When Kerry Dunstan and his partner went shopping for an electric car this summer, one question topped their list: “How’s the battery?” They soon found a 2021 Nissan Leaf with 29,000 miles. The dealer said its state of health (SOH) was still around 93%. That convinced them. For £12,500, they bought an electric car with a spacious boot and enough room for passengers.
Dunstan, a cabinetmaker who also owns a stylish electric Volvo SUV, admits he’s not in love with the Leaf. “I like sporty, jazzy cars – and it’s just a bit ‘meh’,” he says. Yet he’s satisfied with its performance so far. “It’s done exactly what I expected,” he adds.
Battery health replaces mileage as the key question
Used car buyers once focused on mileage and age. In the age of electric vehicles, that’s changed. The battery’s condition now decides a car’s real value. Buyers want to know how it’s been treated and charged. Regularly fast charging to 100% can wear it out faster.
This new uncertainty makes some people hesitate before buying a used EV. But battery analytics firms claim they can provide accurate readings of battery health. Experts even say many EVs are lasting longer than anyone predicted.
Take Dunstan’s Leaf. It lacks the liquid cooling system found in many newer EVs. Nissan fixed this in later models, but older Leafs lose range faster each year, according to US research firm NimbleFins. Dunstan stays relaxed. “I charge my cars when I need to. I don’t overthink it,” he says.
The science of checking electric car batteries
Austrian company Aviloo wants to end the guessing game. “We can independently measure a battery’s true state of health,” says Patrick Schabus, the firm’s chief product officer. Aviloo works with British Car Auctions and offers two main tests.
Its premium test uses a small data logger that drivers plug into their car. Over a few days, it monitors the battery from full charge down to 10%. The second, faster “flash test” takes just two minutes. It reads battery data directly from the car’s software and analyses it with a computer model.
Aviloo’s in-depth test records voltage and current changes, revealing weak cells. Chief executive Marcus Berger says its results often differ from what a car’s own system shows. He disputes the idea that a battery below 80% SOH is finished. “An EV with 75% SOH can still be great – it just needs the right price,” he says.
Real experiences from electric car owners
In New Zealand, EV owner Lucy Hawcroft remembers buying her Nissan Leaf three years ago. The dealer told her the battery was about 95% healthy. A year later, an independent mechanic tested it again. “It had dropped quite a bit,” she says. “My husband was a bit concerned.”
Even so, the car still covers 160km on a full charge. They mostly use it for short trips of up to 10km. “Some of my friends get 400km,” Hawcroft says. “That would be ideal.”
At Cleevely Electric Vehicles in Cheltenham, checking battery health has become standard. “Most customers ask for it,” says sales director David Smith. The company uses independent SOH reports from ClearWatt. “We can’t change the results,” he says. “Once customers see the report, nine times out of ten it helps the sale.” Managing director Matt Cleevely adds that replacing a few cells can often fix a battery at a fraction of the cost of a new one.
How to charge smarter and keep your battery strong
How should drivers treat their batteries to make them last? Stanford University’s Simona Onori says balance is key. “There’s probably a sweet spot between frequent fast charging and avoiding it altogether,” she says. Researchers are still studying where that balance lies.
Battery technology is improving rapidly. Max Reid, head of battery costs at research firm CRU, says older EV batteries lasted only 500 to 1,000 charge cycles. “Now, some reach 10,000,” he says.
Even when a battery no longer fits its original car, it can still serve other uses. Paul Chaundy from Second Life EV Batteries in Dorset says many businesses repurpose them for energy storage. Some firms use them to power electric forklifts when their grid connection limits charging.
But testing methods still vary between carmakers. Chaundy says the industry needs common rules. “We need clear standards for measuring battery health,” he says.
