EV batteries may last 40 pct longer than previously thought, new study shows

New research out of Stanford University in the US shows that fears of EV battery degradation and lifespans – a common concern for doubtful consumers – are overblown.

It turns out that – in real-world driving conditions – EV batteries may last nearly 40 per cent longer than previously thought, amounting to an extra 300,000 kilometres.

The study, published in Nature Energy in December, achieved these results by charging and discharging EV batteries in ways that mimicked real-world conditions – accelerating, braking, queueing in traffic, and parking up for long periods of time.

This differs from typical lab testing, which involves charging the cells at a consistent rate, fully discharging them, and charging them again.

In fact, the more realistic the testing was in simulating real-world driving, the longer the batteries lasted, the paper found.

The researchers, from the SLAC-Stanford Battery Center, tested 92 cells over a period of 24 months across four different EV discharge profiles, ranging from constant discharge to dynamic discharging based on real driving data. All the batteries were cycled in a temperature-controlled chamber at 35 °C.

The study yielded some other surprising results, including that sharp, short accelerations were associated with slower battery degradation, contrary to assumptions.

What’s more, for personal EVs, the degradation associated with time was more impactful than the degradation that occurred from use – charging and discharging.

That’s counter to what has generally been observed for commercial EVs like buses and delivery vans, which are in use for much of the time, and for which use is a critical factor in battery degradation.

In March this year, British insurance company AXA published research that showed that more than a third (37 per cent) of people with no plans to purchase an EV cited concern over battery lifespan was one of their primary reasons.

That data was slightly more heartening than this 2023 report from the Green Finance Institute, in which a whopping 62 per cent of survey respondents who said they wouldn’t buy a used EV cited battery lifespan as a major concern.

The results of this latest study suggest that battery lifespans are currently vastly underestimated, which should assuage the concerns of hesitant customers.

The US government mandates a warranty of eight years, or 100,000 miles (about 160,000 kms) for EV batteries.

The Australian government has no such mandate, but warranties on EVs sold here typically echo those numbers, though manufacturers tend to be more optimistic, with Nissan, which manufactures the Leaf, reporting that almost all the batteries it has produced in the last 12 years are still in use.

And research from fleet management technology Geotab suggests EV batteries on the market today could last 20 years or more. That report found that newer EVs degrade by about 1.8 per cent per year, a significant drop from the 2.3 per cent degradation rate seen in 2019.

Meanwhile, a study published in Nature Energy in January this year found that in the UK, EVs were achieving comparable lifespans to ICE vehicles, even under more intensive use.

Concerns over battery lifespan are thought to stem in large part from common misconceptions, including EV batteries are much like other batteries, like those found in a typical smartphone.

When it comes to second-hand EVs, battery health is also intrinsically linked to how the battery was treated by the previous owner – and warranties are not passed on to second-hand vehicle purchasers.

Fast chargers and higher temperatures, for example, tend to degrade batteries quicker than slower, level 2 charging and cooler temperatures.

To that end, over in the UK the incumbent Labour Government plans to implement a standardised battery health certification scheme. A similar scheme is underway in Norway.

While this is not a requirement in Australia, some used car dealerships or private sellers may offer battery health checks.