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Took my first long(ish) trip today. Observations, and a question

Discussion in 'Model S: Battery & Charging' started by jewilson2, Aug 30, 2018.

  1. jewilson2

    jewilson2 Member

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    Probably not new news to some of you, but i learned a lesson today.

    Left home with a full charge this morning (reading 335 mile range). Entered destination into GPS (120 miles away) and it estimated 54% remaining (180 miles) when i arrive. Noteworthy, as i was planning to drive back same day....no charging.

    Drive around maybe 8 miles in town when i get to destination.

    Return (same route) GPS estimates 9% battery remaining (30 miles) when I arrive. So off I go. I get back in my home town and make a stop; car sits in the sweltering heat for maybe 35 minutes. When i get back in, the alert says 'cabin overheat protection disabled' due to low battery.

    When i finally get home, i have 19 miles of range left. Total trip, 263.6 miles.

    So you definitely cannot take off assuming 335 miles of range (without a planned charge stop) on a super hot day with mixed driving of 45mph - 80mph. You may not make it home....even if your trip is estimated (by you) to require only 79% of your battery.

    Yes, I know this is covered in several topics here (now that I had a reason to search/read).

    Now to my question: Should i avoid plugging the car in immediately considering the 4+ hours of driving in 100 degree heat? Should i let it cool down first, or does it not matter?

    Thanks!
     
    • Informative x 1
  2. Tam

    Tam Active Member

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    No.

    The manual says you should plug in as much as frequent as possible.

    Your main battery pack is automatically thermoregulated even when your car appears to be "off" and the heating/cooling system for human is secondary.

    Your main battery pack enjoys all the power of heating/cooling first then if there's any left it would be given to human occupants last.
     
  3. cpa

    cpa Active Member

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    I certainly believe that you can plug in once you are home. The battery management system kicks in to keep the battery at a proper temperature. Moreover, AC charging is much cooler than Supercharging. I always plug in regardless of outside temps, and it stays over 100 degrees here for much of the summer.

    Your range discrepancy could come from a number of factors. (Not criticizing--) Perhaps you punch the accelerator when the red light turns green. Perhaps you gun it to 80 to pass a line of semis on the interstate. Those quick bursts of speed drain the battery quite fast. Perhaps you rely more on the friction brakes to stop the car instead of coasting to a stop with regenerative braking. The AC draws some current, but not nearly as much as the heater. Perhaps you left the AC on during a stop to keep the car cooler when you returned. There might have been a headwind or crosswind for your journey which eats into range.

    The most telling factor on your trip is to look at your wh/mile in the odometer section of your display. The lower the number the more economically you drive.

    It is said that the "range" miles on a Tesla are calculated at slower speeds than most people drive. I am not sure of the speed, but I think that it is around 55 MPH on a level surface at 75-80-degree outside temperatures.

    For our 2014 Model S, I believe "rated" miles are assumed to be at 283 wh/mile, but I might be off a couple of watt-hours.

    Glad you enjoy your car!
     
  4. jewilson2

    jewilson2 Member

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    Thanks for the replies:

    @Tam something you said sparked another thought. Could one reason the A/C isn't as cool at times during a long, hot trip is because much of the cooling function is going to the battery?

    @cpa critique welcomed. I tried to take all that into consideration. Put it in Chill Mode, Range Mode, and used AP for the entire trip to take my lead foot out of the equation. Duly noted that many things impact the range calc however. This was a "duh!" moment for me. Car is fun as hell to drive though :)
     
  5. ewoodrick

    ewoodrick Active Member

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    There seems to be something wrong with the calculations. If you have 335 mile range and you are going 240 miles, you aren't going to have 54% and 180 miles when you get home. It seems as if there may some misinterpreting occurring.
    And if you get home at 19 miles left, that seems to be a pretty good indication of a very heavy foot. To a degree, going from 70 to 75 mph decreases range 5%. It sounds as if you might have had some speeds with 8s or even 9s in them. That's what will decrease range dramatically. Remember, optimal is around 40 and it is downhill from there.

    Plug it in when you get home. Unless you are referring to a Supercharger, (actually even if you are) the car will run the air-conditioner to cool the batteries down, if needed.
     
  6. Tam

    Tam Active Member

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    That's the idea! Some Arizona residents have complained about that but that will continue to happen until Tesla change its cooling design so human occupants can be priority number one too!
     
  7. SPIKE's M3AWD

    SPIKE's M3AWD Member

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    The 310 combined range is a mix of the following two actual Test Cycles: 321.9 City driving range. 295.5 Highway driving range.

    fueleconomy.gov has all the details. Most importantly the numbers come from the manufacturer.
     
  8. AustinP

    AustinP Member

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    Chill mode, to my knowledge, and I believe stated by Tesla, does not help with consumption. It indeed limit power when accelerating, but has also a lower regen effect when lifting off the foot.
    Range mode might help on range, but it does so by reducing AC and heater power. So with range mode, you might have even less cooling in the cabin.
     
  9. tpham07

    tpham07 Active Member

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    No, because if this was a rule then everyone would pull into a supercharger on their roadtrips and wait an hour before plugging in their cars. The car's cooling system will prevent any sort of battery overheating. worst case, it just stops charging.
     
  10. David_Cary

    David_Cary Member

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    Just to correct somethings posted upstream.

    Tesla does not calculate range. EPA does. It is not based on driving a certain speed, it is based on a mixed driving test that involves relatively slow speeds for the highway portion then it is reduced by a percentage. I will say that Tesla reduces the EPA number on some cars and Tesla does the testing but the protocol is from the EPA.

    Next correction - ideal speed is not 40 mph. It is more like 20 mph. It varies a bit based on temperature and climate control. Several factors here but more time keeping the battery and occupants comfortable favors a slightly higher speed.

    It is a good idea for every new owner to look at the speed vs range charts. My 70D rated at 240 can go 300 at 55 mph. I have done close to that. You can go so much farther as you slow down, it is crazy. Going 400 miles is super easy even in my car. Generally it involves staying off the interstates. Not recommending it but it is helpful if something unexpected happens.
     
  11. RDuke

    RDuke Member

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    When your battery is depleted down that low you definitely want to get it on a charger as quickly as possible.
     
  12. suraj1194

    suraj1194 Member

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    I regularly (1-2x a week) drive 120 miles each way in my 75D, 95% freeway . The car has range mode off, chill mode off and I do about 72-75mph , and use about 270Wh/Mi , giving me almost exactly rated range = actual range in consumption.

    Knowing my ideal Wh/mi and trying to keep to that using the Trip display always worked well for me .
     

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