Electric Vehicles are gaining more and more attention in automotive as they become more prevalent in both popular culture and the automotive market itself. An electric vehicle (EV) is made up of three basic components and are mechanically very simple when compared to most combustion-powered vehicles (gasoline, diesel).
The three components in any electric vehicle are:
- Power Source (battery, fuel cell, grid, etc.)
- Controller / Modulator
- Electric Motor
In simplified terms, the power source provides electricity to the controller, which determines how much power to use and at what rate it is to be sent to the electric motor. The motor itself propels the vehicle by converting electricity to twisting motion (torque).
Electric vehicles can include battery-electric cars such as the Nissan LEAF or the Tesla Model S. They can also include electric airplanes, hydrogen fuel-cell vehicles like the Honda Clarity, and grid-powered trams and buses. Most of the time, though, we think of electric vehicles as being cars functioning through battery power, or battery-electric vehicles (BEVs).
The truth is, every vehicle that is propelled through electric power, including hybrid-electric cars like the Toyota Prius and plug-in hybrid sport utilities like the BMW X5 PHEV, are also electric vehicles.
For our purposes, though, we’ll concentrate on the mechanics of the EV and leave the power source as a battery. Just keep in mind that the battery can be swapped out for any of a number of options while the EV remains fundamentally the same.
An Example of How An EV Works
An electric car works very simply, but that simplicity can be misleading. When the driver sits in the EV, the start button is pressed and the accelerator pedal is pushed. This signals the controller to begin accepting power from the battery and use it to turn the electric motor. The controller decides how much power to send from the battery to the motor based upon the driver’s throttle pedal input. A modulator in the controller converts the DC power from the battery to the AC power required for the motor.
As the car moves faster, more power is sent to the motor through the controller. When the accelerator is released and the car begins to coast, power can be recovered from the kinetic energy of the car’s deceleration by reversing the motor, which then acts as a generator. The generator produces electricity that is modulated by the controller and returned to the battery.
In this basic description of the EV’s operation, we can see that although the three components involved are simple, their operation is not quite as cut-and-dried as might be expected on first glance.
Most EVs use a motor that requires alternating current (AC) as these motors are usually considered more reliable and more powerful. Batteries, of course, store energy in direct current (DC) form, so the power must be converted in order to be used. Most alternatives to batteries, such as fuel cells, also produce DC. Thus one of the more important jobs of the controller is to act as an inverter as well as a power modulator.
On the flip side of that, when the car is no longer being propelled, but is instead slowing down (decelerating), power can be captured from the kinetic energy being produced as momentum is lost. Most electric vehicles can do this and usually do it as part of the braking system. An electric motor can run in reverse, creating power as a generator as it is spun by another energy source (in this case, the car’s momentum). That power can be captured and stored in the EV’s batteries. Vehicles that utilize this are capable of capturing as much as 30 percent or more of the vehicle’s kinetic energy as electricity to be used later. This can greatly increase the range of the EV, especially in stop-and-go driving.
To get a visual idea of how an electric car works, I produced the following video for CarNewsCafe.com, which may be helpful here.