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Understanding Wh/mi (or km)

Discussion in 'Charging Standards and Infrastructure' started by SSD420, Sep 28, 2016.

  1. SSD420

    SSD420 Member

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    IMG_1068.JPG IMG_1069.JPG IMG_1070.JPG IMG_1071.JPG IMG_1073.JPG IMG_1075.JPG IMG_1076.JPG IMG_1077.JPG can someone explain the following pictures in plain English, so I understand all the talk about Wh/mile. I changed my settings to miles for you guys at TMC, since it seems like some of you get confused when I post in kilometres...

    Can you make sense of all this and explain it to me....

    Sorry if there are duplicates. I'm just sitting at the supercharger waiting for my MX to finish..
     
  2. ptitcali

    ptitcali Member

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    Hi SSD420
    So to give a rough comparison, 1l gas contains about as much energy as a 10kWh (so 10'000Wh). So if the car gives say 300kWh/mile, it means it consumes the energy contained in 0.03l/mile, or 3l/100miles

    Now regarding all the values stated in your pictures:
     
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  3. ptitcali

    ptitcali Member

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    Ooops... it posted too quickly. here is the rest
    - regarding the 1st picture, this gives you the information on your average consumption for the last 30 miles. having 353wh/mile on average, it would compare to 3.53l/100mile of an ICE. It is a moving average counting the latest 30 miles.
    - regarding the 2nd picture, the information displayed is on the left, the same as above, and on the right, the range you would have with the actual charging, assuming you would continue driving the same way as you are doing right now. So this value changes a lot.
    - on the 3rd picture, you have the exact same information, except that on the right hand side, it gives you the range you would have with the actual charging, assuming you would continue driving the same way you drove the last 30 miles. So this value changes less and is more accurate.
    - on the following 2 pictures, you have the same information as on the 3rd, except that it consider your driving habit over 5, resp. 15 miles.
    - and on the latest pictures, you have the very same information, except that you are probably charging. So considering that the charging increases, your range increase too.

    In reality, those screens are not very useful and the one showing your actual consumption vs. expected consumption on your trip (trip tab) is much more valuable, as it shows you how close you are to the expected overall range (displayed on the left hand side of the dashboard). If you are below the line, you consume more than what the car expects to consume. If you are above, you consume less and you can drive a little bit more than the displayed range.

    Hope I have been clear, EN is not my mother language ;-)
     
  4. SSD420

    SSD420 Member

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    Any chance someone can explain all this in kilometres if I post pics with km's?

    When you write 1l gas, do you mean 1 litre? @ptitcali

    I'm still confused. It's definitely not your English. It's my lack of understating the energy concept. Hence my vague post.
     
  5. Nitram

    Nitram Member

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    What exactly is it you don't understand?
    wh/mile is your energy consumption in watts x hours / distance.
    It is exactly the same concept as saying your car burns 8 litres of gas per 100km, except we are talking about quantity of energy instead of volume of gas, because when you fill up your tank, you are interested in the volume you put in it rather than its energy equivalent.
    Also, Tesla uses wh/km when many people are used to litres per 100km. Just multiply by 100 and you have it.

    The other pics show the energy consumption graphs. They show the way you used energy in the last 5, 15 and 30 miles and compute the moving average of your consumption. The "average range" is the range you can drive if you keep consuming energy the way you did in the last 5, 15 or 30 miles. The "instant range" is non-sense to me as it serves no useful purpose; it just show how far you can go if you consume energy the way you did in the very last seconds. And finally, the graphs also show the "rated" average, that is the average Tesla says is achievable in good driving conditions, and is around 200wh/km, depending on the model.
     
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  6. jdw

    jdw Member

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    You can choose to average energy use over 5, 10 or 15 miles or show the instantaneous estimate, based on very recent energy usage.

    The Projected range is based on your choices above - if you average usage over 10 miles then the projection will be based on you driving the same way you have for the past 10 miles. The time frames are useful for comparing range in changing conditions. Example, you drive for 30 minutes then it starts pouring rain. You can then look at usage and projections for either instantaneous or average the last 5 minutes to project your range under the current conditions. If you set a trip, the trip panel will calculate a useful dynamic range estimate for you and plot it against your progress in the trip.

    As to energy usage, 333Wh is 1/3 of a kWh, so it would be another way of saying "3 miles per kWh" or in metric, 200 Wh is 5 kilometres per kWh.
     
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  7. lklundin

    lklundin Member

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    Well, good of you to follow Elon Musk's advice and not just waste your time sitting idly while supercharging, but instead posting to TMC. :)

    Your charging power is 404V * 106 A = 43 kW, i.e. only about a 1/3 of the supercharger's maximum charging power.

    What was your battery's State of Charge at that point?
     
  8. SSD420

    SSD420 Member

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    I was about 10 min away from hitting my 90%. I had already been there about 10 minutes whereas I felt I was getting a fast charge. I recall seeing I was getting 475 km/h and climbing. When I took
    Those pics, it was declining dramatically as I was almost done charging
     
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  9. ptitcali

    ptitcali Member

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    1l is 1 liter (we use liters and km over here too ;-)

    Yes, post your pics in l and km, I will have them "translated" for you
     
  10. arg

    arg Member

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    The display of miles/hr (or km/hr) is almost entirely useless while supercharging, as it's an average over the session - hence at the beginning it's misleadingly low, while at the end it makes it look like you are still charging quite fast when in fact it has slowed to a trickle and you are probably wasting your time sitting there.

    Setting the display for kW, or just looking at the figure for amps (and to a lesser extent, volts) gives you a much better idea of how fast you are charging at any given moment.
     
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