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Consumption and efficiency differences climbing various grades

Discussion in 'Model X: Driving Dynamics' started by ohmman, Dec 5, 2016.

  1. mengwong

    mengwong Member

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    So, my Airstream Sport 22FB has been invited to spend New Year's in Tahoe.

    Can my X75D with 220 (÷2) miles of range get it there?

    In theory, it's 78 miles from the Rocklin supercharger to Truckee.

    In practice, it's that plus 9000 feet of elevation gain. What's the rule of thumb? 12 towing miles per 1000 feet? That's more energy going up than across.

    Screen Shot 2017-12-20 at 10.22.28 PM.png

    Ohmman's footnote, and allowing for rain/snow, means I'm probably going to need a CHAdeMO adapter. EvGO has just turned on outlets at Colfax, Dutch Flat, and Emigrant Gap. So I guess that's where I'll be spending most of Saturday Dec 30th.

    Screen Shot 2017-12-20 at 10.54.53 PM.png
     
  2. hiroshiy

    hiroshiy Supporting Member

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    How much does Airstream (plus cargo) weigh approximately? You can at least calculate energy consumption from gravitational energy. Regen is a different story but you are worrying about just claiming up.
     
  3. ohmman

    ohmman Plaid-ish Moderator

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    Depending on your route, you're welcome to stop by and borrow my CHAdeMO for the trip. You'd need to swing through Sonoma. PM me if you're interested.
     
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  4. EV_enthu_jp

    EV_enthu_jp Member

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    In theory, we'll need additional gravitational potential energy than a flat road.
    Gravitational Potential Energy
    PE-gravitational = m * g * h (joules)
    assuming...
    m = 3000kg (X75D) + 2000kg (22FB) = 5000kg
    g = 9.8 m/s^2
    h = 2743 m (9000ft)
    PE-gravitational = 5000 * 9.8 * 2743 = 134,407,000 joules
    134,407,000 joules / 3,600,000 = 37.3 kWh
    We'll need additional 37.3 kWh to pull the vehicle and trailer up 9000 ft.

    assuming...
    The flat road consumption is 110 miles per 75 kWh for the vehicle and trailer, it is 0.682 kWh/mile.
    The flat 78 mile drive needs 78 * 0.682 = 53.2 kWh
    The total energy consumption in theory will be 37.3 + 53.2 = 90.5 kWh
     
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  5. FlyF4

    FlyF4 Son of a MX

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    I'm not an expert in this area, so maybe I am wrong, but I think you are confusing energy and power. I think it might seem that you need more "energy" in a steeper climb, but in reality, you would expend the same amount of energy during a steep bike climb as you would over a gradual climb. It's just that you are required to generate that energy over a shorter period of time in a steep bike climb, so those legs get tired faster. Feel free to correct me.
     
  6. aesculus

    aesculus Still Trying to Figure This All Out

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    My quick estimate is even if you charge to 100% at Rockin you are only going to have 4% when you arrive at Truckee. Better find a charger at Dutch Flat or Emigrant Gap.

    upload_2017-12-21_10-44-4.png
     
  7. EV-lutioin

    EV-lutioin Active Member

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    You will get some good regen coming down from Donner Summit to Truckee. You just have to make it to Donnor Summit. I arrived at DS once with 10 miles left in a raging blizzard (I cut it a bit close because the cold temps, strong winds, and my wife's need for warmth cut into range). The good news is we arrived at Truckee Supercharger with the same 10 miles.
     
  8. mengwong

    mengwong Member

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    Thank you! I ordered one from Tesla but if it doesn't arrive this time next week I'll definitely take you up on your kind offer.

    BTW, for anyone else in future staring at the $450 price tag – there is a map of these kind offers at Tesla Model S CHAdeMO Adapter Loaners map

    I'll be sure to list mine after my trip.

    My research also turned up a CHAdeMO adapter rental service.
     
  9. idoco

    idoco Member

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    tldr...On a dry day with no headwinds and not too cold you would be cutting it close at best...

