Why can't an electric car be self sustaining?

Question

Why can't the motion of the tires or drive train turning be used to generate more electricity to make a self generating system?

Answer 1

law of conservation of energy?

Answer 2

Regenerative braking is not so different from what you propose, and it is very helpful in extending the range of electric cars. The problem is that the motor is about 80% efficient in turning electricity into rolling power, and the generator is about 80% efficient in turning rolling power into electricity, and the battery is only about 70% efficient in storing the electricity and returning it. Also, some of the electricity goes to things like lights, heat, AC, gauges, etc. End result, you need to charge the batteries externally. Of course, you can improve all those efficiencies, but none of them will ever hit 100%.

Answer 3

True it may be impossible,  but at the same time it could improve the range of the electric car.   The range seems to be the biggest problem to overcome.  

Answer 4

everyone is missing the point if you put a generator on the non power train axial you can then charge some batteries while using the others then when the used batteries need charging you can then switch to the charged ones and charge the dead ones while you travel. With an on-board computer you can keep checking batteries on the go and not need extra batteries just switching from one to the other.

Answer 5

sorry, but you can't get more energy out of a process than you put in. the only time that the output energy of a vehicle is equal to the input is when it is when it's power consumption is zero. after that you are always using more than you can recover. Although, the idea of regenerative braking would allow you to increase the efficiency.

Answer 6

A Law of physics.   "Energy cannot be created nor destroyed."  It is not possible to create more energy than the energy used to propel the vehicle.   The energy is lost here in the form of heat from the flexing rubber of the tires, the heat of the moving parts, the wind resistance, the rolling resistance, and the mechanical resistance to movement,  gravitational resistance - just for starters.

Answer 7

Or why can't a wind turbine be placed on the car's roof to charge the batteries while you drive?

You would expect that in this day of age scientist would have perfected perpetual motion!

Answer 8

mainly the second law of thermodynamics. simply put, you cannot, ever, get as much energy out of a system as you put into it. counting all sources.

taking a kilowatt-hour out of a battery always takes more than a kilowatt-hour to replace it. some of it will be wasted as heat due to internal resistance.

by the same token, a kilowatt-hour taken out of a battery cannot be converted into a kilowatt-hour worth of motion. drag, motor heating, wire resistance, etc.

what you could do is cover the vehicle with solar cells to recharge the batts when the sun shines. or hook it to a windmill when it is stopped.

Answer 9

Well, I understand how that may distort you, but energy must be converted from another source, simply rolling the tires will only create friction, as well as only work when going down hill.

Hope it helps.

Answer 10

The question you ask would solve every energy problem the world has ever seen.  Perpetual motion....so far there is no such thing.

Answer 11

You can convert the mechanical energy of your car's motion

back into electrical energy via a generator if it is switched

on while your car is rolling to a stop. Very good when

when rolling down a hill. This electrical energy will return

to your battery and improve your range: regenerative braking

Note, the installed  motor will work as a generator if your

car has the correct kind of electronic motor controller installed.

The second law of Thermodynamics and the Law of conservation of energy

prevent the self sustaining action you seek.