When Kerry Dunstan and his partner set out to buy a new electric car this summer, one of the questions they asked was, "How's the battery?".

They'd found a 2021 Nissan Leaf with just 29,000 miles on it, and the dealer told them the condition of the battery, or its state of health (SOH), was still around 93%.

The couple were sold. For £12,500, they got an EV with a big boot and plenty of room for passengers.

Though Mr Dunstan, a cabinetmaker who also owns a somewhat snazzier electric Volvo SUV, hasn't quite fallen in love with the aging Leaf.

"I like sporty, jazzy cars – and it's just a bit 'meh'," he says.

However, he adds the Leaf has performed exactly as expected during the three months they've owned it.

It used to be that age and mileage were the two headline details pored over by would-be buyers of second-hand cars. But as more people shift to electric, scrutinising the health of a car's battery has become arguably even more important.

How has that battery been treated? Did the last owner regularly fast charge it to 100%, for example? That has the potential to shorten an EV battery's lifespan.

This battery black box problem has put some consumers off buying a second-hand EV. But battery analytics firms say they can reveal the condition of an old EV's battery with high accuracy. And industry experts say some EVs are lasting longer than many predicted.

Take Mr Dunstan's Nissan Leaf. This is a model of EV built without the kind of........

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