A survey of 80 European Model S owners has demonstrated that, on average, most Tesla Model S batteries seem to degrade only 5% after 30,000 miles (50,000 km). After that point, degradation appears to slow down, showing very little further degradation for the next 30,000 miles.
Given the importance of range, battery degradation has been a long standing concern for electric vehicles. Anyone with an old laptop or cell phone can attest to the fact that batteries do not last forever. Fortunately Tesla’s approach of actively cooling and heating the battery in the Model S appears to be paying off for owners. The Model S is on track outperform the Tesla Roadster’s 15% range loss after 100,000 miles.
The information collected in this particular survey was self-provided by European Tesla Motors Club members. Each owner surveyed provided the current range and mileage of their vehicle. 95% of the vehicles surveyed had the larger 85kWh battery installed. All vehicles were manufactured between 2013 and 2015.
One possible negative finding by the survey was the rate in which early battery packs may have been replaced. All owners were asked the question “Do you have a replacement battery?” and 8 respondents out of 80 (10%) marked “Yes. Don’t Know.” It appears that all 8 remarks are true “yes” answers as they all also answered the question “at what km did you replace the battery?” All 8 battery replacements took place in 2013 vehicles with the latest delivered in November 2013. The replacement occurred in nearly 20% of surveyed 2013 vehicles.
It should be noted that all batteries were replaced for free under Tesla’s 8 year, infinite mile battery warranty. Also, the results of the battery degradation data were adjusted to show mileage on the battery, not on the car.
Failures of battery packs in early Model S vehicles, 2012 through 2013 Model years, has been a known issue, but the true replacement rate has been known only to Tesla. The data collected in the survey seems to suggest that Tesla has since fixed the battery issue plaguing early models. Battery pack Version A was replaced by Version B in new Model S vehicles by late 2013.
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That red line looks too optimistic to me. The numbers are still impressive though.
I think the reason why the red line looks so optimistic is because the further you down the line, the less data points they have. They probably couldn’t find too many people that drove 70k+ km in this relatively short period of time. And the ones that they did found, it just so happened that their batteries ended up being in an better-than-the-average state (which in turn caused the red line to actually predict an improvement towards the end of the graph xD hahaha).
It would be very interesting to see the official numbers and statistics from the entire Tesla Model S fleet.