Real-World Data Shows EV Batteries Outperform Lab Predictions

New research from the SLAC-Stanford Battery Center suggests that electric vehicle (EV) batteries may last longer in real-world use than laboratory tests predict. Using data from dynamic driving scenarios, researchers found that the actual longevity of EV batteries exceeds expectations based on standardized lab tests.

Laboratory testing and its limitations

Traditionally, EV batteries are evaluated under controlled conditions, where they are subjected to repeated charge-discharge cycles at constant rates. While useful for efficiency analysis, these methods fail to replicate real-world usage patterns, such as frequent acceleration, braking, short trips and long periods of inactivity. The study published in Nature Energy shows that this oversight may lead to underestimation of battery longevity.

Testing under dynamic conditions

To mimic real-world driving, the research team created four discharge profiles and tested 92 lithium-ion batteries over two years. Batteries subjected to dynamic discharge conditions reflecting typical driving behaviors – like frequent braking and intermittent rest – degraded more slowly than expected.

Interestingly, short bursts of acceleration were associated with slower rates of battery degradation, contradicting common assumptions.

Causes of improved performance

A machine learning model analyzed the data, revealing that dynamic conditions reduce stress on batteries. Additionally, the research highlighted two aging mechanisms: cycle aging, caused by charge-discharge cycles, and time-induced aging, which occurs during inactivity. The findings suggest that time-induced aging is more significant for typical EV owners, as their vehicles are parked for much of the day.

"We've not been testing EV batteries the right way. 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"

Dr. Simona Onori.

Implications for battery management

The study suggests that EV manufacturers could update battery management systems to optimize performance based on realistic driving data. This approach could extend the lifespan of existing battery technologies, reducing replacement costs and enhancing the sustainability of EVs.

"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. 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."

Alexis Geslin

Expanding the findings

Beyond automotive applications, the study’s insights may benefit other fields reliant on energy storage systems, including renewable energy, plastics and biomedical devices. By integrating material science with advanced modeling techniques, researchers aim to refine aging predictions across multiple domains.

Reference: Geslin A, Xu L, Ganapathi D, Moy K, Chueh WC, Onori S. Dynamic cycling enhances battery lifetime. Nat Energy. 2024. doi: 10.1038/s41560-024-01675-8

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