Cost of pushing the pedal down

Discussion in 'Prime Main Forum (2017-Current)' started by Henrik Helmers, Aug 10, 2021.

  1. Henrik Helmers

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    I was reading the thread about EV range, and there's one question I can't get out of my head. Assuming the Prius is driving on electric power, is it meaningfully more expensive to push the accelerator pedal down?

    What is the difference between going up a hill at say 20km/h, or 60km/h?

    Lastly; I like to climb hills slowly, and then go faster on flat terrain. It "feels" like I am being more efficient this way. Is this just in my head? Would the result be the same if I went faster uphill and slower on level ground?
     
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  2. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    Electricity is still energy. Fighting against gravity uses energy, fighting wind resistance uses energy, fighting rolling resistance uses energy. Same as any other car.

    The real advantage is recovering some energy instead of just heating your brakes.
     
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  3. jerrymildred

    jerrymildred Senior Member

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    I'v played with that a bit but never tried to make a study of it. But it often seems to me that when I'm going from red light to red light (the only kind they have here), accelerating smartly to a little over the speed limit while in EV and then gradually slowing to a little under the speed limit before getting to the next light gets me better miles/kWh than spending most of the time accelerating and then slowing more quickly. That is, if traffic permits.

    As for the hills, we don't have any of those here. :D
     
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  4. farmecologist

    farmecologist Senior Member

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    Well..FL *does* have hills. Unfortunately, the the hills are the 'garbage mountains'. (y)
     
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  5. sam spade 2

    sam spade 2 Senior Member

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    Now that's not nice.
    And not true either.
    There are WAY more hills in Florida than most people think.
     
  6. farmecologist

    farmecologist Senior Member

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    C'mon bro..it's a joke. And I was thinking of the southern FL area. We have family in Fort Lauderdale and "mount trashmore" has been a running joke for a looooong time.

    Mount Trashmore (Florida) - Wikipedia

    But yeah...on the panhandle near the northern border there is a 345 foot hill ( Mt Britton ).
     
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  7. sam spade 2

    sam spade 2 Senior Member

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    Kind of an "inside" joke which most people wouldn't understand.

    Truth is.......that if you are not very near to the coast or a swamp, there are "hills" all over the state.
    The routes of most major highways tend to avoid them though so most people never know.
     
  8. Colorado Boo

    Colorado Boo Member

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    lol...."hills in Florida".....let me take some of you up a few of our mountain passes here in Colorado! Some of them go up almost 14,000 feet and have a grade of 7-9 degrees!! On Pike's Peak Highway, they have stopping stations on the way down and they use heat guns to check the temps of your brakes and if it's too hot, they make you pull over and wait a while before continuing. But the most interesting things to see are those special runaway truck ramps when coming down the mountain passes and to see an 18-wheeler in one or wheel tracks from one being used. (I've never seen a ramp that didn't have wheel tracks in it.) Pretty scary stuff, especially when I'm towing my 7,000 pound camper with my Tundra up and down those passes.
     
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  9. jerrymildred

    jerrymildred Senior Member

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    LOL!! That's a big one. And there are some hills to our north along I-75. Not very big. There are even some fairly decent motorcycle roads with curves in the next county to our north. Interesting thing I just discovered about Britton Hill. It is the lowest state high point in the U.S. It's more than 100' lower than the next lowest "high point." Man, I miss the mountains!

    Yup. Very common there. I"m familiar with them. There is one lone runaway truck ramp on the main highway in Togo. It looks terrifying. It's the only one on the whole road. I see lots of crashed and sometimes burned trucks every time I take that road. I'm thinking the drivers like their chances better without that ramp.
    IMG_3359.jpg
     
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  10. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Crude, but effective. And: if it doesn’t stop you, you’ll be in no shape to complain. :cry::eek::ROFLMAO:
     
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  11. Salamander_King

    Salamander_King Senior Member

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    Back to OP's question. I am certain higher speed on EV mode uses more energy than lower speed. You can see the effect by just looking at the instant miles/kWh gauge. Push the accelerator pedal down, you will see the instant miles/kWh gauge goes down. That means you are using more energy. I have never done this myself, but if you drive the same distance, the same route all on EV mode driving 20mph vs 40mph, and see how much SoC is used up or what the miles/kWh for that segment of the trip was. I bet you will see 40mph will take more energy thus cost you more for the same distance driven. But, you will get there in half of the time. So, if your time is valuable, then it may be a wash. ;)
     
  12. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Going faster is always less efficient, regardless of motivation method? Ditto for more aggressive acceleration.
     