    Longer version:
    So using EV trip planner for Model X with several different settings for flat terrain avg usage (planner then adjusts for terrain elevation changes):

    Default without trailer
    333Wh/mile = 123 rated miles

    Lower and upper ranges on forum with Airstream
    575Wh/mile = 212 rated miles
    600Wh/mile = 222 rated miles
    666Wh/mile = 245 rated miles
     
  10. cpa

    cpa Active Member

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    Don't know if this will help or not. I did not run the numbers. But from Folsom to Stateline NV is 87 miles. This route will add some time to your drive.

    But you might be able to make it up Echo Summit on US50 and then downhill to the SC in Stateline and not run out of juice. It would be an easy drive on the Nevada side of Tahoe to reach your destination.

    It might be worth a shot!
     
  11. mengwong

    mengwong Member

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    OK, trip report. Under ideal conditions, it should be possible for a 75D to tow a 2017/2018 Sport 22FB from Roseville / Rocklin to Truckee without CHAdeMO charging along the way.

    How do I know? I left Auburn Gold Country RV Park with a full tank of 230 miles. I arrived at Nyack Shell in Emigrant Gap with 42% SoC, and at Truckee with 17% (37 miles left in the tank). The RV park is about 5 miles out of Auburn. Rocklin is 11 miles out of Auburn, so anyone charging to 100% at Rocklin should arrive Truckee with about 25 miles in the tank. If you're coming from Roseville at 100%, you're cutting it even closer, arriving with 12 miles in the tank. So top off at Rocklin.

    Note that these are ideal conditions: dry and sunny, speed ranging from 45mph to 55mph, AC off for most of the trip and seat warmers only. I don't know my weight but both front seats were occupied, no passengers in the rear.

    Arriving at Truckee,
    My Trip A showed about 72 miles from Auburn to Truckee at 762 Wh/mi.
    My Trip B showed 252 miles from Half Moon Bay to Truckee at 647 Wh/mi.

    If you get to Nyack Shell at Emigrant Gap with anything less than 40% SoC you should probably avail yourself of the EvGO CHAdeMO they have there.

    Detailed report in chronological order:

    We left Half Moon Bay with a full tank.

    We first recharged at the Tesla Service Center in Dublin. We arrived right around closing time. I'm traveling with an MPDG, so while we were mulling options a Tesla exec appeared out of nowhere and generously invited us to use the service center's secret supercharger that they usually use to top off customer vehicles. So we didn't have to unhitch! We probably left there at about 75% SoC, I don't remember exactly.

    IMG_4629.JPG

    We went past Vacaville which are all back-in stalls. We hoped to make it to Rocklin but ended up at Roseville, 109 miles later. Nobody else was there so we just went ahead and blocked most of the bays. We arrived with 19 miles in the tank, charged at 90kW, and spent only about 15 minutes there because the next stop was just 20 miles away.

    IMG_4633.JPG

    IMG_4636.JPG

    We popped by Rocklin to check out the layout. The solar roof claims a clearance of 9', which is a problem because the Airstream's AC reaches 9'3".

    IMG_4647.JPG

    It's probably possible to nose in to the bays but I wouldn't pull all the way through.

    We spent the night at Auburn Gold RV Park, about 20 miles away, and departed with a full tank thanks to the 50 amp service in our bay.

    Auburn Coffee has excellent espresso, nitro cold brew, and kombucha.

    The next day we made it all the way to Truckee without charging along the way, though we were prepared to bust out the CHAdeMO adapter at Emigrant Gap.
     
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  12. mengwong

    mengwong Member

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    The facilities at Nyack Shell in Emigrant Gap:

    IMG_4666.JPG IMG_4665.JPG

    Initial estimate by trip computer:

    IMG_4669.JPG

    Upon arrival at Truckee, final estimate by trip computer:

    IMG_4670.JPG

    (trip began at Emigrant Gap)

    IMG_4672.JPG IMG_4679.jpg

    We blocked a bunch of stalls and apologized profusely to the S, 3, and X that turned up right behind us.

