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Missing 9.3 kWh

Discussion in 'Australia & New Zealand' started by RichardMcN, Jul 6, 2016.

  1. RichardMcN

    RichardMcN Member

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    #1 RichardMcN, Jul 6, 2016
    Last edited: Jul 6, 2016
    Help ! ! Am I missing something here ?
    • I start the day with 84.6 kWh (94% of my 90 kWh battery)
    • I use 65.3 kWh during the day
    • So I should end up with 19.2 kWh
    • But I actually end up with 9.9 kW (11% of 90 kWh)
    This happened the day before as well, leaving me struggling to make a place I thought I could make easily.

    So it looks like I have a Model S 81D not a 90D like I thought. What experience do people have of this sort of thing?

    The only thing I can think of is the low temperature (8 deg at start of day). Consulting the manual ... "Note: A portion of the battery image may appear blue. This indicates that a small portion of the energy stored in the battery is not available on your drive because the battery is cold. This is normal and no reason for concern. When the battery warms up, the blue portion is no longer displayed." But in my case there was no blue portion.

    Any pointers ?????

    Thanks


    START OF DAY
    Start.jpg

    END OF DAY
    Finish.jpg
     
  2. raynewman

    raynewman Member

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    Ya - on the 85 KwH I only get mid 70s KwH in real life.
     
  3. NOLA_Mike

    NOLA_Mike Active Member

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    If you have some time on your hands, you can start reading here.

    Bottom line, you will never get 90 kWh usable from a single charge. There is a certain amount set aside for the battery's health and well being.

    Think of it like a hard drive - formatted capacity is less than advertised.

    Mike
     
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  4. ecarfan

    ecarfan Well-Known Member

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    You are assuming that the car motor can draw up to 100% of the advertised 90kWh. It cannot. A certain percentage is that is not available to you, it is reserved for other purposes. I think all EVs do that.
     
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  5. David99

    David99 Active Member

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    No, the losses due to inefficiencies are accounted for. The energy is measured at the battery. The fact that the motor only converts 90% of it's energy to motion doesn't matter. The energy counter measures everything taken from the battery, how it is used and how efficient energy conversion is is irrelevant.

    The 90 battery doesn't have truly 90 kWh. It's a little less. The bottom 4-5% is not available for driving as it's kind of a safety buffer to keep the battery from being damaged. Here is an example: When my 85 was new, I was able to get 76.5 kWh out of it at the most before it was at zero.
     
  6. EcoCloudIT

    EcoCloudIT Member

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    #6 EcoCloudIT, Jul 6, 2016
    Last edited: Jul 6, 2016
    You probably have the car set to charge to 90% (default) therefore:

    90 - (90kw/11) = 81.8kw available if fully charged to the 90%

    Anyone know, as I can't remember, if the car shows 100% charged when charging to 90% (default setting)?

    Unless you purposely, and you shouldn't unless you really need the range, overrode the 90% and pushed to to 100%...

    So what I am getting at is 94% charged may actually be 94% of the 10% less of 90kw....the the figures stack up to just under 2kw's of your figures.

    90kw - (90kw /11) = 81.8kw x 94% = 76.89kw

    76.89kw - 65.3kw used = 11.59kw at end of the day
     
  7. Blue heaven

    Blue heaven Member

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    image.jpg
     
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  8. RichardMcN

    RichardMcN Member

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    Thanks Blue.

    Looks very well measured and thought out. Where does it come from? I could only find it here, but I'm sure that is not the source.

    The 5.1 kWh "zero mile" protection is really interesting.
     
  9. Keiron

    Keiron Member

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    Hi Richard
    My realworld rule of thumb. Take the Kwhr reading as you unplug from the charger and take 90% of the reading- that'll be very close to the realworld useage down to zero.
     
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  10. David99

    David99 Active Member

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    I know this nice looking graphic shows up a lot, but it is NOT accurate. We have evidence that the total battery capacity of an 85 battery is not 85 kWh. It is only around 79ish. It is based on people who took apart a Tesla 85 battery and tested the cells exactly.
    Whoever made this graphic made up numbers, but they are not correct.
     
  11. rowdy

    rowdy Member

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    From the battery teardowns & CAN bus logging threads you end up with roughly the following usable energy after accounting for the bricking buffer (4kWh in most models)

    60 (58kWh)
    70 (67kWh)
    75 (71kWh)
    85 (77kWh)
    90 (82kWh)

    In general it's best to look at the range ratings (EPA/NEDC) when comparing the models. The 60, 70, & 75 models are slightly more efficient due to less weight (14 battery modules instead of 16).
     
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  12. rowdy

    rowdy Member

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    #12 rowdy, Jul 8, 2016
    Last edited: Jul 8, 2016
    I should add a lot of the confusion comes from the initial naming of 60 & 85. The 60 had 5376 cells and the 85 had 7104 cells.

    (5376/7104) != (60/85)

    They should have named them 60 and 80 but I guess marketing wanted there to appear to be a bigger difference between them.

    These days the only difference between the lower spec'd battery and the higher one is 14 modules instead of 16. So you can just work out the difference by using the ratio 14/16 = 87.5%.

    i.e. a 75D has 87.5% of the battery of a 90D.
     
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  13. lennier

    lennier Member

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    My calculations based on a year of driving and observing charge percentages etc is that a 60kWh has about 55kWh usable. Ie every 10% is 5.5kWh and when charged to 100% you have 55kWh to expend before it will show 0%.

    This is for the original 60 of course, the new one being a 75kWh pack with software limitation and so presumably has a full 60kWh available to use.
     
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