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
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  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.
     
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  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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  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.
     
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  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?
    https://www.carsuk.net/will-toyotas-solid-state-electric-car-battery-be-teslas-nemesis/

    Solid State Batteries: The Next Big Thing In Electric Cars
    https://oilprice.com/Energy/Energy-...ries-The-Next-Big-Thing-In-Electric-Cars.html

    /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
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  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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  11. Carcus

    Carcus Well-Known Member

    In-depth video:
    youtube: battery degradation scientifically explained
     
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  12. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Carcus:

    Your 18650s have a far less harsh duty cycle than any automobile battery would ever see. I am considering temperature and especially current flow in and out.

    From all that you have posted so far - fascinating reading by the way, it appears the only real solution for BEVs is larger packs (raw kWhs) with far less usable capacity. Most HEVs and PHEVs with thermally controlled packs seem to have the solution locked in with a 30% to 90% bottom to top spread and all kinds of current limits allowing 10 years or more of every day use?

    Wayne
     
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  13. RedylC94

    RedylC94 Well-Known Member

    Yes. It's also a lot easier to contrive cooling of a small pack than a large one, even when cell size is identical.
     
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  14. Carcus

    Carcus Well-Known Member

    That's kind of the way it looks. All though I might think the smaller (city) BEVs may (eventually) make up a larger part of the BEV market until battery tech improves**. iow, those in high gas price markets (europe) or govt mandated markets(china)may just give up on long range BEV travel and accept (buy in volume) them as city cars (not acceptable for operations outside of a range of 1 public charge (?)) -- to be kept in a under 200 mile radius or so (?)

    More on longevity: The longest running group we have of thermally controlled 18650s is the Roadster.

    From a nice video: youtube: Tesla roadster everything you've wanted to know (technical) part 2 gruber motors 13:15/28:47
    (I'm surmising % with the roadster range listed from wiki as 244 mi)
    Roadsters are 7 to 11 years old.
    remaining capacity of:
    more than 82% (200 mi) = rare
    57%/61% to 72% (175 to 150/140 mi) = most (my guess is that they got close to the end and the owners decide to mostly store them -- garage queen, driven very infrequently)
    less than 53% (130 mi) Over 100k miles driven = rare

    LOTS of other info in that video

    ADD --
    **it's rumored that the new roadster may incorporate maxwell dry cells (super capacitor) to handle the high current loads --- working along with "traditional" lithium (i.e. taking the high load stress off the traditional)

    "Applications
    The supercapacitor is often misunderstood; it is not a battery replacement to store long-term energy. If, for example, the charge and discharge times are more than 60 seconds, use a battery; if shorter, then the supercapacitor becomes economical.

    Supercapacitors are ideal when a quick charge is needed to fill a short-term power need; whereas batteries are chosen to provide long-term energy. Combining the two into a hybrid battery satisfies both needs and reduces battery stress, which reflects in a longer service life. Such batteries are being made available today in the lead acid family."
    https://batteryuniversity.com/learn/article/whats_the_role_of_the_supercapacitor
     
    Last edited: Aug 19, 2019
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  15. EdwinTheMagnificent

    EdwinTheMagnificent Legend In His Mind

    Hey , has anyone else seen Elon's home movie/SpaceX commercial on Netflix ? It's called "Mars". it's a commercial disguised as sci-fi drama.
    still , kinda interesting.
     
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  16. Carcus

    Carcus Well-Known Member

    I'll look for that. He's certainly got an interesting perspective on Mars.
     
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  17. S Keith

    S Keith Well-Known Member

    It's good. The drama is a little contrived and overdone in some ways, but it's entertaining.
     
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  18. EdwinTheMagnificent

    EdwinTheMagnificent Legend In His Mind

    I admit that when Elon talks , I listen. Neil DeGrasse Tyson , also.
     
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  19. Carcus

    Carcus Well-Known Member

    Sometimes you can ask Quora, ... and get a pretty decent answer:

    What is the charge/discharge cycle durability of Tesla's 2170 cells?
    "Panasonic’s 2170 and 18650 chemistries are very similar, probably identical. Data is very scarce, but early Model S and X batteries have died at 600-800 cycles. Tesloop’s first Model S battery died at 200k miles which is roughly 800 cycles. Sean Mitchell’s Model S 60 died at 130k miles, or 600 full cycles. Bjorn Nyland’s Model X battery died at only 66k miles, which was 500–600 cycles of hard use (towing heavy loads up mountains, playing tug of war with large SUVs, etc.).

    Tesloop later bought a small fleet of Model Xs. I don’t think any batteries failed even though two reached 300k miles and another 4–5 hit 200k. These cars were made around the time Tesla starting talking about adding silicon to the anode. That may or may not have improved cycle life."
    https://www.quora.com/What-is-the-charge-discharge-cycle-durability-of-Teslas-2170-cells

    -------------------
    One thing to note on the tesloop cars. They are probably running at a decent speed day and night (?) like a chauffeured Service running in-between airports would. So their average speed (and cycle times) might be different by a factor of two compared to your typical commuter (twice the speed, half the cycle time). -- which would put them in the "beating the clock" category that Jeff Danh talks about. I might also wonder if the battery cooling is more effective with good airflow on the highway as opposed to idling in stop and go traffic.

    iow,.. i'm not sure the tesloop high mileage cars are going to be very representative of the kinds of cycles (and heat cycles) that your average tesla owner will put his car through.
    -----------------------
    Why do lithium-ion batteries die? (long)
    "So this blue data is the 60-degree data I showed you on the previous slide and the red data is what happens if you go much more slowly. The time a each cycle takes is much longer.

    The the point is that you get a lot of capacity loss per cycle number when you go slow at high temperature because there's chemical reactions going on in the cell that are bad. And when you do charge discharge rapidly, all you're doing is beating the clock. You're beating the clock on these temperature-dependent times (time-dependent parasitic reactions.)"
    https://batterybro.com/blogs/18650-...3090502-why-do-lithium-ion-batteries-die-long
     
    Last edited: Aug 21, 2019
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  20. Carcus

    Carcus Well-Known Member

    If you start to think about aaaaaaallll the different variables that the owners are putting their Teslas through, then add in that Tesla is running different batches of batteries through the cars, different software that controls the car and the charging (and that programming seems to be changing (through OTA updates) frequently) ..... it's not surprising that the Tesla Length of Life appear to be quite varied. When you buy a Tesla you're sort of signing up to be part of the science lab.

    /add ,.. reading the Teslamotorsclub forum, ... capacity degradation seems to be an indicator, .. but not a very good indicator of how much life the battery has left. Rising internal resistance is as big or bigger tell --- so once the car starts to show weak acceleration, .. that's the real indicator that you're about done, ... but that comes on pretty quick.

    //iow, if you're buying a used Tesla, the "charge to full and check the range indicator" will tell you a little, but not a lot.
     
    Last edited: Aug 21, 2019
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