Every EV owner has heard some version of it: "rapid charging kills the battery." For years the honest answer was "a bit, probably." In 2026 we finally have numbers big enough to trust — and they're more interesting than the myth.

What the Biggest Study Yet Actually Found

Geotab's 2026 analysis is the largest real-world look at used EV battery health to date: telematics data from more than 22,700 electric vehicles across 21 makes and models, gathered over several years of actual driving — not lab cycles.

  • Average degradation is now measured at 2.3% per year — up from the 1.8% Geotab reported in 2024, as the fleet ages and older packs pull the average down
  • Heavy rapid-charging use — roughly more than one in eight charging sessions on high-power DC — was associated with degradation of around 3% per year, close to double the rate of predominantly home-charged cars
  • And the reassuring bit: high-mileage EVs past 100,000 miles frequently still returned 88–95% State of Health

Separate UK testing data published this year puts the average State of Health across thousands of assessed used EVs at around 95% — so the typical battery is in better shape than the horror stories suggest.

So Is Rapid Charging Bad?

No — it's a trade you should make knowingly. High-power DC charging pushes more current and more heat through the cells, and heat is what ages lithium-ion chemistry. A motorway rapid charge on a long trip is exactly what the network is for. Living on rapid chargers because it's convenient — that's the pattern the data associates with doubled wear.

The practical rule the numbers support: make slower AC charging (home, work, destination) your default, and treat rapid charging as the road-trip tool it was designed to be. If your circumstances mean rapid is your only option, your battery isn't doomed — it's just ageing on the faster of two curves, which makes knowing its actual condition more valuable, not less.

🔎 The Part That Matters When You Sell

Here's the sting in the data: two identical cars, same age, same mileage, can now be years apart in battery age purely from charging habits — and nothing on the dashboard or the service history shows it. Charging history is invisible to a buyer. The odometer says 30,000 miles either way.

Averages Don't Buy Cars — Individual Batteries Do

A 95% fleet average is genuinely good news for the used EV market. But an average is exactly the wrong tool for the one car you're about to buy or sell. The same studies showing strong averages also show the spread widening as vehicles age — which is why the fleet and leasing industry is moving: the BVRLA and more than 25 organisations have signed an open letter calling for standardised battery health certificates on used EVs, and major leasing firms have started issuing them on every car they remarket.

That momentum reaches private sales next. A verified State of Health figure is heading from "nice to have" to "expected" — and when it's expected, the car without one is the car that gets haggled down.

What This Means in Practice

  • If you're keeping your EV: charge low and slow by default; save rapids for trips. Your future resale value is quietly compounding either way.
  • If you're selling: a certified test turns your good charging habits into evidence a buyer can't argue with — and if the battery tests well, the Aviloo Battery Warranty (£2,700 protection) can transfer that confidence to your buyer.
  • If you're buying: never accept the dashboard range estimate or a seller's word as a battery report. The whole point of the 2026 data is that the damage that matters is the damage you can't see.
📋 Worth Knowing

Degradation rates are fleet-level statistics — individual chemistry, climate, and battery management differ by model, and newer LFP packs tolerate frequent rapid charging better than older chemistries. That's an argument for testing the actual car, not for treating any average as your car's fate.

The Bottom Line

The 2026 data says three things at once: most used EV batteries are healthy, degradation is real and accelerating slightly as the fleet ages, and charging habits can double the difference between two otherwise identical cars. The only way to know which car you've got is to measure it. That's an Aviloo certified test on your driveway — the FLASH test itself takes minutes, the whole visit under an hour — £95, certificate in hand before we leave.