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accelerated degradation concern

Discussion in 'Model S: Battery & Charging' started by David99, Jun 11, 2018.

  1. David99

    David99 Active Member

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    Thanks to Teslafi.com I have data from my car for the last 80k miles. A new feature they added recently is the 'battery report'. It shows the rated range over time thus giving you a great way to see your battery degradation.

    Here is a screen shot of my car. It's a 4 year old Model s 85 with 160k miles. This graph represents roughly 2 years (when I started using Teslafi.com)

    batteryReport.PNG

    The blue lines is the rated range reported by the car from 85k to 160k miles on the ODO meter. It's a little noisy but that's expected. The gray dotted line is just a straight from start to end. The black line is what I added showing the trend the way I would see it. Clearly there is a point where the range drops faster than it did before. I manually recorded data from the first two years of my car. When extrapolating the curve in this graph to the beginning of my car's life it approximately matches the black line before the sudden drop. In other words, over the life of my car, the range dropped at approximately at the same rate (I excluded the first 10k miles where initial degradation is fast).

    Looking at that I'm a little concerned that after a certain amount of miles or time, degradation starts to accelerate. Kind of like an S curve. Fast in the beginning, then slowing down, and then accelerating again. It is not a temporary artifact or noise. The point where it started to accelerate is 10 months and 33k miles ago. Definitely a long enough period to not be noise in the data.

    I tried to find other correlations like temperature or other factors but nothing stands out or coincides with the point where it starts to drop faster.

    Any thoughts?
     
  2. Snowstorm

    Snowstorm Member

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    Can u post your pic again, didn’t show for me. My teslafi shows 1.7% degradation after 1 year at 35000 km.
     
  3. J1mbo

    J1mbo Active Member

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    Have Tesla ever changed the rated range calculation?
     
  4. David99

    David99 Active Member

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    Range is calculated from two numbers. The remaining battery capacity in kWh and the consumption from the EPA test. The consumption has never changed as it's the EPA test result. The way Tesla calculated the remaining capacity on the battery has probably been adjusted and fine tuned over the years. So the only thing that might have changed is that is has become more accurate now.
     
  5. AmpedRealtor

    AmpedRealtor Well-Known Member

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    I'm wondering if you might have some modules going bad?
     
    • Informative x 1
  6. ran349

    ran349 Member

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    You are kind of operating in uncharted waters. Not many people have 160k miles on their Tesla. Based on my car, the non-linear behavior is not surprising, although mine was showing a different behavior. My curve remained flat for about 2 years, then a step function down and leveling off again. But I only have 55k miles so far. You still show less than 10% degradation. It will be interesting to see what happens going forward.
     
    • Informative x 1
  7. scottm

    scottm Active Member

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    Get your car into diag mode next time at SC and look at the individual modules. You might have a something going on with some cells.
     
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  8. Gregsbeach

    Gregsbeach Member

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    Something is wrong. I have a 2013 s85 and I have had less than 2 miles loss on a charge in 5 years and 70,000 miles. It used to charge to 259 miles trip charge and it still charges to that or at the lowest 257!
     
  9. AmpedRealtor

    AmpedRealtor Well-Known Member

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    Make sure you are looking at rated range, not ideal range. Check Units under Settings.
     
  10. AmpedRealtor

    AmpedRealtor Well-Known Member

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    Any updates on this thread?
     
  11. David99

    David99 Active Member

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    I haven't been at the service center yet regarding this matter. I'm going on another 4000 miles road trip soon. When I'm back I will look if this trend is continuing and then decide if it's worth bringing up with the Tesla. Since the warranty doesn't make any statements about how much degradation is normal I doubt they will do anything. It might be worth having them at least pull the logs from the battery. Maybe there is something going on.
     
  12. supratachophobia

    supratachophobia Active Member

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    @David99 I'm tracking my own degradation myself, but are you able do the following:

    "For those that care to check themselves, simply use your CANbus tool to find the Nominal and Usable values, divide by your cars EPA watts/mile at 100% charge and see which number is being used for rated range."

    The reason being is this is what I'm discovering:

    "It appears as though two 90kwh cars are reporting full charge range using Nominal Capacity (which includes the unusable 4kwh brick protection). An 85kwh car is using the proper Usable Capacity to report range at 100%. I'm going to continue to collect more data, but I can't believe I'm saying this, there appears to be an attempt to intentionally hide the battery degradation of the 90kwh packs."
     
  13. supratachophobia

    supratachophobia Active Member

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    Yes, this is important to understand. Your battery pack has a value called Usable_Capacity. The car should be taking that number in kwh and dividing it by your cars EPA consumption in watts per mile. This will give you your "Rated Range".
     
  14. gaswalla

    gaswalla P4201/85/airsusp/pano/19i

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    To put this in perspective, after 160k miles, there appears to be less than 10% degradation
     
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  15. tes-s

    tes-s Member

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    What do you get when you do a 100% charge? I think that would be more accurate.

    I get 244 on my 5 year old S85 with 130k miles. Pretty comparable to what you are seeing.
     
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  16. supratachophobia

    supratachophobia Active Member

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    But can you go 244 miles?
     
  17. tes-s

    tes-s Member

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    Yes, depending on how fast I drive, wind, and elevation change.
     
  18. mongo

    mongo Well-Known Member

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    Way less, that is under a 5% drop (240/251 = 95.6%)
    The graph is so zoomed it, it looks really bad (like TSLA some days). The full range shown 255-235 is only 8% and that includes the above max 255-251....

    Nah, not like an S curve.

    Full 0-100% plot
    degzo.png
     
  19. gaswalla

    gaswalla P4201/85/airsusp/pano/19i

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    100% rated range on a new 85 in 2012/2013 was 265 miles (not sure where that 251 number is coming from)
     
  20. supratachophobia

    supratachophobia Active Member

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    Should have clarified. If you peg your watts per mile at EPA consumption, can you do 244?
     

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