Tesla Model S battery degradation data

Update: Oct 30, 2016.  Tesla Motors provides an 8-year infinite mile battery failure warranty but it doesn’t cover degradation. Therefore it is highly relevant for every Tesla driver to know what to expect of the degradation of the capacity over time, because it is equivalent to the range of your car. In the Netherlands, Merijn Coumans is updating on a regular basis, via the Dutch-Belgium Tesla Forum,  a file of owners’ data, created by Matteo. The most recent (October 30, 2016) version of the results is displayed below. Detailed explanations are also in the google doc file, as well as at the end of this blogpost. The new files also have data input possibilities for USA and other non-km (i.e. miles) drivers.

battery1To put in into perspective, on a 0-100% scale, it looks like this:

battery2In the figure the percentage of range loss is shown on the vertical axis. The horizontal axis displays the distance driven with the vehicles.

The way to measure this is to do a full charge (100%) and then check the EPA rated range (in North America) or Typical range (in Europe and Asia/Pacific). In the plot, these numbers are then compared to the range numbers the car displayed when it was new. For example, for the 85 kWh Model S85 variant, this is about 400 km typical range or 265 mi EPA rated range. Even though this is mostly a reliable method, sometimes the computer in the car can’t accurately estimate how much energy the battery holds and might display an inaccurate range number. To improve accuracy, it is a good idea to run down the battery to almost empty and then charge to 100%, once a month. This is known as rebalancing the battery. However, the battery shouldn’t be left at 0% or 100% for more than 2 hours.

From the figure it is clear that the degradation slows down with more driven km. After say 80.000 km (50,000 miles), the overall range degradation is seen to be approximately 6%, with a rate of better than appr 1%/50.000 km (1%/30,000 miles) from that point onwards. The data collected by Merijn, also include how many Supercharger visits were done, among other details. See the forum for more information, or if you want to upload your data.

Besides Mileage vs Remaining Range, the file includes two other charts: Charge Cycles vs Remaining Range and Battery Age vs Remaining Range.

battery3

battery4

Here is a recent update from the USA with almost 130000 miles driven as max.

tesla-battery-degredation-pluginFrom the USA+ drivers I could find the following previous data of the Plug in America Survey, and used it to generate the following picture:

PlugInAmericaData

I compared all provided data with the EPA 265 miles number for the 85kWh Model S and to the 210 miles EPA number for the 60 kWh models. It is not clear of course how trustworthy this data is, and how peoples measured..

If you like the km version, here it is:

PlugInAmericaDatakm

to be continued….

If you know of any other data file or website with similar data, please add a comment below.

Links on battery degradation:

Here are some plots from 2013

From a Tesla Blogger

A nice video on battery degradation can be found here.

How to prolong Lithium-based batteries?

Some data from 2013 from the Tesla Forum

Here is a very nice report on the Tesla Roadster by Plug-in America, one result is the following one, based on 126 vehicles:

roadster

—–

here are some of the notes supporting the data at the top of this blogpost:

Notes
◘ These charts are updated every time there is a new entry. All charts on this page show entries from all locations.
◘ The trendlines are generated by the chart. Hover over the trendline to see the current formula.
◘ When range mode is on, the displayed range in the car increases a few miles or km. For all calculations, this chart uses range numbers with range mode on because this statement by Jerome Guillen: “EPA testing is [done] with range mode on, given that it is assumed customers will use that function when they want to drive the farthest.” In other words, because the range scores are achieved with range mode on, it is more accurate to do calculations based on range numbers when range mode is on. But users don’t have to turn on range mode just to read their 100% charged range. The chart will calculate that accurately.
A video showing how range mode effects displayed range Youtube
◘ A cycle is when multiple percentage charges add up to 100%. For example charging 5 times from 70% to 90% is 1 cycle. Professor Jeff Dahn who is an expert on Tesla batteries said the following when responding to a question by a Tesla owner:
Quote: “If you charge from 30% to 70% 150 times or from 10% to 70% 100 times, the ageing of the battery will be approximately the same”. Source
A video of Prof Dahn comparing Model S battery to other EVs Youtube
◘ If you don’t see your name on cycles chart, go back to data entry and enter lifetime average energy consumption (Wh/km or Wh/mi).
Replacement Batteries
If you have a replacement battery, don’t be surprised if you don’t recognise the mileage and battery age numbers you see above. These numbers are calculated for your replacement battery. They are different than your car mileage or vehicle age. If you want to know more about how this calculation is done, read on. Otherwise this might be too much detail.

