Why an electric car can't power itself.

FIGURE 1. This is a common configuration I am asked about. In this design, the proposed generator is attached to the rear wheels of a front-wheel drive car. It would supply power to the front wheels. No batteries are shown here as they are not really relevant. With or without batteries, the proposed idea is for the rear generator to produce some or all of the power to drive the car, or recharge the batteries. In the case of recharging the batteries, then that would indicate the batteries are not being discharged while driving the car, which means no power could be supplied to the front wheels if this were the case.

FIGURE 2. This is another way of looking at this configuration. The street in figure 1 is actually doing the exact same job as the belt is doing here in this configuration. I would dare anyone to argue with me that there is any difference between the flow of electrical and mechanical energy in figure 1 and figure 2. Most people, when seeing this arraingment will realize the flaw in the "recharge itself" scenario. Keep in mind, what we see here in figure 2 looks impossible. but just think, we're not trying to actually power anything. In figure 1 we are actually trying to extract power from the situation to move the car down the road.

FIGURE 3. This is just a simplification of figures 1 and 2. The flow of energy is still the same only should be even more efficient. However, this configuration still cannot produce any power on its own.

FIGURE 4. All forms of energy obey the same laws of physics. That energy can be electrical, mechanical, magnetic, radiant, thermal, etc. Some people don't understand electricity well, but in this figure we are substituting the electrical part for a mechanical transfer of energy. Although this scneario may seem obsurd, it is actually more efficient than the electrical scenario because a motor and a generator are not 100% efficient at their conversion of motion to electricity and back. So, if this scenario here in figure 4 won't propel the car by itself, then you can be sure the previous 3 won't because they are less efficient designs.

Frequently Asked Questions

Question: But what if I don't want the car to run completely on its own, what if I just want the generator to help a little bit, just make the car more efficient?

Answer: Even if the scenario were to generate only 15% of the power neccessary to drive the car, that is still 15% power that came from nowhere. It would still be free energy. Remember, energy cannot be created or destroyed. It can only be converted. Where is the energy going to be converted from? In a gasoline car (even in a hybrid gas-electric such as the Prius) the power generated by the alternator is being converted from the energy stored in the gasoline being burned by the car. In an electric car the only source of power is the batteries, so why convert electricity to electricity? Best just to keep it where it is. The truth is, even a small generator or alternator is less than 100% efficient, which means it will always create more drag on the car than any energy it will produce.

Question: What about a wind-turbine?

Answer: Believe it or not, a wind turbine big enough to fit on top of the car would create such a small amount of power as to be inconsequential. Even a 10-foot wide wind turbine would be lucky to create 1000 watts of power during a fierce thunderstorm. Unfortunatly, 1000 watts of power is a drop in the bucket compared to the 20,000 watts most cars need just to move. Highway speeds would usually eat up closer to 40,000 watts of power. So at highway speeds your huge wind turbine on top of the car would be generating about 2.5% of the power needed to move the car. Unfortunatly, it would be adding about 50% more wind drag to the vehicle which means you would probably need an extra 10,000 watts of power just to make up the difference.

Question: What about solar power?

Answer: Solar power isn't really having the car recharge itself. In this case the energy is coming from sunlight. There is nothing wrong with this line of thinking and most people are aware that solar-powered cars exist. The only problem with a typical hobbiest EV conversion made from a gas car is that the car is too heavy and there is not sufficient flat area to mount enough panels. The solar cars you see created by universities are custom vehicles that are extremely lightweight, very aerodynamic, and have very little rolling resistance. They also tend to use solar cells that are more efficient than the consumer variety and are extremely expensive. However, these vehicles are nothing like the general public would be willing to drive. They typically have only room for one passenger and is often very uncomfortable. getting in and out is very difficult, and there is no cargo area. There is also no airconditioning or any other comforts. These vehicles would not stand up to a crash either. Mounting solar panels on top of a regular EV conversion would probably generate about 1% of the power neccessary to move the car. However, when the car is parked in the sun, it may be possible to charge up batteries to store some of that day's worth of power for a short drive.

Question: Why can hybrids charge themselves?

Answer: All current hybrids on the road today charge their batteries from regenerative braking. That means when the brake is being applied, the motor turns into a generator and reclaims some of the car's inertia and converts it back into electricity to store in the batteries. When the batteries are criticaly low, they can also recharge the batteries directly from the gasoline engine when idling or driving. In the case of regenerative braking, many electric cars have this feature just like the hybrids. But again, power is only generated when the car is being stopped. That isn't enough to recharge the car. Typical improvement in efficiency is about 10% to 20% depending on driving conditions and how well the regen feature is implimented. In the case of charging itself while idling or driving, the electricity is being converted from gasoline. in the case of an all-electric car, the only power source being carried is electricity so there is no need to convert it.

Question:But I've heard of people running their car from water!

Answer: Plain and simply, there is no such thing as a water-powered car. Many news stories have been shown recently that tend to suggest this is possible, but they are not telling the whole story. It is possible to use electricity to break up water into hydrogen and oxygen. These gasses can be used in a fuel cell or a combustion engine to power a car. However, more electricity is needed to break up the water than any energy you will get out of the resulting product. So it is impossible for the car to do this onboard. Hydrogen is only an energy carrier, not an energy source. Just as a battery is an energy carrier. Think about it like this, recharging a battery is like stretching a rubber band. The same is true when breaking up hydrogen and oxygen. You'll need the same amount of power to break it up as it will create when recombined. In the case of these cars, the hydrogen is typically converted from water at a house or business using the main electrical grid and then fed into the car for driving. In order to do this onboard the car, you'd need to carry extra batteries to supply the power. If you were going to do that, you might as well just run the car from those batteries as it would be more efficient.

Question:But I've seen these HHO converters for gas cars!

Answer: Most of the websites about these are scams. But keep in mind that using HHO in a gasoline car is only supposed to increase efficiency, not produce power. For example, a modern Hybrid car uses the electric part to increase efficiency. A regular gas car only manages to convert about 20% of the energy stored in the gasoline to actual mechanical movement. So the hybrid system only improves that efficiency of conversion. That is the same claim made by the HHO systems, they should improve efficiency of the gas engine some. There is no free energy being created as the alternator in the gas car must do extra work to break up the water into HHO. However, there is serious doubt cast by most of the scientific community as to whether any benefit is obtained by these setups at all. Many of the websites out there are flat out fraudulent making claims of impossible results. The simple cold, hard truth is that if they worked really well, car manufacturers would put them in the cars from the factory because it would make them sell better if they were more fuel efficient.