When Kerry Dunstan and his partner went looking for an electric car this summer, one question guided their search: “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) stood at about 93%. That was enough to convince them. For £12,500, they bought an electric car with plenty of space for passengers and luggage.
Dunstan, a cabinetmaker who also owns a sleek electric Volvo SUV, admits the Leaf doesn’t excite him. “I like sporty, jazzy cars – and it’s just a bit ‘meh’,” he says. Still, he’s pleased with how it performs. “It does exactly what I expected,” he adds.
Battery health takes centre stage in used car sales
Once, mileage and age were the key numbers for used car buyers. Now, as electric vehicles take over the market, the battery’s condition has become the main concern. Buyers want to know how it’s been treated. Did the previous owner often fast charge it to 100%? That habit can shorten a battery’s life.
The uncertainty around used batteries has made some shoppers wary. But new analytics companies claim they can test battery condition with precision. Experts also note that many electric cars are lasting longer than predicted.
Take Dunstan’s Leaf. It lacks a liquid cooling system to keep the battery at an even temperature. Newer models include one, but older Leafs lose range faster each year, says US research firm NimbleFins. Dunstan doesn’t worry. “I charge my cars to 100% when I need to,” he says. “I just get on with it.”
How experts uncover a battery’s real condition
Austrian firm Aviloo says it can end the uncertainty around used electric car batteries. “We can independently assess the true state of health,” says chief product officer Patrick Schabus. The company provides battery health certificates for British Car Auctions and offers two kinds of tests.
The premium test uses a data logger about the size of a glasses case. Drivers plug it into their car and use it for several days while it records performance from 100% down to 10%. The quicker “flash test” reads the car’s software data and runs an instant analysis. “We can complete it in under two minutes,” says Schabus.
The premium version measures changes in voltage and current to detect weak cells. Chief executive Marcus Berger says Aviloo’s results often differ from what cars report themselves. He also questions the belief that a battery below 80% SOH is done for. “An EV with 75% SOH can still be an excellent car – it just needs the right price,” he says.
What real EV owners are finding out
In New Zealand, Lucy Hawcroft remembers buying a Nissan Leaf with her husband three years ago. The dealer said its battery health was about 95%. A year later, an independent mechanic tested it again. “It had dropped quite a bit,” she says. “My husband was surprised.”
The Leaf still manages about 160km on a full charge. They use it mostly for short trips under 10km. “Some of my friends get 400km,” she says. “That would be ideal.”
At Cleevely Electric Vehicles in Cheltenham, checking battery health has become part of almost every sale. “Most customers want it,” says sales director David Smith. His company uses ClearWatt’s independent reports. “We can’t change the results,” he says. “Once customers see the report, nine times out of ten it helps close the deal.” Managing director Matt Cleevely adds that replacing a few weak modules can be far cheaper than fitting a whole new battery.
Charging habits that keep batteries healthy
So what’s the best way to charge an EV? Stanford University researcher Simona Onori says moderation helps most. “There’s likely a sweet spot between frequent fast charging and avoiding it altogether,” she says. But she adds that researchers still need to study this in detail.
Battery technology itself has improved rapidly. Max Reid, head of battery costs at CRU, says older EV batteries managed 500 to 1,000 charge cycles. “Now, some new models reach up to 10,000,” he explains.
Even when a battery no longer suits its original car, it can still work elsewhere. Paul Chaundy from Second Life EV Batteries in Dorset says many companies reuse them for power storage. Some firms use them to charge electric forklifts when their grid connection can’t handle multiple charging points.
Different carmakers still use their own ways to calculate SOH, and Chaundy wants more consistency. “We need clear and unified standards,” he says.
