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Low SOC = Terrible Supercharging

Discussion in 'Model S: Battery & Charging' started by JohnnyLounge21, May 11, 2017.

  1. Lump

    Lump Active Member

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    I just drove 3200 miles, I would depart once energy graph predicted 20% upon arrival at next destination but ussually arrived with~7% SOC remaining due to driving +15mph over the speed limit, (always had an eye on weather & charged to 30% when faced with rain & headwinds).
     
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  2. apacheguy

    apacheguy S Sig #255

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    The trip planner supposedly accounts for variation in driving style by using efficiency numbers and average speed. I find that it consistently fails to account for this (accurately, at least). There is always a big drop off in the first 30 miles of each leg where I always lose ~10% off the predicted value.
     
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  3. mspohr

    mspohr Well-Known Member

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    Interesting. I usually find a 10% increase after the first 30 miles.
    Probably making adjustments for driving style.
     
  4. ShockOnT

    ShockOnT ⚡️⚡️⚡️⚡️⚡️

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    I also wonder if the difference between the new 75/90/100 packs and the older packs is more to do with software than will abide chemistry changes.
    It's possible that Tesla's ongoing monitoring (and growing battery expertise) has prompted them to change the charging algorithms, but that so far they've only written the software to update the algorithms for the current packs.
    They may yet release software to change the charging rates on the earlier packs.
     
  5. dhanson865

    dhanson865 Active Member

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    How would you not start a trip with an ICE car with one gallon in the tank. Do you have a gas pump at home?

    If you answer is you'd go to a gas station to get more, congrats that's what the OP did by going to the Supercharger. They went to get more.
     
  6. mspohr

    mspohr Well-Known Member

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    There aren't enough details in the OP to understand why he drove 22 miles to a SC rather than charge at home or some other local charge point, etc. As I said, I wouldn't start a trip with only 40 RM unless there was no other option. Same thing with ICE, I wouldn't start a trip with only one or two gallons unless there was no other option. I have local options for EV charging for my Tesla and gas stations for my ICE car so I would use these in both cases. I wouldn't try to drive 22 miles with only a gallon or two in the tank (or 40 RM) unless there was no other option.
     
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  7. EV-lutioin

    EV-lutioin Active Member

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    Yep, always charge at least 10% past the "you have enough energy to continue your trip" message to account for factors such as headwind, otherwise you may have to reduce speed en route to your next charging stop.
     
  8. David99

    David99 Active Member

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    Good question, but what I noticed is the car's trip planner is very keen on you arriving at at least 6% battery. I have noticed that on my many road trips.
     
  9. dhanson865

    dhanson865 Active Member

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    #49 dhanson865, May 13, 2017
    Last edited: May 13, 2017
    Starting point: you are present a car with 1 gallon of gas.

    Do you A drive it to a gas station or B tell the presenter to shove off and sit in a corner and pout?

    Saying you wouldn't leave on the start of a trip with low gas is the same as saying you wouldn't leave at all.

    When you had a gas car did you previously stop for gas every time your car got below 3/4 of a tank? Was your day like this:

    Morning, I drove to get gas, then to go to work
    Lunch, I drove to get gas then to get lunch
    after lunch I drove to get gas then drove back to work
    afternoon I drove to get gas then drove home
    Evening, I drove to get gas then drove to the grocery store
    later, I drove to get gas then drove home

    Seriously, no one drives like that. They get gas when it's convenient or when needed to go further. Saying you wouldn't start a trip because you were low on fuel is nonsensical.

    Going one step further with an EV, your destination (work or home) is usually where you fill up. If I'm going to get groceries its 1-3 miles each way. If I have 10 miles range left I'll leave the house, get groceries, charge when I get home. My car works just as well on low charge as it does high charge (assuming you aren't drag racing). I'm not drag racing when I do a short trip so I don't need a full charge to drive <10 miles.
     
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  10. David99

    David99 Active Member

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    Tesla has a 5% low point protection. When the car shows zero, the battery has about 5% left. The data bus on the car shows this clearly. So even if you drive the battery down to zero, you are never below 5%. The old cells are mostly fine charging at full speed even when at zero. The charge rate does ramp up gently over the first 60 seconds, though. In the new cell batteries (75/90/100) when the battery is at zero, it appears charging starts slow and gradually ramps up until about 6% is reached.

    buffer.jpg
     
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  11. No2DinosaurFuel

    No2DinosaurFuel Active Member

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    I don't think Tesla would be murdered... Actually quite the opposite if Tesla replaces the pack with better ones. They would be praised quite a bit. Now if they don't replace the packs then sure I agree.
     
