“We’ve not been testing EV batteries the right way,” said Simona Onori, senior author and an associate professor of energy science and engineering in the Stanford Doerr School of Sustainability. “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.”
For example, the study showed a correlation between sharp, short EV accelerations and slower degradation. This was contrary to long-held assumptions of battery researchers, including this study’s team, that acceleration peaks are bad for EV batteries. Pressing the pedal with your foot hard does not speed up aging. If anything, it slows it down, explained Alexis Geslin, one of three lead authors of the study and a PhD student in materials science and engineering and in computer science in Stanford’s School of Engineering.
“We battery engineers have assumed that cycle aging is much more important than time-induced aging. That’s mostly true for commercial EVs like buses and delivery vans that are almost always either in use or being recharged,” said Geslin. “For consumers using their EVs to get to work, pick up their kids, go to the grocery store, but mostly not using them or even charging them, time becomes the predominant cause of aging over cycling.”
