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How many kWh are realistically available?

Discussion in 'Model S: Battery & Charging' started by Redaxis, Jul 12, 2016.

  1. Redaxis

    Redaxis Member

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    How many kWh are realistically available from a 90kWh battery? My man maths make a 90% charge 81kWH then leaving a 10% charge left makes it 72kWh and maybe take 5kWh for systems/reserve etc... Should mean around 67kWh usable?

    On my last charge/drive from 90% to 11% I used 55.5kWh... Where is the rest of my kWh?

    Cars only 2 1/2 weeks old and coved 800 miles, so I doubt much battery degradation.
    P90D
     
  2. Adam W

    Adam W New Member

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    I talked to a Tesla Tech Rep at my service center the other day about this same issue. The answer I was told was the energy percent you see on the Tesla screen is incorrect. They leave a 10% buffer after you hit 0%. The reason they do this is because it is very bad for the battery to go below 10% and they do not want people to count on it.
     
  3. AWDtsla

    AWDtsla Active Member

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    0 means 0. Sometimes the car is wrong about 0. Probably 84kWh, assuming you count it yourself and don't trust the trip meters.
     
  4. Boatguy

    Boatguy Member

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    #4 Boatguy, Jul 13, 2016
    Last edited: Jul 13, 2016
    I've been measuring how quickly the rated miles come off my S90D, and over five trips and about 400 miles I've found that 1 rated mile is removed for each 273Wh consumed. This is in total contradiction to the Energy graph which shows rated miles and Projected mile equal at 290Wh/mi. But it's been very consistent. With that in mind, my current 100% is 289RM which implies an available battery pack of 78.9kWh.
     
  5. llavalle

    llavalle Member

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    I don't know about the 90 pack but on my 85, I've done full cycles a couple of times now and I had around 77.6 - 77.8kWh usable when I got the car and now I'm down to around 77.3 or 77.4 (how to really do a test for me right now).

    One thing to keep in mind is that the energy usage in the trip meters don't account for the time the car is not driving. So if you're in the car, with the A/C ON, playing with the screen or listening to music, the kWh counter does not increase if the car is OFF (Unsure if it does when car is ON but in Park). Same goes for the vampire drain : the energy that is consumed by your 12V accessories when the car is parked.

    To do a real, real test, you need to charge to 100% SOC then drive continuously until your contactor opens or you reach 0 RM. And don't drive too fast : if you pull too much power from the battery, you'll lose capacity to the internal resistance of the cells and you're basically just heating the pack.

    You could also use the diagnostic connector on the car to log CAN messages from the battery management system. There's a specific message for nominal energy in the pack. Mines reads 77.3kWh + 4kWh reserve (aka, 81.3kWh total in the pack). I have just over 40 000kms (25k miles)
     
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  6. ArtInCT

    ArtInCT Always Learning

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    In my typical use of the P90D, I am achieving in a range of 2.9 to 3.1 miles per 1 percent of battery, as I have my units set to percentage not rated miles. Now if I go "spirited" or up hill or deep cold winter those numbers will go down I am sure. Usually I charge up to 80% per day which in this current weather, and with my use would probably give me a range of 210 miles with a 10% or 30 mile spare cushion.

    On my console display I show the trip data, which shows information for the latest trip leg and data since the last charge. Therein, you can see the total kWh used since the last charge and the total miles.

    One thing I would like to do is charge to 90% and run down to near zero percent charge to see what the reported kWh used would be on the 90 pack... I do not know that number. Does anyone have that number? I am aware there are a few versions of the 90 pack. I have the earlier one, Feb, 2016 build.
     
  7. Boatguy

    Boatguy Member

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    That is really excellent. You're seeing 300mi of odometer driving range with a 100% charge.

    I have my S90D set to display rated miles and I've observed that it consistently clicks off one RM for every 273Wh of consumption on the trip meters. Since my lifetime average is 310Wh/mi (California moderate temps), that's about .88 miles over the ground for every RM. My 100% charge shows 289RM so my effective over the ground range is just 254 miles, dramatically less than you're experiencing in your P90D.

    Well done!
     
  8. ArtInCT

    ArtInCT Always Learning

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    My typical drives are in the 40 to 45 mph range due to the roads I travel on.
     
