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A senior tesla executive's comforting answer to concerns re: "loss of range"

Discussion in 'Model S: Battery & Charging' started by Super Gizmo, Mar 26, 2014.

  1. Super Gizmo

    Super Gizmo Member

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    We contacted Jerome Guillen VP, W W Sales & Service yesterday regarding the loss of range on our and many others' Model S and what the solution was. To our pleasant surprise we received a prompt reply from him today which should allay everyone's concerns regarding this issue which has generated several threads on this and the other forum. We decided to post his reply on the forum to help ease everyone's worries and bring back the "Tesla smile". So, here is his reply to our query -

    Thank you for your message and bringing this concern to my attention.

    Recently, some Model S owners have been concerned regarding displayed decreases in their vehicle's predicted range. We understand the importance of accurate range prediction, and have taken these concerns seriously. After investigating many of the cases, we have found no indications of actual battery problems in the vast majority of these cases. However, we have uncovered a software problem that, under certain charging conditions, yields incorrectly low range estimates over time.

    The range estimate displayed in the vehicle is based on several different factors. One important factor is the battery's actual capacity at a given point in its life. This is the amount of energy the battery can hold when fully charged. Since battery capacity cannot be measured without fully charging and discharging the battery, this value is calculated in software. We have found that in cases where the battery is consistently charged to a lower state of charge- between 60-80% -capacity estimation becomes less accurate and tends to underestimate the true capacity of the battery. The result is an incorrect reduction in the displayed range estimate. This does not affect the true range of the vehicle, as the end-of-drive conditions are based on real-time battery measurements of reducing battery power rather than software estimates. In any case we recognize the inconvenience and negative user experience associated with this incorrect and reduced range estimate and we are developing a solution.

    The inaccuracy of the capacity algorithm will show up in any Model S that is regularly charged under the conditions mentioned above (it seems it is the case for your Model S). We will develop and implement a firmware updates in the coming weeks (timing TBD) to address the concern you outlined. That being said, the amount of actual energy stored in the battery has not changed. The physical distance you can drive the vehicle from full to empty remains the same, only the displayed estimate has changed. You are correct that avoiding charging to high states of charge optimizes battery capacity retention. You should continue this behavior as best meets your daily range needs. We also recommend opportunistically charging, i.e, charge frequently, charge often. Avoiding deep discharges is another best practice for optimum capacity retention. The advice by the Service Center to "let the range drop down to about 20 miles and then charge it to max Daily Range" is misleading. They are correct that it will mitigate the inaccuracy of the capacity algorithm, resulting in a higher displayed range, but it is misleading as the actual amount of stored energy does not change.

    I hope that this addresses your concern. Please let me know if I can be of any additional assistance.

    Thanks for your continued support. Best regards,

    Jerome Guillen I VP, WW sales and service

    P.S. By the way we installed 5.9 last evening prior to a max Daily charge and noticed an increase of 12 miles immediately!
     
    • Informative x 1
  2. Odenator

    Odenator P2607

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    So if Jerome is correct, and he understands what his engineers are telling him, is he saying that I could have driven more than 40 miles past 0 rated miles as displayed on the battery bar based upon the apparent loss of range as assumed to be from an unbalanced pack (264 miles - 231 miles + 15 hidden miles)?
     
  3. Doug_G

    Doug_G Lead Moderator

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    I would not leap to that conclusion. Actual driving distance depends on power draw and battery state. If you drive fast and draw more than about 280 Wh/mi, you're not going to get the full rated range of the battery - no matter what it displays.
     
  4. brianstorms

    brianstorms Member

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    If I drive like a saint, observing the speed limit and carefully accelerating and so on, no matter what I do, I get over 300Wh/mi.
    I don't think I've ever been able to get it below 300 for any length of time.

    I mostly drive local, and it's hilly. I had the same problem with ICEs: I routinely got 10-12mpg on cars rated 18city 23highway.

    All that said, I'm eager to see if the new changes Jerome mentions will improve my rated range. I always charge to about 120-150mi of range, so I keep the battery essentially at one-half full. Only on long supercharger drives do I either max out, or, more often, charge to around 200mi. I suspect this puts me in the use case Jerome describes.
     
  5. Kraken

    Kraken Member

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    So all this seems to jive with what I've been saying in the other thread. It also seems to explain why the actual battery symbol in the past (pre 5.9)seemed to indicate that there was quite a bit left (maybe 40 miles of rated range) even though the numbers were near 0.
     
  6. rcc

    rcc Model S 85KW, VIN #2236

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    I'm sure it does. You also want to think about how deeply you discharge the battery. The battery will probably be happier if you charge to 80% and draw down to 40% than if you charge to 50% and draw down to 10%.
     
  7. jaenoh

    jaenoh New Member

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    So, deep charging gives you more accurate (increased) measure of the range but the real range goes down because the deep charging is not the method for "optimum capacity retention"?

    Kinda ironic...

    I wonder how much of this inaccuracy is fixed by the 5.9.
     
