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battery degradation threshold for warranty: 70% of what?

Discussion in 'Model 3' started by jedi2b, Jan 22, 2020.

  1. jedi2b

    jedi2b Member

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    The question is the following:
    -I bought the my Tesla Model 3 SR+ back in june 2019, it has around 20,000 km now (13,000 miles)
    -Back when I bought it, the displayed range was 380km, as advertised by Tesla at the moment of purchase
    -Later, as it can be seen on the Tesla site nowadays, the EPA range was augmented to 402km. As far as I know no hardware changes (i.e. battery or motor) changes were made to the production line, it was just a change on the displayed value in the car, and the value used for advertisement purposes. So I think my car is rated for 402km autonomy.
    -My car battery diplayed range, after 20,000 km, goes around 360km, but it's quite erratic (see green line below, as presented by TeslaMate, that records the value provided by the car API over time)

    upload_2020-1-22_9-23-29.png


    Assuming the range calculated by the car is correct:
    -if I consider 380km as the theoretical battery maximum, I have lost about 5-6% of capacity
    -If I consider 402km as the theoretical battery maximum, I have lost 10-11% of capacity

    So which one is true? because warranty kicks in at 30% degradation, this value is important to know. As you can see on the crazy graphic, I had one episode of the car reporting 280km capacity, which is, depending on the maximum we consider, already out of warranty (70% would be 266km for a max capacity of 380km, and 281km for a maximum capacity of 402km)

    I had a chat with Tesla online support. Then, unhappy with the (lack) of information, They had no idea which value was the one to take in consideration for warranty purposes.

    I opened a service center appointment, and SC just called back. Technician told me the car logs show no problems. When asked if this level of degradation is ok, he said yes, but couldn't provide figures in terms of the normal expected degradation after 20,000km. Still no info on warranty threshold calculation either. SC person should get back to me when/if they find out the answer.

    Do you know the answer? Is my car battery warranty 70% of 380km or 70% of 402km?
     
  2. tomas

    tomas Only partially psycho

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    What is the exact source of your numbers? “The car’s API” and teslamate is not definitive. What does your car show at 100%? 90%

    I think you are worrying unnecessarily. There is not a history of degradation. The batteries tend to lose 5% capacity or so in first year and little thereafter. Loss is not straight line.
     
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  3. jedi2b

    jedi2b Member

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    Well, if the capacity reported by the car is not trusted information, how do we check that the capacity is above the contractual obligation signed by Tesla (i.e. warranty)?
    BTW, as far as I can tell, that same diplayed range value is used by the service center. They never mentioned any other source of information, and never expresed any concerns about the validity of the information either.

    I'm afraid, if people has to trust this new technology, a bit more detail than "carry on, all seems to be good" would be necessary.
     
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  4. JCannonTech

    JCannonTech Member

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    The range when you purchased the vehicle was 380 km, that is what the agreement is based on for sure.

    Regardless, you are measuring capacity in a completely inaccurate way that isn’t entirely representative of your real status of degradation.
     
  5. SigNC

    SigNC Active Member

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    The point tomas is trying to make is battery capacity is basically a BMS guess unless the pack is charged to 100% to see. Even then it may need to do some balancing to get actual full capacity.
     
  6. webbah

    webbah Member

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    The “range” is not necessarily what you should be looking at in miles or kilometers. In winter we lose efficiency and range and in spring/summer we gain efficiency and range. You have roughly a 75 kWh battery in the car. 70% of 75 kWh is the warranty.
     
    • Informative x 1
  7. Sherlo

    Sherlo Member

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    Suggest sending your question to [email protected]

    They were responsive to my email a couple months ago
     
  8. AlanSubie4Life

    AlanSubie4Life Efficiency Obsessed Member

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    It’s a good question. The warranty is written for “battery capacity,” not rated miles and these things don’t correspond 100% and a rated miles change would not change your battery capacity.

    The only question in my mind is what do they use for the initial kWh number? My interpretation is they should use the number from the EPA document. For your car for 2019 that would start at 54.5kWh. But for a 2020 SR+ it would only be 52.5kWh... I am not sure my interpretation is correct.

    The CAN bus reports a projected full capacity independent of temperature (not what TeslaMate is reporting - that is messed up because there are two different API SoC values at play). So they would read that value and compare to whatever the initial value was “supposed” to be (and what is that initial value? - that’s a good question).
     
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  9. AlanSubie4Life

    AlanSubie4Life Efficiency Obsessed Member

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    OP has an SR+. The LR battery is between ~78.2kWh and ~79.7kWh depending on which year and exact variant you are looking at, according to Tesla’s documents.
     
  10. webbah

    webbah Member

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    Roger that, but the main point of my post remains the same. Looking at range via miles or kilometers is futile due to seasonal changes. I know you know this as I’ve seen many of your posts as well.
     
