The Lifespan of EV Batteries May Exceed Expectations By 40% – CleanTechnica

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Pleasant Surprises about the Lifespan of EV Batteries

I was puzzled as a new EV driver in 2015 as to why the EV was advertised as having 84 miles of range. When I drove around town, gently applying my regenerative braking and taking off swiftly with my newfound torque, my battery showed that it had more than 105 miles. Whoa. It’s fascinating how operating a short-range electric vehicle teaches us about energy. A new study gives me even more of an understanding of these once mystifying experiences in an EV. For instance, the study found a link between slower degradation and abrupt, brief EV accelerations. This went against the long-held beliefs of battery researchers, including the team conducting this study, that EV batteries suffer from acceleration peaks! I remember the sudden torque was wonderful to get safely and easily past other cars. To find out now that aging is not accelerated by forcefully pressing the pedal with your foot is another note of EV ease.

According to Alexis Geslin, one of the study’s three lead authors and a doctoral candidate in computer science and materials science and engineering at Stanford’s School of Engineering, “if anything, it slows it down.”

“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.” —Simona Onori, Associate Professor of Energy Science and Engineering

Better, Longer Lasting, and Cheaper

Since the early 1990s, the cost of a lithium-ion battery has dropped by over 97% per kilowatt-hour, making electric vehicles more competitively priced than gasoline-powered cars. When did you first hear about lithium batteries and large lithium batteries? Especially those big lithium batteries that could instantly boost torque in a variety of electric vehicles. Whenever it was, they were probably a lot more expensive at the time than they are now.

It may be more plausible to think of the lithium-ion battery as a slow, steady accumulation of several ideas and inventions essential to make a battery practical and realize its full potential. Like solar and other clean technologies, batteries have a long history of development that dates back to the Voltaic era before the 1800s. One of the original inventors of the electric battery is credited to be the Italian chemist Alessandro Volta.

As impressive as that is, what is even more timely and dynamic is the recent announcement from a Stanford-SLAC study encouraging drivers that EV batteries may last up to 40% longer than expected.

“Consumers’ real-world stop-and-go driving of electric vehicles benefits batteries more than the steady use simulated in almost all laboratory tests of new battery designs, a Stanford-SLAC study finds.“

“The batteries of electric vehicles subject to the normal use of real-world drivers — like heavy traffic, long highway trips, short city trips, and mostly being parked—could last about a third longer than researchers have generally forecast, according to a new study by scientists working in the SLAC-Stanford Battery Center, a joint center between Stanford University’s Precourt Institute for Energy and SLAC National Accelerator Laboratory. This suggests that the owner of a typical EV may not need to replace the expensive battery pack or buy a new car for several additional years.”

“We’ve not been testing EV batteries the right way,” said Simona Onori, senior author and 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.”

Battery scientists and engineers almost invariably test the cycle lifetimes of new battery designs in laboratories with a steady rate of discharge and recharging. Using that methodology, they swiftly determine whether a new design is good or bad for life expectancy, among other factors. According to a study published on December 9 in Nature Energy, however, this is not a reliable method of predicting the life expectancy of EV batteries, particularly for those who purchase EVs for daily travel. Batteries still make up over a third of the cost of a new EV, despite a 90% price drop over the past 15 years. Thus, EV commuters, both present and future, may be pleased to hear that there are a lot more miles ahead.

The research team also looked for differences in battery aging due to many charge–discharge cycles versus battery aging that just comes with time. Your batteries at home that have been sitting unused in a drawer for years will not operate as well as when you bought them, if they work at all.

“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.”

“Going forward, evaluating new battery chemistries and designs with realistic demand profiles will be really important,” said energy science and engineering postdoctoral scholar Le Xu. “Researchers can now revisit presumed aging mechanisms at the chemistry, materials, and cell levels to deepen their understanding. This will facilitate the development of advanced control algorithms that optimize the use of existing commercial battery architectures.”

The study implies that the ramifications go beyond batteries. The concepts could be employed by researchers and engineers in additional energy storage applications, as well as in other physical sciences devices and materials where aging is important, such as solar cells, plastics, glasses, and some biomaterials used in implants.

One remarkable aspect of the growth of the lithium-ion battery is how tricky it is to forecast the course of research. Appreciation to all scientists and researchers and to those who provide researchers the opportunity to explore what they believe is promising.

Source: Stanford Report