  9. Naonak

    Naonak Member

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    I've calculated my P90DL to be in the mid 70's for usable power - usually somewhere around 76 - 78 kWh
     
  10. FlatSix911

    FlatSix911 918 Hybrid

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    Here is a graphic that shows the energy allocation on a Model S 85. :cool:

    85 kWH .jpg
     
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  11. David99

    David99 Active Member

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    Can we please please let go of this incorrect graphic. It keeps getting posted here but it is not correct. The 85 does not have 85 kWh capacity.
     
  12. FlatSix911

    FlatSix911 918 Hybrid

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    No worries ... can you provide an updated graphic?
     
  13. Boatguy

    Boatguy Member

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    Ahh, that explains the great range! My driving is mostly at 65-75.
     
  14. MP3Mike

    MP3Mike Active Member

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    There is also no "zero mile" protection. So, yes, people need to stop spreading the misinformation.
     
  15. Asciidv

    Asciidv Member

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    I was (am) disturbed over the lack of battery capacity of my 90D (4 months old). I sent the following note to the service manager and am waiting a reply.



    Tesla Model S - 999JJJ , Battery Capacity Concern

    I purchased my new Model S from you at the end of February this year. I have for some time had the suspicion that the battery capacity is below what is correct.


    At the moment the vehicle has covered 7000 miles with an average consumption over that period of just under 300 Wh/mile.


    Recently I under took a journey from the Northampton Supercharger home to Northumberland in a single unbroken journey taking 4 1/2 hours without the need of any auxiliary power drain such as the climate control or heated seats/screens. These were the starting conditions;
    [​IMG]
    [​IMG]



    At the end of the unbroken journey these were the reported conditions;

    [​IMG]
    [​IMG]


    From these figures you can deduce that 81% (90-9) of the battery capacity is equivalent to 62.5 kWh. Therefore 100% of battery capacity is 77 kWh. Of course all the Tesla forums concur that a '90' battery pack only has 83-85 kWh available for use. I am concerned that I am already 10% down on this figure after a matter of a few months. My 90% charge is 246 miles and at the moment is falling by a mile virtually every charge in three.


    Do you have a better way to validate battery capacity? What can be done so that my Tesla can have the capacity that it should have?


     
  16. brantse

    brantse Member

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    What is your normal charge limit/habits?
     
  17. Asciidv

    Asciidv Member

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    Brantse,
    I only ever charge to 90% and usually at around 20-25% remaining capacity. Usually charging 3 times per week, once at a Supercharger and the other two times from a 3 phase 415V supply but just with the single on board charger (around 33 miles per hour).
     
  18. FlatSix911

    FlatSix911 918 Hybrid

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    Again, please provide an updated graphic with corrected data. Thanks. :cool:
     
  19. Boatguy

    Boatguy Member

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    Actually your numbers come up pretty much the same as for my three month old S90D. Here are the maths.

    290 rated miles with 100% charge (294 when new)

    273wh / RM (derived from numerous observations and dividing power consumed by RM consumed, verified again just this morning)

    273wh * 290 = 79.1kWh

    At best it was 294 * 273 = 80.2kWh when new.

    Per the title of this thread, I think a new S90D starts out with about 80kWh of capacity usable for driving.
     
  20. Asciidv

    Asciidv Member

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    A discussion with Andrew Reeves the Service Manager at Manchester Tesla (UK) revealed a Tesla document describing the causes of the discrepancy. Six points were listed, primarily the bulk of the missing kW/Hrs were at the bottom end, and yes I think 'zero mile protection' is an adequate description. This reserve being such that you can always make zero miles, even when the calculation of battery capacity has been over optimistic. Also emphasis was placed on the fact that the energy recorder only records motive power and not the auxiliary drains. Finally there was the suggestion that battery capacity was measured under laboratory conditions and therefore not real world capacity.

    Other points which came from the discussion is that Supercharging does degrade battery capacity compared to normal slow charging and that it is charging to 100% which forces a more accurate calculation of battery capacity.

    Boatguy, thanks for your contribution yet again. You provided useful information to me, when we had the same discussion earlier in the year when I was even more concerned about battery capacity.
     
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