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40kWh Model S Battery degradation?

Discussion in 'Model S: Battery & Charging' started by ratsbew, Feb 22, 2016.

  1. ratsbew

    ratsbew Member

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    Since the 40kWh Model S uses a 60kWh pack that is software limited, is Tesla keeping the SOC right in the heart of the sweet spot so that there is practically no wear on the cells? Is there any data out there about lost range on the 40s?
     
  2. apacheguy

    apacheguy Sig 255, VIN 320

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    Yes and no. The 40 only charges to 69% SOC which is well under 4 V per cell. Trouble is that the 40 never top balances.
     
  3. Sogorman

    Sogorman Member

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    Rumor has it that the SC will do a 100% charge (of the full 60kwh) for you during your annual service appointments if you request it.
     
  4. sorka

    sorka Active Member

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    Geez, with all the recent hacking, you'd think someone would have figured out how to turn a 40 into a 60 or at least allow it to charge to 150% (100% charge of 60).
     
  5. deonb

    deonb Active Member

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    The 40 is literally a 60 where you can't move the charge slider above the 70% mark. They don't even have a different UI for it. So it never shows 100% normally.

    If you somehow did managed to charge it to 60kWh, it would then be at 100% - not 150%.
     
  6. sorka

    sorka Active Member

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    150% in software relative to it's 40kWH maximum.

    Has anyone tried setting it to higher than 100% through the REST API?
     
  7. deonb

    deonb Active Member

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    Again, it doesn't report 100% anywhere. Not in the UI. Not in the phone. Not anywhere. You simply have a battery which you can't fully charge. Other than that one upper limit on the set, the car thinks it's a 60.

    So the challenge through the Rest API won't be to set it at 101%, but to set it at 71%. The phone definitely doesn't allow you to set it at 71%.


    I can't imagine anybody at Tesla being so stupid as to put that check in the UI instead of on the server, but it's worth confirming. And if they really did that, we should seriously ourselves if we trust a company who would do something like with the software that is between the accelerator pedal and the motor?
     
  8. MP3Mike

    MP3Mike Active Member

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    At least one of the hackers has said that he could change a 40 into a 60, but he wouldn't if they hadn't paid for it.
     
  9. sorka

    sorka Active Member

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    So you're saying that the UI only reports 69%? So it doesn't map 69% of actual charge to 100% of virtual charge? Is that done as a constant reminder that they could upgrade?

    Has anyone tried to set it to 100% through the API?
     
  10. MP3Mike

    MP3Mike Active Member

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    I would assume that they put the restriction in the car itself, not in the app and/or server.

    - - - Updated - - -

    They probably did it that way because it was easy and required very little work. I suspect it gets much more complicated if you were to virtualize it.
     
  11. sorka

    sorka Active Member

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    From a daily driving standpoint, there's not a 20kWH difference between the 40 and 60. You wouldn't change a 60 up to 100% every day but rather 80 or 90%. But there's no reason not to change up to 69% every single day. Interesting.
     
  12. PhatGloves

    PhatGloves New Member

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    All,

    I just spoke with Tesla by phone regarding a drop in mileage from 176 to 162, this happened within the past few days...was told this was due to a recent update to reflect a more "accurate total EPA adjusted mileage" however am still upset my Model S losing almost 15 miles...


    Anyone experience something similar?
     
  13. SabrToothSqrl

    SabrToothSqrl Active Member

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    Well, technically speaking you didn't lose anything. It's just a number on the dash. I wouldn't worry about it. It's not like they made your range less, just changed the display a bit. Hopefully it's more accurate. It sucks, I agree, but I'd wager those miles were never really there.

    I felt a bit mislead at first when I bought mine in Feb. cold kills range, and before buying I don't think I knew that 90% was the 'standard' charge...

    just drive it :)
     
  14. fluxemag

    fluxemag Member

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    After the most recent update, my rated range went from 130mi to 125mi. I don't think this has anything to do with the actual usable energy in the pack, since I'd be lucky to get 110 miles on a charge anyways (at 300Wh/mi). This was true even when my car was new and rated range read 145mi. Those miles were never really there.
     
  15. okashira

    okashira Member

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    I have never reversed the tesla BMS nor fiddled with a 40 pack, but I can say with great certainty this is not true. I am sure the 40 is balanced just like the other packs.

    It would be trivial to mod a 40 to charge it to 100%. Just run some wires right to the pack terminals and hook up your own external charger, and pray the car's BMS doesn't freak out. :-D
     
  16. apacheguy

    apacheguy Sig 255, VIN 320

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    There was evidence in the hacking thread from a 40 owner that his pack does not top balance. How else do you suggest they balance if they never reach the CV charging phase?
     
  17. dragyoul

    dragyoul Member

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    The objective of cell balancing is to keep every cell at the same voltage level. Being so, you can balance the cells to 3.9 Volt if you want to. It is not an actual recommendation if you want to optimize lifetime of your battery (always better to balance at 100% SOC), but it is much better than no balancing.
     
  18. apacheguy

    apacheguy Sig 255, VIN 320

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    Unfortunately, Tesla appears to only top balance. We learned this from wk.

    Having said that, all of my bricks are within 6 mV of each other and I rarely charge to 100% so it's possible something changed.
     

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