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3.0 Battery Longevity

Discussion in 'Roadster' started by bolosky, Feb 14, 2017.

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  1. bolosky

    bolosky Member

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    I haven't, although I did do linear regressions for each of the lines here: 3.0 Battery Longevity and then a two-variable linear regression here 3.0 Battery Longevity. I should try the exponential, too.
     
  2. Kerios

    Kerios Member

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    Those comments about the Model S made me wonder whether there are similar date sets available for the S, particulary for those with batteries we think have similar chemistries to the 3.0 Roadster pack, additionally is there any data where packs have been replaced and subsequently had the performance/degradation mapped?

    If we could point to similar cells showing either a trend, or difference it might help our argument collectively if/when those with 3.0 packs need to make it...
     
  3. JRP3

    JRP3 Hyperactive Member

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    I don't think the Roadster cells are similar to any S cells.
     
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  4. gregd

    gregd Active Member

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    ...nor any other cells that anyone could find (if I recall the earlier discussion) being used in an automotive application. So, we're on our own here.

    That would be ok, if a) we knew it going in, and b) Tesla would engage with us to collect data on cell performance, etc. as part of a 2-way research project. 2-way in that we would be getting some benefit from that research down the line in the form of a yet better battery pack. Though, I think $29k is kind of steep to be charging a research subject.

    Perhaps I'm overstating the experimental nature of putting the cells into this application. After all, that's what the original car was, too. But given the data we're collecting, and the implications of it, I would certainly prefer to have a bit more engagement by Tesla in the matter. If the trend is primarily driven by time, and if it continues along the current slope, these cells won't last half as long as the original ones.
     
  5. JRP3

    JRP3 Hyperactive Member

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    I thought they were found to be quite similar if not the same as a NMC LG cell.
     
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  6. gregd

    gregd Active Member

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    Yeah, that sounds about right. So the cells are known and available, but when asked if anyone had used them in an automotive application, nobody could name one. That's what has me concerned, since the application can have significant impact on cell life.

    Countering that, if we are seeing calendar time being the major factor, the application probably isn't a factor, which is inconsistent with Tesla choosing them for this use. So, the more I think about this, the more confused I get.
     
  7. JRP3

    JRP3 Hyperactive Member

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  8. Mark77a

    Mark77a Member

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  9. bolosky

    bolosky Member

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    Updating with a couple of weeks' data for #33 (he did a long drive and had a step drop in his CAC) and mine (I ranged charged once and had a small gain). Also adding #2, which is an extreme case of low mileage. It hasn't been driven even a tenth of a mile since July, and has 109 miles in 414 days since upgrading an essentially new original battery (CAC 156.4). It looks like a real outlier on the days graph, but it seems like the CAC algorithm doesn't run unless you drive the car some, which isn't happening. The CAC hasn't changed at all to seven digits precision since 12/8/2016 at 56.8 miles on the new battery. So, I'm not sure we learn much except that not driving means not updating the value. My guess is if it went out and drove a few hundred miles that we'd see a gigantic step drop in CAC to ~200.

    CAC vs. Mileage.jpg CAC vs. Days.jpg
     
  10. bolosky

    bolosky Member

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    Just for reference, here's the latest update date, days on 3.0 battery and miles on 3.0 battery for each car:

    # Date Miles Days
    670 1/20/18 25,461 463
    181 1/5/2018 16,241 512
    33 1/18/2018 6,256 522
    425 10/11/17 7,308 460
    537 7/12/2017 4,407 455
    660 10/20/17 2,422 335
    330EU 10/2/17 1,268 102
    277 9/30/17 4,679 125
    255 11/30/17 2,626 134
    707 9/24/17 406 125
    209 11/3/17 3,273 223
    541EU 11/4/17 1,528 240
    2 1/13/18 109 414

    [I formatted this nicely as a table, but the forum software is taking out the multiple spaces and making it look bad. I'm sure there's a better way to do this, but I don't know how. Mods: if you feel like fixing this, be my guest.]
     
  11. supersnoop

    supersnoop Tesla Roadster #334

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    Wrap it with the code tag. See above.
     
  12. dpeilow

    dpeilow Moderator

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    A friend brought this thread over in the Model S section to my attention: Early 75/75D pack degradation

    It seems @wk057 has found evidence of accelerated battery degradation in some of the 75 and 90 kWh packs. Is there any likelihood of a link to what we are seeing on the 3.0?
     
  13. JRP3

    JRP3 Hyperactive Member

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    I don't think so, different cell manufacturer and different cell chemistry, from all available evidence.
     
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  14. twiersum

    twiersum Member

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    I'm curious if anyone is seeing a related decrease in actual range or is it just the CAC? IE you could drive 300 mi and have 30 left before, now the CAC has dropped but if you drive 300 mi do you have any range left?
     
  15. dpeilow

    dpeilow Moderator

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    Yes I have seen a slight range decrease in proportion to the 3 point CAC drop on my car.
     
  16. Marius

    Marius Member

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    David,
    You have a remarkable pack, it is already more than 7 months old and only 3 CAC points down. Do you know what they fiddled around with your electronics at the beginning because first you started with CAC 205 and then it was altered to the promised 215 and now it does not decline.
    All the others decline more rapidly
     
  17. twiersum

    twiersum Member

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    What about those of you that have dropped to 185? What real world range are you getting?
     
  18. bolosky

    bolosky Member

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    After range charging yesterday, I got this. I fear I may have seen the last of the 300 mile ranges.

    In terms of real-world range, who knows? I haven't driven it to empty, and that depends so much on conditions, route, driving style, etc. that it's hard to measure. My informal observation is that it behaves pretty much like it always has, getting somewhat less than one real mile per ideal mile unless you're painfully careful. That is, it's not acting substantially better or worse than ever, and as far as I can tell the ideal range is still an accurate estimate of the useful energy in the battery.

    Roadster Range.jpg
     
  19. dpeilow

    dpeilow Moderator

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    I don't think there were any electronics changed, from the log files it looks like the same firmware was reinstalled.
     
  20. Marius

    Marius Member

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    So, it could be a nice option to have Bolosky ask the SC to reinstall his firmware as well and see if this gives him back some CAC points?
     

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