  13. jerrymildred

    jerrymildred Senior Member

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    With gas, yes. But I think electric is pretty linear on acceleration except there's a little more heat loss at higher currents but it's also for a shorter time. So, you lose heat at a low rate for a long time or you lose it at a high rate for a short time. Granted, the sooner you get up to speed, the sooner you'll encounter higher wind resistance, but if you let off the throttle once up to speed and almost glide to the next stoplight if it's only a mile or less from where you started, you go a lot farther on little or no energy compared to using higher than cruising speed energy for a long distance and then braking. When traffic won't let me do that I get noticeably fewer miles per kWh than when I can accelerate quickly (not flooring it by any means) and then ease off on the throttle. I like getting 1 or 2 miles per kWh for a couple hundred yards and then getting 10 or 20 for the rest of the mile.
     
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  14. CharlesH

    CharlesH CA HOV Decal #5 on former PiP

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    In an ideal universe without energy losses (the kind you have in physics classes in school :)), it takes a certain amount of energy to get a given mass up to a particular speed. How quickly you do this is irrelevant. In the real world, we have things like heat losses in motors when producing a lot of power and pulling a lot of current. But as mentioned, electric motors have a pretty flat power vs rpm curve, unlike internal combustion engines.

    A lot of things that we learned with internal combustion engines don't apply in a world of electric motors. Like when people see the official mpg ratings for hybrids or battery electric cars, and see that the city mpg is higher than the highway mpg, which is due to the regenerated energy from start/stops, vs. wind resistance at high speed, which is a pure loss.
     
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  15. GregersonIT

    GregersonIT Member

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    I gained 30 Percent on my battery down one of the mountains of death valley once in like 5-10 minutes of driving. Had to keep on pressing the brakes for 16-18 seconds then ride off the brakes for 12 seconds then 16-18 seconds with a little bit of extra brake to keep from getting too much speed. I think I achieved 21miles per kw that day with 38 percent ac load. LOL. My gas mileage at 114 degree's though, wasn't that great. I think I averaged like 36mpg going through the mountains and valleys with a total trip of 45mpg once I got to the flat part it was much better though.
     
  16. farmecologist

    farmecologist Senior Member

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    Headed to Colorado soon and have been there quite a few times!

    Taking a road trip to Utah and going through Colorado and RMNP on the way. We will then take the 'northern route' through Kremmling, Steamboat Springs, and then South on Hwy 13 due to I70 being closed through Glenwood canyon. The I70 closure REALLY threw a wrench in my planning. It isn't optimal...but my brother is coming with for the first time ever..and wanted to hit RMNP.

    Any suggestions on where to stop along that route? I also have quite a few breweries marked along the route because we like to sample the local brews on the way. Don't worry...my 19 year old son can drive if we sample too much..lol (y)

    The only downside? We are taking my brother's Honda Accord...but hey he offered...so why not. It will be strange driving an ICE vehicle in the mountains...I'm used to using 'braking mode' on our hybrids.

    Edit - for those interested :

    It Has Been 12 Days Since Mudslides Shut Down I-70 In Glenwood Canyon, And There’s No End To The Closure In Sight – CBS Denver
     
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  17. Trollbait

    Trollbait It's a D&D thing

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    Depends on the car. The slow and steady method of acceleration that helps a hybrid could hurt a traditional car. The load on the engine can be below the point of its efficient range, and it means more time an automatic transmission spends outside of lock up. These lead to more gas being burned, which is why pulse and coast works for saving fuel.
     
  18. Mendel Leisk

    Mendel Leisk Sand Pounder

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    In a Wayne Gerdes (CleanMPG) hypermiling video I watched, he mentions keeping the “bar”* between 1/2 and 3/4, as optimum zone.

    *Can’t remember official acronym
     
  19. fuzzy1

    fuzzy1 Senior Member

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    Faster means more energy lost as air drag (wind resistance). Slower means greater total overhead spent on fixed non-propulsive loads in the machine controls, computers, systems, and accessories.

    For a Gen3 non-plugin on flat ground, a couple long ago sources doing some energy modeling determined the most efficient speed to be roughly 15 mph (one source), or between 10-20 mph (other source). This didn't account for your time having any value.

    But I haven't seen any comparable workup for a Prime in EV mode for flat ground, let alone for hill climbing.

    Or even about the same speed for both? If battery-to-wheel energy conversion efficiency is both fairly high and fairly consistent with load, then you'll likely get something close to this for reasonable hills, not diverging much until you get to steeper climbs. But actual %-slope will be part of the equation, and ours hills have a very wide variety of slope numbers.
     
  20. jerrymildred

    jerrymildred Senior Member

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    I read about that closure. What a mess. Not a lot of alternate routes in the mountains. I bicycled your route back in the early 70s. It's way prettier than I-70. But obviously not nearly as quick.
     
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