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Here's What A Battery Researcher Told Us About The Tesla Roadster's Crazy Performance Claims

Discussion in 'Roadster 2020' started by DerekJoseph, Nov 22, 2017.

  1. DerekJoseph

    DerekJoseph New Member

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    "To learn more about how the Roadster could reach rally car-like acceleration figures, I spoke with Carnegie Mellon’s Venkat Viswanathan, a mechanical engineering assistant professor who works at the Wilton E. Scott Institute for Energy Innovation and focuses on next-generation battery technology. He’s also published studies on battery technology. He told me he thinks the 1.9-second figure actually seems reasonable."

    https://jalopnik.com/heres-what-a-battery-researcher-told-us-about-the-tesla-1820558723

    Great little article that is a must read for those contemplating buying a new Roadster. The article fact checks Elon's claims.

    Here is an important quote that replies to those who say that the prototype car may not have the 200 KWh battery now and that Elon is basing the range on expected future battery technology:

    "The most interesting thing he said is that Tesla’s claimed battery capacity of 200 kWh isn’t just there to contribute to a higher cruising range, but it’s also an enabler for fast acceleration times".

    This means the prototype most probably have the 200 KWh battery capacity now!!

    Cheers
    Derek

    P.S. This is my first post, go easy on me.
     
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  2. Xenius

    Xenius Member

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    Good article, saw it posted elsewhere earlier today. Welcome to the club!
     
  3. SageBrush

    SageBrush 2018: Drain the Sewer

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    I came to the same conclusion: WHAT tyres does that car have ?!
     
  4. jelloslug

    jelloslug Active Member

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    Considering that the Model S can pull off low 2 second 0-60 runs on street tires, I would imagine that they are nothing terribly exotic.
     
  5. SageBrush

    SageBrush 2018: Drain the Sewer

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    You may be right, since the Model S time is limited by power delivery during the run.

    IIRC, maximum braking times imply traction of around 1.4G. That is the average acceleration rate required from the 1.9 second time to go 0 - 60 mph.
     
  6. gavine

    gavine Petrol Head turned EV Enthusiast

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    Michelin Pilot Sport Cup 2's
     

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  7. SageBrush

    SageBrush 2018: Drain the Sewer

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    #7 SageBrush, Nov 22, 2017
    Last edited: Nov 22, 2017
    Google says that tyre goes from 62 -> 0 in 33.66 meters

    If my arithmetic* is correct, that is a traction of 1.165G. Not nearly enough

    *

    v =a*t
    t = v/a

    2x = a *t *t
    2x = a * v/a * v/a
    2*a*x = v*v
    a = (v*v) / 2*x
     
  8. gavine

    gavine Petrol Head turned EV Enthusiast

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    Your math is Greek to me.....does it account for tire width? The tires on the Roadster look to be extremely wide.
     
  9. AudubonB

    AudubonB Mild-mannered Moderator Lord Vetinari*

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    #9 AudubonB, Nov 22, 2017
    Last edited: Nov 22, 2017
    Correct me if I'm wrong. I am quite sure the Koenigsegg Agera that just smashed a whole series of land speed records used the Sport Cup 2s.

    On edit: Yes. and here are the records it broke (from Bloomberg, here): How Koenigsegg Broke the Land Speed Record With Its Agera RS -

    a top speed of 277.87 mph across two runs in the $2 million coupe on a 11-mile, closed-off stretch of Highway 160 near Pahrump, Nev. That beat the previous record of 267.8 mph set by a Bugatti Veyron Super Sports model seven years ago in Germany. It also beat the Hennessey Venom GT and McLaren F1 that had previously owned or approximated similar top speeds. What’s more, Lilja set records for highest speed in a single direction on a public road (284.55 mph); a zero-400-zero km/h run (33.29 seconds); the highest average speed for a mile with a flying start on a public road (276.36 mph); and the highest average speed for a flying kilometer on a public road (276.9 mph).
     
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  10. gavine

    gavine Petrol Head turned EV Enthusiast

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  11. ecarfan

    ecarfan Well-Known Member

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    For 10 times the cost of the new Tesla Roadster. Wow.
     
  12. SageBrush

    SageBrush 2018: Drain the Sewer

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    Units clarified:

    62 mph to 0 mph.
    62 mph is 27.7165 meters per second

    The above algebra starts from
    v = dx/dt
    a = dv/dt

    And works backwards since we know the distance travelled and the velocity.
    Integrating the above equations gives
    v = a*t
    x = 0.5 * a *t *t
    When initial conditions are zero

    The rest is just substitutions
     
  13. CarlK

    CarlK Member

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    Pilot Sports Cup 2's were shown in the video. Plenty good for the acceleration but probably not enough for 250 mph run.
     
  14. Doom

    Doom Member

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    The Koenigsegg Agera RS that went 285.8 mph had the same tires. Video of the tires:
     
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