Electric motor power output, battery size, weight, and aerodynamics are all factors that affect an EV’s overall range. But the answer to building a long-range EV isn't as simple as plopping in a big ol’ battery pack. Whether it’s on the basis of cost, weight, or vehicle packaging, big batteries just aren’t always the answer. One factor that’s well-known to EV veterans but becoming increasingly important as electric adoption spreads isn’t just range—it’s efficiency.
Today, there are plenty of EVs on the market that take massively different approaches to attaining good efficiency. But is there a tried and true way to get the most range?
Will a powerful (or dual) motor setup negatively affect range? How important is aerodynamics in securing high efficiency? Is weight reduction actually that important? Is there a sweet spot for range, considering battery size, power output, and vehicle size? To break this all down, InsideEVs spoke with Jason Fenske of the popular YouTube channel Engineering Explained to better understand the fundamentals of vehicular efficiency.
A Crash Course In Efficiency
Though we’ve been used to them for a century now, internal combustion engine (ICE) cars are actually rather inefficient at turning chemical potential energy into usable energy that can make your car move. In the combined highway and city fuel economy cycle, only around 16 to 25 percent of the liquid fuel in an ICE car’s gas tank will translate to vehicular movement, according to data from the EPA. Why is this? For one, the combustion process is an exothermic reaction, meaning that heat is a byproduct of the chemical reaction. Since some of this fuel is lost as thermal energy, that portion won't be used to propel the car.
In the book Power Play: Tesla, Elon Musk and The Bet of the Century, reporter Tim Higgins recounts a story from early Tesla battery guru J.B. Straubel that goes like this: burning petroleum for motion is “like being cold, spying a table in the room, and burning it for warmth. Yes, it created heat, but you were left with a room full of smoke and no table.” EVs are meant to solve this engineering problem in a far more efficient way.
Another aspect of a fossil fuel-powered car's inefficiency lies in friction. Regarding propulsion, there is simply an extensive chain of command from the engine to the wheels. From the engine, the energy reaching the wheels must usually travel through a crankshaft, flywheel, transmission, and sometimes, a propeller shaft and differential (some EVs will feature the latter). But the most significant loss of energy is the friction brakes.
For instance, a 4,000-pound SUV traveling 65 miles per hour will have about 766,000 Joules or 0.21 kilowatt-hours of kinetic energy. When decelerating using a non-hybrid car's friction brakes, all this energy will be lost as heat (and slight wear on the brake pads). A visual representation of this is a race car's red-hot, glowing brakes after rapidly decelerating. This energy is expelled into the environment and wasted. So how can EVs do this better?
Efficiency In The EV World
In an electric powertrain, one can disregard many of the shortcomings of an internal combustion engine. Out goes the fossil fuel-powered engine and its repertoire of gadgetry and in comes a battery pack mated to an electric motor (or motors) via an inverter. While there is no denying the complexity of a battery pack, especially considering the cells' cooling and management, the system is incredibly efficient at storing energy to use at a later time.
Based on data presented by the EPA using a 2012 Nissan Leaf as a basis, EVs can generally transmit between 65 and 69 percent of the energy supplied from shore power to the wheels. But the 65 to 69 percent figure only tells part of the story. Considering the SUV mentioned earlier, regen braking improves an electric car's efficiency to between 87 and 91 percent. A vehicle with such high efficiency is a big deal, but there are implications.
For electric cars, efficiency is typically measured in miles per kilowatt-hour. Miles per kilowatt-hour simply designates the miles an EV travels on a kilowatt-hour of energy stored in the battery. Anything above 4 miles per kilowatt-hour is regarded as good. In Tom Moloughney’s 70-mph range test, the 2021 Model 3 secured 4.27 miles per kilowatt-hour, which is incredibly efficient. Most other electric cars typically see efficiency figures of between 2.5 and 3.5 when at highway speeds. Electric trucks, like the Rivian R1T or Ford F-150 Lightning, are on the lower side—around 2 miles per kilowatt-hour.
