JUN  19, 2019

How Do All Electic Vehicles work?

Here’s a little trivia you can impress your gas-guzzling friends with. The first all-electric vehicle (AEV or EV) was built in 1839. By 1900, 38% of all cars in America were all-electric. And then Henry Ford revolutionized the way cars were built, and oil was cheap, and the internal combustion engine became the default power source for the automobile.

But that may be about to change.

All-Electric Vehicles

At the heart of it, all cars are essentially energy conversion devices. They both convert stored energy (gas in a tank or electricity in a battery) into kinetic mechanical energy (moving) to propel the vehicle. How that energy is converted and how that kinetic energy makes the wheels go round are the principal differences between a “conventional” auto and an electric vehicle.

Probably the easiest way to explain how an electric vehicle works is to compare it to a conventional vehicle, so let’s start by looking at the components.

Electric Motors vs. Engines

That engine in your car needs to spin to work efficiently. Sometimes it needs to spin thousands of times per minute (RPM) even though your wheels aren’t spinning anywhere near that amount. Often, the power that an engine can produce is far different from what a driver needs. For example, when you pull away from a street light, you need torque but not speed. But if you are passing on a two-lane road you need speed and not torque. Generally speaking, in a gas engine, maximum torque isn’t achieved until the engine is in a higher RPM range when it also provides maximum acceleration.

There are really only three ways to control the output of mechanical energy from an internal combustion engine. The first is to provide more fuel (stepping on the gas) to make it spin faster. The other two are the gearbox and clutch which control the amount of power from the engine that is directed to the wheels.

Electric motors operate completely differently. Generally speaking, they do not rely on spinning in order to develop torque or power. As a matter of fact, electric motors have instant torque. Max torque is delivered with the first ion and remains at maximum until it hits higher speeds where it starts to tail off. The net result is the electric motor is delivering the kind of torque and power the driver wants when he wants it.

GKN's 'eTwinsterX'  (GKN Automotive)
GKN's 'eTwinsterX'  (GKN Automotive)


Drivetrains are another big difference between EV autos and gas driven rides. An internal combustion vehicle has a multi-speed gearbox with numerous ratios; nearly every electric vehicle has a single-speed transmission. Electric vehicles don’t need a clutch to disengage the engine from the drivetrain to allow the internal combustion engine to idle when at a stop. An electric vehicle motor simply stops when the car does.

Electric vehicle motors have a dramatically broader RPM range than internal combustion engines. Typically, an electric motor can sustain 20,000 RPM so there is no need to gear up or down. A single gear ratio is all that’s needed. What EVs need, like internal combustion cars, is a differential.

Actually, most electric vehicles use two motors so they need two differentials. When a car takes a curve or makes a turn the left and right wheels have to operate at slightly different speeds to accommodate the different distances that the arc of the curve or turn create. For example, a right turn requires the left wheels to go faster than the left to compensate for the greater distance they have to travel.


Gas vs. Batteries

Batteries are the elephant in the room. Everybody knows electric fuel generates zero emissions and electric vehicles are more fuel-efficient than gas-powered cars. But everybody also knows that batteries have limited range and take longer to recharge than filling a tank with gas.

Batteries need some work.

There are two big problems. Gas is far more energy-dense than a battery meaning more energy can be released from gas tank than from a battery with the same mass. Secondly, gas and the energy it contains is a liquid and can be pumped into a tank rapidly. Batteries require a recharge which takes significantly longer. Range by itself is not an issue. A bigger battery will hold more energy and take you farther. But a bigger battery will weigh much more and take much longer to charge.

The good news is there have been quantum leaps in battery technology and ranges and refueling times have dramatically improved over the past five years. When you get upscale manufacturers like BMW and Porsche adding electrical vehicles or hybrids to their lineup, you know the research that led them to that decision points to electricity as the fuel of the future.

In the meantime, you have a number of excellent EV choices ranging from commuters to luxury sedans and sport cars.