Tesla batteries aren't forever in the same way that diamonds are, but they're still pretty awesome.
Forever is a shorter stretch of time than some of us might have imagined. In a new video post (above), the folks over at Teslanomics make the provocative and controversial claim that Tesla batteries — those lithium ion cells which power the all-electric Models S, 3, and X — will "last forever (basically)." Never has a statement been more in need of a cautionary YMMV (your mileage may vary). You see, in the eyes of the youngish presenter, forever, in terms of battery life, is about 23 to 25 years.
That's how long he suggests it will take the average driver to reduce the useful capacity of their Tesla's battery to 80 percent of its original ability. In terms of most people's car ownership experience, indeed, 20-some years is long past the time a trade-in will occur. For others, including ultra high-mileage drivers and used-car buyers, batteries aren't as forever as diamonds. Even those from Tesla.
Still, Teslanomics does back up its claim with some amount of proof, mostly collected from a number of different owners who've been contributing their data to a shared Google document. After many deep discharge cycles, a graph compiled from their results shows a surprisingly small amount of degradation: about 8 percent after 240,000 kilometers (149,129 miles). Extrapolating from that finding, and assuming performance of the cells will continue to degrade in a linear fashion, than eighty percent battery capacity would be reached at around 780,000 kms (484,669.53 miles). Not forever, but pretty darn impressive.teslanomics
Now, this doesn't mean all lithium ion batteries are created, or managed, equally. Even the original Tesla Roadster batteries didn't perform this well (although, they don't seem too shabby, either) and the issue prompted Nissan to settle a lawsuit involving early owners of the Leaf and replace other's packs. Luckily, the technology and our knowledge of how to better prolong cell life is improving, and this appears to a far smaller issue today. Perhaps the day isn't far off when battery are, truly forever.