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What’s a kWh? What’s a kW? What Does PHEV Mean? What’s Regenerative Braking? (EV 101)

New to electric vehicles? Here are 5 electric vehicle terms and concepts you need to know!

All over the world, electric vehicles (EVs) are getting more and more popular. More vehicle manufacturers are adding EVs to their lineups and new models are hitting the market every week. With this surge in EVs available on the market comes many questions for new potential EV owners who are interested in purchasing one of their own. What is the difference between BEV and PHEV? What are kW and kWh? How do you charge your new EV? How long does it take to charge your EV? We will try to explain some of these EV terms and concepts so that you can have a better understanding of EV terminology.

What is the difference between a kW and a kWh?

First, a little history on kilowatts (kW) versus kilowatt-hours (kWh). Back in 1736, a young lad was born in Scotland named James Watt. James was a Scottish inventor, mechanical engineer, and chemist who improved on Thomas Newcomen’s 1712 Newcomen steam engine with his Watt steam engine in 1776. James brought the concept of horsepower to the world and the SI unit of power. Thus, the term “watt” was named after him. Okay, so now you know a few cool historical facts about the term watts, but what is the difference between a kW and a kWh?

A  kW (kilowatt) is a measurement of power — 1000 watts. kW is used in terms of EVs to describe how much power can be put into the car when charging, or in terms of how much power the motor can put out. Power is basically the rate at which energy is generated or used.

A  kWh (kilowatt-hour) is a measurement of energy (something like you’d see on your electricity bill). A kWh is typically used to describe how much energy is stored in the EV battery. Energy can be described as a measure of how much “fuel” is contained within something, or used by something over a specific period of time.

When referring to a gas-powered vehicle, one would say its has a 4.0L 6-cylinder engine with 150 horsepower, for example. When referring to an electric vehicle, one would say they have a 100 kWh battery and an 87 kW motor, for example. As with gas-powered cars, there is  huge variation in EVs. For example, the Fiat 500e has an 87 kW motor, whereas the Tesla Model 3 Performance has two motors with a total of 377 kW!

So, when you refer to kWh, it is the amount of energy that can be stored in it. When you refer to kW, it is the amount of power generated by the motor. So, instead of saying you got “X” amount of miles on a tank of gas, you would say you got “X” amount of miles on a single charge — from the kWh in your battery. A car with a 50 kWh usable battery would be able to turn out 10 kW of power for a total of five hours before it is depleted.

What is regenerative braking?

fastest Tesla Model 3

Photo by Zach Shahan | CleanTechnica.

Regenerative braking, also known as “regen,” is something that EV drivers are partial to, and it makes sense, as regenerative braking takes back the energy that would otherwise be completely lost. So, how does this work? The motor that is in the EV is able to generate electricity by slowing the car down. Essentially, it’s taking the kinetic energy of the moving vehicle and turning it into chemical energy stored in the battery.

It is really simple for the diver. When you lift your foot off the accelerator, the motor begins to slow the car down and recharge the battery. This technique is completely different from how a traditional combustion car works. With a gas-powered vehicle, friction is applied to the brakes as they clamp down on the brake discs, causing the vehicle to slow the car, with all of that precious energy being wasted.

With regen braking, it harnesses a lot of that energy and puts it back into the battery. The level of regen can be adjusted in some EVs to suit the driver’s needs.

What is a BEV, PHEV, or ICE car?

The term BEV stands for “battery electric vehicle. With a BEV vehicle, 100% of the energy used to move the car is stored in the battery. These types of vehicles will have to be charged to get them to move.

The term PHEV stands for “plug-in hybrid electric vehicle.” This type of vehicle consists of a mix of a combustion engine and an electric motor. You can operate them with gasoline or in electric mode. You can also plug them in to charge the battery. They typically have much smaller batteries than BEVs, so will usually be limited to something like 25–45 miles of range on electricity alone.

The term ICE stands for “internal combustion engine.” It generally refers to the standard gasoline and diesel cars that we are familiar with. The engines that burn fuel in those cars to move them are internal combustion engines.

Charging — How to do it and how long does it take?

When referring to charging an EV, let’s cover some of the basics first. There are two types of power sources that are used in charging an EV — AC charging and DC charging.

AC stands for alternating current. In general, slower AC charging is done at about 7kW to 19kW, typically at home or in parking spots with dedicated charge points. You could also plug your EV into a general domestic AC socket and draw about 1–2kW, which is much slower charging but fine for many EV owners, including CleanTechnica CEO and Editor in Chief Zachary Shahan.

DC stands for direct current. This is typically done much faster charging at a rate of 50 kW, 150 kW, 250 kW, or even 350 kW. Older EVs such as the Nissan LEAF drew up to about 48 kW, but some modern EVs such as the Lucid Air, Hummer EV, and Rimac Nevera can draw above 300 kW!

The industry breaks charging speeds for charging an EV into three categories: Levels 1 and 2 both utilize AC charging, while Level 3 uses DC charging.

Level 1

Level 1 equipment, the slowest charging option, provides charging through a common 120-volt (120V) residential AC outlet. Level 1 chargers add about 3–4 miles of driving range per hour.

Level 2

Level 2 equipment offers charging through 240V (in residential applications) or 208V (in commercial applications) electrical service. It is common for home, hotel, workplace, park, and shopping center charging. Level 2 chargers can add about 15–30 miles of driving range in an hour. (Note that most people drive fewer than 40 miles per day.)

Direct Current Fast Charging (DCFC)

The fastest option, direct current fast charging equipment enables rapid charging along heavy-traffic corridors at installed stations. DCFC equipment can charge a BEV to 80 percent in just ~15 minutes to 1 hour.

How much range does an EV have?

So, how much range do EVs have? Well, that depends on a lot of factors, including your driving habits. The range of an EV depends on the size of the battery, and how efficiently the car uses that energy. For example, a light EV that is aerodynamic will get better range than an SUV with the same size battery.

There is a standard test cycle among EVs that’s called the Worldwide Harmonised Lightweight Vehicle Test Procedure or WLTP for short. This puts the EV through a series of tests to determine the range the EV can travel with the energy stored in the battery. For example, the Mazda MX-30 has a WLTP range of 200 km (124 miles) from a 30 kWh battery. The Tesla Model 3 Long Range has a WLTP range of 614 km (382 miles) from a 75 kWh battery.

One thing to keep in mind with the WLTP test cycle is that it sometimes can be ambitious. Although it is possible to exceed the standard WLTP range, it is not probable given different driving conditions in the real world. For example, although the Tesla Model 3 is capable of doing over 373 miles on a charge, something more like 280–310 miles is more likely.

The range of an EV is dependent on driving habits, terrain, road conditions, etc. You can dramatically increase your range by driving slower or decrease it by driving faster.

Source: The AA

 
 
 
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Written By

Tim holds an electronics engineering degree and is working toward a second degree in IT/web development. He enjoys renewable energy topics and has a passion for the environment. He is a part-time writer and web developer, full time husband and father.

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