  8. Martini

    Martini Member

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    No because of this: as the end-of-drive conditions are based on real-time battery measurements of reducing battery power rather than software estimates.

    The displayed range estimate at low levels probably relies more on this than on the software estimate. The inaccuracy will be only at high states of charge.
     
  9. VolkerP

    VolkerP EU Model S P-37

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    Exactly. You can measure if a battery is nearing empty because the voltage approaches the lower discharge limit. You can measure the voltage approaching the upper limit when charging the car. But you cannot measure the amount of energy contained in a battery. It requires software guesswork depending on charge current measurement and a lot of other factors. That is the area affected by the FW fix announced by Jerome.
     
  10. ThosEM

    ThosEM Space Weatherman

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    I submit that Tesla should calibrate and monitor the battery capacity in absolute energy units.
    This business of introducing a rated range between owners and the real capacity of the battery just introduces confusion and uncertainty regarding the time evolution of battery capacity. I suppose it does provide Tesla with some wiggle room, but I'm not sure I want them to have that. I'd prefer that we mutually agree on what the best interpretation of battery state is at any given time, without questions about software that implements a range calculation.
    FWIW...
     
  11. scaesare

    scaesare Active Member

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    Wow... your terrain/conditions must be really working against you. During warm weather I've taken several road-trips here in the mid-Atlantic region and managed overall averages in the 270-280's while driving 70+ on highways...
     
  12. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    I have the same problem. I live in a rural area, about 2 miles from the state highway, and it's hilly with turns. The first 2 miles and the last two miles always come out @ 400-500 Wh/mi, unless you're driving < 40 mph and trying to baby it. The small villages spaced out on the 55 mph two-lane create the need to accelerate for about 3-4 miles then slow back down to 30-35 mph for a mile or so.

    I can generally make a long trip turn into ~280-300 Wh/mi, but the short 15-30 mile trips always come in at ~350ish.

    EDIT: I'm happy to see there is knowledge of what is happening. This affected the people who charged to 90% too, although it was very minor (recovering maybe 1-2 mile when a trip allows for recalibrating). Anything we can do to get the estimates better!
     
  13. yobigd20

    yobigd20 Well-Known Member

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    gee, this is the exact same thing I've said time and time again on those many threads. I guess because I'm not a "Tesla executive", nobody believes what I was saying as true. Now you have your official answer which is the exact reiteration of everything I've said. Thank you.
     
  14. Kraken

    Kraken Member

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    The typical way to doing this is a percentage of battery (think about how your cell phone shows that). We've seen images suggesting that they might do that in the future, but they were trying to give us something more practical.
     
  15. bonnie

    bonnie Oil is for sissies.

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    I don't think it's personal. I think people were looking for an answer from someone within Tesla who could speak from fact, rather than speculation (no matter how reasonable the speculation seemed).
     
  16. scaesare

    scaesare Active Member

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    I'll point out that even if using "absolute energy units" (I assume you mean Wh...), determining S0C anywher other than "empty" or "Full" is still an exercise in estimation. Displaying "52.7 Wh remaining" is not necessarily accurate.

    Your point about not introducing yet another estimate on top of that one (mileage) is well taken, however. I'd support user-selectable options for displaying pack capacity estimates in Wh or percentage...
     
  17. dennis

    dennis P85D

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    #17 dennis, Mar 27, 2014
    Last edited: Mar 27, 2014
    But now you have confirmation that you are smarter than everyone else (at least on this topic). :biggrin:
     
  18. yobigd20

    yobigd20 Well-Known Member

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    sorry, I'm a bit grumpy today. Just getting over this stomach bug that's been going around that really knocked me down for a few days.
     
  19. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    The problem with using a percentage is this: a percentage of what? Original design capacity? Or last known full capacity of that battery?

    The former provides a way to estimate "miles per % of battery at a given Wh/mile", but means that on a range charge, it may only show 82% when "full" with degradation.

    The latter provides a true indication as to the relative percentage of charge left, but the number of miles you'll get out of a % of the battery will begin to vary. This is what we get with cellphones, when people start saying that their phone seems to be sucking more and more juice over its life. 20% comes much more quickly.

    Knowing absolute energy units isn't useful to me because I have to do units conversation to tell how far I can drive. This is why rated miles, as flawed as they can be, is more useful. Knowing the battery has 57 kWh of power left doesn't really tell me how far I can go. I can learn over time, of course, but it's easier for me to know that 150 rated miles is roughly 140 miles for me in summer or 120 in winter, because I'm using the same units, rather than learning that 50 kWh roughly means 130 miles.

    Think about how you use the fuel gauge in an ICE. I used a combination of the fuel gauge to give me a rough indication of where I was fuel-wise with the "miles to empty" calculation to advise me when to stop.

    YMMV, of course. Scientists and battery engineers and die-hard technophiles have the ability to think about this constantly. I, unfortunately, have to constantly worry about having duct tape on hand so the little knowledge I have won't fall out of my head.
     
  20. roblab

    roblab Active Member

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    But I said it months before! So *I'M* smarter. Oh, well, you people will learn, someday:smile:
     

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