This site appears quite informative regarding battery degradation. Short of it is they reckon on average from their sample (the contents of which apparently aren't disclosed) all vehicles averaged 2.3% capacity loss per year resulting in a bit over 80% remaining capacity after 8yrs.
It's skewed though. People with fleet cars or using them as minicabs are likely to be fast charging all the time, thus have much higher deg than those being used for private use where 95% or more of the charging is done overnight.
Otherwise after 4 years of driving my ID4 I'd have lost 10% of overall battery capacity. I've lost next to nothing.
Arguably the numbers aren't terrible, however it does beg the question of the viability of such cars for those of us who run their vehicles on a tight budget if these cars are going to end up beyond economic repair after 10-15yrs..
Because ICE vehicles that are 10 to 15 years old have no problems at all...?
They aren't going to end up beyond economic repair after 10-15 years. I refer you to Wizzy. Wizzy was Nissan Leaf purchase by a taxi fleet in 2013. In 2015, at 100,000 miles and over 1700 rapid charges it had near full battery health and was still on its first set of brake pads.
In 2017, Wizzy had done 170,034 miles and been rapid charged 3786 times. It was still going strong. I believe Wizzy has now retired.
Now bear in mind that Wizzy was a 2013 Nissan Leaf and it is now 2026. Battery tech has improved massively in the last 13 years.
As a contrast, I offer you my Renault Grand Scenic. Purchased in 2012 and given the heave ho in 2022 after 10 years and 100,000 miles. At the point it was sold, the upholstery was collapsing on the driver seat, the 12v battery was on its last legs, the accelerator kept sticking and it needed a ton of work doing. It had already had replacement shocks on the rear, oil changes. Oh - the heating kept giving up. A radiator leak had to be fixed. It was worth £2500 to we buy any car.
On Autotrader, there are 12 cars which are 2016 reg and 100,000+ miles. All of them are worth more than my old Scenic. Ten of them are Tesla Model S at between £46k and £21k. The other two are a zoe and a leaf. If I remove the year criteria and just leave the mileage, there are 218 vehicles. Tesla, Hyundai, MG, Kia, Jaguar, Polestar etc etc. Clearly they aren't all at the end of their lives.