2 liter engines.  The "breakthrough" for hybrids in the US will be when we get decent diesel gas and a couple of nice modern small turbodiesels.  A prius using a modern high efficiency diesel ought to get another 50% improvement in fuel efficiency with no additional emissions or reduction in drivability.  What that'll do to the price of diesel is another story of course, and we'll see the price of both diesel and regular consumer goods go up when diesel becomes more popular because truck shipping expenses will skyrocket.  Independent truckers are already feeling the pinch, and it's only a matter of time before the effects trickle down to prices at wal-mart.