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Wh/mi discrepancy

Discussion in 'Model S: Battery & Charging' started by tomas, Jan 30, 2017.

  1. tomas

    tomas Only partially psycho

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    my 2012 P85 is at ~35k miles with lifetime wh/mi of 317. I have aftermarket 20" wheels.

    While it was in for service, my loaner was a 2013 S85 with 38k miles riding on 19" wheels.

    Service took 5 days. I have a regular drive I do several times per week of about 25 miles round trip. In my car, I consistently average around 315 wh/mi for that trip. The loaner S85 averaged ove 340 wh/mi. Neither car in range mode.

    I thought S85 was rated more efficient than P85. My experience exactly opposite. What gives??? Any guesses?
     
  2. Andyw2100

    Andyw2100 Supporting Member

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    When you say you usually average 315 wh/mi on the trip is that across all weather conditions, and was it perhaps colder than average when you drove the S85?

    (I know you've been around TMC a long time, so I'm doubting that is it.)

    Another possibility to account for some of the difference could be very new tires, with higher rolling resistance, on the loaner, and older tires on your car.

    The 19" wheels vs 20" wheels would give the edge to the loaner, so I've got nothing there.

    Do you have a theory?
     
  3. Blup85

    Blup85 Member

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    Its crazy how much watts/mi vary. Check this out..

    Brought my p85 to dealer for Annual maintenance averaging 340w/mi+

    Loaner car they gave me (s85) averaged 305watt/mi for 5+ days while getting serviced (same tire size as my p85"

    Got my car P85 back, got closer to 310watts/mi (alignment was about the only big change)

    Brought P85 back to dealer after 3 months with bad door handle, and rear motor was making a little more noise so they replaced the motor (~345w/mi).
    Received EXACTLY same s85 I drove 3 months earlier as rental. Rental s85 now averaged 350 watt/mi for 5+ days while I had it...and had a nasty wheel vibration at 65+

    Got my P85 back and for the last 5 days, averaging about 320 watts/mi...

    I blame wheel alignment and tire pressure. I also know my front rotors are just slightly warped as well. (working on a replacement)
     
  4. Sparrow

    Sparrow S105/ Roadster 189

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    I was under the impression that in 2012 the P85s and S85s had the same range ratings.

    In any event, I have a 2012 Signature P85 and have never had a loaner that got as low a Wh/mi as my car. That includes an S60 as well as numerous S85s and P85s. The only dual drive car I had was a P85D and it too did not get as low a Wh/mi as my car.

    I think the tires are a big part of it. I also think that if you are really trying to get low Wh/mi number, you need to get use to the most efficient way to drive that particular vehicle.
     
  5. tomas

    tomas Only partially psycho

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    I don't think weather was factor. I had forgotten the impact of alignment and tire pressure, though that alone doesn't seem to explain the variance.

    I'd like to believe @Sparrow that our 2012s have some edge. Only difference I can think of being A pack battery. Could it be they are better discharge in some way?

    I know there's a lifetime wh/mi thread which has collected a ton of data. I'll go ask over there too.
     
  6. No2DinosaurFuel

    No2DinosaurFuel Active Member

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    As far as I know, the P85 and S85 are identical. The only change is the the SW (to limit acceleration). I think wk057 posted something where he hacked the firmware of the S85 to make it think it was a P85 and got close if not the exact same performance. Hence I would not be surprised if one is less efficient than another depending on how you drive. Also keep in mind, weather, climate control, as well as age and degradation of the battery. As battery ages, then develop higher impedance, thus overall less efficient as they produce more heat when using them at higher current.
     
  7. tomas

    tomas Only partially psycho

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    I'm pretty certain P85 has different drive unit. It is different part number. While I'm sure you could tell lesser DU to perform like a P, on a sustained basis you would be risking reliability. So WK's experiment would not prove same unit.
     

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