美国东部时间2024 年 1 月 18 日下午2:00

作者：安德鲁·兰布雷希特

电动机功率输出、电池尺寸、重量和空气动力学都是影响电动汽车整体续航里程的因素。但制造远程电动汽车的答案并不像安装一个大型电池组那么简单。无论是从成本、重量还是车辆包装的角度来看，大电池并不总是解决问题的办法。电动汽车资深人士都熟知但随着电动车普及而变得越来越重要的一个因素不仅仅是续航里程，还有效率。 

如今，市场上有大量电动汽车采用截然不同的方法来获得良好的效率。但是否有一种经过验证且正确的方法可以获得最大范围呢？

强大的（或双）电机设置会对行驶范围产生负面影响吗？空气动力学对于确保高效率有多重要？减肥真的那么重要吗？考虑到电池尺寸、功率输出和车辆尺寸，续航里程是否存在最佳点？为了打破这一切，InsideEVs 采访了 YouTube 热门频道Engineering Expanded的 Jason Fenske ，以更好地了解车辆效率的基本原理。 

效率速成班https://cdn.motor1.com/images/mgl/7ZZ0LV/s1/bmw-i4-epa-ratings.jpg

尽管我们已经习惯了一个世纪，但内燃机 (ICE) 汽车实际上在将化学势能转化为可以让汽车行驶的可用能量方面效率相当低。根据 EPA 的数据，在高速公路和城市综合燃油经济循环中，内燃机汽车油箱中的液体燃料中只有约 16% 至 25% 会转化为车辆运动。为什么是这样？首先，燃烧过程是放热反应，这意味着热量是化学反应的副产品。由于部分燃料会以热能的形式损失掉，因此这部分燃料将不会用于推动汽车。 

在《Power Play：特斯拉、埃隆·马斯克和世纪赌注》一书中，记者蒂姆·希金斯（Tim Higgins）讲述了特斯拉早期电池大师 JB Straubel 的一个故事：燃烧石油进行运动“就像在寒冷中监视桌子上的动作”。房间，然后燃烧它取暖。是的，它产生了热量，但你只剩下一个充满烟雾的房间，而且没有桌子。” 电动汽车旨在以更有效的方式解决这一工程问题。

化石燃料汽车效率低下的另一个原因在于摩擦。至于推进力，从发动机到车轮有一个广泛的指挥链。从发动机到达车轮的能量通常必须经过曲轴、飞轮、变速器，有时还经过传动轴和差速器（某些电动汽车将采用后者）。但最显着的能量损失是摩擦制动器。 

例如，一辆重 4,000 磅的 SUV 以每小时 65 英里的速度行驶，将具有约 766,000 焦耳或 0.21 千瓦时的动能。当使用非混合动力汽车的摩擦制动器减速时，所有这些能量都会以热量的形式损失掉（以及刹车片的轻微磨损）。对此的直观表现是赛车在快速减速后炽热、发光的刹车。这些能量被排放到环境中并被浪费。那么电动汽车如何才能做得更好呢？

电动汽车世界的效率https://cdn.motor1.com/images/mgl/kNMqM/s1/nissan-leaf-2010-model.jpg
在电动动力系统中，人们可以忽略内燃机的许多缺点。化石燃料驱动的发动机及其所有小玩意被淘汰，取而代之的是通过逆变器与电动机（或多个电动机）配对的电池组。虽然不可否认电池组的复杂性，特别是考虑到电池的冷却和管理，但该系统在存储能量以供以后使用方面非常高效。 

根据 EPA 提供的数据，以 2012 款日产 Leaf 为基础，电动汽车通常可以将 65% 到 69% 的岸电能量传输到车轮。但 65% 至 69% 的数字仅说明了部分情况。考虑到前面提到的 SUV，再生制动可将电动汽车的效率提高到 87% 至 91%。具有如此高效率的车辆是一件大事，但也有影响。 

对于电动汽车，效率通常以每千瓦时英里数来衡量。每千瓦时英里数只是指电动汽车使用电池中存储的每千瓦时能量行驶的英里数。任何超过每千瓦时 4 英里的里程都被视为良好。在 Tom Moloughney 的 70 英里/小时续航里程测试中，2021 款 Model 3 每千瓦时可行驶 4.27 英里，效率极高。大多数其他电动汽车在高速公路上行驶时的效率通常在 2.5 到 3.5 之间。Rivian R1T或福特 F-150 Lightning等电动卡车的续航里程较低，每千瓦时行驶约 2 英里。

