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A new study has found that the lifespan of electric vehicle (EV) batteries can be up to 40 percent longer than previously assumed.
Scientists at Stanford University discovered this possibility by changing the way they evaluate the life cycles of these batteries: Instead of conducting usual tests that involve a constant rate of discharge followed by recharging, they evaluated the batteries under everyday conditions stop and go
When batteries were evaluated that were subjected to normal, real-world use, such as heavy traffic, long highway trips, short city trips, and being parked for a while, the researchers found that the batteries could last much longer than which had indicated the previous forecasts.
These findings suggest that EV owners may not need to replace their expensive batteries or buy new cars for several additional years, according to the study, published Monday in Energy of nature.
“We haven’t been testing EV batteries the right way,” said lead author Simona Onori, an associate professor of energy science and engineering at Stanford’s Doerr School of Sustainability.statement.
“To our surprise, real driving with frequent acceleration, braking that puts a bit of strain on the batteries, stopping to go into a store and letting the batteries sit for hours at a time helps the batteries last longer than we thought.” Onori added.
Battery scientists and engineers typically cycle new batteries in labs, using a constant rate of discharge, followed by recharging, the authors explained. They then repeat this approach many times to see if a new design could benefit battery longevity.
Onori and his colleagues determined, however, that this is not an ideal approach to predicting the life expectancy of EV batteries, a finding of particular importance since batteries still represent about a third of the price of a new EV.
To draw their conclusions, the researchers designed four types of electric vehicle discharge profiles, ranging from standard constant discharge to dynamic discharge that mimicked real-world driving data.
They then evaluated 92 commercial lithium-ion batteries over two years in these profiles. The more realistic the profiles, the higher the life expectancy of electric vehicles, according to the study.
Among the study’s key findings was a correlation between sharp, short EV accelerations and slower degradation, meaning that pushing the pedal hard doesn’t necessarily accelerate aging.
The researchers also identified some key differences between battery aging due to repeated charge and discharge cycles, which occur in commercial fleet operations, and battery aging that simply occurs over time.
Life-cycle aging plays a bigger role in commercial electric vehicles such as buses and delivery vans, as these vehicles “are almost always in use or recharging,” said co-author Alexis Geslin, a student at PhD from Stanford in materials science and engineering. a statement
“For consumers who use their electric vehicles to go to work, pick up their kids, go to the grocery store, but mostly without using them or even charging them, time becomes the predominant cause of aging on cycling,” Geslin said.
Looking ahead, the researchers said automakers could update their electric vehicle management software to take advantage of the new findings, helping to maximize battery life in real-world settings.
It will also be important to evaluate new types of chemistries and battery designs that reflect realistic demands, added co-lead author Le Xu, a postdoctoral researcher in energy science and engineering.
“Researchers can now review the presumed mechanisms of aging at the level of chemistry, materials and cells to deepen their understanding,” added Xu.
