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Failed range calculation left me stranded

Discussion in 'Model S: Battery & Charging' started by Twiddler, May 17, 2018.

  1. Twiddler

    Twiddler Member

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    So I am on my way home with a reasonable amount of range in excess of my destination (home). Not excessively hot, dusk, normal driving conditions. I have roughly 6 miles of range left for my 2.5 miles remaining when I get a warning that the vehicle is shutting down, and I end up stranded 1.4 miles from home with 4 miles of range reading. Outside temp 76F. How is this not an error on the vehicle's part? I get that you cannot rely on there being excess range after zero, but now you cannot trust that the range provided is accurate?! How can one trust the vehicle at all? I am no stranger to dealing with these cars, and have put over 100K miles between our Model S and Model X, but in my opinion the inability of the car to accurately represent it's remaining range is unforgivable. I hope that Porsche does it better, because Tesla just lost a former fanboy.
     
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  2. TexasEV

    TexasEV Well-Known Member

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    It’s no different “now”, you never could trust that the range is that accurate. Battery state of charge can not be measured directly. In any car, even a Porsche. It’s always an estimate, and it can be more or less accurate depending on how you’ve charged recently. You just shouldn’t be cutting it that close. Sorry, I don’t agree that you had a “reasonable amount of range in excess of your destination”.
     
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  3. McRat

    McRat Well-Known Member

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    We had a pickup that done that. Yup. Said it had some fuel left. Then it got me.

    Worst day of my life. Took her out behind the barn and put a bullet in her radiator while the kids were at the neighbors. I still miss the old gal.

    Son, once a car bites you, you gotta put it down. It just ain't safe to have it around kids.
     
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  4. tpham07

    tpham07 Active Member

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    I mean I've run out of gas in ICE vehicles where I swore the needle was not on that E.

    Have fun with the Porsche, and the lack of superchargers.
     
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  5. Twiddler

    Twiddler Member

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    Wow. A hyper-defensive, sarcastic set of responses. I am shocked.

    The range calculation should always be an underestimation. End of story.
     
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  6. commasign

    commasign Tesla Superfan

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    First I've heard of a Tesla shutting down before the zero. We know not to trust the listed range, but I too would have assumed a listed range of 6 miles would have been enough to cover 2.5 miles. I.e. if I was 2.5 miles from home and my range said 6 miles, and there was a L2 charger a block away, I would not stop to charge.
     
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  7. tpham07

    tpham07 Active Member

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    On a slightly more serious note, there have been MANY reports of owners being able to drive for a few miles after the rating says 0mi left. Funny how those people didn't complain about an inaccurate range meter. This is why most prefer to leave it on a % vs a rated miles scale.
     
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  8. silentsnow31802

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    If I was in ANY car I would not let it get that low. My butt puckers once anything says its below 40 miles left. Any range calculation is an estimate not a 100% sure thing. I thought everyone knew this?
     
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  9. Krugerrand

    Krugerrand Well-Known Member

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    #9 Krugerrand, May 17, 2018
    Last edited: May 17, 2018
    Why? So you can then say, ‘it’s okay, I can drive another 8 miles before I really hit 0’. And then come here to report it only went 7 below 0 and you got stranded again?

    How about just being reasonable and logical and not running the battery down to nothing? It’s just like driving a fossil fuel car, run it to E often enough and eventually you’re going to have to walk the rest of the way.

    Zero sympathy. End of story.
     
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  10. tpham07

    tpham07 Active Member

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    It is also well known and common knowledge that it is technically difficult to calculate how much usable energy is left in a battery. The science and technology behind measuring how much power you have left in a battery is shoddy at best. Combined that with a computer that has to extrapolate how many miles it thinks you can drive, that's asking for trouble.
     
  11. goto10

    goto10 Member

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    Calculating battery state of charge is not like measuring the amount of fuel in a gas tank. The only 100% accurate measurement is made by draining the pack at which point the value is no longer any use to you. Otherwise it's measured through indirect proxies like pack voltage, voltage change rate, delta between measured charge and discharge power, etc. It's like measuring how full a barrel of water is by listening to the sound when you bang on the outside or watching how fast it pours out when you open the spigot.

    Tesla does actually design their capacity reporting to attempt to over-estimate on the low end. There are many stories of people driving several miles past "0" but you can't count on it because it's just a (fairly accurate - relatively speaking) estimate. You were just unlucky to be a few miles off in the other direction.

    I sympathize with your frustrating experience, but now you know better about the state of battery capacity measurement so you're equipped to avoid this situation with future EV trips.
     
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  12. EVSteve

    EVSteve 110% Solar Powered

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    Let’s compare. How many of us would continue to drive an ice car if it said 6 miles of range left? Most wont even show a distance to empty below one gallon for this very reason.

    It’s also my understanding it’s bad for the cells to go below 10%? Correct me if my assumption is off. Why anyone would do this then complain when the car shuts down is beyond my comprehension. There were no places at all to put an extra kWh or two in the battery? Come on.
     
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  13. McRat

    McRat Well-Known Member

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    Somebody please correct me if I'm wrong:

    The battery computer looks at the voltages of all modules independently. The battery shutdown is based on the lowest module. Not all modules will read the same.

    The Guess-o-meter is based on the pack voltage.
     
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  14. Skysurfer

    Skysurfer Member

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    As lithium batteries age their internal resistance increases, which in turn reduces the amount of current which can be drawn from the batteries for a given voltage level. The battery pack has hard cut off limits for the voltage ranges, so to try preventing an early trip of the lower cut off voltage, Tesla puts a power limit in place at low charge levels. This helps but is not 100% fool proof, especially if you suddenly draw a lot of power or if a given module is weaker than others due to aging, then the cut off limit could potentially be hit earlier than predicted.
     
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  15. gsteele

    gsteele Member

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    I try not to even drive my 90D down to the point the range meter turns yellow. The is like the low fuel light in an ICE car.
     
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  16. tpham07

    tpham07 Active Member

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    Although I won't lie, I've driven my car down to 3 miles before. but if I ended up stranded, I wouldn't have been mad at Tesla since it was my own damn fault for bringing the car down that low, and I most certainly would've have thrown my arms up in the air and declare im buying a whole new different car after one incident lol.
     
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  17. commasign

    commasign Tesla Superfan

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    Again, this is the first time I’ve seen a post about a Tesla shutting down above zero (have there been others?). So it’s a useful PSA type learning experience worth sharing among the Tesla community. I can’t be the only person that would have thought the same as the OP in this scenario. Now I know differently. Learn something new every day on these forums.
     
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  18. Lloyd

    Lloyd Well-Known Member

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    I arrive home with <10 miles on a pretty regular basis with no issues, though I don’t go< 5 !!!
     
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  19. Veritas1980

    Veritas1980 Electric Viking

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    It is not that unusual, the range will only be an estimation based on the calculated energy left in the battery. It is not a exact measurement but an (often good) estimate.

     
  20. Exiom

    Exiom Member

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    I am sure you have had your mobile phone or laptop shutdown on you before it said 0%... this is no different... did you buy a new device?
     
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