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Out of juice - battery issue, UI issue, or user mistake?

Discussion in 'Model S: Battery & Charging' started by stevepeck1, Aug 18, 2015.

  1. stevepeck1

    stevepeck1 Member

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    My Ellen took our 201 P85+ on a Charleston South Carolina to Charlotte round trip this weekend. Used Santee and Charlotte Superchargers and the latest software update trip planner both ways. Charlotte elevation 751. Santee Elevation 128. Basically flat the whole way home. No headwind. Clear weather. Unseasonably cool-ish temps. Running in Range Mode. Well-inflated tires. Three soccer kids. Two ladies.

    All was well enough on the return trip. I looked on the app to check on range and make sure they were OK on miles. At that time they were 115 road miles to Santee with 151 showing "in the tank." That's a 24% surplus. In fairness, Ellen can be a lead foot, but with a dose of Range Anxiety from a Florida adventure where we cruised at "0" for several miles so she kept to the flow of interstate highway traffic. (well, she got to 80 once per the log)

    My own experience is to a sub-zero reserve and multiple websites report, "The estimated range on the driver’s dash will read 0 however it’s not the end. There is an extra reserve good for another 10 – 20 miles, depending on your power consumption, after reaching the 0 mark."

    She called me concerned as they could literally watch the last 70 miles of range tick down to zero far faster than the odometer and the car would drive no more than 40 MPH. The last 26 miles to Santee is back road. As zero vigorously approached, the warning came that the car could shut off unexpectedly. 12V battery indicated an error (which Tesla says is "normal" to protect the HV pack). She had only 2 miles to the Supercharger and the car had several miles of range on the meter. I reminded her that the car has a "reserve" and she only had 2 miles to the charger. She immediately pulled off the road anyway and bam the car shuts off.

    3.5 hours for AAA to arrive, and Ellen now has zero faith in this car for road trips.

    Tesla engineer says there were no battery faults, just that it ran out of power. No accounting for why the last quarter of the battery capacity wasn't accurate. Tesla said nobody really gets 260 miles in real world conditions - I get that but dang. When the last 70 miles gets you less than 30, and the car flatly shuts off, that signifies a problem to me.

    Puzzled!

    And for what it's worth, the Ranger service is no longer a flat $100. It's $3/mile each way. $1,000.
     
  2. efusco

    efusco Moderator - Model S & X forums

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    A 600+ elevation gain is significant, particularly over a long distance.
    The speed was killer here I bet. When you see that range vs distance mismatch you have to start slowing down. What did the Trip meter say while she was driving? I think this is a "ran it out of juice" situation too.
    What was the temperature outside and what were the climate settings?

    To me, this sounds like it was avoidable if changes had been made 20-30 miles before it became critical.

    That all said, I wasn't there. If it car truly said there was range left in the pack, then it's hard to fault her. But having run a battery dry in my car, it tends to give you more than ample warning.
     
  3. mknox

    mknox Well-Known Member

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    The trouble is, you can't always do a lot with that warning other than to find a safe place to pull over and stop. With an ICE, you can just decide if you want to stop at the gas station in sight, or the one 1/4 mile ahead.

    WRT the "reserve", others have reported the car shutting down while there were still a few miles showing. I think it might depend on how well the algorithm is calibrated based on your prior driving/charging patterns.
     
  4. techmaven

    techmaven Active Member

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    #4 techmaven, Aug 18, 2015
    Last edited: Aug 18, 2015
    That doesn't sound normal at all for rated miles... Do you have it set to ideal miles? There should be more to this story than that... The car presents all sorts of range warnings now... Did she get these?
     
  5. Max*

    Max* Autopilot != Autonomous

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    What did the trip tab on the energy graph display?
     
  6. jaguar36

    jaguar36 Member

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    How many miles were left when it wouldn't go above 40mph? If it was still 70+ then that is definitely not normal. If it was single digits, it could be. I've taken ours down to single digits before and was still able to go 75mph.
     