Let’s assume somebody entered this data:
◘ Mileage: 30,000 km
◘ At what km did you replace battery? 24,000 km
◘ What happened to typical range after replacement? Improved 5 km
◘ Typical Range at 100% charge: 390 km
◘ Ownership duration: 350 days

Mileage calculation for replacement battery: If the battery hadn’t been replaced, typical range would be 390-5= 385 km on the old battery at 30,000 km.
If 30,000 km equals to 400-385 km range loss
then X km equals to 400-390 km range loss
Cross multiply. X= 30,000 * (400-390) / (400-385) = 30,000 * 10 / 15 = 20,000 km. The chart will display 20,000 km
◘ Why does the chart display 20,000 km even though actual mileage on the replacement battery is only 30,000-24,000= 6,000 km?
Because this replacement battery was refurbished and had some mileage on it.
◘ Why does the chart display 20,000 km even though mileage on the car is 30,000 km?
Because the chart displays mileage on the current battery not on the car and it has calculated that the replacement battery has 20,000 km mileage on it.
◘ How would the chart calculate age on the replacement battery?
Age = 350 * (400-390) / (400-385) = 350 * 10 / 15 = 233 days
◘ What mileage would the chart show if the replacement battery still had 400 km range?
Even though the calculation would result in zero miles (X= 30,000 * (400-400) / (400-395) = 30,000 * 0 / 5 = 0 km) the chart recognises that the calculation shouldn’t be less than what the user reported. In this case odometer shows 30,000, replacement happened at 24,000. Therefore mileage on the replacement battery is at least 6,000 km. Therefore the chart would display 6,000 km. The age calculation for the replacement battery would result in zero days too because the typical range is still 400 km (same as a new battery). Of course zero days would be incorrect too because the battery has 6000 km on it. Again the chart wouldn’t use zero and would calculate the time that corresponds to 6000 km mileage as follows:
If 30,000 km equals to 350 days
Then 6,000 km equals to X days
X= 6,000*350/30,000= 70 days
Updates
◘ 30 July 2015: The Mileage Chart now switches between km and miles depending on location of selected username. We have now more entries from USA than before. So I thought this would be useful. Matteo
◘ 11 Feb 2016: The trendline for the first chart (Mileage vs Remaining range chart) has been updated. The old trendline was a third order polynomial trendline. It worked fine for 0-120,000 km where there are lots of entries but after there were no more entries it showed a sharp drop. The new trendline is polynomial until the data ends but linear afterwards. Like the old trendline this new trendline is also calculated automatically by the chart and updates when there are new entries. Matteo
◘ 9 Aug 2016: I added a script that clears the username selection in E1 every 2 hours. Matteo

37 thoughts on “Tesla Model S battery degradation data

  1. These numbers will not work as the 100% number can increase with several 100% charges in a row.

    My car increased about 10km after three 100% charges in a row. Cells need balancing, so the only way to check max range is by doing several full charges combined with deep discharges. Only then can you balance the pack enough to get an indication of real degradation.

  2. Nice article, the only part that is missing in my opinion is that the capacity of the battery is affected by the ambient temperature. In the winter period the (EPA) is probably less than in the summer. At least that is my experience with the Renault Zoë and Nissan Leaf.

    • Range is definitely less in colder weather, but I doubt if it affects the calculation of the range (directly after charging) that much as the battery is heated because of the charing. When the battery cools down you will see a ‘loss’ of range caused by the dropping temperature of the battery.
      I also made a visualization of the results colored with the average temperature for the day when the range charge was done. There doesn’t seem to be a strong relationship between the temperature and the maximum range above or below average: http://www.daglievemensen.nl/tesla/maxrange_temp.htm

  3. Our results from the MisterGreen demo after 50.000 km in a P85, including a trip from 8.000 km from The Netherlands to North Cape while Supercharging 2 times per day during 10 days

    Typical range 386 km = 3,5% degradation

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  5. Thank you for this chart !
    Very interesting !
    But do you know the age of these batteries to separate the time effect and the cycling effect…
    Or do you know the annual mileage distribution and what is the average yearly mileage done by these Tesla drivers ?

    • Yes, we have the delivery date of the cars and thus can calculate the yearly mileage.
      In this graph the yearly mileage is plotted against the deviation from the trend line (describing battery percentage vs. mileage):

      There doesn’t seem to be a correlation between both values.
      If battery age would account for a significant loss of range, the red dots (negative deviation from trend line) would be found in the lower left and the green dots (positive deviation from trend line) would be found in the upper right, since cars with a high yearly mileage would then have an ‘advantage’ relative to cars with a low yearly mileage (losing their range because of age instead of mileage).

      Also the ambient temperature (at the moment of range charging) doesn’t seem to correlate with the deviation from the trend line:

  6. Maarten, een erg interessant artikel. Misschien leuk om een keer een stukje te schrijven over hoe het opladen van elektrische auto’s werkt. Mijn ervaring verteld me dat hier in ieder geval veel ontwikkelingen in zijn. Ben nieuwsgierig of jij hier meer over weet.

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  10. Does this take into consideration that the km remaining at 100% charge has been modified several times in software?

    I know they’ve changed the calculation method at least once during the past 12 months, which resulted in an approx 5% drop in “perceived capacity”, but not “real capacity”.

  11. NB;
    The Tesla guarantee is NOT against “normal” degradation, but only exceptional loss due to manufacturing defect. Nobody really knows what “normal” means, yet, for the TM battery packs.

