Elevation revisited

Discussion in 'General' started by hobbit, Jul 16, 2021.

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  1. hobbit

    hobbit Well-Known Member

    I've been searching through old posts to find any meaningful figures on how elevation change
    [taken alone] affects real world range. This thread didn't really get into numbers, but it
    should be a simple "mgh" calculation from lifting X amount of mass Y distance, and getting
    (some of) it back on the down. Roughly converting feet of height into EV kWh and thus miles
    on the flat, for the Kona at a tad over 4000 lb gross I get about 6 - 7 miles lost per 1000 feet
    rise, which doesn't seem like a whole lot to worry about unless you're in serious mountains.

    How heavy is a typical Model S? Ballparking something over 5000 pounds, that might be closer
    to 8 - 9 miles. One benchmark I have is that it takes almost exactly 12 kWh indicated to drive
    a Model S from the gatehouse to the top of the Mt. Washington auto road in NH, a rise of 4200
    feet and distance just shy of 8 miles. I learned this at an energy/vehicle festival up there
    a few years ago. The math for that seems to work out reasonably well: ~ 9-ish kWh for the hill,
    and 3-ish for traversing the often rough road.

    What are other folks' observations, if any?

    _H*
     
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  3. For the Kona 6-7 seams about right. From Bakersfield to Tehachapi where I live is about a 3500 foot climb which uses an extra 20-30 miles of range
     
  4. Bruce M.

    Bruce M. Well-Known Member

    I have gone from San Francisco, elevation maybe 60-70 feet, to visit family in the Sierra foothills, elevation about 2,800, in my Kona Electric. It's about 155 miles one way, but I used about 175 miles of range, as reported by the car -- and gained pretty much all of it back on the way home
     
  5. bwilson4web

    bwilson4web Well-Known Member Subscriber

    Test Vehicle
    • 2019 Std Rng Plus Model 3, Odometer 49824 mi
    • Version 2021.4.18.2
    • 4,000 lbs weighed in 2019 at truck stop scale
    • 18" Bridgestone ECOPIA, light weight rims, 50 psi
    Test Protocol
    • 73 F, 4:30 AM, no wind, dry pavement, 63 mph, Autopilot steering and speed control
    • Flat segment:
    • upload_2021-7-17_5-16-7.png
      • 1st pass: 1.5 mi, 229 Wh/mi
      • 2nd pass: 1.4 mi, 226 Wh/mi
    • Hill climb and descent:
    • upload_2021-7-17_5-19-50.png
      • Climb: 1.4 mi, 776 Wh/mi ~= 1,086 kWh
      • Descent: 1.5 mi, -241 Wh/mi (charged) ~= -239 kWh
      • ~2.9 mi, 847 Wh, ~292 Wh/mi
      • 292 - 228 ~= ~64 Wh lost ascending and descending 525 ft hill
      • 121.9 Wh / 1000 ft or ~0.53 miles / 1000 ft
    • Vehicle energy graph:
    • upload_2021-7-17_5-27-2.png
    I do have the original photos. Questions?

    Bob Wilson
     
    Last edited: Jul 17, 2021
  6. hobbit

    hobbit Well-Known Member

    Yes. First, I don't think you used over a megawatt-hour to go up a hill. Second, I'm not talking about
    round trips, despite the usual truth that what goes up must come down. Reading between the figures,
    though, it looks like you would lose ballpark 4.6 miles per 1000 feet rise, which is not bad. Maybe I'm
    off with the mgh math. Does a M3 really only weigh 4000 lb loaded? That's on par with the Kona,,

    _H*
     
    bwilson4web likes this.
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  8. I'll take your number of 6 to 7 miles per 1000 feet as a useful rule of thumb, taken alone, when travelling at speed. Thank-you.
    Not taking it alone has me making an observation. Roads over and through hills are sometimes quite twisty, and so we have to slow down. Probably this has been commented on elsewhere, but there are hilly roads that are "self correcting". My son and his partner live 85 kms away on the other side of a range of hills called the Remutakas, and we go over there weekly. The journey is at 100kph from sea-level to the foot of the hills, then a five minute climb up to the 556 metre high Remutaka Pass via a very twisty but not particularly steep road, then 10 minutes down a similarly twisty road, and then on the flat back at 100kph to the destination. At the end of this the consumption and range is the same as it would have been on the level, because the slow speed going up and down the hill has reduced the aerodynamic drag, making up for the difference in energy used hauling the car up, and what was regenerated coming back down. Very cool! And you get the fun of driving the road. There are only three passing sections on the uphill lanes, which are not long and certainly not straight, and the grunt of the EV makes overtaking feasible.
    So this hill has not affected the range, just the journey time.
     
