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Here's How Big of a Hill You Need to Fully Recharge a Tesla

Discussion in 'Model S: Battery & Charging' started by RScottyL, Jan 10, 2017.

  1. RScottyL

    RScottyL Member

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    From Here's How Big of a Hill You Need to Fully Recharge a Tesla

    One of the great things about many hybrid and electric cars is that they're able to recharge the batteries a little bit every time you get off the throttle and use the brakes. You'll only get a little bit here and there, but over time, the electricity generated adds up. It also leads to a fascinating question. Exactly how big of a hill would you need to fully charge a Tesla?

    To find the answer, Engineering Explained's Jason Fenske broke out his signature white board and did the math. To keep things as simple as possible, he chose a Tesla Model S 60 for this hypothetical scenario. But even choosing the Model S with the smallest battery pack, the height of the hill he figures you'd need is more than twice as tall as Mount Everest. So theoretically it's possible, but in reality? Not really.


    Of course, if you have a Nissan Leaf, the battery pack is much smaller, so it might be close to fully charged by the time you got to the ocean from the top of Mount Everest. Then again, that also doesn't account for rolling resistance or drag. Nor does it account for the fact that a Model S 60 really has a 75 kWh battery pack. But it's still a fun thought problem.
     
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  2. Fresh Start Detail

    Fresh Start Detail Local Vendor - Northwest

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  3. Andyw2100

    Andyw2100 Supporting Member

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    It also doesn't account for the fact that you can't drive a Model S down Mount Everest...
     
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  4. Bangor Bob

    Bangor Bob Member

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    Hmmm. Maybe Olympus Mons? Lower gravity, but much taller...
     
  5. Saghost

    Saghost Active Member

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    Cute. His equations look pretty solid, but he did make a significant mistake in one of his comments...

    The Leaf would only be fully filled by the half height/Mount Everest descent if it weighed as much as a Model S, a good third more than it actually weighs.

    I'm also not sure how the 10% grade suddenly showed up - it wasn't relevant to the original math, and seems kinda arbitrary when it abruptly appears.
     
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  6. Barry

    Barry Member

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    One flaw in his analysis is regen is limited to about 60 KW, and decreases as the battery fills, similar to supercharging.

    Maximum regen gain I've experienced was 20 miles of charge, descending Mt Evans in Colorado. Top is a little over 14000 ft ASL and base is in the 7000 ft range.
     
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  7. Cyclone

    Cyclone Cyclonic Member ((.oO))

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    The 2016 onward S60 won't limit less than 60 kW of regen due to approaching fully charged since the battery itself is still less than 90% (of its 75 kWh capacity) and regen isn't limited until the high 90s SOC.
     
  8. gregd

    gregd Active Member

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    Wasn't there a guy who drove a Leaf to the top of, I think, the Matterhorn, barely making it, then had it recharged by the time he got to the bottom of the other side? Besides violating a few laws of physics, one in particular, I suspect it's Internet Legend. But I know I read it somewhere... :) I think he was also "credited" for recharging his car by towing it behind a truck, and a few other such feats.
     
  9. Polly Wog

    Polly Wog Member

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    His math seems pretty close to reality, from my experience. I've gained up to 32 miles in my descent of Haleakala here on Maui, which is 10,000 feet. If you multiply by 6 (roughly 2 x Mt. Everest), you get 192 miles, which isn't too far off of the range of a 60.

    Maximum Regen - Can Someone Top This?
     
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  10. Chuq

    Chuq Member

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    As it happens, I have a Leaf, and there is a 1260m mountain close to my home city - with a road to the top.

    I took the Leaf for a drive to the top a couple of months ago. Here are my statistics:

    The route:
    [​IMG]

    The elevation:
    [​IMG]

    The statistics:
    [​IMG]

    For those of you unfamiliar with the Leaf, the "GOM" column refers to the range prediction on the display, which is known as the Guess-O-Meter because it is wildly inaccurate. It bases your range on the last few kilometres of driving and fluctuates a lot. The number of bars is the more accurate measure.

    You can see the biggest downhill regen was from the Pinnacle to Davey St, an elevation drop of 1197 m over a distance of 18.5 km. It regenerated two bars of range (about 1/6th of the battery capacity).

