|MadSci Network: Engineering|
Greetings: Yes indeed the electric motors that drive electric cars can be used as generators and they are used in that mode on the General Motors EV1 electric automobile! Electrical motors and electrical generators are not 100% efficient, more energy must be put into them than the output power that they provide. The net result of putting generators on a vehicle is that the generator requires more mechanical power from the vehicle to rotate it than the electrical power that the generator or alternator can produce to charge the batteries. However; there is one important exception to this and that is during braking.. When a conventional vehicle brakes to slow or stop, the mechanical friction on the brake drums and disks generates heat which is lost energy that was originally provided by the batteries to keep the car moving. By changing the electric drive motors into generators during braking, the energy used to slow down the vehicle can be used to generate electricity to help recharge the batteries. This concept is called regenerative braking and it has been used on electrical railroad locomotives for many years. In case the electric car must stop more quickly than the regenerative braking can provide, electric cars also have conventional friction brakes. It takes a skilled operator of an electric vehicle to attempt to use only regenerative braking to put the maximum amount of electrical charge back into the battery during a braking maneuver. Onboard computers can aid the driver to conserve this energy usually lost as heat. GM EV1 G a l i l e o B r a k i n g S y s t e m The systems of the GM EV1 can be found at the following URL : http://www.gmev.com All of the electric cars system are described in these Web pages including it's Galileo Braking System. The following information is from the Web Pages: "The electric car's advanced "brake-by-wire" system eliminates almost 100 parts (compared to a standard hydraulic system). This system interprets electronic signals when the brake pedal is pressed, calling for the hydraulic modulator to apply pressure at the front calipers to stop the car. The rear braking system is electronically activated and has an automated parking brake. Intelligent software constantly monitors driving conditions, engaging traction control or anti-lock brakes to help avoid hazardous situations. In addition to providing power assist, traction control, anti-lock, tire inflation and system diagnostics monitoring, the Galileo Braking System also includes a new concept in braking: regenerative braking. It works like this: when you step on the accelerator of the electric car, you get an energy discharge from the battery. When you brake, you are actually capturing kinetic energy from the vehicle (with the motor) and putting energy back where it originally came from--into the battery. Depending on how you drive, you may actually improve your range." While regenerative braking can extend driving range, several new types of batteries are under development along with hybrid vehicles that combine internal combustion engines and electric motor/generators that can significantly increase the range of current electric vehicles. Best regards, your Mad Scientist Adrian Popa
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