A new study has revealed electric car batteries last a lot longer than you think

A massive new study has shown EV batteries don't degrade as fast as many people fear. On average, cars lose two per cent of their capacity a year. That means that at 10 years old they'd still have 82 per cent of their capacity – in other words a 320-mile car would become a 262-mile car. The report also discovers ways a driver can make the deterioration even less than that.

The data comes from fleet management company Geotab. It used detailed telematic data from 22,700 EVs of 21 different models. Some were vans, and they skewed the data slightly downward – vans on average lose 2.7 per cent a year, largely because they have shorter real range and so have to charge more often, and those charges are more likely to be rapid. Those two things, we learn, are not great.

So here are the top tips. First, avoid frequent DC rapid charging. The report separated those vehicles (cars and vans) for which fast charging was less than one in eight of all charges. They saw degradation of just 1.5 per cent a year.

The ones that rapid-charged more than that saw an average of 2.2 per cent if those rapid charges were less than 100kW. Those that used 100kW+ charging lost 3.0 per cent a year.

Some context. If you do 8,000 miles a year and you go a real 250 miles between charges, that's 32 charges a year. So four journeys of up to 500 miles, starting full and with a rapid charge en route, puts you at one in eight charges being rapid.

The study shows some interesting data about charging to 100 per cent and discharging to an indicated zero. Most cars have dash-screen warnings against doing this, but the data shows it doesn't matter much.

Well, it doesn't matter much unless you park for a long time at either of those states. If the vehicle spends 80 per cent at an extreme battery state it degrades 0.5 per cent faster. So charge up and get driving. Go flat and get charging.

Very hot climates accelerated the degradation rate by 0.4 per cent. So try and park in the shade.

The stats are expressed as degradation per year. But what about mileage? No surprise that when looking at vehicles that go through more charge cycles – that is, drive more miles a year – there's an effect. Degradation average is 1.5 per cent a year for vehicles that do less than a cycle a week, which is a generous 13,000 miles for our 250-mile car. It's 2.3 per cent a year for a cycle every one to two days, which is likely to mean a loaded van with a short electric range doing a lot of miles.

Anyway, as a company that advises fleets, Geotab says, basically, don't worry. The logic is it's most profitable to work your EVs hard, doing lots of miles and not wasting time slow charging, so as to maximise the value you get from the asset.

It's pretty clear that normal private drivers who charge overnight will find their battery deterioration rate very much at the low end of the spectrum. An average mileage car, charged mostly at home, would likely be at a solid 90 per cent capacity after 10 years.