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  14. Hi. This is Teo. I created the charts above in the Merijn survey. In the article you said “replaced batterie cases are left out because their mileage is not known”. This is not correct. All replacement batteries are included and their mileage is calculated accurately. Not only is their mileage on this owners car considered but the mileage on the previous car is also calculated because most replacements are refurbished. All this is explained in great detail at the bottom of the charts page.

  15. Why is the difference between typical rated range with Range Mode off and the correction that small (ca. 5 km for the S85 and 3,5 km for the S60)? Shouldn’t it be about 35-50 km?

      • The terms daily charge and trip charge apply to Tesla Roadster but they don’t apply to the Model S because the Model S doesn’t have these buttons. In the video you see the green battery image. On bottom right of the green battery there is a white arrow. That is a slider. You can move that to 100%, 90%, or whatever percent you want.

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  22. Hi Steinbuch,

    This is Matteo aka Teo. I’m the person who created the graphs in Merijn’s survey and I provide continuous technical support for this project on a volunteer basis using Google sheets. There are a few things you could change in your article if you want:

    1) You could change this sentence:
    “The way to measure is to do a range (full) charge (100%) and then check the typical (in the US this is called rated) or rated (in the US this is called ideal – NEDC) range.”

    To this:
    The way to measure this is to do a full charge (100%) and then check the EPA rated range (in North America) or Typical range (in Europe and Asia/Pacific).

    Reason: In the survey we never use Ideal range or NEDC rated range. These two units are hardly used by Tesla owners because they are less realistic than the other two alternatives. In North America the car can display either EPA rated range or Ideal range, depending on what the user selects in the settings menu. Almost all Tesla owners use EPA rated range. Therefore we use that too for North America.

    Everywhere else in the world the car displays either Typical range or NEDC rated range. NEDC rated range is overly optimistic and Typical range is very close to actual range. Therefore almost everybody uses Typical range. In the survey we use that too outside North America.

    2) You could change this sentence:
    “In the plot, these numbers are compared to the 0 km range data – for a 85kWh Model S this is about 400 km typical or 500 km rated (EPA).”

    To this:
    “In the plot, these numbers are then compared to the range numbers the car displayed when it was new. For example, for the 85 kWh Model S85 variant, this is about 400 km typical range or 265 mi EPA rated range.”

    3) You could change this section:
    “Update: June 7, 2016. Tesla Motors gives an 8 year infinite miles battery guarantee. Nevertheless, it is highly relevant …”

    To this:
    “Update: June 7, 2016. Tesla Motors provides an 8-year infinite mile battery failure warranty but it doesn’t cover degradation. Therefore it is highly relevant …”

    4) You could drop the following sentence:
    “Do not put too much attention to the automatically generated polynomial fit (red line).”
    Reason: The red line that you see is not an automatically created polynomial trendline. Polynomial trendlines that Google sheets creates would not fit accurately. Therefore for the first two charts a special trendline was added that is half polynomial, half linear. The trendline starts curved and then changes to linear midway through. Creating this trendline slows down the file slightly therefore the other charts don’t have this special trendline. They used to the regular polynomial trendline but I removed those because people were paying too much attention to the inaccurate automated trendlines.

  23. Hi Steinbuch,
    This is Matteo. I have some feedback. You could change the following sections in your article if you want. Thanks

    1) You could change this sentence:
    “Although there is uncertainty because of the range estimation, as well as because of the state of the battery (balanced or not), the rated (US: ideal) measure is seen as the most reliable, especially if before the range charge the battery was almost empty.”

    To this:
    Even though this is mostly a reliable method, sometimes the computer in the car can’t accurately estimate how much energy the battery holds and might display an inaccurate range number. To improve accuracy, it is a good idea to run down the battery to almost empty and then charge to 100%, once a month. This is known as rebalancing the battery. However, the battery shouldn’t be left at 0% or 100% for more than 2 hours.

    2) You could change this sentence:
    “Merijn (Matteo also known as Teo) also plotted the degradation as a function of age and of milages, see below.”

    To this:
    Besides Mileage vs Remaining Range, the file includes two other charts: Charge Cycles vs Remaining Range and Battery Age vs Remaining Range.

  24. Using the cars calculated total range from 100% full charge seems troublesome unless you know how that number is calculated. For example, it is possible that the number is calculated by dividing the rated kWh capacity of the battery by some long term average kWh per mile. If this is true, battery degradation will never be discovered. It will only reveal long term changes in energy consumption per mile.
    The car offers a much better way to calculate battery capacity. On the Trip page, a value for energy used since last charged is displayed. If you divide that by the change in state of charge, you have a direct measure of battery capacity. For example: If that page shows that you used 40 kWh since last charged, and your state of charge went from 80% to 30%, then the total capacity of the battery is 40 divided by 50%, or 80 kWh. Of course this calculation will be better the longer the trip, it seems like the best way to estimate/calculate battery capacity.
    Peter Lucas

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