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  11. tomas

    tomas Only partially psycho

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    OP has STILL not indicated their method of measurement sufficiently that they should be taken seriously.

    rated range does NOT vary seasonally. The battery’s ability to take a charge can be impacted by cold weather, but that’s maybe 1-2% at most.

    it is correct that kWH is the metric that is warranted, but rated range @ 100% x appropriate wh/mi constant should be darned close, so nothing wrong with using rated range as a proxy.

    this is maybe the 100th thread by a relatively new owner consternated at first year degradation, incorrectly assuming that will continue straight line, confused by the lack of definitive info from Tesla, and worrying unnecessarily. I’d recommend researching degradation curve. That should put everyone’s mind at ease. It should be a WIKI that is required reading for all members before allowing a degradation post.
     
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  12. Msjulie

    Msjulie Active Member

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    For some yes, some other lucky folks have lost (seem to) have lost more, especially if we're using the "old" numbers of all Model 3 LR getting 310 miles..
     
  13. ewoodrick

    ewoodrick Well-Known Member

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    5% is a pretty decent settling down number.
    But I suspect with some battery condiinicond that it can be higher.

    Stop worrying about it
     
  14. MP3Mike

    MP3Mike Well-Known Member

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    As far as I know the new range rating only applied to the 2020 Model 3s. They didn't retroactively change the rating on older cars.
     
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  15. AlanSubie4Life

    AlanSubie4Life Efficiency Obsessed Member

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    The erratic nature is due to temperature and TeslaMate using the incorrect SoC (there are reasons to use it but not for projecting 100% with a warm battery). But your battery is at 360km.

    This works out to 49kWh. The test article Tesla used when they did their testing had 54.5kWh. Yours may have started with 53kWh or so (no idea). So 7.5 to 10% loss of capacity depending on how you want to look at it.

    As others have said, the loss of capacity will likely slow down a lot now.

    Expect 10% loss of capacity as a good rule of thumb. That is normal and not a big deal. EVs lose significant capacity! It is as certain as it is that the sun will rise. There is nothing you can do about it but expect it and plan your purchase accordingly.
     
  16. jedi2b

    jedi2b Member

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    Well, i'm not worried, I just want to understand how can I, a regular customer, know when and if the battery of the car goes past the threshold the vendor set for warranty.

    This is what Tesla has to say about the displayed range:
    Range

    "Displayed range in your Tesla is adapted based on fixed EPA test data, not your personal driving patterns. It’s natural for this to fluctuate due to the nature of battery technology and how the onboard computer calculates range."

    So is there a reason this displayed range can't be used as a measure of battery health?
     
  17. AlanSubie4Life

    AlanSubie4Life Efficiency Obsessed Member

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    As long as it is not cold, nope, no reason at all you can't use it! I'm not sure why people are up in arms about using an inaccurate method, though they may have been taking offense to your concern about cold weather measurements (which cannot be relied upon because there is less energy available from a cold battery but it is only temporary). This method of using rated range is possibly optimistic if your car still displays the max rated range (some initial degradation may be hidden), but once it drops below that max rated range (which is when you would start caring), it is perfectly acceptable to use. For maximum accuracy, you should really charge to 100% (or at least 90% - but there is about 3-4 miles of uncertainty at 90% if you are not careful to get the decimal point on the SoC (which is not visible)). But 90% is obviously going to get you to within about 1% of the correct value.

    For your SR+, it's ~219Wh/rmi/1.6093rkm/rmi*360rkm = 49kWh

    As I said, your original question: "What is the starting point?" Is a good one. You might think it is 219/1.6093*380 = 51.7kWh, but I believe that is too low (the EPA test vehicle was 54.5kWh for the 2019 SR+).
     
  18. jedi2b

    jedi2b Member

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    Thanks foir the analysis.

    I have used other means to estimate the battery capacity, and I reach the same conslussion as you: my cars has between 49 and 50Kwh of battery capacity as of now: TeslaMate shows, for each supercharging session, the start SoC, end SoC and KWh charged to the battery. Going thru several charging sessions I get, extrapolating, 49-50 KWh total capacity as of now.

    Regarding the starting battery capacity, it appears Tesa published the real number a while ago:
    Tesla, TSLA & the Investment World: the 2019-2020 Investors' Roundtable
    TL;DR : Essentially 54,5 KWh for SR+

    So my degradation as of today, seems to be around 9%

    To circle back to my original question, and comparing to the 9% just obtained:
    -360km reported/380km EPA = 5.3% degradation (too low)
    -360km reported/402km NEW EPA=10.4% degradation (a bit too high, but nor bad)

    So, as far as I can tell, taking the displayed range and dividing it by the new EPA (402km), is a decent quick indication of battery degradation
     
    • Disagree x 1
  19. OCR1

    OCR1 Active Member

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    I think the OP’s question is a good one, and I’m not sure any of us have the answer. Warranties are often written in such a way that they are easy for the manufacturer to wiggle out of having to cover anything because they have so many exclusions or gray areas as to what they are responsible for.

    It would seem to me that comparing the KwH of a brand new car to a car with a warranty claim would be the most logical way to measure degradation. But Tesla does not state what the KwH capacity of their battery is in the warranty section, so it’s not clear what they are using as a baseline to measure with.
     
  20. Fresnel

    Fresnel Member

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    Might be worth asking someone who has actually gotten the battery replaced under warranty to get accurate information. Search on youtube. I don't remember his name but there's a guy that posted a video about him replacing his battery for being under 70% under warranty
     

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