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Degradation at 94.000 miles

Discussion in 'Model S: Battery & Charging' started by David99, Nov 20, 2016.

  1. David99

    David99 Active Member

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    We are all concerned with battery degradation. How does the battery age over time and use. Being at 94,000 miles after 2.5 years I thought I share my findings here to give everyone an idea what to expect.

    I have been keeping track of my rated range over time and wrote down the numbers. I've also added my car to a battery survey regularly (MaxRange Tesla Battery Survey). Later I started using a tool that looks at the CAN bus data and displays the available capacity in kWh. This is not available through the normal UI.

    How much has my battery lost in those 2.5 years and driving 94k miles: aprox 21 miles. When brand new, it had 271 miles, now it's 250 miles when fully charged. That would be 7.75% loss. Not too bad, but this is only half the truth. Looking at the data I and other have collected, it shows that degradation starts 'fast' and then slows down and it seems to flatten out.

    Here is a screen shot from the mentioned Tesla battery survey. The blue dots are all entries, the pink dots are my entries. What's interesting is how the battery loses capacity quickly at the beginning and then the curves becomes pretty much a flat line. It seems that after an initial drop in capacity the batteries are holding up extremely well without loosing additional capacity. My data shows I have not lost any capacity in the last 30-40k miles.

    MaxRange.JPG

    Here are screenshots of the app that shows the actual usable capacity reported from the car. The one on the right is when I started using the app at 70k miles in April '16. The usable capacity shows 73.4 kWh. In November '16 at 94k miles it shows 73.6 kWh. Technically it went up a little but small variations are normal and due to other factors.

    steady.jpg


    A little more info about my car. I obviously drive a lot.

    About 40k miles I have driven on road trips only charging at Superchargers. Aprox 500 times have I charged on a Supercharger.
    I live in Orange County, CA which has a pretty high average temperature.
    Many trips were around Arizona and Nevada where the temperatures are very high.
    My lifetime energy usage is 320 Wh/mile
    I usually charge to 80% daily and about twice a month (on average) I charge to 100%.
    I have charging set to 2 am at night.
    On road trips I regularly drive the battery down to less than 10 miles.
    About 6 times have I driven the car beyond 0 miles.

    Conclusion:
    - Degradation appears to be fast in the beginning and then slows down significantly and seems to almost be non existing after the first 50k miles.
    - Frequent Supercharging doesn't seems to hurt the battery.
    - Hot ambient temperatures don't seem to hurt the battery as much as I thought.
    - using the full capacity (charging to 100% and driving all the way to almost zero) doesn't seem to hurt much.
    - Tesla is keeping the battery very healthy no matter what I do.
    - My car is and 'old' 85 with the old cells. I assume the new cells (70/75/90/100) are better in terms of degradation.
     
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  2. Canuck

    Canuck Well-Known Member

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    Great information. Thanks.
     
  3. ThosEM

    ThosEM Space Weatherman

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    Can you clarify the vertical scale in %, please? Is100% defined by the trend curve, or how do the points extend above 100-% at low mileage?
     
  4. Saghost

    Saghost Active Member

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    It'll be interesting to see how the new batteries age; I don't think there's any reason to expect them to be better, but I'd be happy to be surprised on that account.

    I'm not very worried about it - more Superchargers will mean less need to make longer hops as time goes by...
     
  5. David99

    David99 Active Member

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    I think the person who is running the battery survey explained it somewhere. 100% is what the rated range official is when the car was sold. In my case for example it was 267 miles. When I got mine it showed 271 miles, though. That's why my first entry is above 100%. To be honest those initial 271 miles didn't last long anyways. The first few miles seem to drop pretty quick.
     
  6. Matteo

    Matteo Member

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    Hi @ThosEM. 100% refers to a different number for each model. For example, for the S85 it means 269 miles rated range with range mode on. You might say, doesn't the S85 have 265 miles EPA rated range? It does but as you can see in this video when you turn range mode on, it instantly increases the displayed rated range. Therefore during the survey users also enter their range mode setting. If range mode was off, the chart adjusts the entered number to what it would have been if range mode was on. This is shown in column K.

    However, if the range was 265 miles with range mode off, it wouldn't be 269 with range mode on. It would be 268. Then why do we use 269? Because the official rating is not actually what the cars displayed on average when they were new. In the survey, in column AA and AB we ask users what the 100% rated range was when the car was new. This data is then used to fine tune the 100% rated range numbers with range mode on. Let me know if you have more questions.

    @David99, your data is looking good. It is amazing how close you are to the trendline.
     
