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High (2x) usage first 10ish kilometers after charging?

Discussion in 'Model S: Battery & Charging' started by krnshh, Jul 21, 2015.

  1. krnshh

    krnshh Member

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    Hi,

    Owning my 85D for about 3 months now. Had a question:

    - Why does my Wh/km be around 400-415 for the first few kilometers after I unplug it? After around 40kms the average comes down to 180wh/km which I understand is normal. Is there a way to reduce this initial high usage or minimize it? If yes, how? Btw, this doesn't happen if I park (unplugged) it for a while and then continue using the car.

    Also, is there a way to break down the usage so I know what is causing the high usage and accordingly adjust my driving style?

    Thanks!
     
  2. Soolim

    Soolim Member

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    I have the same experience. I think the higher than usual Wh/km after you have a new charge is normal. The average Wh/km since the last charge starts with 0 Wh / 0 km which is indeterminate. In the first few km, the car use energy (Wh) to condition the battery to its normal operating temperature hence the Wh consumed is out of proportion to the normal energy efficiency of the car. Once you drove a more significant number of km (mine is around 20km) the average energy efficiency returns to the normal of 173 Wh/km. When you park but did not charge, the Wh/km is not reset, therefore you continue to see the average Wh/km from the last time you charged.

    Hope this makes sense.
     
  3. krnshh

    krnshh Member

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    Alright I see. Thanks. Does pre-conditioning help offsetting that to some extent?
     
  4. ThosEM

    ThosEM Space Weatherman

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    #4 ThosEM, Jul 21, 2015
    Last edited: Jul 21, 2015
    I'd like to understand this behavior, also. It's really annoying when starting out on a leg and the estimated energy remaining at the end of trip declines quite significantly during the first 10-20 km. One worries that "this isn't going to work"! But then it bounces back up when this effect dies away. Better that way than the opposite, but still...

    One speculation is that the energy use while sitting is being spread / bookkept into the consumption shown while underway, to avoid an initial spike. But I believe I'd rather see the spike and have accurate information while underway, if that is the actual cause.

    Another speculation is that the battery management system has gotten behind in cooling the battery while charging and needs to continue cooling after getting underway for some period, analogous to departing with a cold battery that is insufficiently preconditioned. If that's the case, there's not much that can be done about it, except to improve the Nav energy estimate by teaching it to better account for the impact of this on the bottom line.
     
  5. Soolim

    Soolim Member

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    #5 Soolim, Jul 21, 2015
    Last edited: Jul 21, 2015
    Theoretical yes, but it depends on how Tesla implements the pre-conditioning power sourcing. i.e. does the pre-conditioning 1) use the AC power from you home or 2) does it use the battery power while the car is still plugged-in? answer 1) would make sense, but i am not sure. Only way to find out is to try it.
     
  6. JohnQ

    JohnQ Active Member

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    For energy use after supercharging I would agree with this speculation. Still cooling the battery while driving

    For 10 kW charging, assuming warm exterior temps so no battery warming, I haven't seen a spike that lasts more than a mile (if that). Dead of winter is a whole different issue.
     

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