[mikestew]

Someone please correct me if I'm wrong.

Lithium batteries degrade. 15-20% capacity loss per year.

I'll correct you with empirical evidence: there are a ton of five year old Nissan Leafs that, by your math, shouldn't be able to pull out of their own driveway by now. My wife drives ours to work every day five years after we bought it.

There are ways to cheat though, design your battery electronics to pretend to have a lower capacity at first and then gradually allow them to discharge more and more as the battery ages.

After five years, given the geekery surrounding the Leaf and other EV, I'd be shocked that someone didn't figure out that the Leaf doesn't really have a 24Kwh battery.