Battery re-powered from wheels of a car?

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    Battery Car Wheels
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Discussion Overview

The discussion revolves around the concept of generating electric power from the wheels of a Battery Electric Vehicle (BEV) using a system of fan-like blades connected to the wheels and placed within a magnetic field. Participants explore the feasibility of this idea, considering the principles of energy conservation and efficiency in electric vehicles.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that connecting fan-like blades to the wheels could generate electric current through motion in a magnetic field, but expresses uncertainty about the underlying principles.
  • Another participant asserts that while some power can be produced, it cannot exceed the power consumed by the system, leading to eventual battery depletion.
  • Several participants highlight inefficiencies in the proposed system, indicating that only a small portion of the power would be returned to the batteries.
  • Regenerative braking is mentioned as a method to capture energy during braking, but some participants clarify that the original proposal seems to imply continuous energy generation while driving, which is contested.
  • One participant explains that extracting energy from the system would require additional power to drive the wheels, effectively negating any benefits.
  • A practical example is provided to illustrate the inefficiencies in the proposed energy loop, emphasizing that the battery would ultimately supply more power than it receives.
  • Participants discuss the concept of moving against a magnetic field and its implications for slowing down the vehicle, linking it to the principle of regenerative braking.

Areas of Agreement / Disagreement

Participants generally agree that the proposed method of generating energy from the wheels is flawed due to energy conservation principles and inefficiencies. However, there is no consensus on the feasibility of the initial idea, as some participants express confusion or seek clarification on specific points.

Contextual Notes

Discussions involve assumptions about energy conservation, efficiency rates, and the mechanics of electric vehicle systems. The limitations of the proposed setup are not fully resolved, and the implications of regenerative braking are explored but not definitively concluded.

Jay_
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Hi,

I was just learning about Electric Vehicles, and how they are powered. Let us consider a BEV (Battery Electric Vehicle), and not a hybrid. So we just have the battery powering the drive train and the wheels.

The other day a friend of mine asked why the each wheel of the car can't in turn be connected to an axle (going into the car parts, not outward), with fan-like blades at the end. As the wheels moved, the fan-blades would move too and if these blades were placed within the magnetic field of a strong permanent magnet, by Faraday's law this should generate electric current. This current could e used to charge the battery again.

The idea seems great, but probably reveals a lack of basic understanding of a certain law. I am aware of the energy conservation principle and all, but I can't figure what would actually happen in such a set-up. I have had similar idease earlier (of using motion between a magnetic field to get electric enegry "again"), but I understand there is a flaw in it, which is why it hasn't been used till date. Can anyone explain?
 
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yes you will produce some power
But you you cannot produce as much or more power from the system that that being used by the system. So in time the battery is still going to go flat.

Dave
 
Inefficiencies! You will lose power in many different areas, meaning that only a small part of the power will be put back into the batteries.
 
There is a system called "regenerative braking", where the energy (momentum) of a moving car is captured by reversing the process: generate electric power by switching a moving wheel into a generator. Google it.
 
Bobbywhy said:
There is a system called "regenerative braking", where the energy (momentum) of a moving car is captured by reversing the process: generate electric power by switching a moving wheel into a generator. Google it.
Yes, this is used. For starters, see:
http://en.wikipedia.org/wiki/Regenerative_brake
 
Last edited:
Regenerative braking let's you reuse some of the energy that would be otherwise lost during braking, I have a feeling OP asks about producing energy all the time. That would just increase power needed to move the car - TANSTAAFL.
 
To add that specific point: The moving blades would be braked by the field they are moving in - you would need more power to drive the wheels if you try to extract energy like that. With 100% efficiency, this "more power" is exactly the power you get back in your additional setup.
 
He is trying to produce energy by driving with the brakes on. That, of course, will not work.
 
Jay...

What you propose amounts to the following circuit..

Battery---> motor ---> wheel ---> generator--> back to the battery

Lets suppose the generator is delivering 100W back to the battery and each step in the chain is 90% efficient.

That means the wheel must supply the generator with..

100*100/90 = 111W

But the wheel is being turned by the motor so the motor must supply the wheel with an extra..

111*100/90 = 123W

but the motor is being powered by the battery so the battery must supply the motor with an extra...

123*100/90 = 137W

So the net result is that the battery is supplying 137W and getting 100W back.

This is a practical example of this theory in operation...

http://en.wikipedia.org/wiki/Conservation_of_energy
 
  • #10
mfb said:
To add that specific point: The moving blades would be braked by the field they are moving in - you would need more power to drive the wheels if you try to extract energy like that. With 100% efficiency, this "more power" is exactly the power you get back in your additional setup.

Okay, this made me understand it. As in moving against the field would mean moving against "something" and that would actually slow the wheels down, right?

And in corollary, IF we need to slow down, we can activate such a mechanism to recharge the battery - which is regenerative braking.

Is that right? Thanks guys :)
 
  • #11
As in moving against the field would mean moving against "something" and that would actually slow the wheels down, right?
The movement in the magnetic field from one side induces a magnetic field in the other side as well, and the interaction between both slows the rotation.

IF we need to slow down, we can activate such a mechanism to recharge the battery - which is regenerative braking.
Right.
 
  • #12
Okay, this made me understand it. As in moving against the field would mean moving against "something" and that would actually slow the wheels down, right?

Yes. Otherwise you have made energy from nothing.
 

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