Stanford: EV batteries may last much longer than expected

A new study suggests electric vehicle (EV) batteries could last up to 40% longer than previously estimated when evaluated under real-world driving conditions.

Conducted by Stanford University researchers, the findings indicate that current testing methods may underestimate battery longevity, which could reduce the frequency of costly battery replacements for EV owners.

The study, published in Nature Energy, examined how batteries perform in everyday driving scenarios, such as stop-and-go city traffic, highway travel, and periods of inactivity.

The researchers found these conditions allow batteries to degrade more slowly compared to the traditional constant discharge-and-recharge tests often conducted in laboratories.

How were the tests carried out?

Instead of relying on conventional testing, which discharges and recharges batteries at a constant rate, the team developed four discharge profiles to simulate varied driving behaviours.

Over two years, they tested 92 commercial lithium-ion batteries under these conditions. The results showed that dynamic discharge profiles mimicking real-world driving led to longer battery life expectancy.

The study highlighted specific findings, including a slower rate of battery degradation during sharp, short accelerations — contrary to the assumption that hard acceleration accelerates aging.

It also distinguished between degradation caused by repeated charge-discharge cycles, common in commercial EV fleets, and degradation due to natural aging over time, which is more relevant for private EV owners.

“For consumers using their EVs primarily for commuting and errands, time-related aging plays a greater role than cycling,” said Alexis Geslin, a co-lead author and PhD student in materials science and engineering at Stanford.

In contrast, commercial EVs such as buses and delivery vehicles experience more significant cycle-related degradation due to near-constant use or charging.

What do these results mean for EV owners, and brands?

The findings suggest EV manufacturers could improve battery management software to optimise longevity based on real-world usage patterns.

Researchers may need to revisit how battery chemistries and materials are tested and developed, focusing on conditions that reflect actual driving habits.

The study underscores the importance of refining battery testing and design to align with real-world demands, potentially reducing costs and extending the lifespan of one of the most expensive components in EVs.