续航里程范围优先https://cdn.motor1.com/images/mgl/BX2BMA/s1/hyundai-ioniq-6-aerodynamic-efficiency.jpg

凭借如此高效的动力系统，电动汽车平台比化石燃料动力平台更容易受到空气动力学和重量相关变化的影响。这就是为什么与不牵引外部负载相比，以 80 英里/小时或 70 英里/小时的速度行驶或牵引拖车时，行驶里程会明显缩短的原因。为了让电动汽车获得更大的行驶里程，最权宜的答案是添加更大的电池。更大的电池可以提供更大的续航里程，但同时也会增加重量和成本。提高续航里程的最有效方法是重新设计，专注于更具空气动力学的设计。

“当长途驾驶时，空气动力学就是一切，”芬斯克告诉 InsideEVs。为了支持芬斯克的说法，请考虑梅赛德斯-奔驰。这家德国汽车制造商报告称，在开发超高效EQXX 轿车时，62% 的续航里程损失源于空气动力学，即巡航时将空气推开。在内燃机汽车中，效率已经很低，四四方方的设计不会像电动汽车那样影响其总燃油范围。但在电动汽车中，更时尚的设计可以显着提高效率（并最终提高续航里程），从而减少添加更多电池的需要，从而减轻重量。电动汽车必须具备良好的空气动力学性能。 

“滚动阻力是第二大的部分，”芬斯克补充道。“因此滚动阻力既是车辆的重量，也是您使用的轮胎的重量。” 梅赛德斯表示，滚动阻力占 EQXX 效率的 20%。虽然空气动力学是更大的目标，但在选择低滚动阻力轮胎的同时将重量保持在最低限度是解决效率难题的必要组成部分，不应被忽视。这就是为什么 BMW i3 采用碳纤维硬壳式车身以及极其窄的轮胎，从而减轻了重量并减少了与道路的接触区域。 

在梅赛德斯的研究中，剩下的 18% 用于各种电动汽车零部件，如电池、电机、逆变器等。“我不会首先提出动力系统效率，因为如果你拥有超级空气动力学设计和超轻量化设计，你可以很好地隐藏低效的动力系统，但显然这很重要，”芬斯克说。在 Silver Arrow 品牌的同一项研究中，考虑到电池、逆变器和电机，EQXX 的动力系统效率约为 95%。请记住，这是高端的概念车，旨在证明其功能，而不是您可以实际购买的东西。 

但正如 Fenske 指出的那样，仅仅拥有极其高效的动力系统并不一定会影响电动汽车的整体续航里程。虽然最大限度地提高通过这些组件的功率流是有益的，但动力系统效率只占总效率的一小部分 (18%)，而且大多数组件的效率已经非常高 (95%)。在优化资源和工程能力方面，关注动力总成效率通常是追求收益递减。另一方面，空气动力学和滚动阻力则不然。

我可以拥有一辆续航里程长、功能强大的电动汽车吗？ https://cdn.motor1.com/images/mgl/JlnNn/s1/tesla-model-s-plaid.jpg

有趣的是，拥有一辆具有强大电机的驾驶乐趣的电动汽车并不一定会以牺牲续航里程为代价。

“对于汽油车，你所看到的只是所谓的制动特定油耗图，”芬斯克说。“它会显示的是：你的油门百分比是多少，你提供了多少扭矩？然后通过这两个轴，你将形成小岛——[最有效的区域]——所以在例如，假设转速为 2,000 RPM，然后在 90% 负载下，这也许是该电机运行时最有效的区域。因此，对于电动机来说，情况就是这样。”

基于这个前提，有时更强大的电动机可以更高效。一个例子是更新的 2024 年大众 ID.4。尽管提供与即将推出的 2023 年车型相同尺寸的电池组，但新款车型配备了 282 马力（210 千瓦）的电动机，而不是 201 马力（150 千瓦）。除了增加更多动力之外，新电机还改善了散热性能，从而提高了效率，并且 EPA 续航里程等级从 275 英里增加到 291 英里。值得注意的是，如果您像现实生活中的赛车手一样驾驶，在《极品飞车》游戏中，随着时间的推移，您将从电池中消耗更多能量，从而降低效率。但如果你正常行驶，新的设置可能会产生更大的范围。 

电动机的另一个很酷的技巧是通过在每个轴上放置一个电动机来将它们加倍。有时，尽管重量增加，但两台电动机的效率可能比一台电动机的效率更高。由于考虑到转速和负载，电动机在特定点可以更加高效，因此有时单个电动机设置可能会超出其峰值效率区域。通过两台电机，计算机可以确定运行一个或两个驱动单元是否更有效，以减少能耗。但正如上面提到的，没有一个一刀切的答案。 

