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Discussion Starter #1
I know I don't understand logistics, but why won't putting a line of alternators on the rear axle to run everything after the car is moving work, please someone explain it to me it seems after the car is moving at a certain speed the alternators would keep the batteries charged, or at least someone with brains could figure it out
 

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Tanstaafl

Alternators and generators don't turn for free, they require more mechanical energy input than they return in electrical output. It would just put drag on the car, making it less efficient.

Something like that is used for regenerative braking, in fact... causing the drive motor to generate elecricity which is returned to the battery pack. The fact that the result is a decelerating force should tell you something.
 

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I'm not trying to be a jerk or belittle you on this, but check out the search function in the tool bar. This subject comes up every couple of months or so and there are already many long discussions about why you can't have a free lunch. I think just search for "alternator" or "generator" and you should find those old threads.

Basically, unless you are talking about regenerative braking, placement of the alternator, either on the engine or the axle, really doesn't matter. Regenerative braking does help charge the battery but it slows the car down, so it is a great way of recapturing already spent energy but doesn't keep the battery fully charged. The Volt will employ this technology.
 

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Discussion Starter #5
please help

Thanks for the replies, but couldn't you use a bigger motor to take care of the drag? I'm really trying to understand this but I might be to old, seems like someone could figure this out, we went to the moon we should be able to make it work, I really do want a free ride
 

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Thanks for the replies, but couldn't you use a bigger motor to take care of the drag? I'm really trying to understand this but I might be to old, seems like someone could figure this out, we went to the moon we should be able to make it work, I really do want a free ride
Google "laws of thermodynamics" for some insight.

These aren't laws like the speed limit, you can't break them, even if you want to. You simply can't get more energy out than is put in. Even if you had 100% efficiency in all aspects of the system (which isn't possible in the real world) you wouldn't benefit from the system you describe unless it was only in use for regenerative braking, in which case it would just be excessive because you can use the drive motor for that and save weight and complexity. While the Volt isn't an Apollo project in its level of complexity as compared to the general level of technology today, there ARE some smart engineers on the project.
 

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The kids section of the local science museum has a very simple exhibit to demonstrate the problem here:

They have a stationary bike with an electrical generator attached to the pedals.

The generator is attached to a switch and a light bulb. The switch turns the light bulb on and off.

If the light switch is turned off, the bike is really easy to pedal. The generator turns easily because there is no electrical load on it.

Once you turn on the light switch, the bike becomes incredibly difficult to pedal.

If you turn the switch off, pedal the bike really fast, and turn the switch on, the bike will come to a screeching halt almost instantly.

The effect would be the same in a car. You would take the energy from the momentum of the car and divert it somewhere else.

That's essentially how regenerative braking works.
 

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Sticky subject

The forum should have a "sticky" post explaining the basics of thermodynamics as they apply to energy generation and transfer, and a list of the "ideas" that won't work including their debunking.

In general, if the post start with something like "I don't understand. . ." or "I'm not an engineer, but. . . " and the poster has some wonderful idea about how to generate or recapture energy, it would probably be best for the poster to just click the "back" button and leave with an intact ego.

Leave the engineering to the engineers - that's their day job . . . ;)
 

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What you are thinking of is the same thing as plugging in an electric generator into your house wall outlet, and then have the electricity you make from the plug in generator power your whole house. It can't work because it is a perpetual motion machine that would defy all laws of physics.

By the way when I was kid I had a bicycle with a small electric light hooked up to a generator the gt it's power from the wheel/tire. I never used the light very much because that little generator made it feel like I was peadeling up a steep hill.
 

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I know I don't understand logistics, but why won't putting a line of alternators on the rear axle to run everything after the car is moving work, please someone explain it to me it seems after the car is moving at a certain speed the alternators would keep the batteries charged, or at least someone with brains could figure it out
In a sense, that's exactly what existing hybrids already do! (Well, technically 1 or 2 BIG generators and not a series of them as you suggest)

Whether you can "see" them on the drive-line is irrelevant, they ARE there and mechanically connected to the drive wheels and/or the ICE - but are somewhat hidden INSIDE the hybrid transmission or transaxle. So their rotating members can be powered either by the engine OR from the wheels and driveline during coasting to create energy for the battery then reverse the current flow to become electricaly powered by the battery in electrical "motoring" modes.

HTH
WopOnTour
 
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