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General Driving Efficiency

Discussion in 'EV (Electric Vehicle) Discussion' started by bwilson4web, May 29, 2023.

  1. bwilson4web

    bwilson4web BMW i3 and Model 3

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    These are general guidelines, not hard and fast rules which are vehicle specific:
    • gas ignition engines
      • Pays a 'warm up' cost of heating to operational temperature.
      • Pays a waste heat cost keeping the drivetrain cool enough.
      • Pays a partial throttle cost from reduced compression-to-expansion ratio.
      • Pays a transmission loss matching engine speed to wheel speed.
    • diesel ignition engines
      • Pays a 'warm up' cost of heating to operational temperature.
      • Pays a waste heat cost keeping the drivetrain cool enough.
      • Pays a transmission loss matching engine speed to wheel speed.
    • hybrid, Toyota style
      • Pays a 'warm up' cost of heating to operational temperature.
      • Pays a waste heat cost keeping the drivetrain cool enough.
      • Avoids partial throttle cost by operating engine at peak efficiency.
      • Uses electric for partial power mode so engine runs at peak efficiency.
      • Pays a low transmission loss matching engine speed to wheel speed.
    • battery electric, Tesla style
      • Insignificant 'warm up' cost.
      • Insignificant waste heat cost keeping the drivetrain cool enough.
      • Insignificant partial power mode loss.
      • Insignificant transmission loss.
    This was brought home last night when on a single charge, I reduced my speed to achieve 5 miles/kWh and avoid a charging stop. Normally, I get about 4 miles/kWh at posted speed limits. At higher traffic speeds, this falls to 3-3.5 miles/kWh. Had I been in any other vehicle, going slower would be 'less bad' but the waste heat and transmission losses would cost.

    When driving at traffic speeds (i.e., posted speed + 10 mph,) I have to go fast DC charger to fast DC charger. Arrival at each fast DC charger is at minimum battery level so charging is as fast as possible. Charging duration is often less than the necessary biology break.

    Bob Wilson
     
    #1 bwilson4web, May 29, 2023
  2. hill

    hill High Fiber Member

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    Might not the efficiency observations include "utilizing" waste heat from plug-in ICE - to both warm cab & traction pack, plus recharge traction pack - as well as range extending? Especially during sub zero temps?
     
    #2 hill, May 29, 2023
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  3. bwilson4web

    bwilson4web BMW i3 and Model 3

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    If I saw evidence of waste heat usage beyond cabin comfort, yes. But the waste heat is about two orders of magnitude greater than cabin heating requirements.

    As for BEVs, the example of mine, the cabin is preheated or important in Dixie, cooled by grid power. Within the time it takes from deciding to leave and getting in the car, ~10-15 minutes, it is done. The comfort maintenance energy is much less than cold aerodynamic and tire effects. Air conditioning is fairly low. More recent Teslas use a heat pump for even less loss.

    Bob Wilson
     
    #3 bwilson4web, May 29, 2023
  4. Isaac Zachary

    Isaac Zachary Senior Member

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    I've contemplated putting a heat storage tank on an ICE vehicle and coming home to use it instead of a hot water heater.

    On the flip side I've thought of running a generator at home to charge an EV and using the waste heat to heat water or the house.

    (Either way I don't think my landlord would aprove).

    Everything has pros and cons. Using just a onesided approach doesn't mean that there are no cons. Take charging an EV at home for an example, which may be easy for some people but near impossible for others. I write this from a home with two ICE vehicles that are regularly driven and a 30A 120V power service for the entire house.
     
    #4 Isaac Zachary, May 29, 2023
    Last edited: May 29, 2023
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  5. fuzzy1

    fuzzy1 Senior Member

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    Install rooftop solar generator to charge the EV, and to operate a heat pump water heater, and to operate heat pump HVAC, and handily beat all of the above.

    That would scuttle my suggestion too.
    That must be ancient. I think even the current local "tiny houses" have greater service than that.
     
    #5 fuzzy1, May 30, 2023
  6. ammdb

    ammdb Active Member

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    After using the i3 as a daily driver for over a year now, I've found it cost the same or even a bit more than when I was driving the '01 Prius. I do all my charging at home, so on paper this doesn't make sense. Part of it might be electric rates have gone up, but I think it's mostly due to the extra power used to precondition the car during the colder months, and getting all the cabin climate control from battery power. In winter there's no extra cost for heat with an ICE. When the ICE idles it waist energy, but some of that goes into the AC on hot days.
     
    #6 ammdb, May 30, 2023
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  7. Isaac Zachary

    Isaac Zachary Senior Member

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    In countries like the USA, yes.

    But in places like every country from Mexico to Argentina and in between, that's pretty much standard. Of course some would contend that in those countries there aren't enough drivers or typical driving distances to make much of a difference if they drive ICEVs or EVs.
     
    #7 Isaac Zachary, May 30, 2023
  8. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    Ah cripes, you may have just coined another acronym.
     
    #8 Mendel Leisk, May 30, 2023
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  9. Trollbait

    Trollbait It's a D&D thing

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    Actually been around for some time. I believed coined around the time of HEV and HHV, which happened before they were used here. Context of our discussions, mostly means it is safe to drop the V. Which lead to most not knowing there was an ICEV.;)
    I think there is a SAE Lexicon out there that gathered all these terms up, if not actually create them.

    HHV = hybrid hydraulic vehicle
     
    #9 Trollbait, May 30, 2023
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  10. bisco

    bisco cookie crumbler

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    big difference in climate between indy and bama as well
     
    #10 bisco, May 30, 2023
  11. Isaac Zachary

    Isaac Zachary Senior Member

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    Doing some quick googling, there seems to be a little over 50 million vehicles driven in Mexico and another 50 million in Brazil. By contrast there are around 238 million drivers in the USA. I'm not sure exactly how vehicles vs drivers relate between these countries, but I'd be willing to guess that the vehicular air pollution problem from all of Central and South America is comparable to the entire USA, if not actually worse.
     
    #11 Isaac Zachary, May 30, 2023
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