The world is rushing head first towards a new “Electro-Digital Age” marked by high-tech commodities and extractive mining operations. Large, resource-intensive lithium ion batteries powering emerging electric vehicle fleets are already straining global mineral supply chains. Nearly one in five cars sold worldwide last year was electric, a ratio that’s expected to increase rapidly in the coming years. Carmakers and governments alike are rushing to shore up more lithium, cobalt, and other “critical minerals” needed to build those batteries.
But new research suggests these batteries, once thought to have short-lived, inherently expendable shelf-lives, may actually last significantly longer than expected. In some cases, properly cared for EVs may even outlive their fossil fuel counterparts. That’s potentially good news: longer-lasting EVs might buy manufacturers much-need time to fabricate components needed to meet increasing global demands.
The new findings, published today in the journal Nature Energy by researchers from the SLAC-Stanford Battery Center, suggest EV batteries may actually last about a third longer than previous forecasts. That means drivers could potentially keep driving their modern EV without replacing the battery for several additional years. The researchers note the shocking disparity in battery life estimates stems from fundamentally unrealistic testing environments that became an industry standard. When the researchers tested batteries for two years in ways they say are more closely aligned with how drivers actually use EVs day-to-day, the battery life expectancy improved significantly.
“We’ve not been testing EV batteries the right way,” Stanford associate professor and paper senior author Simona Onori said in a statement. “To our surprise, real driving with frequent acceleration, braking that charges the batteries a bit, stopping to pop into a store, and letting the batteries rest for hours at a time, helps batteries last longer than we had thought based on industry standard lab tests.”
SLAC-Stanford Battery Center states on its website that its ultimate goal is to “accelerate the deployment of battery and energy storage technologies at scale,” in an effort to address climate change. The research paper was primarily funded by the National Science Foundation Graduate Research Fellowship Program and the Stanford Chevron Fellowship in Energy.
Related: [ ‘Everything has a cost:’ High-tech products and the new era of mineral mining ]
More ‘realistic’ driving led to less battery degradation
Researchers tested 92 commercial lithium ion EV batteries over two years across four different types of driving profiles. The industry standard approach uses a “constant rate of [battery] discharge” followed immediately by a recharge. In the real world, this would look like someone driving their vehicle until the battery is almost fully diminished and then plugging it in to charge completely. This process of constant battery expenditure and recharging resembles how most people use a smartphone.
Stanford school of engineering PhD student and paper coauthor Alexis Geslin told Popular Science these “constant current rates” were adopted as the testing default because it generally requires simpler hardware and is easier to implement for the lab user.
But that’s not how many drivers actually use their vehicles. EV owners, the researchers note, who drive their vehicle in short bursts to and from work or around town, may go several days or even a week without recharging. The researchers attempted to represent that more realistic, periodic driving method in one of the driving profiles. In the end, the more realistic profile resulted in an increased battery lifetime by up to 38%.
“This work illustrates the importance of testing batteries under realistic conditions of use and challenges the broadly adopted convention of constant current discharge in the laboratory,” the researchers wrote in the paper.
The findings similarly seem to contradict commonly held assumptions about what types of driving quickly degrades batteries. Though many drivers believe rapidly accelerating and braking degrades EV batteries faster than steady driving, the researchers found a correlation in their data suggesting sharp, short accelerations may actually lead to slower battery degradation. Pressing down hard on pedals with a lead foot didn’t seem to speed up battery aging. It may have actually had the opposite effect.
“The key point of the study is that the way users may actually drive will not be detrimental to their battery lifetime compared to the lifetime that could have been estimated from constant current lab studies,” Geslin said. “The findings also shed some light on best practices EV owners can take to prolong the life of their batteries as well.” Geslin told Popular Science owners should probably avoid charging their vehicles every time they come home if they can avoid it. Drivers should stave off their “range anxiety”—the common fear among EV owners that they won’t have enough power to reach a destination—and leave the battery only partially charged. Keeping battery levels above 15%, he said, is a “good starting point.”
“Keeping your battery at elevated State-of-charge (high battery percentages) will definitely be detrimental to lifetime… Intuitively, at high state of charge, your battery stores the most energy, so [it] is more prone to side reactions and thus degradation,” Geslin said.
Used electric vehicles may be more viable than previously thought
The findings build on a growing body of optimistic research newer EVs may last longer than than previous iterations. A recent analysis of 5,000 EV batteries by telematics company Geotab, recently cited by Wired, found an average battery degradation of around 1.8% per year. That’s compared to 2.3% average battery degradation for older EVs studied in 2019. Those findings suggest battery management systems are improving. Some estimates suggest an EV vehicle purchased today could theoretically last 20 years, which is a longer life expectancy than some cars with internal combustion engines.
Whether or not car owners actually use the same car for that long remains to be seen. The average age of cars on US roads in particular are older than in previous years though the trend hasn’t fully translated to EVs. It’s possible that will change as EV costs trickle down and more drivers make the switch away from more traditional internal combustion engines. Longer lasting EVs could potentially ease the burden on global supply chains which are currently racing to open new mineral mineral and battery facilities.
Update 12/10/24 8:52AM: This post was updated to additional context from researcher Alexis Geslin.
