I had a ride in my buddy's Leaf yesterday.
140,000 km and 7 years later, the "battery capacity" monitor in the digital instrument cluster still shows 100% health.
That said, he has the impression that it might actually be down a bit from new ... though he also admits it might be recency bias based on the unusually cold & snowy winter we are just beginning to leave behind. It walloped his usual range.
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I will admit I have been occasionally looking at old Leafs in the used car ads. Seems like there are plenty of 1st gen ones with somewhat degraded batteries for around $4k Canadian. They're good for about 60-80 km range (~42-50 mi.), which would be fine for a second car for local trips.
The question is what will the capacity of one of those cars be in another 3 or 4 years?