When Kerry Dunstan and his partner went car shopping this summer, one question mattered above all: “How’s the battery?” They soon found a 2021 Nissan Leaf with 29,000 miles on the clock. The dealer said its state of health (SOH) was still 93%. That was enough to convince them. For £12,500, they drove away with a roomy and reliable electric car.
Dunstan, a cabinetmaker who also owns a high-end electric Volvo SUV, admits he hasn’t fallen for the Leaf. “I like sporty, sharp cars – and this one’s a bit flat,” he says. Still, he’s happy. “It’s done exactly what I expected,” he adds.
Why battery health beats age and mileage
In the past, used car buyers focused on mileage and model year. Today, it’s all about the battery. People want to know how it’s been treated. Did the previous owner charge it to 100% too often? Did they rely heavily on fast charging? Those habits can shorten its life.
This uncertainty has made many cautious about used EVs. But new battery analytics firms say they can measure real condition with surprising accuracy. Experts add that some EVs are lasting far longer than early forecasts predicted.
Take Dunstan’s Leaf. It lacks the liquid cooling system used in newer models. Nissan has since added that feature, but older Leafs tend to lose range faster, according to US firm NimbleFins. Dunstan isn’t concerned. “I charge both my EVs to full when needed,” he says. “I don’t stress about it.”
The rise of precision battery testing
For buyers worried about hidden problems, Austrian company Aviloo offers reassurance. “We can independently measure a battery’s state of health,” says chief product officer Patrick Schabus. Aviloo works with British Car Auctions and offers two main tests.
The premium version uses a small device that tracks the car’s battery over several days as it discharges from 100% to 10%. The faster “flash test” pulls data from the car’s battery software and analyses it within two minutes.
The premium test captures detailed voltage and current patterns, showing how healthy each cell is. Chief executive Marcus Berger says Aviloo’s findings often differ from what cars show. He also disputes the idea that batteries below 80% SOH are useless. “A car at 75% can still perform well – it just needs the right price,” he says.
What everyday EV owners are learning
In New Zealand, Lucy Hawcroft and her husband bought a Nissan Leaf three years ago. The dealer said its battery was 95% healthy. A year later, an independent mechanic found it had dropped noticeably. “My husband was a bit shocked,” she recalls.
Even so, the car still drives around 160km on a full charge. The couple mainly use it for short 10km trips. “Some of our friends get 400km,” she says. “That would be perfect.”
At Cleevely Electric Vehicles in Cheltenham, battery checks have become standard. “Most buyers ask about it,” says sales director David Smith. His company uses ClearWatt’s independent SOH tests. “We can’t alter the results,” he explains. “Once customers see the report, nine out of ten go ahead with the sale.” Managing director Matt Cleevely adds that repairs are often cheaper than replacements. “You can swap a few modules instead of changing the whole pack,” he says.
Smarter charging and better technology
How should drivers care for their EV batteries? Stanford University researcher Simona Onori says balance is key. “There’s probably a sweet spot between fast charging often and avoiding it completely,” she explains. But research continues.
Battery technology has also evolved quickly. Max Reid from CRU says older batteries lasted 500 to 1,000 charge cycles. “Some new ones reach 10,000,” he says.
Even worn-out batteries still have value. Paul Chaundy from Second Life EV Batteries in Dorset says companies reuse them for energy storage. Some use old EV batteries to charge forklifts when the grid can’t handle multiple chargers.
Chaundy believes the industry now needs clear standards. “We should have consistent rules for measuring and reporting battery health,” he says.