  7. ChadS

    ChadS Petroleum is for sissies

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    #7 ChadS, Aug 18, 2015
    Last edited: Aug 18, 2015
    Sorry to hear this happened. Of course it's hard to explain for sure afterwards. If I get time later today I may take a deeper look and see if I can offer anything.

    But for now one slightly tangential message I want to make sure is clear for any newbies reading this thread:

    THE MODEL S DOES NOT HAVE A HIDDEN RESERVE!

    Tesla has always been consistent in saying there is no reserve. Having one would be inconsistent with Tesla's desire to market the highest possible range. And it doesn't help with running out; you'd still have the same number of miles, and people would just count on it - but now it would complicate their calculations. When it says zero, the car can shut down.

    The battery does not store miles, so the miles display is not a true indicator of what's in the battery. The car shuts down to protect itself when the voltage reaches a certain level. The "miles left" display is Tesla's ESTIMATE of when you might get to that voltage. There are more than a dozen factors involved in that calculation, and most of them Tesla doesn't control and a few they can't even measure with any reasonable accuracy. So it is an educated guess.

    It is a fairly conservative guess, so that it is more likely that you will be able to drive past zero than it is that you will run out before zero. People making it past zero and thinking the "miles left" display is accurate is how we get rumors that there is a reserve.

    You MIGHT be able to drive past zero. But you absolutely can not count on it.
     
  8. apacheguy

    apacheguy Sig 255, VIN 320

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    Sorry about that experience. How many miles of rated range were showing when the car unexpectedly shutdown? IMO, that's total BS. The BMS has a predetermined trigger voltage where it will enter bricking protection. It's not a guess, prediction, or estimate. It is an absolute certainty. Absolutely no error in the calculation should be tolerated at this point. Tesla needs to fix this.

    Heard this argument before. While I certainly agree that rated range is an estimate, the uncertainty in the calc is negligible when at the bottom. If it's still showing range, then that is indicating to the driver it is NOT at the trigger voltage. IMO, this is simply unacceptable.
     
  9. jbcarioca

    jbcarioca Active Member

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    I have made this trip several times in my P85D. From what you report the issue is likely to be the assumption that "rated range" means what you will get in reality. It is not, it is an estimate. On one of my trips Charlotte-Santee I left CLT with 253 miles RR and arrived at Santee with 25. However, I drove quite aggressively (could it really have been triple digits at one point?) and gave a few "insane" demos in CLT before I left. Going Santee-CLT I arrived Charlotte with 121 miles RR left. I left Santee with 248 miles RR and drove 55 mph the entire was using the cruise control. Thus, the moral is. The Tesla energy usage is just like ICE, you blow energy with aggressive driving and can produce miracles with very conservative driving. No question, an EV is different than an ICE because you must plan 'refueling'. FWIW, the lowest reserve i have ever had is that 25 miles at Santee. Problems inevitably will happen when going low on 'fuel'. Running out of gasoline once on a Sunday morning in rural South Africa with no gasoline station open within 150km cured my tolerance for low fuel, so my conservative planning was part of my ICE habit too. When i wan to be aggressive i plan to stop for charges very often! So far, so good.

    It's too bad we do not have the equivalent of a 'gas can' so she could have gone to Santee for a fill up supplement to get her the last two miles. Frankly, we do need such a solution, don't we?
     
  10. wk057

    wk057 Senior Tinkerer

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    I've done Santee <-> Hickory NC non-stop several times without issue and stuck pretty close to rated in my P85. Not quite as good in the P85D but still wouldn't be anxious.

    If the car shut down at or past 0 miles on the dash, then... well you should have planned better. If it shut down with 1 or more miles on the dash then Tesla has some explaining to do and some service/towing refund checks to write.

    For the record, driving at 40 MPH doesn't necessarily mean better range. On a flat, level, straight road in perfect weather it might be, but in the real world I've found about 60-ish to be the best overall speed, personally, at least in this part of the country. If you're going at 40 MPH you're actually spending more time, and thus other loads (HVAC, 17" screen, etc) are drawing more power per mile.
     
