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This Tesla Model S has logged 146k miles. How’s the battery doing?
Posted on March 30, 2020 by Charles Morris
Lithium-ion batteries degrade over time—that’s a physical fact. But how much capacity loss can you expect over the life of a vehicle, and how much do factors like operating temperatures and frequency of DC fast charging affect battery life? Unfortunately, there’s a paucity of hard data available to answer these questions—Tesla’s Model S has been on the road for less than a decade, and there simply aren’t a lot of truly high-mileage specimens out there.
Image: Branden Flasch
There are more than a few, however, and anecdotal evidence is accumulating. We’ve reported on several Tesla owners who have logged 200,000 miles or more, and their experiences suggest that capacity loss tends to be moderate. Finnish taxi driver Ari Nyyssönen passed the 250,000-mile mark in his 2014 Model S85 back in 2017. Steve Sasman crushed the 200,00-mile barrier in his 2012 Model S in April 2019. Tesloop, a California shuttle service, owns several Teslas that are approaching the 500,000-mile mark. Teslanomics analyzed battery degradation using data from 2,636 Teslas.
The latest addition to the knowledge base comes from Branden Flasch, who posted a video that explains how he calculated the capacity loss on his 2015 Tesla Model S 70D. Our colleague Tom Moloughney, an EV expert and prolific writer on EV topics, wrote about Flasch’s experience in an article for InsideEVs.
Above: A look at how the battery is doing after nearly 150,000 miles (YouTube: Branden Flasch)
Flasch’s car has logged 146,000 miles and over 1,000 charging cycles. He charged his battery up to 100%, then ran it down to zero, a rough-and-ready way to measure the amount of energy the pack is storing. According to Flasch’s calculations, current capacity is 62.4 kWh. Taking into account the pack’s 4 kWh built-in buffer, that means it retains about 90% of the original 70 kWh capacity. That works out to about a 1% loss of battery capacity for every 15,000 miles driven.
Of course, several questions remain unanswered—we don’t know if the degradation is linear (does the rate of capacity fade increase as batteries age?), and we don’t know whether mileage or calendar age is more significant. Most importantly, we don’t know if Flasch’s vehicle is typical. To really be confident of predicting the rate of capacity loss, we need data from at least a couple hundred vehicles, including information about their driving and charging history.
However, every Tesla owner’s story is another piece in the puzzle, and if you’re concerned about how your battery will hold up over time, the anecdotes from long-time owners that we’ve seen should set your mind at rest. (So go ahead and order that Tesla—you know you want to!)