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Average CAC drop for a winter

Discussion in 'Roadster: Technical' started by marco2228, Dec 8, 2014.

  1. marco2228

    marco2228 Roadster Signature #34

    Nov 19, 2010
    Cologne/Bremen , Germany
    There are several posts, where TMC members wrote about a CAC drop in the winter. But I never found any numbers.
    Since this is my first winter with the Roadster it would be good to know some numbers, what I can expectant don't have to worry about.

    time frame: 1.5 month
    approx. temp difference in the CAC decrease time frame: 15 - 20 K
    lowest temp: -5 °C
    CAC decrease: 2.5 Ah

    Would be great to collect some data sets (of these four values) of other Roadsters.

  2. PV-EV

    PV-EV Member

    Jun 3, 2011
    #2 PV-EV, Dec 19, 2014
    Last edited: Dec 19, 2014
    My experience has been a bit different than others. Here are some numbers for our car from last winter. The car is garaged at about 10C overnight and days when it isn't driven. Driving temps in the winter are generally well below 0C.

    DATE CAC. ODO S.miles/R.miles
    10/05/13 156.55 17408
    10/17/13 157.01 17810
    10/25/13 157.77 17849
    10/31/13 158.06 18111
    11/12/13 158.74 18473
    1/19/14 159.39 18726
    1/22/14 159.39 18855 258
    2/24/14 159.27 19072
    2/26/14 159.41 19089 254
    3/3/14 159.45 19326
    3/9/14 159.71 19345 254
    3/31/14 159.70 19954
    4/24/14 158.52 20105 246
    4/29/14 156.75 20327
    6/8/14 155.76 21239 187

    Sorry my Excel spreadsheet didn't copy very well
  3. dpeilow

    dpeilow Moderator

    May 23, 2008
    Winchester, UK
    So your CAC *goes up* in winter? Your battery seems in very good condition.
  4. PV-EV

    PV-EV Member

    Jun 3, 2011
    Yes. It went up. At least last winter. I don't have data for the previous year. Some local factors that might effect our situation:

    It is seldom hot in Alaska. Rarely over 25C.
    A typical week is:
    Charge to full in standard. Drive 110 mile commute. Charge to 50%. Three days later charge to full in range mode. Return 110 miles commute. Four days later charge to full in standard. And so on. Car spends a lot of time around 50% SOC.

    The battery does seem to be in excellent condition. Unfortunately the car currently has a few other problems :(

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