  11. TexasEV

    TexasEV Active Member

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    Just because a few people have been able to go a few miles past 0 doesn't mean there is a reserve you can count on. Lots of variables here, but you should plan on 0 meaning 0.
    The biggest problem was driving fast when concerned about running out of battery. "Driving with the flow of interstate traffic (well, she got to 80 once per the log)" is just asking for trouble when you're concerned about range. The number one thing to do is SLOW DOWN. Better to let cars pass you at 60 than to run out of battery.

    - - - Updated - - -

    The why was the Model S distance record set at a speed of 23 mph?

    Also realize the rated range is an estimate, it's not going to be exact to the mile, so I wouldn't blame anyone but myself if it shut down with 1 mile showing.
     
  12. yobigd20

    yobigd20 Well-Known Member

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    THERE IS NO RESERVE despite what you read. Never expect to get anything past 0. Expect the car to shut down right at 0 (or even before 0 which has happened to a few). Ignore everyone who says otherwise. I'm sorry that so many people misinformed you and have lots of misinformation spread across these forums and other online groups. Zero means zero.
     
  13. apacheguy

    apacheguy Sig 255, VIN 320

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    Hello folks. The OP claims range was still showing. Hence, he was not counting on a reserve so let's stop mentioning it!
     
  14. TexasEV

    TexasEV Active Member

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    Yes, he said he was counting on a 10-20 mile reserve.
     
  15. yobigd20

    yobigd20 Well-Known Member

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    also two little tricks for everyone ->

    1) increasing the PSI in your tires will get you better efficiency. I usually run mine between 48-50psi and its not hard for me to get sub-300Wh/mi even at 70-75mph on a flat highway. and yes my tires are still wearing even. (anything more though and you risk burning out the middle treads). it is super critical to check your PSI once every other week minimum and maintain that psi consistently (they seem to slowly leak 1-2 psi here and there, not uncommon for me to find them down at 41 psi if i let them go a little while without checking).

    2) draft 18 wheelers. it's not hard to get as low as 200Wh/mi or even lower doing this. that will extend your range. it is also dangerous and will destroy the front of your vehicle from rock chips but hey when you're in a bind you do what you gotta do lol.

    - - - Updated - - -


    actually its easy accounting = the battery state of charge is NEVER accurate. It's a best guesstimate. there exists no accurate way to determine a lithium ion battery cell state of charge. they have to take many measurements and estimate what the state of charge is. it's complicated. therefore both a '100% range charge' rated range display is never really accurate either along with how many actual miles you can get once you get towards that '0 rated range'. you may get 5 'extra' miles. you may get none. it may even shut off before your display hits 0. again, it's not accurate, and it never will be. best advice i can give is to try and plan your trips so that you never go below 20 or so rated miles. then you never really have to worry about it.
     
  16. stevepeck1

    stevepeck1 Member

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    Respectfully, I'm not misinformed about sub-zero reserve. I can personally attest that there IS a 10-20 reserve since we had that happen before in FL in November. Here's a pic where we, too have driven at highway speeds for miles at sub-zero range on the gauge. You can see the SC stop on the display.
    Florida 016.JPG
    This trip from Charlotte was entirely an elevation DECREASE.
    It was set to rated not ideal miles. "Ideal range" is just where unicorns live.
    Temperature was 85. Sunroof closed. No leadfooting. The graph showed plenty of miles at arrival, the whole way... except for the last 50 miles when it was like someone poked a hole in the gas tank.
    Highway traffic cruise set at 70, which we've done for thousands of miles. Uses more power than 60 but not THAT much. 60 with glass closed yields best range on flat roads.
    40MPH speed taper came in the last 30-40 miles, which contains the slow driving part of the trip and where the yellow went to red far faster than the odometer.
    Pack in September 2014 charged to 266 miles. Once. Now only charges to 253-259.
    Algorithms Alchemy and other magic aside, seems to me that the pack is failing but they saw no errors and say the pack is fine, even though it went to zero like there was a hole in the bottom of the car and we were towing a truck and it shut down hard at 4 miles. No reserve capacity.
     
