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Vampire Drain Measurements

Discussion in 'Model S' started by Haxster, Aug 14, 2017.

  1. Haxster

    Haxster Member

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    Location:
    Silicon Valley
    While on vacation, I left our December, 2016 build HW2 90D MS connected through the Tesla Mobile Connector to 240V. The car has ~4,800 miles on it. The charge rate was set to 50% at 5 Amps. Energy Savings was ON and Always Connected was checked. Cabin overheat protection was on (D’oh!), but the interior never got hot enough to turn on the AC (or at least I believe this to be the case with the car in the garage and no high ambient temperatures logged by our weather monitor).

    The kWh meter was set to zero well after the car was charged to 50%.

    Here’s what I observed while periodically checking with the “Power for Tesla” iPhone app:

    1. The “miles” fluctuated from 140.4 (48%) to 146.3 (50%).

    2. The total energy used over 13 days was 8,262 kWh. That’s about 26W/hour. At 315 W/mile, that works out to around 2 miles a day.

    Note: The Mobile Connector uses about 3W in standby. So, the incremental power to charge the car is closer to 23W/hour when the Mobile Connector is always plugged into the wall.

    More details about my home charging setup can be found here: www.youtube.com/watch?v=Tc8jErJ28hQ
    13 days.JPG
     
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  2. David99

    David99 Active Member

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    I measured the energy using using the CAN bus. For a 24 hour period my car used aprox 1.6 kWh. That's about 5 miles of range. My car was set to 'always connected' and the energy saving option was turned off. I also have two apps/services connecting to the car every minute. That is probably the worst case scenario for an idling car.
     
  3. SucreTease

    SucreTease Teslarian

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    Huntsville, Alabama
    Your units should be Wh/hour (which is the same as simple W) and Wh/mile.
     
  4. Haxster

    Haxster Member

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    Yup. I stand corrected.
     
  5. SDRick

    SDRick Member

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    Jun 25, 2015
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    Location:
    SD CA United States
    Never thought of my car as a big wall wart. 25W per hour doesn't sound like much until you add it up over time or convert to miles. It's quite a bit of energy!
     
  6. Thiago

    Thiago S75D

    Joined:
    Aug 15, 2017
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    Location:
    St Julien en Genevois - France
    I post this here as a serious life and death question. Okay. Maybe I am exaggerating. I have a S75D.
    I plan to go skiing and I will arrive at the top of the resort (Tignes) with about 40% battery remaining. Whether I can charge there is unknown. How much battery drain can I expect in 4 days considering the temperatures will likely be in the -10C range on average?
    Thank you for your help.
     
  7. mknox

    mknox Well-Known Member

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    Toronto, ON
    Mine has gotten worse at it ages. I see about 2.5 to 3 kWh of vampire loss every day it sites idle. Same summer or winter. When new it was less than half that.
     
  8. David99

    David99 Active Member

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    I don't think it's the battery itself. I think it's a lot of added features and processes running using up more energy. For example I have the issue that my dashboard screen locks up once a day. It started after a firmware update a few months back. Service center said it is running low on memory. It never did that before. So it seem the hardware is having trouble running all the new tasks leading to higher consumption.
     
  9. mknox

    mknox Well-Known Member

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    Perhaps, but mine seems to track quite a bit higher than others who report with newer cars. I've read that lithium batteries can tend to self-discharge at a higher rate as they age. Mine is nearly 5 years old with just about 100,000 miles.
     
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  10. David99

    David99 Active Member

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    I think the newer cars were designed to use less energy when parked. I know they really focused on that with the Model 3.

    Another interesting data I found recently on the CAN bus was the total charge and discharge cycles on my battery. First I thought, why would there be two separate counters and why would they not be the same? Then I realized the charge cycles are always higher because of the natural self discharge of batteries. Comparing those numbers you can figure out how much was lost through battery self discharge. In my case I have 857 charge cycles and 507 discharge cycles. In other words, on average I lose about 6% energy due self discharge. I'm not sure if the discharge cycle counter includes the onboard systems usage or not.
     
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