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Charging efficiency and battery longevity

Discussion in 'Model S: Battery & Charging' started by Stoobie777, Feb 2, 2013.

  1. Stoobie777

    Stoobie777 New Member

    Joined:
    Feb 2, 2013
    Messages:
    3
    Location:
    Prospect, KY
    My car is currently being build and I opted for the dual charger and high power wall connector. I am running a 100 amp circuit so I will be able to charge at 80amps, I know I can set the charge rate on the screen in the car from as low as 5 amps to as high as 80 amps and anywhere in between. Does anyone know at which amp rate the charger is at its highest efficiency , and does anyone know what amp rate is optimal for the batteries longevity ? As an example if I have 24 hours before I need to drive the car again and I only need to charge 40 miles to full, so speed of charge not being an issue. Would I want to set the amps to 5, 10, 20 .......80 or does it simply not matter?
     
  2. bob_p

    bob_p Member

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    Apr 5, 2012
    Messages:
    939
    When I had my garage wired, I had the electrician install the 100A circuit - and connect a 14-50 outlet to the circuit (since the HPWC is still back-ordered). I've been using that to charge the car the last 10 days since it arrived - and typically get 22-25 Wh/hour charge with the 14-50.

    When the HPWC comes in, I plan to have it connected to a second outlet on the same circuit - so I'll have the choice of charging with either the 14-50 or HPWC. Should the HPWC ever have problems, I can drop back and use the 14-50.

    Good question about the impact of charging at various amp levels vs. battery life. If that really has an impact, hopefully Tesla will provide charge timers - and automatically adjust the amp level to provide optimum charging within the available (overnight) time.
     
  3. Robert.Boston

    Robert.Boston Model S VIN P01536

    Joined:
    Oct 7, 2011
    Messages:
    7,842
    Location:
    Portland, Maine, USA
    Tom Saxton investigated the efficiency of charging at various rates up to 240v/70A on the Roadster; his blog summarizes his findings. His conclusion:
    All of the rates we can achieve with AC charging are well below 1C; in fact, on the big battery, 20kW / 85kWh = 0.235. Charging LiIons at a rate below 1C is generally fine. More to the point, Tesla has included battery management that ensures that your charging won't hurt the battery.

    @bob_p: I hope your electrician installed a 50A breaker on that 100A circuit running with the NEMA 14-50. Otherwise, it's not NEC compliant.
     
  4. tezco

    tezco Sig P85

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    Nov 9, 2012
    Messages:
    818
    Location:
    Colorado
    Both my Leaf & the S have to run ancillary systems (charger coolers & battery heaters on the S in times of cold) so low charge currents extend the charging time and thus extend the time that these "nonproductive" loads gobble electrons from the wall. Efficiency might be maximized by starting a charge when you first get home in the winter (battery is still warm), but waiting a bit in the summer (battery too warm). Some posts also discuss ways to plan your charging so that the battery heats up slightly just prior to your next departure (if too cold, regen is very weak and battery power is used to heat the pack back up).
     
  5. SigS905

    SigS905 Sig S 905 + X 5

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    May 9, 2012
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    198
    Location:
    FV, CA
    Charged at the Hawthorne super charger today.
    IMAG0189.jpg

    IMAG0192.jpg
     
  6. Lloyd

    Lloyd Active Member

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    Jan 12, 2011
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    4,885
    Location:
    San Luis Obispo, CA
    How many spots does Hawthorne have now? I will need to charge there next month.
     
  7. SigS905

    SigS905 Sig S 905 + X 5

    Joined:
    May 9, 2012
    Messages:
    198
    Location:
    FV, CA
    When I checked online this morning with Recargo, it said that there were two working. Tha far right one was supposedly having charging issues, so I just went the the next one. Didn't check any of the other chargers. Roadster parked in the far left one, but not charging.
     

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