Used EV batteries are outlasting early forecasts, but health data stays messy

When modern electric vehicles started reaching roads around 2010, the warnings were stark. The New York Times wrote that year that estimates of EV battery pack lifespan, which nobody knew for sure, ranged upward from seven years, NPR reported on 2 March 2026. The average car on the road is more than 12 years old, and that gap made plenty of would-be buyers nervous.

The data now tells a different story.

Recurrent, a research firm that pulls data from more than 30,000 EV drivers, describes battery aging as an S curve: a rapid decline at the start, a long level stretch, then a faster drop at the end. Liz Najman, the firm's director of market insights, compared it to breaking in a pair of shoes. "It's very much like breaking in a pair of shoes," she told NPR, adding that the shoes start stiff, quickly gain some give, then last until "it's all over, it's a rapid decline." Two things are becoming clear from that curve: the initial drop is milder than feared, and the sharp end-of-life phase is taking a long time to arrive.

What the auction lanes and the data show

Adam George, a vehicle services director at Cox Automotive, which runs used car auctions around the country, said the company expected trouble. "We were expecting battery health to be experiencing mass degradation over the first one to three years of owning a vehicle," he told NPR. "What we have seen, though, is that these 2, 3, 4-year-old off-lease cars that are coming back have battery health scores well upwards of 95%." Cox Automotive has tested nearly 80,000 EVs and found an average battery health of 92%, a figure skewed toward younger vehicles because most EVs on the road are new.

For older cars, Recurrent's community data offers a rough answer. Among EVs 10 years old or older, only 8.5% have ever had a battery replacement, and more than 90% still run on their original pack. "EV batteries are holding up phenomenally well," Najman said. Among EVs of any age with more than 150,000 miles and no replacement, owners still get at least 83% of original range.

The caveats matter. That older-car dataset is small, and some of the oldest EVs cannot connect to Recurrent's opt-in network. Batteries also age in two ways: calendar aging, from time passing even in storage, and cyclical aging, from repeated charging and discharging. Neither can be avoided.

"An EV with a state of health below 80% can still be a great car... It just needs to be priced [appropriately]."

That quote comes from Marcus Berger, chief executive of Austria-based battery analytics firm Aviloo, speaking to the BBC for a 16 October 2025 report by Chris Baraniuk. Aviloo sells battery health certificates to the major UK outlet British Car Auctions and offers two tests: a premium version that logs battery performance over a few days of driving from 100% charge down to 10%, and a flash test that reads data from the car's battery management software. Chief product officer Patrick Schabus said the flash test can be done "at a standstill in under two minutes."

Berger also said Aviloo's results sometimes diverge "substantially" from the state-of-health percentages produced by cars' own built-in systems. That inconsistency is a real problem for buyers. Paul Chaundy of Second Life EV Batteries, in Dorset, told the BBC: "We need more standards around that, I think."

Some dealers use independent reports as a sales tool. David Smith, sales director at Cleevely Electric Vehicles in Cheltenham, said his company uses state-of-health reports from ClearWatt. "They're completely independent. We can't interfere with the reports," he said. "Once customers have seen the report, that aids the sale nine times out of 10." Matt Cleevely, the managing director, added that replacing groups of cells or modules inside a pack is often possible and far cheaper than fitting a whole new battery.

The Leaf problem and the charging question

Not every model ages gracefully. The Nissan Leaf was built without the liquid-based battery cooling common to many other EVs, and earlier generations show a considerable shortening of range year by year, according to data analysed by US insurance and research firm NimbleFins. Nissan has changed that in the latest generation, the BBC reported.

Kerry Dunstan, a cabinetmaker, bought a 2021 Leaf with 29,000 miles for £12,500 after a dealer told him its state of health was around 93%. Three months in, he said the car performed exactly as expected, though he called it "a bit 'meh'" and charges both his EVs to 100% without worrying. In New Zealand, EV owner Lucy Hawcroft bought a Leaf about three years ago, got an SOH reading of roughly 95% from the dealership, then saw it "drop quite a bit" when an independent mechanic checked a year later. The car still does about 160km (100 miles) on a full charge.

Charging habits may matter less than buyers assume. Simona Onori at Stanford University told the BBC: "There is likely a sweet spot between frequent fast charging and avoiding it altogether." She added that, to her knowledge, this has not been thoroughly studied.

Cell chemistry has improved regardless. Max Reid, head of battery costs at market research firm CRU, said older batteries might last 500 to 1,000 charging cycles. "Now, it's 10,000 cycles in some of these new EV cells coming out," he said.

Retired packs are not necessarily waste. Paul Chaundy's customers include businesses that use former EV batteries to store electricity on site, for example a firm with six electric forklifts but a grid connection that can only charge two or three.

Warranties soften the worst case. EV battery warranties typically cover at least 8 years and 100,000 miles, and automakers replace the pack if it fails inside that window, according to NPR. Out-of-warranty replacement can run roughly $5,000 to $20,000. Defects remain the main reason for very early replacement, and NPR reported that multiple large-scale battery recalls have occurred.

For a used buyer, the practical lesson is narrow. A high state-of-health number from a dealer is not proof on its own, and independent testers exist but disagree with car systems often enough that the numbers should be treated as estimates. The range on the dashboard, checked over a real drive, may still be the most honest figure in the classified ad.