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  12. AmpedRealtor

    AmpedRealtor Well-Known Member

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    I've rolled into a Supercharger with less than 5 miles remaining and never experienced a delay in Supercharger ramp-up, this on a hot 105+ degree day as well. I have a 2013 P85.
     
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  13. jchag

    jchag Member

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    Hot day = happy battery
     
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  14. kingjamez

    kingjamez Member

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    Cold limits battery performance temporarily. Heat destroys battery performance permanently.

    Nissan learned that the hard way.
     
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  15. mspohr

    mspohr Well-Known Member

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    That's why Tesla has a battery coolant system... to eliminate excess heat. The Leaf didn't have one.
     
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  16. dgpcolorado

    dgpcolorado high altitude member

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    Wow! I don't think I've ever seen an energy plot that flat before. That sort of thing just doesn't happen here in the Intermountain West. Here is an energy plot from Colorado:
    Denver to Silverthorne energy plot1796cropsf 10-17-16.jpg
    I agree with @Naonak that the Tesla projection is way too optimistic — in my car it would have me leave at 11% to 13% estimated reserve — and I usually use more energy than projected unless driving slow speed roads. In my experience "Tessie" just can't account accurately for speeds above 65 to 70 mph and the speed limits here are usually 75 or 80 mph, depending on the state. And, no, I never exceed the speed limit on road trips — 80 mph is plenty fast enough for me. The speed limit on that trip I posted above is mostly 75 mph once one clears the city, with a lot of elevation change, of course.

    I've learned to charge to a larger buffer than Tessie recommends and expect to do worse than the original trip projection unless I get lucky and have a tailwind. (Perhaps my car needs an alignment or something.)

    Can't recall seeing my charge throttled at low SOC on my old style battery, but the lowest I've been at is about 3%. Don't like to get lower than that. I've seen Supercharging throttled when the battery is cold, of course, but that's a different issue.
     
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  17. wcfinvader

    wcfinvader Member

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    Started at 20 rated miles ended with 230 rated miles after 45 minutes supercharging at the Council Bluffs Supercharger.
     
  18. JohnnyLounge21

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    This is spot on. I was in a situation where my overnight arrival point (hotel with no EV plug or even a 110V they would let me use) had no Supercharger between me and the destination. I had plotted my course to leave me with 60 miles to get from the hotel to the closest Supercharger the following day (which was 22 miles away). I arrived the night before in the low 40s and got in the car to head to the Supercharger the next day with exactly 40. I suppose could have found a 110V in the area and sat there for 4-5 hours to take on 20 miles more charge. . . Using the ICE example, this would be akin to using your gas can that I suppose you carry in your trunk and then twiddle your thumbs for half a day to equal the time lost. . . But instead, I headed to the Supercharger with relative confidence.

    I'm glad there's this community to discuss this through and continue learning. Every car seems to have its own slightly unique personality. I'm learning mine as I go - to be sure! I have a SD to SF road trip coming up in about a month and I'll certainly be making some itinerary changes than to what I had when I plotted the course a few weeks ago. . .

    So I implore you - why did the Tesla call center (and the on-hand technician) recommend the tow when this could be construed as normal behavior on the Supercharger at low SOC? I really could have done without that!
     
  19. Galve2000

    Galve2000 Member

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    Funny, I usually ignore these messages unless I *know* I am cutting it close.

    This has been my experience also. If I don't know the roads I am travelling on I tend to go for a 30% buffer, just to be on the safe side. I have also never arrived at a SC with less than 6 or 7% in the pack.

    Stupid question:

    Where is the trip energy plot?

    If I am cutting it close I usually check the projected range (both "instant" and "last 30 miles") to be able to gauge if I will make it to my destination. So far so good.
     
  20. Max*

    Max* Charging

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    Click on the energy button (the one that shows you the last 30 miles Wh/Mi usage, on the top taskbar), and it's the 2nd tab.

    It's only available on the 17" screen. And I believe you have to be navigating somewhere for it to work.
     
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