New research from the SLAC-Stanford Battery Center suggests that under real world use conditions, EV batteries could last up to a third longer than previous estimates suggested. These findings could mean that EV owners may not need to replace their batteries or purchase a new car for several additional years.
In nearly all battery tests to date, researchers and engineers have used constant discharge and recharge rates when analyzing a batteries performance. The cycle is then repeated in rapid succession to evaluate a batteries life expectancy and other qualities. However, according to the study, this method may not provide an accurate life expectancy estimation for batteries in real world use conditions.
"We've not been testing EV batteries the right way;' said Simona Onori, 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."
In their research, the team developed four EV discharge profiles and tested 92 commercial lithium-ion batteries over the span of two years. Ultimately the data demonstrated that the more realistically a profile represented real world use, the longer the batteries life span. Additionally, when comparing time-based aging and cycle aging, the team discovered that time-based aging played a larger role in battery degradation than previously believed for the average EV consumer.
"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."