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Uphill - Distance/Elevation vs Range

Discussion in 'Hong Kong' started by wslam, Jun 5, 2014.

  1. wslam

    wslam Member

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    I wonder if anyone may know... perhaps a Roadster owner?
    Say if one drives from Pacific Place to the Peak Galleria, according to Google Map, that's 6.2km.
    What kind of 'range' do you think is realistic that will be used for this 1800ft climb?
     
  2. miimura

    miimura Active Member

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    The rule of thumb is that it requires an additional 7 miles (11 km) of range for each 1,000 foot of elevation gain. You might gain almost 6 miles (9.6 km) of range for each 1,000 ft of descent, as long as you don't have to use the friction brakes. Your example is only 6.2km according to Google Maps, so you would probably consume 20km of range for that trip.
     
  3. mchk

    mchk Member

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    Thanks for that bit of information. I live up on a hill/mountain as well and was wondering the same thing.
     
  4. DITB

    DITB Charged.hk co-founder

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    Where it becomes really interesting is how you charge at home, when you live at the top of a mountain.

    If you start out with a full battery, then you will have to use the mechanical brake when you leave your home, as the battery cannot absorb any more.

    Luckily, the Tesla Model S allows you to charge up to different levels, so just charge to 70% or 80%, whatever is needed to keep the regen active (I am not sure what charge level it cuts off, and I think it is gradual).

    The mountain test is really interesting, in terms of testing how efficient regen is. I don't have South Lantau access permit, but I would really like to try to drive back and forth between Tung Chung and Cheung Sha several time, and compare the km driven when you keep going up a steep mountain road like that, and then regen on the other side going downhill, to a trip where you just go straight and level for a while. There will be losses, but how much? No doubt that in an ICE car, all becomes excess heat in brakes and forced high revving engine. If the battery isn't too full, can you keep the speed down on the downhill, without touching the brakes? Just let go of the pedal on top of the hill and see what maximum speed it goes to.

    I read somewhere that if the downhill is optimum descent gradient, then you can more or less keep the range, i.e. if you have 300 km range at the top, you will have just around the same at the bottom of the hill.

    South Lantau is great because there are not really any significant turns, but one probably have to do it at 4 in the morning, to avoid being stuck behind a bus, and if no South Lantau permit ... hopefully the Sheriff is sleeping tight.
     
  5. wslam

    wslam Member

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    Thank you! This is very helpful. Is this based on your experience or is this some calculation based on some kind of principles?

    ws

    - - - Updated - - -

    Exactly. I do not intend to charge to full as it is not recommended. so lets say if I charge to 80% on top of a hill, when I drive down, I assume at best it will go up to say 82 to 85%...

    - - - Updated - - -

    Exactly. I do not intend to charge to full as it is not recommended. so lets say if I charge to 80% on top of a hill, when I drive down, I assume at best it will go up to say 82 to 85%...
     
  6. DITB

    DITB Charged.hk co-founder

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    Don't expect it to go up too much (according to what I have read), more like getting the distance for free. Yes, I was surprised as well, yet it depends on how consistent the decline is, and whether or not you need to use the brakes.
     
  7. miimura

    miimura Active Member

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    This is based on experience from Model S owners. However, if you break out the math to calculate the energy required to lift the mass to that height, it is well supported.
     
  8. stevezzzz

    stevezzzz R;SigS;P85D;SigX

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    The S has so much excess power for the up hills and so much regen braking for the downhills that you can literally set the cruise control at any speed you want at the bottom of the steepest hill you're likely to encounter, and never touch either pedal all the way to the top and back down the other side.

    As for adding range on the downhills, watch your kWh used on the trip meter: you won't see the Rated range climb until you add one full kWh through regen. There is a long descent I've driven several times here in Colorado where I actually add an extra 6-7 miles of rated range, a little more than 2kWh added to the pack.
     
  9. GasDoc

    GasDoc Member

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    I've found the tools at GreenRace to be very accurate in judging energy usage.

    The UI leaves a bit to be desired but once you enter your waypoints and car configuration it works well.
     
  10. wslam

    wslam Member

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    Haha, that would be nice, but will never happen! Please understand that in HK, there is ALWAYS traffic, even at 2am, it is not easy to find a stretch of road that is empty.
    I just checked my Toyota Vellfire. The Vellfire's spec states 11.2km/L.
    I get 4.7km/L on mine, mainly due to the multiple hill climbs I have to make every day.
    If my 500km becomes 205km, it may be a challenge for the battery in terms of range on a busy day when we have to make multiple runs.

    - - - Updated - - -

    Thanks! I just tried. Not looking good... this is only a 5km drive, and look! Screen Shot 2014-06-07 at 0.53.54.png
     
  11. GasDoc

    GasDoc Member

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    Did you check the configuration of the car? I think they might default to a 60kWh battery.
     
  12. wslam

    wslam Member

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    This is with the 85kWh battery charged to 85%.
    This is just a ~6km route! I am starting to worry!
     
  13. GasDoc

    GasDoc Member

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    Reverse the trip and see what the round trip uses in terms of kWh. Regen is wonderful.
     
  14. wslam

    wslam Member

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    Reverse, I end up with 737km. But that does not help. I live on the hilltop. So it will be the end of the day when I need to make this climb...
     
  15. wslam

    wslam Member

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    EVTripPlanner gave me totally different results (which seems more realistic)

    Screen Shot 2014-06-07 at 16.25.32.png
     
  16. stevezzzz

    stevezzzz R;SigS;P85D;SigX

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    I have a lot of faith in EVTripPlanner's model. Regen is very efficient, so if you can stay off the friction brakes it does recapture about 85% of your potential energy during the descents (and a similar percentage of your kinetic energy as you slow down using regen only).
     

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