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.
     
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  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.

    https://uwspace.uwaterloo.ca/bitstream/handle/10012/12177/Catton_John.pdf

    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?)
     

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