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Math Test for you Tesla Geeks!

Discussion in 'Model S: Battery & Charging' started by Daniel Scherer, Apr 13, 2013.

  1. Daniel Scherer

    Daniel Scherer Junior Member

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    Ok you number crunchers. Does it make more sense to drive slow and efficient or fast and furious to get to your destination to get plugged in as soon as possible to get charging. I commute one way 104 miles, all highway and plug into a 208v 14-50 outlet and I have 4 hours to top off for my trip home. Is the power you are trying to conserve worth the time lost for charging? What is your opinions on the tortoise vs hair regarding an EV?
     
  2. Al Sherman

    Al Sherman It's about THIS car.

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    Excellent conversation starter for a rainy Saturday morning.
    I think it's a personal preference thing given this scenario. I'm a tortoise. Always have been. With everything else being equal (their are tons of variables) I'd say 104 miles in a P85 is a green light to drive however you want. I like the energy conservation game. I'm enjoying keeping my projected range above my rated range. If you want to max perform the MS on the way (within SOME limits obviously) go for it.
    You can't charge any faster than me but it doesn't matter because assuming we left the house with a standard charge full battery; we'll both easily put on enough charge to get home with either driving style. You'll just arrive at either place 20-25 minutes before me, and it'll cost me less.
     
  3. Daniel Scherer

    Daniel Scherer Junior Member

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    I've tried it slow 66 and faster 72 in both directions and the trip going there in the morning always uses more power. I suspect it's an uphill climb 400' elevation over the 104 miles driving north then west. Coming home east then south, I can drive 80-85 and use as little as 320wH average 20 to 40 miles of battery power savings difference 40 degree temps. I'm thinking coming off a fresh charge and heading home has the battery warmed up and the drivetrain is still warmed up so its more efficient.
     
  4. stevezzzz

    stevezzzz R;SigS;P85D;SigX

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    Hills and headwinds :: range killers.

    But Al is right: with four hours to charge @40 amps and a 208 mile round trip, you can drive pretty much any way you like. Unless the charger fails or isn't available: then you might have to hypermile it home if you had a spirited morning commute...

    Do you pay for the charge at work??
     
  5. Daniel Scherer

    Daniel Scherer Junior Member

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    This timing out and losing reply's is annoying.

    Yes! On one -8 degree day the old 14-50 outlet had a ground fault and I had to plug into a 110 which maintained my battery level but I got home with 10 miles remaining. I was sweating bullets that day. My company installed a new dedicated 14-50 outlet in a secure area for me. I deduct miles gained at $.03 cents per/mile from my mileage report so no one can claim I'm getting it for free. I sought executive permission to plug in 2 months before I got the car and they gave me a written authorization to keep in my car so I can plug in at any one of my company locations. I've given a few VP's a performance ride and they responded with the typical "Holy [email protected]!" Response on launch.
     
  6. dave

    dave Member

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    Nice set up. I'm starting a new job Monday, and I'm wonder when/if I should ask them to put in a charger.

    Do you cart your UMC around with you every day? Seems like that would get old.
     
  7. ItsNotAboutTheMoney

    ItsNotAboutTheMoney Active Member

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    Hills kill. You're working against gravity and for a heavy car that makes a big difference. Although BEV efficiency is more linear, you still lose efficiency as you work the motor and battery harder. A compromise is to lower speed on the steepest part of your drive, to balance the increased gravity with decreased drag and rolling resistance.

    Other things to consider:
    - Climate control: it has a serious effect on BEV efficiency math; the slower you drive the more your use, and the amount of use depends on temperature; climate control offsets gains from decreased speed.
    - Temperature: lower temperatures increase drag and rolling resistance. Slowing down will have a greater benefit in lower temperatures.
    - Wind: headwinds increase drag, tailwinds decrease drag, sidewinds can really mess with drag. You can adjust driving to prevailing winds and slow down on legs with unfavorable wind.
    - Traffic: braking and re-acceleration or bursts of acceleration for overtaking reduce efficiency; as a guy called Broder found, it's easy to think you're driving at one speed while you're actually varying speed to deal with traffic. Antipatory focus and driving with a good buffer helps efficiency as you can decrease the amount of sudden maneuvers; find a speed that minimizes maneuvers and your drive should be more relaxed (it helps if you can mentally brush off tailgaters).
     
  8. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    However, you can mitigate some of the effects of hills by allowing the car to slow down a bit when going up.

    The biggest climate control hit is getting the car to the right temperature to start with. Precondition the car while charging before you take off and the climate control will have less of an effect.

    Yes indeed.
     
  9. Jason S

    Jason S Model S Sig Perf (P85)

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    104 miles plus 4 hours to top off on a 50A circuit? Pfft, drive as fast as possible since you get almost all the miles back on the 4 hours of charge.

    If the question was zero charge at the far end then you'll need to be more efficient at some point. Prolly traveling near the speed limit would be good enough (assuming 65mph).

    Or... what they said. ^^^
     
  10. Daniel Scherer

    Daniel Scherer Junior Member

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    I'd ask right away. Scout out electrical options at your work site and see if you can easily tap some existing feed near where you will park. I did this and contacted a local electrical contractor and got pricing for the 14-50 outlet. I also put together the costs of the electricity usage at peak demand as most people don't know how cheap it is to charge. They think it will cost $75 not $2.50. Yes I take my UMC with me. Having this included in the written request helped seal the deal at first request. I did prep everyone by forwarding them info about the car. 90% had never heard of TESLA.
     

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