Prioritizing Range
With such an efficient powertrain, an EV platform is more susceptible to aerodynamic and weight-related changes than a fossil fuel-powered one. This is why you'd get noticeably less range when driving at 80 versus 70 miles per hour or towing a trailer compared to not hauling an external load. To get substantial range in an electric car, the most expedient answer would be to add a larger battery. A larger battery will deliver more range, but it also adds weight and cost.. The most efficient way to boost range is back at the drawing board by focusing on a more aerodynamic design.
"[When] driving long distances, aerodynamics is everything," Fenske told InsideEVs. To back up Fenske's statement, consider Mercedes-Benz. The German automaker reported that when working on its ultra-efficient EQXX sedan, 62% of range losses stemmed from aerodynamics— or pushing air out of the way when cruising. In an internal combustion engine car, the efficiency is already so low that a boxier design will not impact its total fuel range as much as in an EV. But in an electric car, a sleeker design can yield significantly better efficiency (and ultimately improving range), thus reducing the need to add more battery cells, saving weight. Good aerodynamics for EVs is de rigueur.
"Rolling resistance is the next largest piece of the pie," Fenske added. "So rolling resistance is both the weight of the vehicle and the tires you're using." Mercedes said rolling resistance makes up 20 percent of the EQXX's efficiency. While aerodynamics is the bigger target, aiming to keep weight at a minimum while selecting low rolling resistance tires is a necessary piece to the efficiency puzzle that shouldn't be disregarded. This is why the BMW i3 featured a carbon fiber monocoque along with incredibly narrow tires—it resulted in a lower weight and a smaller contact region on the road.
In Mercedes's study, the remaining 18 percent goes to various EV components, such as batteries, motors, inverters, and more. "I don't bring up powertrain efficiency first because you can hide an inefficient powertrain really well if you have a super aerodynamic design and a super lightweight design, but obviously it matters," Fenske said. In the same study by the Silver Arrow brand, the EQXX has a powertrain efficiency of around 95%, considering the battery, inverter, and motor. Keep in mind that’s on the higher end of things—a concept car designed to prove what’s capable, not something you can actually buy.
But as Fenske pointed out, just having an incredibly efficient powertrain won't necessarily make or break an EV's overall range figure. While it's beneficial to maximize the power flow through these components, powertrain efficiency makes up a small part of the total efficiency (18%), and most of the componentry is already very efficient (95%). In terms of optimizing resources and engineering capabilities, focusing on powertrain efficiency is usually a pursuit of diminishing returns. Aerodynamics and rolling resistance, on the other hand, aren’t.
Can I Have A Powerful EV With Lots Of Range?
Interestingly, having a fun-to-drive EV with a powerful motor doesn’t necessarily come at the expense of range.
"For a gasoline car, what you would look at is just called a brake-specific fuel consumption map," Fenske said. "And what it would show is: what is your percentage of throttle and how much torque are you providing? And then with those two axes, you're going to have little islands that form up— [the most efficient regions] — so at like, let's say 2,000 RPM and then at 90% load, perhaps that's our most efficient possible area that this motor operates. So it would be something like this for electric motors."
Based on this premise, there are times when more powerful electric motors can be more efficient. An example is the refreshed 2024 Volkswagen ID.4. Despite offering the same size battery pack as the outgoing 2023 model year, the new one comes with a 282 horsepower (210 kilowatts) electric motor instead of 201 (150 kilowatts). Besides just adding more power, the new motors have improved thermals leading to improved efficiency, and the EPA range rating increased to 291 miles, up from 275. It's important to note that if you're driving like you’re a real-life racer in a Need For Speed game, you'll draw more energy from the battery over time, making you less efficient. But if you're going normally, the new setup will likely yield more range.
Another cool trick with electric motors is to double them up by placing one on each axle. Sometimes, two electric motors can be more efficient than just one, despite the added weight. Since electric motors can be more efficient at specific points, factoring in RPM and load, there are times when a single motor setup can be out of its peak efficiency zone. With two motors, the computer can determine if it's more efficient to operate one or both drive units to reduce energy consumption. But as mentioned above, there isn't a one-size-fits-all answer.
