Results of Tesla Roadster Battery Capacity Tests Show Pack Should Retain Up to 85% Capacity After 100,000 Miles; Heat Not an Issue

4 years ago by Eric Loveday 8

Blue Tesla Roadster

Blue Tesla Roadster

A Plug in America study of Tesla Roadster user data shows that Roadsters should retain 80-85% of their original battery capacity after 100,000 miles.

Tesla Roadster capacity vs. mileage chart

Tesla Roadster capacity vs. mileage chart – click to enlarge

The projected 80-85% figure far exceeds what Tesla suggested back in 2006.  Tesla had stated that the Roadster would retain at least 70% of it capacity after 5 years and 50,000 miles.

The graph to your right shows actual data compiled from Roadster owners who agreed to participate in the study.  A further explanation of the participants and methodology is posted below.

Worth noting is that mileage seems to be the only variable that impact the Roadster’s retained battery capacity.  Heat (or radical climate variations) doesn’t seem to play a role here as it does with the Nissan LEAF’s air-cooled pack.

The full study can be viewed in PDF form by clicking here.

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8 responses to "Results of Tesla Roadster Battery Capacity Tests Show Pack Should Retain Up to 85% Capacity After 100,000 Miles; Heat Not an Issue"

  1. GeorgeS says:

    Whoa. I don’t know about the statistical accuracy of this. It looks like they had to extrapolate the data to 100,000 miles. Also looks like they only had 1 vehicle with a highest mileage of 88,000 miles and only 4 vehicles over 60K miles.

    The high to low numbers at 25,000 miles suggest that some cars were plus or minus 10% of the average. So I guess you would speculate that the results presented should be that the range after 100,000 miles would be 75-85% capacity.

    At any rate that is pretty good…but we need a bigger sample. time will tell

    1. Assaf says:

      As a statistician I second George S. Eric, please change the article’s title from “retained” to “projected to retain”, and the exact number “85%” to “around 85%” or something like that. Furthermore, the uncertainty increases dramatically away from the dataset’s support (i.e., the range of actual observed mileage numbers, which maxes out at <90k in this dataset) – and as George says and even the article admits, the impact of climate or age in years cannot be accurately extrapolated as well given the paucity of data on the high end.

      That being said, overall the dataset does seem to be good news. The bogeyman of EV's supposedly super-short battery life seems to exaggerated.

      That Leaf driver, Marsh, who charged to 100% twice a day (against recommendations) and cranked nearly 80k miles out of his car in 2 years before seeing maximum range decrease to 90%, also seems to point in the same direction.

      1. Eric Loveday says:

        Title altered slightly….Jay isn’t fond of my ultra-long titles, but in this case it’ll have to work…Oftentimes titles are “clipped” to meet a certain word threshold we’re supposed to stick to. But we don’t mind breaking the rules sometimes. Hopefully Jay doesn’t see this title 🙂

        1. Assaf says:

          Thanks! I think for a specialized news outlet (and you guys are doing an amazing job overall) it’s more important to build a name for reliability, than always have the catchiest title. So it’s much better now.

      2. Josh says:

        Plug In America already did a Nissan LEAF survey that showed much greater degradation rates and high sensitivity to climate (heat). Keep in mind that battery cell life is typically counted in charging cycles, not miles. 100,000 miles in a Roadster is comparable to 50,000 miles in a LEAF. As the pack size get larger, there is also a positive effect of not charging/discharging the top/bottom of the pack, respectively. This has an even greater positive effect on battery life.

        1. Eric Loveday says:

          Link to Plug In America’s Nissan LEAF battery survey results: http://www.pluginamerica.org/surveys/batteries/leaf/Leaf-Battery-Survey.pdf

  2. Bill Howland says:

    If I can defend the survey results ( I participated in it at 22,000 miles) , the issue of a lithium battery losing a significant percentage of loss after the first year is significant. If true, then the range loss SHOULD be much less in upcoming years, or, stated another way, the loss over the lifetime of the battery is not linear, and is greatest at the beginning.

  3. EV says:

    already aware of this, tesla motors club forum the guys share their range on their roadsters along with total miles and most still have over 200+ on a full charge