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  7. Falkirk

    Falkirk Member

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    I didn't catch the app name. Please share, looks handy to always have more information from the start.

    Thanks
     
  8. smsprague

    smsprague Member

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    Another data point. My 2014 MS 85 is about 2.5 years old.

    38,000 Miles
    337 Wh/mi lifetime average
    262 miles on a 100% charge when new
    255 miles on a 100% charge now
    Charge to 80% each night
    204 miles on an 80% charge
    Car is garaged
    100% charge about 4 times a month
    Supercharge about 5 times a month but only to get me to my destination (so never past about 220 miles)
    Only been below 20 miles of range once
     
  9. mknox

    mknox Well-Known Member

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    I noticed the fast and then flat degradation pattern as well. My S85 (with A-pack battery) was built in February 2013 and currently has about 76,000 miles on it.

    When new, I would get 265 Rated Miles at 100% and 240 Rated Miles at 90%.

    I now see 248 Rated Miles at 100% and 221 Rated Miles at 90%.

    So my 100% has dropped by 17 miles or 6.4%
     
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  10. sorka

    sorka Active Member

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    P85D with 30K miles on it (20 months old). 100% charge when new was 253 and is now 251. 90% when new was 227 and is now 226. So does this mean my 2 mile loss after 30K miles is the worst degradation I'm going to see?
     
  11. Vince Cobelo

    Vince Cobelo Member

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    I have not researched it but where do you suppose the 8 year warranty on battery and motors would kick in regarding degredation. Why can't Tesla identify battery packs that have degraded the most and replace them at a cost as a wear and tear item? My 2017 85D started at 271 and is only down to about 268 after 21K but I sure think about it.
     
  12. ecarfan

    ecarfan Well-Known Member

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    David, thank you for your very informative post. It is in line with other high mileage owners who have posted on TMC with similar battery degradation losses: a few percent over the first year or so, than around 1%/year but decreasing.

    I was surprised to see that both you and Vince report starting out with 271 miles of displayed range at 100% charge. That is unusually high for a brand new 85 battery. When my Dec 2013 S was brand new it maxed out at 265. After 42K miles it now maxes out at 254-256, about a 4% loss. I expect to have my car for at least another year before I replace it with a Model 3 and it will be interesting to see where it is at a year from now.

    I still run into people who confidently claim that EV batteries need to be replaced after several years. When I explain the documented data on Tesla batteries to them they are shocked. Some of them don't seem to be able to accept what I'm saying. They have a pre-conceived idea of why EVs are flawed vehicles and don't want to deal with real world data.
     
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  13. ThosEM

    ThosEM Space Weatherman

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    I guess I experienced the fast initial drop before I even took delivery if an S85 in Dec. 2013: When it was brand new, it showed 231 miles range at 90%, implying 257 miles at 100%, which is a built in 3% drop. Since then it does not seem to have dropped at all and still shows 231 or 232 at 90%. This is at just approaching 50,000 miles.

    I had not noticed the indicated range to change when entering "range" mode, but will have a look now...
     
  14. apacheguy

    apacheguy S Sig #255

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    Nominal full pack energy is susceptible to fluctuations based on season. Mine went up from 75.4 kWh in March to 76.3 currently. I expect it to decline during the winter.

    Regarding rated miles, mine went from 267 to 258 over the course of 4 months. Since then it has held steady. The pack energy reported via CAN does not always seem to correlate with rated miles I've noticed.
     
  15. mknox

    mknox Well-Known Member

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    I think it's been mentioned, but using Range Mode will also affect the numbers. While not truly based on the season, I often use Range Mode in the summer (to keep the a/c compressor "roar" down) but not in the winter where I find it makes little difference in my actual range.
     
  16. apacheguy

    apacheguy S Sig #255

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    I don't believe range mode affects nominal full pack energy but rather the divisor. I'll check later.
     
  17. mknox

    mknox Well-Known Member

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    It's been a few firmware updates since I've tried it, but I have actually seen the Rated Miles display change by a few miles when I would switch Range Mode on or off. If I recall, you'd have to wait a couple of minutes to see the display change, but change it did.
     
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  18. apacheguy

    apacheguy S Sig #255

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    Well that's rated miles. I'm talking about nominal full pack energy which is a variable reported on CAN.
     
  19. Solarman004

    Solarman004 Member

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    Does anyone know of a CAN bus tool for the Model X that can read this data?
     
  20. David99

    David99 Active Member

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    TM-Spy is an app (in development). You also need an adapter cable and a bluetooth transmitter. It is described in one of the discussions called 'using TM-Spy' or something similar.
     

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