"There are examples of this, like the Model 3 Performance versus the Model 3 Long Range, there is a significant efficiency penalty,” Fenske said, noting the Model 3 Performance’s motor setup favors power as opposed to efficiency “And that is coming from a different motor and a different inverter that perhaps allows for more power but aren't as efficient, so you'll see worse efficiency numbers on the Model 3 Performance than Model 3 Long Range: not because it has more power, but because it is less efficient.” Having said that, he added “there probably are little edge cases where if you're at a really low load and you've way oversized your motor, then perhaps there is a range penalty, but it's not huge."
The Battery Itself
Ignoring the many battery cell chemistries powering the millions of EVs on the road, there are two main battery cell designs: power and energy. Power cells are designed for a high charge and discharge applications. Power cells are not usually very space-efficient and generally take the shape of pouch cells. The Chevrolet Volt and Cadillac ELR use such power cells. Energy cells are built for lower charge and discharge rate applications and are more space and weight-efficient, assuming the form of cylindrical cells. The Tesla Model Y (with the automaker’s 4680 battery pack) and Cybertruck utilize energy cells. The best way to conceptualize these batteries is by thinking about the surface of a paper towel compared to that of a beach towel.
When exposed to water, a paper towel can quickly absorb water and can also dry out in a short period of time. It doesn’t hold a lot of water, but can expel it in a timely fashion. This is like the old Cadillac ELR’s power-focused battery pack. While the battery’s capacity is only 17.1 kilowatt-hours, the electric motors make 233 horsepower. That ratio yields 13.6 horsepower per kilowatt-hour. “For a vehicle like the Chevy Volt with a V, you want to use power cells, because otherwise you have such a small battery that you're not able to use the power from it,” Fenske said.
An energy cell design is more similar to that of a beach towel– it can hold a lot of water, though it takes a lot of time to absorb and evaporate. This is like the Tesla Model Y AWD’s 4680 battery cell design. The crossover makes a substantial 390 horsepower and its battery capacity lies within the realm of 67 kilowatt-hours. Using the same calculation as above, the Model Y AWD’s horsepower to battery size ratio is just 5.8, a massive disparity from that of the ELR.
Since energy cells prioritize total battery storage over power output, it’s necessary to find a happy medium to accommodate both fast charging (and discharging) as well as packaging. While the Model Y can discharge enough energy at a moment’s notice to allow for quick acceleration, its charging performance is a different story. The 4680 cell Model Y has received its fair share of criticism over its unimpressive charging speeds (in comparison to other Teslas), which are likely derived from the cells’ physical dimensions that have fatter cathodes and anodes. In terms of going the distance, energy cells are usually the answer.
The Key To A Long Range EV
Building a long range EV is no easy feat. Aerodynamics, weight, tire selection, high-voltage component efficiency, and battery structure are all attributes that must be considered when designing an electric car that can go the distance. However, all of these have trade-offs. For instance, a super aerodynamic form factor comes at the expense of a sleek and muscular design, efficient components come with a monetary expense, and battery structure can impede on power delivery or total range.
But when building EVs, it’s vital to know that these components can also complement each other. For instance, if the vehicle uses a low-weight energy-dense battery, then the overall weight will reduce, thus minimizing the rolling resistance losses. Select the optimal electric motors and silhouette and there can be a significant range advantage. Toyota, for one, thinks it can get an EV with 620 miles of range without opting for a massive pack, also by downsizing various components. That seems to be the direction much of the industry is headed in.
"And if we make everything as efficient as possible, we can use a smaller battery. And if we use a smaller battery, we can use smaller everything else," Fenske said. . "And if we use smaller everything else, the weight comes down too. If you start with efficiency as the goal, you can have a lighter vehicle, because you can have a smaller battery, and that just compounds along the way."
