Know These Seven Terms and You’ll Be an Electric-Vehicle Expert


New words and concepts are a part of any new automotive technology; remember when you had to explain what a turbo was? Gas-powered cars have been around so long that almost everyone understands the key terms that enable us to compare everything from horsepower to fuel economy to the number of gallons the gas tank can hold. EVs are different—very different—from gas cars and still new enough that some of the terminology used to compare them isn’t well understood. We’re here to help you become an EV expert.

From energy storage to high-voltage electronics, here’s our guide to the seven terms you need to know to understand the key elements of EVs and to talk as confidently about them as you do conventional cars.

Battery Pack

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An EV’s battery is made up of modules, which are essentially boxes of many individual cells that have been wired together. The modules are then connected to one another to form the battery pack. The pack is usually housed in a large metal box with connectors for both current flow and cooling liquid—which is required to keep it in the optimum operating range. It may weigh as much as a half ton or more. In most EVs the pack is almost as wide as the car, runs under the passenger compartment from the front to the rear axle, and is less than a foot high. That large amount of mass down low gives many EVs a low center of gravity that aids handling.

Power

Electrical power is measured in kilowatts (one kilowatt is equal to 1000 watts); the abbreviation is kW. To get an idea of how much energy that is, consider that those old incandescent light bulbs were 60, 75, or 100 watts. One kilowatt is equivalent to 1.34 horsepower, so an EV motor rated at 100 kW has 134 horsepower. Most manufacturers convert their propulsion systems’ power output from kW to horsepower to make it more easily understood by shoppers. If by chance they don’t, we do so in our spec panels.

Battery Capacity

Think of a vehicle’s battery pack as its gas tank: it’s where the energy is stored. The energy capacity of a battery is measured in kilowatt-hours (kWh), which is how much power, in kilowatts, can be delivered over a period of time, in hours. For instance, a battery with a capacity of 80 kWh can deliver 80 kW—107 horsepower—for an hour. That may not sound like much, but today’s vehicles use only a fraction of their available power to move themselves in normal traffic. That’s why that same car can drive for many hours and miles on its 80-kWh battery before needing to recharge. While this same example pack could also theoretically make 800 kW (1073 hp) for six minutes, there are physical and chemical limits on how much peak power a battery can make. In fact, an EV’s peak horsepower is typically limited by how much power the battery can flow, not the limitations of the motors.

EPA Range

The EPA’s estimated range number for how far an EV can travel on a single charge comes from exactly the same scienced-out laboratory test that has been applied to gasoline cars for decades. Vehicles are put onto a chassis dynamometer that replicates road driving conditions and run at required speeds for specific amounts of time. The number on the window sticker is the “combined” figure that is based on 55 percent of the “city” result and 45 percent from the “highway” test. EVs are much more energy-efficient at lower speeds, so in real-world driving they will generally exceed their range rating around town but fall short of it at highway speeds. We’ve confirmed the latter on our 75-mph highway test. The EPA range numbers can be found both on the EPA’s website,