    IMG_4678.JPG
     
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  13. ohmman

    ohmman Plaid-ish Moderator

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    Wow! Thanks for the report, @mengwong. You said speeds of 45-55mph - I'm assuming that the cars were passing you at about 70-80mph, yes? Any issues with the speed differential?

    Also: look at that cable length on the service Supercharger! Liquid cooled? Can we have at least one of those at each Supercharger location... please?!

    If I recall correctly, you're using a weight bearing hitch setup. Any reason you didn't just unhitch at Truckee? I'm guessing because it looked vacant on arrival. Your unhitching process must only take a few minutes, based on my experience with our more complicated hitch. Did you install an electric tongue jack?

    Thanks again for pioneering this oft-traveled route. Gives me some optimism that our somewhat degraded (~244 RM @ 100%) 90D can make it without a CHAdeMO stop.
     
  14. mengwong

    mengwong Member

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    It wasn't a problem because I-80E has three lanes on the inclines. It's kind of relaxing to be the slowest vehicle on the road. Everyone was passing me – regular cars, semis, other RVs, even other trailer rigs boldly flouting the 55mph tow limit.

    Yeah, I must be the only one of us without any weight distribution or sway control. Truckee was indeed vacant on arrival and even with me blocking half the stalls there was still room for everybody who turned up behind me. So it wasn't too bad. Even with an electric tongue jack, unhitching is not kind to my old knees. Wrangling the safety chains is hell on my knuckles. And chocking and unchocking the trailer adds yet more time. Didn't seem worth it since we were only there to log the waypoint … we could've gotten to our RV park (Coachland) without stopping at the supercharger at all! So we just took off after it started getting crowded.

    BTW, towers arriving Truckee during office hours will want the supercharger behind the Safeway at Donner Pass Road … it's much more navigable than the Brockway location off 267, which is in the middle of a busy car park and was almost fully ICEd the other day at lunchtime.
     
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  15. ohmman

    ohmman Plaid-ish Moderator

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    Definitely understand that. I keep a small foam gardening mat in the back of my X when we're towing, and it's the first thing I pull out when unhitching. I bought it at a Fred Meyer while Supercharging in Bend during our last trip. Only took a few stops before I realized how much I needed that.

    The safety chain hooks on the original Bosal are a bear as they're hidden and recessed. My Draw-tite loops are quite prominent, so it's an easier task.

    Enjoy Tahoe, looks like some of this precipitation might fall as snow next week.
     
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  16. idoco

    idoco Member

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  17. mengwong

    mengwong Member

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    Here’s the downhill for contrast from Truckee to Rocklin at 55mph, no rain, about 10F

    2CB86E03-37E3-413F-A187-698F31900E36.jpeg 3B7389FB-93B3-4068-BC36-E286C603F3CF.jpeg 1E0BD831-3F4A-416F-9E5D-D8EEDB897A7A.jpeg F1C6A95A-CBF4-4D24-98E8-55933B27225B.jpeg 0B14A46B-14A1-4E99-B15F-A42707CF71F7.jpeg
     
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  18. mengwong

    mengwong Member

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    Sorry, I meant to say 5–10C, about 40–50F
     
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  19. ecarfan

    ecarfan Well-Known Member

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    #39 ecarfan, Jan 19, 2018
    Last edited: Jan 19, 2018
    Thanks for your report! Glad your trip went well.

    I will start my towing adventures in less than two months. Your photos showing your energy usage screens while towing appear to indicate that the X firmware factors in the higher energy usage when towing into the energy usage prediction calculations when a destination is entered into the navigation. I have been wondering about that for a year now while reading posts by @ohmman and others about energy usage while towing as I think they have also observed this. Comments anyone?
     
  20. mengwong

    mengwong Member

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    Apparently the thing to do is toggle in and out of Trailer Mode to see the estimates change. I’ll do that next chance I get.
     
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