The basic operation of an electric car is very simple. An electrical motor is powered by a battery, or bank of batteries. The batteries are generally rechargeable and are very heavy (weight-wise) in comparison to the amount of energy that can be contained within a standard gas tank. The electric motor can be connected directly to the wheels of an electric car. There is no need for a transmission. In fact, a separate electric motor can be connected to each of the four wheels, and this allows for operation even when one of the motors fails, and it also allows for some incredible performance advantages as well. No ICE-powered car can lose its engine and keep on running.
In addition, in an electric car, there is no need for the complex transmission system that an internal-combustion engine requires. Internal-combustion engines work well only when they're running hard, or fast — that is, the crankshaft in the engine is spinning at higher revolutions per minute (RPM). Most of the time — like when the car is going slowly — that kind of power isn't needed. The transmission's purpose is to match the engine's power with the vehicle's speed, which it does with a complex series of gears and shafts. When the vehicle is travelling slow, a low gear ratio ensures that the engine is still operating hard (or fast). As the car's speed increases, the gear ratio changes as needed. (If you've ever driven a manual transmission car, you manually shift from lower to higher gears as the car speeds up. An automatic transmission takes care of these shifts automatically.)
In an electric car, the motor's drive shaft can be connected directly to the wheels of a car, without need for a transmission. This considerably reduces the weight overhead of an electrical car, and it also makes the car simpler and less expensive to maintain.
Not needing a transmission is a distinct advantage that an electric car has over internal-combustion-powered vehicles. In an ICE, as the rotational speed (RPMs, or revolutions per minute) increases, so does the power output (this is why race cars always run near the "red-line" on the tachometer). The faster the engine is going, the more cylinders are firing in a given amount of time and the more power is available (refer to Chapter 16 for an explanation of how internal-combustion engines work).
With electrical motors, the power curve is much flatter than for an ICE. In an electric motor there are no cylinders, and no individual power impulses when each separate spark plug fires. The power output of an ICE is a series of small power blips, but the power output of an electric motor is continuous (okay, let's not get overly technical here — for all practical purposes it's continuous). An electric motor may be operated over a wide range of rotational speeds (RPMs) without sacrificing power output. In addition, you can get the same acceleration from an electric car as a bigger ICE brother. In fact, the acceleration is smoother and doesn't entail the jerking motion conventional vehicles exhibit when the gears are changing.
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