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Battery degradation or just goofed calculations?

Discussion in 'Model S: Battery & Charging' started by Trnsl8r, Feb 9, 2015.

  1. Trnsl8r

    Trnsl8r Blue 85kwh since 12/8/12

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    Question to the collective braintrust that probably has been asked before and will be asked again... Have my battery really degraded this much?

    With the new percentage indicator I've done some comparisons between that and rated range, after I noticed a fairly low range after a range charge yesterday:

    99% charge showed 252 miles of range (regen limiter pointing at about "4 o'clock")
    65% charge showed 166 miles of range
    49% charge showed 125 miles of range

    If you extrapolate these, they all show ~255 miles of range at 100%, where I would expect 265 miles.

    Background:
    S85: Have had the car since December 2012, has "A" battery, and driven about 35k miles. Done a fair bit of road-tripping and supercharging, probably four-five times a year, rarely done range-charging and I don't know if I ever actually finished a range charge (meaning I've always unplugged and drove off before it stopped charging).

    Is this battery degradation or is the meter just off its calibration, or is the battery pack unbalanced?
    If actual degradation, is this along what one should expect for this amount of use or is it "too much"?
     
  2. mknox

    mknox Well-Known Member

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    My March 2013 car with a bit over 41,000 miles and A-pack shows about 218 Rated Miles at 90% and about 242 miles at 100%. It was just in for service and I asked them about this. They said that Engineering checked the battery and determined this is normal degradation.
     
  3. scaesare

    scaesare Active Member

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    I haven't range charged in a long while.. but my weekday 70% charge is about 177-178 miles, and my 90% weekend sharge is about 228-229 or so. That's right around 255 for a 100% charge.

    If the thoughts that "complete" balancing may only happen at 100%, and it's been so long since I've done that, I guess I might have a few extra miles to be gained there and/or with the algorithm getting a chance to re-calibrate .
     
  4. ChadS

    ChadS Petroleum is for sissies

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    #4 ChadS, Feb 9, 2015
    Last edited: Feb 9, 2015
    The battery does not store miles, so the estimated miles on the display is not an accurate measure of your battery's capacity.

    9 months ago my Roadster's battery finished an 80% charge at 166 miles. Yesterday, it finished at 178. The battery did not improve, but rather there's been better balancing (charging to 90% or more) and more trips that dip near the bottom of the battery so the car's estimation algorithms can get a better sense of how much capacity is really there. It can also vary slightly with charging voltage, ambient temperature, humidity, strength of draw while driving, etc.

    You can expect to really lose a few miles of range fairly quickly, though. IIRC (from a chart on these forums about 2 years ago) the Model S chemistry loses a couple of percent capacity faster than normal at the very beginning, but then is relatively stable. The Roadster battery appears to maintain 80% or more after 100k miles and everybody seems to think the Model S battery will do better than that.
     
  5. Trnsl8r

    Trnsl8r Blue 85kwh since 12/8/12

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    I guess losing 10 miles is really only a ~4% loss over two years. Maybe I shouldn't complain...
     
  6. Benjamin Brooks

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    Basically in line with my typical numbers. S85 since Feb 2013, B pack, 28K miles. I figure it is real lost battery capacity.

     
  7. cpa

    cpa Member

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    A few others have suggested that you switch to "ideal" miles to get a better grasp of any battery degradation, as that algorithm it not as froggy as the one that calculates "rated" miles. Don't know if it is true or not, but I just thought that I would throw it out there.
     
  8. Saghost

    Saghost Active Member

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    I'm not 100% certain, but I've read that the various firmware updates have changed the 0 line, which would presumably also change the top end reporting as well.

    I'm not sure that there's a good way to disentangle Tesla's changes from battery degradation - or from battery unbalance.
    Walter
     
  9. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    In my opinion:

    1. Don't use daily charge as any kind of an indicator--only use range charge.

    2. Use ideal miles. It's easy to see that (at least in my car) rated miles/265 gives a different result from ideal miles/300. It's not much of a difference in my car, but it's not zero either.

