A couple of weeks ago, I wrote about some interesting comments Tesla CTO JB Straubel made regarding vehicle-to-grid technology and using old EV batteries for stationary energy storage (for homes or the grid). There was a tidbit in there that I wanted to further highlight on its own, since itâ€™s such a common question and concern â€” the tidbit about EV battery life.
JB stated, â€œWe expect 10 maybe 15 year life at a minimum from these batteries. And, you know, the degradation is not entirely linear.â€
Before we go further, though, I think itâ€™s important toÂ note that batteries degrade fromÂ basically two things: cycling (being charged and discharged) and time (ah, old Father Time).
Itâ€™s unclear from this short statement whether JB is saying that the lifespan will come to a close after 10â€“15 years (minimum) moreÂ because of cycling or age.
Humorously, this expected lifespan flies in the face of a 2013 commentsÂ made by Sven Bauer, the CEO ofÂ BMZ, which at the time was Europeâ€™s largest battery manufacturer (and perhaps still is, but Iâ€™m not seeing current data on this topic). He stated that â€œthe battery life is not very longâ€ for the battery cells Tesla uses, and that â€œthey are never going to achieve 20 yearsâ€™ battery life.â€
Whoops. Well, we areÂ yet to see how long Teslaâ€™s batteries will last before maxÂ capacity drops toÂ 80% of initial max capacity (not that 70% isnâ€™t good enough in most situations anyway), but a â€œ10 maybe 15 year life at a minimumâ€ sure sounds like some of them could hit 20 years, or at least come close to that. In any case, â€œnot very longâ€ seems to have been absurdly pessimistic.
Of course, as I noted in this article, Sven seemed to make an incorrect assumption, that Teslaâ€™s 18650 battery cells are the same as the 18650 battery cells used in consumer electronics like laptops â€” theyâ€™re not the same, even though they are the same size.
So far, even Tesla cars that have driven over 80,000 miles are seeing little battery degradation.
Update: Hereâ€™s a chart from CleanTechnica community manager Bob Wallace showing the same data plotted by % of initial max range remaining:
Note that these resultsÂ canâ€™t be relied on 100% since theyÂ could suffer from self-selection bias, butÂ they imply that Teslaâ€™s batteries are holding up quite well.
Weâ€™ll know much more in the decade to come, but Iâ€™d take it as a great sign that Teslaâ€™s highly regarded CTO is saying â€œWe expect 10 maybe 15 year life at a minimum from these batteries.â€