    Last edited: Jul 17, 2021
    bwilson4web likes this.
  9. bwilson4web

    bwilson4web Well-Known Member Subscriber

    Some additional technical details:
    • 4,000 lbs - was measured at the Pilot Travel Center, 3240 Point Mallard Pkwy, Priceville, AL using their "CAT" scale. The stock, 2019 Std Rng Plus Model 3 comes with ~55 kWh battery, the smallest Tesla sells. At the scale, the extra weight included me and wife's three dogs and tool box using stock tires and wheels.
      • For the hill climb benchmark, it was just me, down 20 lbs, and four tires+wheels that save about 10 lbs each. The tires and low rolling resistance wheels are part of an effort to reduce the expect 5% battery decline in the first year. I'm measuring ~3.3% decline after 2 years and 4 months. (NOTE: I'm using staggered tires, fronts are lower than rear, and all are ~10 mm narrower than the stock tires.)
    • 63 mph (101 kph) - based on earlier Prius studies, this speed gives EPA mileage results. Fortunately many trucking companies limit their level road speed to 65 mph making dynamic cruise control a simple solution for longer range.
    • Heart of Dixie Highway (Brindley Mountain, Hwy 231) - one of the few straight sections that has an ~8% grade, ~1.2 mi length, and 525 (160 m) elevation. There are taller hills but their former logging roads have hairpin curves. Regardless, it is my 'benchmark' hill as from a standing start at the base, I do a full power climb. Our past Prius barely reach about 95 mph at the crest. The BMW i3-REx is speed limited to 94 mph and reaches it well before the crest. The Tesla Model 3 exceeds 110 mph while accelerating and we have to heavy brake to avoid the 85 mph limited curve after the crest.
    • 'kWh' vs 'Wh' - opps! I'm used to dealing with charging versus Wh units. Fixed below signature.
    Bob Wilson

    Test Vehicle
    • 2019 Std Rng Plus Model 3, Odometer 49824 mi
    • Version 2021.4.18.2
    • 4,000 lbs weighed in 2019 at truck stop scale
    • 18" Bridgestone ECOPIA, light weight rims, 50 psi
    Test Protocol
    • 73 F, 4:30 AM, no wind, dry pavement, 63 mph, Autopilot steering and speed control
    • Flat segment:
    • [​IMG]
      • 1st pass: 1.5 mi, 229 Wh/mi
      • 2nd pass: 1.4 mi, 226 Wh/mi
    • Hill climb and descent:
    • [​IMG]
      • Climb: 1.4 mi, 776 Wh/mi ~= 1,086 Wh
      • Descent: 1.5 mi, -241 Wh/mi (charged) ~= -239 Wh
      • ~2.9 mi, 847 Wh, ~292 Wh/mi
      • 292 - 228 ~= ~64 Wh lost ascending and descending 525 ft hill
      • 121.9 Wh / 1000 ft or ~0.53 miles / 1000 ft
    • Vehicle energy graph:
    • [​IMG]
     
    Last edited: Jul 18, 2021
  10. Texas Niro EV

    Texas Niro EV Active Member

    Tom Moloughney established a factor of 1.5 kWh per 1,000 feet of elevation increase on his Nissan Leaf range chart years ago. I use that factor for the planning on all my long EV trips and the factor has always worked well for me. If you are driving an EV that has significant weight difference compared to a Leaf then you probably want to factor in the weight difference in your range calculations.

    I think you guys are way over thinking this. Just pick a factor and adjust it based on your own experience. Remember to apply the KISS principle.
     
    bwilson4web likes this.
  11. hobbit

    hobbit Well-Known Member

    1.5 kWh per 1000 ft matches my original scenario pretty well, in fact.

    _H*
     
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