    Of course, the only real way to tell is to run the car to zero and then do a range charge and measure how much energy was replaced, but that's likely to degrade the battery more, so it's not recommended.
     
  10. JohnQ

    JohnQ Active Member

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    Just as another point of reference, I have 28k on an 'A' battery delivered April 2013. 100% is 250, 90% is 225. Similar to your situation.
     
  11. Mario Kadastik

    Mario Kadastik Active Member

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    Well I noticed that going from 5.9 -> 6.1 that my typical range dropped 10km at 100%. I charged to 100% on 19th of January, got 6.1 on 24th and range charged the same day and again this week and I'm seeing now consistently 10km less at max charge, I've written to Tesla just an hour ago asking for clarification on this on wether the range has been moved below 0 or what happened?
     
  12. brianman

    brianman Burrito Founder

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    When listing your numbers, it's useful for current and future calibration to include the firmware revision reported by the car.

    As an example, my 90% rated range for all of 2014 was 221-223 mi (higher during CA driving than WA driving) whereas in January '15 (with 2.2.113 and 2.2.115 firmware) I'm seeing 235-241* mi. for my 90% rated range. My odometer is nearing 45k mi for my Nov 2012 delivered Sig P85.

    * I'm mostly seeing 235ish but I did see 241 once (43,957 mi., 48°F, Sun Jan 11, 6:09pm).
     
  13. mknox

    mknox Well-Known Member

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    That's a good tip. FWIW, my numbers do not seem to change even by one mile over software revisions, but have been on a downward trend overall.
     
  14. AmpedRealtor

    AmpedRealtor Active Member

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    Also, make sure you compare numbers with range mode OFF. Enabling range mode will bump up your estimated range by 3-4 miles.
     
  15. brianman

    brianman Burrito Founder

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    That was true for me until one of the flavors of 6.1 that arrived. So if you're on < 6.1 maybe it's something to hope for...
     
  16. mknox

    mknox Well-Known Member

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    Nope. I'm on my third flavor of 6.1 and each morning at 90% the Rated Range was exactly the same. I know others have seen bumps up or down when new firmware comes, but not me.
     
  17. Benjamin Brooks

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    Actually, I have seen range bumps on many of the recent 6.x releases, but they only last for one charge cycle. Rare is it that I've heard people get "permanent" higher range numbers directly correlating to FW updates, more often I've seen it due to raising the daily charge level to higher than was being performed (I.e. 70% to 90%)
     
  18. Alysashley79

    Alysashley79 Member

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    I just spoke to my SC manager and she told me that the algorithms in the % and rated miles is off between 60% and 80%. It's not displaying the correct mileage and is a known issue they expect to be fixed in 6.2.

    I had had called to ask where the sweet spot daily charging was because since we now have a % it's easier for me to know exactly what I use daily. The engineers have decided that 70% to 80% is the best place. But just keep in mind the rated miles may not display properly.
     
  19. mknox

    mknox Well-Known Member

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    I had heard that as well, and for most of last summer was charging to 70% and ending my day at around 30%. I figured playing in the center of the battery's range was likely the best approach. The problem was when I went to do a 90 or 100% charge for a trip I was taking, I found I had "lost" about 30 miles of Rated Range. I got about 5 miles of that "back" by charging daily to 90% and doing one or two very low to 100% charge cycles. I was not sure if my summer of 70% screwed up the car's calculation algorithm or if I did see some sudden degradation. Tesla ran some tests at my last service visit and said my battery is fine and this is just normal degradation.
     
  20. IceAge

    IceAge Member

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    I have the opposite experience. After the last 6.1 update, I gained more than 20 miles. Rated 90% was 224, now 245, and 100% is now 274, where it was previously 251 or so.

    A pack, 33,000 miles, Dec 2012 delivery.

    In the past, I've seen big jumps after a software update that disappear after the first charge/day, but it's been more than a week now, including running the battery down to 8 miles then charging back to 90%.

    I expect the range to go back down eventually, there's no way I should have more range now than when new.
    274.jpg
     

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