    This isn't scientific of course - the capacity is only shown to the nearest 1/12. But if you do the maths, you would need an elevation drop of 7182m to fully charge it. So almost as high at Mt Everest :)

    Oh - and the view :)

    [​IMG]
     
  11. Festerfeet

    Festerfeet Member

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    Wow, thats great.

    I am going to have a go when the weather improves, there are quite a few mountains over 12,000ft local to me but it is finding the right one with a decent road and a clear run. Quite a few get closed due to snow and ice at this time of year and I also have to find a good bet near-ish a supercharger.

    I doubt I could beat it but would love to see how close I can get.

    Time to spend some time on google earth I think. Also need to make sure my wife isn't in the car, apparently she doesn't care how flat the Model X corners on a switchback... :eek:
     
  12. Scott-P

    Scott-P Member

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    Yes, but how much energy does it take to get it to Olympus Mons? That's a Falcon Heavy at least... Plus the 2+ year Hohman transfer orbit is a LONG wait for a recharge... ;-)
     
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  13. RScottyL

    RScottyL Member

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    So, would the angle of decent have anything to do with it?

    If you had a smaller angle, the length of the road down would be longer,but might not give as much resistance on the regen braking.

    If you had a larger angle, the road length would be shorter but the vehicle weight would be pushing harder on the regen braking!

    Or, would they both cancel each other out?

    Anyone?
     
  14. Saghost

    Saghost Active Member

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    Angle of road matters a lot, but not to the analysis done here. Likewise, the speed of the car will matter in the real world, but not to the math here.

    The analysis here is just the energy to charge the battery - it doesn't include the energy required to drive down that road at a given speed while recharging the battery. If the road is sufficiently shallow and the car is sufficiently fast, the energy required to move the car will equal (or even exceed) the energy granted by descending, resulting in no net regeneration.

    If you're trying to figure out the amount of actual energy you'll get back from a given hill at a given speed, you can get a pretty good approximation by doing the math here for the hill height, then subtracting off the energy need to drive the length of the descent on level ground at that speed.
     
  15. 1208

    1208 Active Member

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    Someone helicopter their tesla to the top of Everest and do it for real. Its the only way we will know for sure.

    For science!
     
  16. David99

    David99 Active Member

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    Yes it is a legend that could not have happened. Going up and going down is still driving which uses energy. So you cannot possibly get as much back as you used to go uphill. In reality it is about 30%. I did a test and a video about it.

     
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  17. Saghost

    Saghost Active Member

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    It's not easy to find a helicopter that can carry 5,000 pounds of cargo up over 30,000 feet, let alone for hundreds of miles at that height.

    Actually, I'm not sure there's any helicopter that can safely operate that high. Modern Chinooks are rated for 20,000 feet on oxygen, but that's the highest rating I've seen.
     
  18. adiggs

    adiggs Active Member

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    The road quality deteriorates pretty badly as you get close to the summit of Everest as well.
     
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  19. EL-Mundo

    EL-Mundo Member

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    Hi guys. Just tried to get a possible trip on EVPlanner from different high roads in the world. Mount Evans, America's highest paved road, 5th on Tellus. Gosl wiuld be to get to a decent city, at low altitude since the sea is to far away. I ended up with Kansas City since the trip would need to go somewhere low altitude place
    i imagine doing this trip during the night or perhaps during the total solar eclipse in August if I got my P100D model S there on top of the mountain. Normal speed on this trip would be in average 60% of speed limit which I prametered into EVplanner along with Choice of carmodel and 19"wheels.

    EVPLANNER RESULTS:
    Distance: 661.7 miles(1064km),
    Total Energy used: 89.6kWh
    Elevationchange: -13238 ft (-4035m)
    Avg. Efficiency: 135 Wh/mile(84 Wh/km)

    Sine the world records are 550.3 miles (885.62 km) on a single charge in a Tesla this might
    Be doable as long as nobody sets ant limits for elevation change for the trip:)
     

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  20. Zooomer

    Zooomer Member

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    He made the assumption that no one is in the vehicle. Doing this test, you'd load the car with as much weight as possible reducing the distance considerably. I'd question the 60% efficiency as well. Should be easy to test for someone with a large hill handy tho.
     

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