Tesla Model S Battery Degradation

Discussion in 'General' started by Carcus, Apr 4, 2017.

  1. BillLin

    BillLin MASS: 2018 Bolt EV and 2017 Prime

    I'm glad Tesla has thought of these high/low temperature storage/parked issues.

    I think this is getting awfully complicated. How does one trade off keeping the car fully charged (bad for storage and battery longevity) and plugged in to keep the battery properly heated/cooled versus keeping the battery moderately charged for long term durability? The BEV manufacturers are going to have to design the system to survive the battery's expected life expectancy with "normal" use. I don't see how "they" can void warranties for the BEV not being plugged in all the time, as that is not reasonable to ask of BEV owners.

    One way this might work is to require the always-plugged-in model of usage and to design excess capacity in the battery to never be used. Maybe when batteries get cheaper and more energy dense? Or the battery chemistry will change and this hot/cold thing will not be a problem.
    RedylC94 and Carcus like this.
  2. Carcus

    Carcus Well-Known Member

    Interesting study here on LifePo4 batteries. Particularly on pgs. 129, 130, fig 85, 86. Highlights the effect of heat and calendar aging. In a hot climate (Tampa) the calendar aging is the primary degradation factor. In the Waterloo car, the calendar (because it wasn't sitting in the heat so much) was less important than the cycling.

    Both cars (hot, cold/ Waterloo (CA),Tampa) had a tough time making it to warranty (i.e 8 years in an auto) .. The Tampa car tapped out significantly earlier. Even if you allowed for a 40% degradation, the Tampa car would be done at about year 7. The Waterloo might make it to 10.


    maybe this shows why Tesla will sacrifice some cycling (phantom draw) in order to keep the batteries cool in the hot parking lot to limit summertime calendar degradation -- artificially turning every car into a "waterloo car", no matter where it's parked.
    Last edited: Jan 30, 2019
  3. RedylC94

    RedylC94 Well-Known Member

    By running a compressor, or only fans? That doesn't seem like a workable solution for long-term parking in the hot lot.
  4. Carcus

    Carcus Well-Known Member

    Pretty sure it’ll run the compressor.

    /could revive the old prank phone call: Is your Tesla running?
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  5. EdwinTheMagnificent

    EdwinTheMagnificent Legend In His Mind

    I just had to run out in the parking lot to see if the Prius was running.
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  6. Carcus

    Carcus Well-Known Member

    The daily cycle on the Waterloo/Tampa simulation was "at 30oC from 10% DOD all the way down to 90% DOD" (p. 126, fig. 81). This is far deeper cycling than most Teslas will encounter on a daily basis. The typical Tesla degradation due to cycling might be far less (1/2 or 1/4 , .. even less?)
    BillLin likes this.
  7. Carcus

    Carcus Well-Known Member

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  8. EdwinTheMagnificent

    EdwinTheMagnificent Legend In His Mind

    Looks like "Big Brother" Elon is watching over ( controlling ) us.

    At least Yota doesn't get into my car's software unless I bring the car to them.
    BillLin likes this.
  9. Carcus

    Carcus Well-Known Member

    .... and that may not be the only advantage Toyota has over Tesla ...

    "Now, as we revealed earlier this month, Toyota plans to reveal a car powered by solid state batteries ahead of the Tokyo Olympics next year, and although it may not be production ready, we can’t imagine Toyota ‘Doing a Tesla’ and showcasing something that’s effectively ‘vapourware’."

    "......it looks like Panasonic has now woken up and smelled the move from Toyota, entering a joint venture with Toyota earlier this year to deliver next-gen batteries and is going cold on Tesla, declaring it would make no further investment in Tesla’s Gigafactory.

    All of which could signal a forthcoming perfect storm of problems for Tesla."

    Will Toyota’s Solid State Electric Car Battery be Tesla’s Nemesis?

    Solid State Batteries: The Next Big Thing In Electric Cars

    /of course, we've heard these solid state battery promises before, .. but Toyota does appear to be jumping in with both feet (and several of the other Japanese auto manufacturing feet as well(partnering subaru, suzuki, mazda (plus Honda, Isuzu and others -- I think)). I'd say 'something' is afoot.
    Last edited: Jun 28, 2019
    BillLin likes this.
  10. Carcus

    Carcus Well-Known Member

    Anecdotal evidence: ---

    I have a few 18650 cells (unknown manufacturer, same size format as in Tesla model X,S) which are used for a bicycle headlight. 2 are 5 years old, one is 7 years old. All cells have been kept in a reasonable temperature environment for almost all of their lives (i.e. 55 to about 88 deg F), Not a lot of cycles on the cells (max of 40 per year would be my guess) sometimes going without use for months at a time (one torch, 3 batteries), stored at -- who knows what SOC? ( probably 50% to 100% SOC when not being used in the "torch").

    Tested recently from full to voltage cutoff. All three cells have very little degradation (less than 5%, I think**) with the 7 year old cell actually having the most remaining capacity.

    **not a full test with a battery charger, just testing with run-times.

    / so anyway, these 18650s used in this manner look like they could last for ---? I dunno ...20 years or more?
    Last edited: Aug 5, 2019
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