Fenske 表示：“有这样的例子，比如 Model 3 Performance 与 Model 3 Long Range 相比，效率有很大的损失。”他指出 Model 3 Performance 的电机设置偏向于功率而不是效率。不同的电机和不同的逆变器可能会提供更多功率，但效率不那么高，因此您会看到 Model 3 Performance 的效率数据比 Model 3 Long Range 更差：不是因为它具有更多功率，而是因为它更少高效的。” 话虽如此，他补充道，“可能存在一些边缘情况，如果你的负载非常低，并且你的电机尺寸过大，那么可能会出现续航里程损失，但不会很大。”

电池本身https://cdn.motor1.com/images/mgl/QeYlbB/s1/storedot-pouch-cells-2022.jpg

忽略为道路上数百万辆电动汽车提供动力的多种电池化学成分，主要有两种电池设计：动力型和能源型。电池专为高充电和放电应用而设计。动力电池通常不太节省空间，并且通常采用软包电池的形状。雪佛兰 Volt 和凯迪拉克 ELR 使用此类电池。能量电池专为较低充电和放电率应用而设计，采用圆柱形电池形式，具有更高的空间效率和重量效率。Tesla Model Y（配备该汽车制造商的 4680 电池组）和 Cybertruck 使用能源电池。概念化这些电池的最佳方法是将纸巾的表面与沙滩巾的表面进行比较。 

当纸巾接触到水时，它可以迅速吸水，也可以在短时间内变干。它容纳的水不多，但可以及时排出。这就像旧凯迪拉克 ELR 的以电力为中心的电池组。虽然电池容量仅为 17.1 千瓦时，但电动机的功率为 233 马力。该比率产生每千瓦时 13.6 马力。“对于像带有 V 的雪佛兰 Volt 这样的车辆，您需要使用电池，因为否则您的电池很小，您将无法使用它的电力，”Fenske 说。 

能量电池的设计更类似于沙滩巾——它可以容纳大量的水，但需要很长时间才能吸收和蒸发。这类似于特斯拉 Model Y AWD 的 4680 电池设计。这款跨界车的功率高达 390 马力，电池容量约为 67 千瓦时。使用与上述相同的计算，Model Y AWD 的马力与电池尺寸之比仅为 5.8，与 ELR 存在巨大差距。

由于能源电池优先考虑电池总存储而不是功率输出，因此有必要找到一种既能适应快速充电（和放电）又能适应包装的合适媒介。虽然 Model Y 可以立即释放足够的能量以实现快速加速，但其充电性能却是另一回事。4680 电池 Model Y 因其充电速度不佳（与其他特斯拉相比）而受到了相当多的批评，这可能是由于电池的物理尺寸具有较粗的阴极和阳极。就长途旅行而言，能量电池通常是答案。 

长续航里程范围是电动汽车的关键https://cdn.motor1.com/images/mgl/Oozjey/s1/2023-lucid-air-touring.jpg

打造远程电动汽车并非易事。空气动力学、重量、轮胎选择、高压组件效率和电池结构都是设计可行驶距离的电动汽车时必须考虑的因素。然而，所有这些都需要权衡。例如，超级空气动力学外形因素是以时尚和肌肉感设计为代价的，高效组件需要金钱费用，电池结构可能会阻碍电力输送或总里程。 

但在制造电动汽车时，重要的是要知道这些组件也可以相互补充。例如，如果车辆使用低重量的能量密度电池，那么整体重量将会减轻，从而最大限度地减少滚动阻力损失。选择最佳的电动机和轮廓，可以获得显着的续航里程优势。例如，丰田认为，它可以在不选择大型电池组的情况下获得续航里程为 620 英里的电动汽车，也可以通过缩小各种组件的尺寸来实现。这似乎是该行业大部分公司正在努力的方向。 

“如果我们让一切尽可能高效，我们就可以使用更小的电池。如果我们使用更小的电池，我们就可以使用更小的其他一切，”芬斯克说。。“如果我们使用更小的其他东西，重量也会减轻。如果你以效率为目标，你可以拥有更轻的车辆，因为你可以拥有更小的电池，而且这一点会一路复合。”

原文阅读

Why EV Efficiency Is So Important For Getting The Most Electric Range

We spoke with Jason Fenske of Engineering Explained to discuss the keys to making a long range EV.

Jan 18, 2024 at 2:00pm ET

By: Andrew Lambrecht

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."