Does single-pedal driving actually extend EV range? It’s complicated
With the rise of electric vehicles, regenerative braking has become a whole lot more common, and many drivers of EVs assume that using maximum regenerative braking settings means they’re getting a better range. Part of this has to do with how EV manufacturers present regenerative braking — as a way to recapture energy that would otherwise be lost.
But when you really think about it, using single-pedal driving may not necessarily be that much more efficient. What’s the best way to get maximum efficiency from your electric car? Turns out, it’s complicated.
What is regenerative braking?
In an EV, regenerative braking essentially recaptures the kinetic energy produced by a car when it slows down, which is then converted into energy and stored in the battery to be used later on. It’s a way to ensure that your vehicle is capturing as much energy as possible, which could theoretically maximize range in a world of range anxiety.
Most of the time, regenerative braking essentially involves spinning an electric motor in reverse, essentially turning it into a generator instead of using it to expend energy. As it generates electricity, that energy is stored in the battery to be used later, when the vehicle needs to use it to accelerate.
In an EV, regenerative braking usually refers to using the braking system in a car to capture kinetic energy, and charge the car. Most EVs use regenerative braking even with regenerative braking settings turned off. That’s because electric cars these days usually use regenerative braking when you push down on the brake pedal, only resorting to using friction brakes when you push hard on the brakes in an effort to slow down quickly. Even in events of more aggressive braking, most EVs use some combination of regenerative braking and friction brakes to slow down the car — ensuring that some amount of energy is recaptured.
But depending on the level of regenerative brake settings you set, your vehicle will often slow itself down to recapture energy when your foot is lifted off the accelerator, and in an extreme case, easing your foot off the accelerator can slow down the vehicle enough that you only have to use the accelerator pedal to drive. This is called single-pedal driving. Most EVs allow the driver to set the level of regenerative braking that they want to use, with the most aggressive being single-pedal driving.
Why wouldn’t single-pedal driving increase range?
With higher levels of regenerative braking active, your car is essentially using and recapturing energy all the time. In other words, when you push down on the accelerator, you’ll use energy, and when you lift off it, your car will recapture energy. But with regenerative braking off completely, when you lift your foot off the accelerator, you’ll coast, meaning that the vehicle doesn’t slow down, and you’re not expending energy to stay up to speed quite as much.
“Coasting, where you let the car move forward without applying power or brakes, allows the car to maintain its speed with minimal energy usage,” said Daniel V. McGehee, Ph.D., an industrial and systems engineering professor at the University of Iowa.
Not only that, but you’ll never be able to recapture 100% of the energy you expend when you engage regenerative braking. There is always going to be some energy that’s lost in the process. Thus, it makes sense that using less energy by coasting more would be arguably more efficient than using more energy to stay up to speed and then recapturing that energy when you slow down.
“Regenerative braking, while efficient, isn’t 100% efficient. Some energy is always lost during the conversion process from kinetic energy to electrical energy and back again. By coasting, you avoid this conversion process altogether, which can be more efficient if you don’t need to slow down quickly,” McGehee said.
The truth is somewhere in between
That’s where confusion starts to come in. Many EVs will adjust their range estimates depending on the settings that you have enabled, and in most cases, EVs will show a higher range estimate with more aggressive regenerative braking settings.
But some of that has to do with exactly how the vehicle expects you to drive — and where. Like anything else, the best way to get the most range is a little complicated.
The general consensus seems to be that in stop-and-go traffic, maximum regen or one-pedal driving is the way to go, for multiple reasons. For starters, it’s more convenient — you don’t have to constantly move between two pedals. But on top of that, it really doesn’t negatively impact range when there isn’t much opportunity to coast anyway.
But on highways, and especially on hills, it may well be more efficient to turn regen braking settings down and take advantage of the momentum of the vehicle. Sure, you won’t be capturing as much energy — but you also won’t be expending it. In some situations, you might even be able to remain up to speed with a light regen mode enabled — for example, if you’re going down steep hills.
The end result is that if you’re really concerned about getting the maximum range from your EV, then you might need to switch between regen modes a little. In stop-and-go traffic, go ahead and use one-pedal driving if it’s convenient for you.
“The optimal approach depends on the specific driving scenario,” McGehee said. “One-pedal driving is beneficial in stop-and-go traffic, urban environments, and when you anticipate needing to slow down frequently. Coasting might be more efficient when you’re cruising at a steady speed on highways or going downhill where you don’t need to slow down. In practice, a combination of both — using one-pedal driving for regenerative braking when needed and coasting when appropriate — will help you maximize range most effectively.”
EV manufacturers seem to agree with this assessment. We spoke to Vivek Surya, senior manager, technical product management on regen braking at Rivian, who noted that it’s not as simple as saying that using one-pedal driving is more efficient or less efficient.
“As with any situation, this comparison is very dependent on many factors, including specific driving speed/distance profiles,” said Surya in an email to Digital Trends. “However, on the whole Rivian’s one pedal drive with regen braking is the better and more efficient option on our vehicles for the same stop-and-go speed profile than coasting.”
Other advantages of regenerative braking
While the efficiency of one-pedal driving or high levels of regenerative braking may vary depending on how you drive, there are other advantages to regenerative braking that make using it better than not.
Perhaps the biggest advantage is how much easier it is on your car’s brakes. With regenerative braking, your car’s friction brakes are rarely used — essentially meaning that they’ll last a whole lot longer. That keeps you safer with less risk of brake wear, and it means that you don’t have to pay to have them replaced as often, if ever. Again, of course, this is true regardless of whether you use single-pedal driving or not — as your EV will automatically use regenerative braking when you hit the brake pedal in all but the most aggressive brake events.
For many, single-pedal driving is also more convenient. As someone who has personally driven many of the most popular electric cars, I can confidently say that I much prefer one-pedal driving in most situations, especially stop-and-go traffic. Of course, most cars that have one-pedal driving also have adaptive cruise control and lane-centering for essentially autonomous driving in stop-and-go traffic — but that’s besides the point. Single-pedal driving is a little annoying in highway driving — as it means that you constantly have to modulate the position of your foot to stay at the right speed, but after all, that’s when you might want to turn off more aggressive regen settings anyway.
Too long, didn’t read
Don’t care about all the interesting facts and incredible writing above, and just want a pointer on how you should use regen braking? Basically, in stop-and-go traffic and most city driving, stick to using the highest level of regen braking that you can stomach, and disable it when you’re driving on long stretches of the highway and could benefit from the ability to coast. That will allow you to take full advantage of the energy recapturing tech on offer by the car, along with the added convenience of only using a single pedal — while ensuring that on long highway stretches you don’t have to be quite as proactive about the positioning of your foot on the pedal.
Source: www.digitaltrends.com
