Charging

EV Battery and Charging Lingo

January 25, 2022

Expand Your EV Vocabulary

One of the more confusing aspects of researching and purchasing an electric vehicle has to do with all of the new terminology associated with electric motors and the batteries that power them. For over 100 years, we’ve been accustomed to words associated with gasoline engines, like horsepower, cylinders, and miles per gallon; with electric vehicles, there’s a whole new set of terms to learn. Fortunately, once you’ve learned what each of the new terms means, it’s easy to relate them to their traditional equivalents, and compare electric vehicle specs to figure out which one is best for you. All electric driving ranges based on EPA estimates.

Battery Capacity

When comparing electric vehicles, one of the key points to consider is battery capacity. Think of this as the size of the gas tank on a gasoline-powered vehicle. The bigger the battery, the more electrical energy you can have “on board” the vehicle, which should give you more range.

EV batteries are typically measured in kWh, or kilowatt-hours. A base 2021 Nissan Leaf, a commuter car, has a relatively small 40 kWh battery, while the Porsche Taycan, a high-performance luxury car, has a 93.4 kWh battery, more than double the size. But, that doesn’t necessarily mean that the Taycan will deliver more than double the range.

That’s because a kilowatt (1,000 watts) is a unit that measures the expenditure of energy over time; equivalent to about 1.34 horsepower. The Nissan Leaf has a 140-horsepower electric motor, while the Porsche is available with up to 750 horsepower, at which point it’s drinking electricity up to five times as quickly. This explains why a base model Leaf has a 150-mile range and a Taycan only adds about 50 miles to that total, these ranges are EPA estimates.

As with a gasoline car, the amount of an electric vehicle’s power potential you use – basically, how aggressively you drive it – can significantly impact its range. Make use of all of the Taycan’s 750 horses and you’ll see its EPA-rated range reduced even further.

Efficiency and Range

An EV’s battery size, the power output of its motor(s), and other factors like its weight, size, and aerodynamic characteristics will affect its overall efficiency, which can be measured in a number of different ways. Using basic math lets you determine how far you can go on a charge.

One method is measured in MPkWh, or miles per kilowatt-hour. The higher the MPkWh, the more efficient the vehicle. For instance, an EV with a 100-kWh battery rated at 2.5 MPkWh will deliver range of about 400 miles.

You may also see ratings for kWh/100 miles. Divide the battery’s capacity by the kWh/100 miles rating then multiply by 100 to determine your range. An EV with a 75-kWh battery rated at 35 kWh/100 miles will go 214 miles on a full charge. (For those of you that think in metric, a similar measure is kWh/100 km.)

Many manufacturers and media outlets are now using a MPGe (or miles per gallon equivalent) rating; this gives you a sense of the overall efficiency of the vehicle you are considering, but makes it more difficult to calculate the range of the vehicle, even if you know its battery capacity.

Charging and Electricity Lingo

The other major consideration for most potential EV buyers is, “how quickly can I charge?” The majority of charging will be done at home, overnight, on a charger in your garage or driveway, at which point, charging speed isn’t really an issue; you’ll probably leave home with a full “tank” every morning. When taking a longer trip, however, one beyond the nominal range of your EV’s battery, there can be significant differences in charging speed, based not only on your vehicle’s ability to charge, but also on the specs of the charger you’re hooking up to.

On the vehicle side of things, there are two major stats to look out for: the voltage rating of the car’s electrical system, and its maximum kW rating.

Think of voltage as the electrical “pressure,” how fast electrons can flow through a pipe. The higher the voltage of your EV’s system, the faster electrons can be pushed into it (and, also, the faster those electrons can be pushed to the motors, increasing the vehicle’s responsiveness). The kW rating is a measure of energy over time. Think of it as the size of the pipe delivering electrons from the charger to your car. The bigger the kW rating, the bigger the pipe, the faster your car charges. All other things being equal, a vehicle with a 200-kW rating can charge twice as fast as a vehicle with a 100-kW rating.

Different Charging Levels

How quickly your vehicle can ingest electrons may be limited by how quickly a charger can push them out. This is a big difference from gasoline vehicles. Gas pumps have a standard-size “pipe,” and with a bit of variability, deliver fuel at the same rate. But not all chargers can vary significantly. We’ll discuss the detailed differences between level one, level two, and level three charging in another article, but when you’re on a trip and want to get a fast charge, know that only level three chargers will be able to juice up your car quickly.

Level three chargers use DC current, meaning a direct pipe into your EV’s battery. That pipe can be as “skinny” as maybe 50 kW, or as wide as 350 kW. The kw rating of the charger will give you a rough approximation of how quickly your vehicle’s battery can be charged. Again, it’s worth doing some simple math to explain. If your car has a 100-kWh battery, on a 50-kW charger, will take roughly two hours to fully charge; that same battery connected to a 100-kW charger would only require roughly one hour for the same result; on a 200-kW charger half an hour, and so on. Why do we say “roughly?” Most chargers will not deliver their full speed until they’ve been connected for a few minutes, and other conditions may affect performance as well.

Remember: just because a charger can push out electrons at a high rate may not mean your car can ingest them that fast. Ultimately, charging speed will be limited by your car’s kW rating. For instance, a Volkswagen ID.4, which can be charged at 125 kW, will only ever charge at 125 kW, even if it’s connected to a 350-kW Electrify America charger, while a Hyundai Ioniq 5 can make use of the full 350 kW.

Wrapping Up

If all of this sounds like a lot, it is… for a little while. The more you read about electric vehicles, the more familiar you’ll become with doing the basic math that lets you easily compare the vehicles you’re considering.

More importantly, the technology and charging infrastructure in the EV space is moving so quickly that you’ll need to do less math, and less guessing, over time. More EV chargers are being opened every day and new technology is making charging your EV faster. Once you get used to the basic EV lingo, you’ll be more comfortable with going green!