Electric vehicles come with new challenges in understanding how they make and control their power through batteries, cables, contact boxes, motors, and transmissions. In order to best understand how electric cars use and control electricity, it’s helpful to understand the basic terms as one runs into them across this (and other) sites. I’ve compiled a list of common terms to expand your vocabulary and allow you to speak “electric car” with ease.

Ampere

Imagine you are sitting and looking at a wire. You see an electron zip by! “Wow,” you think to yourself, “I just saw electricity!” Then you see a few more zip by. Then, thousands and thousands start flying through the wire, but you magically can keep counting them even as the number reaches the millions. You decide to start grabbing some electrons to hold. You end up holding quite a lot. Roughly 6,241,509,074,460,762,608 of them, in fact.

Congratulations. You are holding an ampere (or “amp”) of electrons. It’s like a bushel of apples or a gaggle of geese, except super exacting in number.

Energy

drake

“I got enemies, got a lot of enemies. Got a lot of people tryna drain me of my energy.”

— Drake

Before Drake’s career was clouded with problematic accusations involving texting teens, he made some good music, including “Energy.” He notes in that particular tune that he’s “got a lot of people tryna drain me of my energy.” To expand on what he was talking about, the next line could have been “which is quantitative property that must be transferred to an object in order to perform work on, or to heat, the object.”

Alas, it was not.

There are many types of Energy, such as Kinetic, Potential, and Chemical energy. The International System of Units (praise be to thee) uses Joules as the unit of measure for Energy, but you can measure Energy using many different units. Common ones are kilowatt-hour, British Thermal Units, calories, and Foot-Pounds (not to be confused with Pound-Foot). These are all different ways of measuring the same thing.

In EVs, the most important thing to know when it comes to Energy is that your battery holds Chemical Energy that is converted to Kinetic Energy when you drive your car. The more Energy you can store in your battery, the faster and/or longer your EV can go.

Crucially, how much Energy a battery does not inform how quickly it can leave and/or enter the battery. This means, a battery can hold a lot of energy – but take a long time to charge. And/or, it can hold a lot of energy but not be able to transfer that energy to the electric motor very quickly.

Kilowatt-Hour

How much energy does a battery contain? That’s often measured in kilowatt-hours (kWh) in EVs. It’s the energy equivalent of one kilowatt of power sustained for one hour. Batteries in modern EVs range from ~25 kWh to ~100 kWh. As a general rule, the more kWh, the longer the range, with 25 kWh typically netting around 80 miles of range and 100 kWh getting you in the vicinity of 300 miles. kWh capacity of batteries has no relation to how quickly energy can go into or out of the battery, and says nothing of battery density. It’s just how much energy potential the battery has.

Power

Kany West

“Thinkin’, no one man should have all that power. The clock’s tickin’, I just count the hours.”

— Kanye West

Before Kanye West really got in deep with his mental issues (get well, Kanye), he made some good music, including “Power.” He notes in that particular ballad that he is “just counting the hours.” If during that time what he was counting instead was energy consumed or created, then he’d truly be measuring power!

See, power is just energy over time. Measuring a joule used over a minute? Power! Kilowatts used in a lifetime? Power! Blueberry muffins consumed in one afternoon? Power!

Torque

When you rotate a handle to open a door, you are using torque. Torque is the application of force to rotation. You can measure it many ways. It’s often measured by the “pound-foot” or the “newton-meter.” If you put a pound of weight on the end of a foot-long wrench that’s parallel to the ground to try to take off a nut, congratulations, you just put a “pound-foot” of effort into it.

For more about torque, read “ICE vs. EVs: What does ‘Torque’ really mean?”

Watt

A watt is a measurement unit of power. When you move some energy from hither to thither, you might want to measure the rate at which it moves. A watt is a handy-dandy, and common, way to measure that.

James Watt was a Scottish inventor, and that’s who this unit of power is named after.