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My car's fuzzy range math

Discussion in 'Model S: Battery & Charging' started by derekt75, May 21, 2013.

  1. derekt75

    derekt75 Member

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    Location:
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    Here are the facts:
    Starting range: 236 miles
    Ending range: 161 miles
    Distance: 47.9 miles
    Total Energy: 19.1 kWh
    Avg Energy: 399 Wh/mi


    As normal, my consumption is 4/3rds the rated 300 Wh/mi.
    However, if I take 47.9 * 4 / 3, I get 64 miles, but I lost 75 miles of range. Where did the other 11 miles go?

    Similarly, I lost 19.1 kWh and 75 miles of range. The listed range of my car is 265 miles, but 19.1 * 265 / 75 = 67.5 kWh, and I have an 85 kWh battery.

    This is really quite typical for me:
    It seems I lose about 1 mile of range for every 1 km I drive, even though my usage is "only" 400 Wh/mi.

    My question is will this continue all the way down? Does my ending range of 161 miles mean I can only go about 161 * 47.9 / 75 = 103 miles? or can I go 161 * 300 / 399 = 121 miles?


    In a related question, is the vampire drain included in "total energy" consumed? My car was outside yesterday, and it was in the high-80s.
     
  2. efusco

    efusco Moderator - Model S & X forums

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    Need more data. Weather, type of driving...hwy, city, speeds, etc.
     
  3. ckessel

    ckessel Active Member

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    Why? He listed the energy stats per mile. What does it matter what conditions caused that usage?
     
  4. Zextraterrestrial

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    I have run these #'s for 500 trips and get 94% of rated (average)
     
  5. efusco

    efusco Moderator - Model S & X forums

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    Because he's asking for projections/predictions. If his use has been short trips, high speeds, hard acceleration in a city his experience for the next 150 miles of driving on open 45mph rural roads holding a steady speed with few or no stops will be completely different.

    If he's asking if he'll get the same numbers driving exactly the same way he's been driving and under the same conditions, then the obvious answer is "yes"...why would anything change?
     
  6. ckessel

    ckessel Active Member

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    That's not what I got. He's not asking for projections of range per se, but asking if the mismatches between reported energy will continue all the way down (which, of course, affects range).

    The gist of his post, the reason for the title of the thread, is that Tesla's math with rated range and kWh used isn't adding up.

    He lost 75 miles of rated range on his trip, which is 75 * 300 = 22.5 kWh.

    However, he only used 19.1 kWh for his trip.
     
  7. efusco

    efusco Moderator - Model S & X forums

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    I see.
     
  8. dgmanny

    dgmanny Member

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    here are my stats yesterday for business trip. I was gone for 12 hours. I did a range charge that finished right before i left.

    Starting range: 269 miles
    Ending range: 62 miles
    Distance: 197.4 miles
    Total Energy: 57.6 kWh
    Avg Energy: 292 Wh/mi

    85/57.6*197.4=291miles or 57.6kwh + (62rated miles*.307rate range)19.0= 76.6

     
  9. Johann Koeber

    Johann Koeber Member

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    The car estimates the range based on your driving the last X miles. After driving about X miles the rnage estimate will have caught up with you and be stable for the future. Unless your consumption during the last X miles varies.

    Gonig down long hills tends to INcrease range left. Variations to be expected depending on speed, wind and other factors. These are partly not under your control. Whenever the range got lower than the miles I have to drive, I influence the range aspects that are within my control:

    Number 1: drive slower.

    Let us hear if that works for you.
     
  10. derekt75

    derekt75 Member

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    I'm planning to drive the way I always drive, which almost always has the car reporting that I'm using about 397 Wh/mile, but always has me losing about 75 miles of range for 50 miles of driving.
    So my question is which is correct? Should I expect to continue to lose 75 miles of range for every 50 miles of driving, or should I expect to lose 399 / 300 * 50 = 67 miles of range for every 50 miles of driving?

    - - - Updated - - -

    I don't believe that rated range adjusts based on my consumption for the last X miles.
    There's a projected range that I never use, but that's not what I'm talking about.

    - - - Updated - - -

    So you lost 207 miles of rated range, but only drove 197.4 miles, and you were driving more efficiently than the rating assumes. So, like me, there's a dozen miles of range loss unaccounted for.

    Are these lost miles lost per hour or are they lost per mile?
     
  11. Kipernicus

    Kipernicus Model S Res#P1440

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    Vampire losses are NOT included in the trip meters. If there's any significant amount of time sitting around in between your Starting Range and Ending Range, or running the HVAC when the car is not "on", that should account for the fuzzy differences.
     
  12. dgmanny

    dgmanny Member

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    I think the miles are lost per hour regardless of whether you are driving it, which i am hoping they fix at some point. i have an energy meter on the line with the charger and I am getting about 25% in losses compared to the miles/kwh on the car. i have a volt and the charging losses are only 15%.

    I've also read that the entire 85kwh battery isnt available for use. someone mentioned that 3-5kWh is left in reserve.

     
  13. derekt75

    derekt75 Member

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    Good to know, thanks.

    So what exactly is included in the kWh used total?
    Is everything on the 12V supply ignored?
    Is HVAC while the car is on included?
     
  14. Al Sherman

    Al Sherman It's about THIS car.

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    It does NOT appear to me to be included. I haven't done any calculations except to say that my miles since last charge added to my current rated range never adds up to the rated range I started with. Always less. No exact numbers but I'd guess in the 5% range.
     
  15. daveruns

    daveruns Member

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    Wow, I have been using about 300 Wh/mile. Most of the time at low speed, it drops below 300, but if I am running at 75 mph with the air conditioning running and the stereo blasting it goes to 320. I don't seem to able to get to 350 using the 30 mile average. But then I don't have the performance version.
     
  16. Merrill

    Merrill Active Member

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    Can anyone tell me that when you go into the control setting and trip it shows that my total mileage is 736 and total kWh is 225, can this be translated to the amount of kWh that I used when charging the car. If not is there a way to accurately tell the energy used while charging. I have looked at the energy chart on the Tesla web site and dialed in the numbers but have no clue how many kWh of electricity that I have used so far to charge the car.
     
  17. jomo25

    jomo25 P4398

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    Did you Pre-heat/Pre-cool or run the AC/heat while the car was 'off'? I think it's been confirmed that kWhs used by that are not counted.

    - - - Updated - - -

    Just saw this and the previous post. All kWhs used while car is off are not included in the energy app numbers. All kWhs used while the car is on are counted, including those used by AC/heat.
     
  18. gregincal

    gregincal Active Member

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    That value doesn't count vampire load of 3-5kWh per day and it doesn't count charging inefficiencies (for every 10kWh used it takes more like 11.5 kWh to replace it). There's no way to know exactly without monitoring energy usage at the plug, but the following formula should give you a rough idea (at least this is the formula that works for me):

    (kWh used / .85) + (3.5 * # of days you've owed the car)
     
  19. 100thMonkey

    100thMonkey Member

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    I suggest not paying much attention to the range calculator... it can't tell the future. when you need it, charge to full and often, stay in the green and have peace of mind if at all possible and always have a plan B.

    I personally wish there was an option to display a simple old fashioned gas gauge with and E and an F with no calculator, it would be kind of retro and help get people out of the mindset of being exact with range predictions, it's just not possible except on flat open roads with constant wind and temps.
     
  20. Merrill

    Merrill Active Member

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    No, have not pre-heated or pre-cooled, nor run the ac while car is off.
     

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