  17. hiroshiy

    hiroshiy Active Member

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    Sorry for what happened to Ellen... I'm not 100% confident but it might be AC, combined with speed.

    The elevation gain was 600+ feet so it would account for only a few rated range. Also if Ellen sees 70 miles rated left then she wouldn't be keeping over 70mph.

    AC can be very tricky. If you set the temp to, say, 72F and if the outside temp drops below 72F, she needs to turn off AC or LOWER the temp settings to conserve power. If she did nothing in such situations, cabin heater kicks in and she'll lose 20% range. This could be happening when temp is gradually dropping.

    I always wonder why Tesla didn't think about this. At least they could give us a separate "Heater ON" indicator to see if the cabin heater is on.
     
  18. wk057

    wk057 Senior Tinkerer

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    Where? Sure wasn't done anywhere around here, and I'm also pretty sure that would be an average speed. The reason lowering speed on flat straight roads increases range is the lower wind resistance and lower C-rate draw from the battery overall as a result. In real world conditions, at 23 MPH you will still pull 40kW+ in some places, far more than wind resistance would cause normally. The ratio of the power increase due to climbing and the power increase due to wind resistance at a given speed is highly variable in the real world.

    I wouldn't climb Black Mountain at 23 MPH in my Model S, that's for sure.
     
  19. mikeash

    mikeash Active Member

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    I'm afraid you're holding it wrong.

    First of all, the car could probably do a better job with the UI here. The default is to show the battery state in "miles" which is kind of misleading. But given how the car displays it, it's important to understand how to use it!

    The miles displayed on the dash are "rated miles." These have only a vague correspondence to actual miles you can drive. That number is basically saying, "if you drive at a steady speed, on flat ground, with these simplifying assumptions applied, you will be able to go this far." Your actual distance will match that only to the extent that your driving matches those assumptions, which is often not very close at all. Depending on actual conditions, a 24% surplus could be far more than you need, or it could be not nearly enough.

    To monitor how you're doing to get to your destination, ignore the dash display and use the Energy app on the trip tab. This will graph your projected and actual energy usage for the whole trip. It will predict what battery percentage you'll have at the destination. You can then watch how you actually perform relative to the prediction. If the prediction starts to slide towards zero then slow down! If you can't get it to stabilize then start looking for a closer place to charge. Get the PlugShare app on your smartphone. Barring that, load PlugShare - EV Charging Station Map - Find the nearest location to charge your electric car! in your car's browser. It's a bit slow, but it works well.

    It's possible this would have gone wrong as well, but without knowing what the car predicted and how your real-world usage compares, it's impossible to say. My own (limited) experience is that rated miles can easily be way off, but the Energy Trip prediction is extremely good, and if it starts to deviate you can bring things back in line by adjusting your speed.

    Now, the fact that the car shut down with miles left on the clock is definitely a big problem. If it says five miles, that may not mean five miles of actual real driving, but it means there's something left. You can't count on a reserve, as others have said, but at the very least it shouldn't shut down before zero.

    When you say the car wouldn't go over 40MPH, at what remaining range did that happen? I can't tell if you meant to say that the 40MPH limit started with 70 miles remaining, or if it occurred at a lower state somewhere as the remaining 70 miles started to drain. If it was limited to 40MPH at 70 remaining then something was definitely wrong, because that shouldn't happen at all. I've driven the car down to 40 or so and not seen any limits noticeable in normal highway driving. From what others report the car will start to limit power as you near zero, but you have to be a lot closer.

    - - - Updated - - -

    It's important to distinguish between "there is a reserve" and "you can sometimes drive beyond zero."

    There's no doubt that you can sometimes drive beyond zero. Your own experience shows this, and many others have seen the same thing.

    But that does not mean that there is a reserve! A reserve is something that is guaranteed to be present. Depending on how accurately your car estimates the energy in your battery, you might have extra energy beyond zero, or you might not.

    There is no reserve, so don't count on anything below zero. You might succeed sometimes, but you might not.
     
  20. Zextraterrestrial

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    pretty sure you want(ed) to do 26 mph in a 85kW car for the longest range.
     

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