What automakers are learning about electric vehicles, veterans of Weight Watchers already know: It’s hard to keep the pounds off once you’ve lost them.
EVs are posting eye-popping curb weights, wiping out the lightweighting progress automakers have made in the past decade. The heavy batteries required to provide hundreds of miles of range are the culprit. The battery pack in the GMC Hummer EV pickup and SUV weighs 2,818 pounds — just 52 fewer pounds than the entire curb weight of the Chevrolet Cruze, the compact sedan that ended production in 2019.
No better example of the vehicle diet yo-yo can be found than the former king of lightweighting, the aluminum-bodied Ford F-150.
The 2012 steel-bodied F-150 SuperCrew 4×4 pickup sported a curb weight of 5,586 pounds. An aluminum version replaced it in 2015, shaving roughly 700 pounds. Yet today’s electric F-150 Lightning SuperCrew ranges from 6,015 to 6,893 pounds depending on the battery pack — as much as 1,307 pounds more than the steel-bodied pickup.
And that’s svelte compared with other so-called light trucks.
The Hummer pickup and SUV lead the EV league with a curb weight over 9,000 pounds — nearly 2,000 pounds more than the gargantuan original diesel-powered Hummer H1. General Motors’ electric Chevrolet Silverado, GMC Sierra and Cadillac Escalade IQ — which share the Hummer’s underpinnings — are also super-heavyweights at around 8,500 pounds.
The massive horsepower and torque from electric motors allow EVs to feel lighter than they are. But those added pounds limit driving range and create safety concerns.
A National Bureau of Economic Research study found that an extra 1,000 pounds increases the chance of crash fatalities by 47 percent. Other studies have found that heavy EVs are increasing pollution by causing tires to shed tiny rubber particles.
Experts say decreasing the weight of EVs will be far more difficult than the combustion engine vehicle diet craze. Most EVs already have some aluminum body components and other lightweight materials, restricting avenues for weight reduction.
“It’s a vicious cycle,” said Sam Abuelsamid, e-mobility analyst at Guidehouse Insights. “If you have a 9,000-pound vehicle versus a 6,000-pound vehicle, you need bigger brake rotors and calipers. You’ve also got to have heavier wheels and tires as the vehicle goes up in weight.”
Besides the heavy batteries, EVs have gained weight because they are over-engineered for safety, according to experts.
“No one wants to have a fire, and no one wants a vehicle that isn’t crashworthy,” Detroit teardown and cost guru Sandy Munro told Automotive News. “There is over-engineering, and it’s being done to ensure that if something does go wrong that lives won’t be in jeopardy.”
A decade ago, automakers plowed billions of dollars into cutting vehicle weight to meet ever-tightening fuel economy and emissions standards.
Ford Motor Co. made the biggest powertrain investment in its history when it rolled out the EcoBoost line of turbocharged engines to replace larger-displacement engines.
Many other automakers also downsized and boosted their engines. They started using aluminum body panels and structural components made of carbon fiber and magnesium.
GM cut weight by adopting a mixed-materials manufacturing strategy, employing the lightest, strongest metals in strategic locations in many of its largest vehicles. BMW and Toyota invested heavily in carbon fiber. And nearly every automaker turned to 3D printing to design lightweight parts.
But it isn’t just the weight of the EV battery pack that’s putting the pounds back on.
The addition of advanced electronics that enable automated-driving features — lidar, radar, cameras, sensors and the computers that run them — has contributed as well. Multiple screens, two and three electric motors and all-wheel-drive systems also add pounds.
That doesn’t leave much in the way of low-hanging fruit on a vehicle’s body or powertrain for automakers to reduce curb weight, Munro said.
“If you look at the skateboard chassis and squint, it looks a lot like a body-on-frame with a top hat,” he said. “There’s not much we can really do to reduce weight when you move to a skateboard, which has to have quite a bit of structural integrity because it is carrying the load.”
The biggest opportunity to cut the weight of an EV resides in its batteries and in the steel or thick aluminum enclosures that house them.
Improvements to battery chemistry and packaging of the enclosure will reduce weight, said Royston Jones, chief technology officer at Altair Engineering. The body-in-white, or skeletal, structures of EVs also can weigh less, he thinks.
Automakers will make weight reductions once they have a better idea how EVs perform in real-world crashes and as they study how consumers are using them, Jones said.
“I think there is a long way to go with design optimization, where the complete structure is taken into consideration,” he said.
At least one automaker has already started that process. The top of the battery pack enclosure is also the floorboard that mounts the seats on some configurations of the Tesla Model Y. On most other EVs, the battery enclosure is a complete assembly under the floorboard.
But it is the battery cells themselves in which much of the weight could come out of future EVs. In most of today’s EVs, cells are spaced apart to reduce fire risk should one cell overheat or the battery enclosure become damaged in a crash. If automakers could safely pack cells closer together, they could shrink and lighten the size of the pack without losing range.
“If you open up current battery packs, you’ll find you have a box within a box with cells in the inner box,” Abuelsamid said. “The downside of that modular architecture is there’s a lot of wasted space.”
One battery chemistry with the potential to reduce wasted space is lithium iron phosphate. These cells are not lighter than today’s lithium ion cells, but they are far less prone to fires caused by overheating and crashes. Lithium iron phosphate could enable major weight-saving changes: Cells could be packed closer, and cooling systems could be smaller, enabling the enclosures to weigh less.
Our Next Energy, the Novi, Mich., startup, is developing lithium iron phosphate cells for EVs that could be packaged in lightweight carbon fiber enclosures without affecting safety, said Sam Haberl, vice president of automotive business development for the company. The cells themselves could also play a role in structural rigidity.
“Another thing we are developing at Our Next Energy is structural cell-to-pack, using the cells as a compressed honeycomb that creates the strength of the pack itself, and that minimizes the need for other materials,” Haberl said.
The company has contracts with BMW and several commercial fleet EV makers.
The weightiness of EVs has another consequence. Higher EV weights are causing sticker prices to increase because automakers are using more raw materials in the larger tires and bigger brakes, for example.
Ned Curic, Stellantis’ chief technology officer, told Automotive News Europe that the situation “is not good for the environment, it’s not good for resources, it’s not good for efficiency.”
“It frustrates me,” he said, “that all of our cars — for the industry as a whole — are just too heavy. The cost is becoming unaffordable for the middle classes.”
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