The vast majority of electric vehicle batteries will outlast the usable life of their vehicles, according to a new study that quashes fears that battery degradation will be an issue either for fleets or second life owners.

Analysing data from over 6,300 fleet and private EVs of different makes and models, the research found that the typical EV battery degrades by 2.3% per year. Translated into real world terms, this means that an EV with a working range of 240km (150 miles) would lose about 27km (17 miles) of range over five years. Such a shortfall is not sufficiently significant to impact most fleet duty cycles. The study also suggests that battery packs should have abundant life left long after most eight year, 160,000km warranties have expired.

The findings are positive for fleets and leasing companies looking to maximise the residual values of EVs, given fears among the general public that EV batteries will degrade at the same pace as laptop and mobile phone batteries.

While studies into automotive battery degradation are still in their infancy, given the newness of the technology, this latest research by Geotab says batteries are showing a non-linear decline. Their capacity drops initially, then slowly declines, and only towards the end of their life is there a significant deterioration in performance. However, too few batteries have reached this end-of-life drop to forecast when this is likely to happen.

There are, however, notable differences in battery resilience between vehicle manufacturers. Analysing two of the older EVs, Geotab has found that the Tesla Model S has an average annual degradation of 2.3%, while the Nissan Leaf declines at 4.2% per year. OEMs can enhance battery health through thermal management as well as building in buffers to limit the minimum and maximum states of charge.

From a fleet perspective, the study reaches an encouraging conclusion that high-use duty cycles do not negatively impact battery health, so long as EVs recharge slowly. But regular rapid DC charging, which causes high temperatures in the batteries, can damage batteries. Rapid charging three times per month is enough to have a noticeable impact compared to vehicles that only ever AC charge. “Many automakers suggest drivers and fleet managers limit the use of DCFC to prolong their electric vehicles’ battery life,” writes Charlotte Argue, Geotab thought leader on electric vehicles.

However, research by Recurrent Auto, based on analysis of 13,000 Teslas from 2012 to 2023 (90% from 2018 or later, and 57% from 2021) found no statistically significant difference in range between cars that rapid charge more than 70% of the time and those that fast charge less than 30% of the time. But Recurrent does warn that the vehicles it studied were relatively young, so it is too early to know whether the charging will have an impact over a longer period. It also advises drivers to avoid rapid charging when the car battery is either very hot, or very cold, or at an extreme state of charge – such as 5% or 90%. In these situations, it said, rapid charging can put extra stress on both the battery and the battery management system.

The weather may be beyond a fleet manager’s control, but Geotab did find that EVs driven in hot climates showed a notably faster rate of decline in their batteries than those driven in moderate climates. Temperature also affects the day-to-day range of EVs – the colder the weather, the shorter the range.

The swirl of information and misinformation around long-term battery degradation is one of the key reasons that policymakers and remarketers are working to create independent battery health certificates. These would reassure buyers of used EVs that there is still a long and viable lifespan left in the batteries.