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Performance Questions

Discussion in 'Roadster' started by Pantera Dude, Mar 8, 2013.

  1. Pantera Dude

    Pantera Dude Member

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    I assume that in order to protect the battery, it's output is limited? Does anyone know what the max output would be in amps? I have never looked at the amp read out under full acceleration, got to see where I'm going! :biggrin: I'm curious as to how much the accessories hurt 0-60 times? Or does the battery always give the drive train the same amount of juice whether the accessories are running or not?
     
  2. djp

    djp Roadster 2.0 VIN939

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    #2 djp, Mar 9, 2013
    Last edited: Mar 9, 2013
    As a rough guess, you can take the maximum power from the power gauge (200kW) and the nominal pack voltage (375V) to calculate max amps.

    I = P / V = 200,000W / 375V = 533A

    The cabin heater and AC are the most power hungry accessories. They draw a couple of amps on low and 10A or so on full blast. Still insignificant compared to the motor.
     
  3. dhrivnak

    dhrivnak Active Member

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    I believe the non-sport is limited to 700 amps. And yes other systems detract from that but they rarely go above 20 amps. So they are not a big draw.
     
  4. smorgasbord

    smorgasbord Active Member

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    I believe the max power is 185kW. If the actual output was regulated by the gauge markings, then Spinal Tap would be the loudest band in history. And, everyone knows that the loudest band in the universe is Disaster Area, right?
     
  5. Doug_G

    Doug_G Lead Moderator

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    42.

    The most important limit to Roadster performance is motor cooling, in my experience.
     
  6. woof

    woof Model S #P683 Blue 85 kWh

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    Well, to be fair, Disaster Area doesn't bother to book gigs in the uncharted backwaters of the unfashionable end of the western spiral arm of the galaxy, so it's fair to say that Spinal Tap is a local maximum.
     
  7. hcsharp

    hcsharp Active Member

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    I've never seen more than mid-600's on the display. So 700A is probably pretty close for a warm battery in perf mode. I have a 2.5 non-sport. My kW gauge goes up to 215 and my sales invoice says my car has a 215kW motor. The software limits the output from the PEM and at lower RPMs the sport PEM outputs more than the non-sport.

    It feels to me (but no definitive evidence) that I have less power while running high-amp accessories, especially heat. But I suspect it's more a function of colder tires with less grip, and colder battery.
     
  8. djp

    djp Roadster 2.0 VIN939

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    The current draw will be higher when the pack is at a low voltage. The Panasonic NCR18650 cells have a max of 4.2V and a min safety cutoff at 2.5V. If we assume Tesla uses 3.1V to 4.1V, then the pack voltage ranges from 307V to 406V (9 bricks per sheet, 11 sheets per pack, all in series).

    At a full Range/Performance charge:
    Current = 215,000W / 406V = 530A

    At zero:
    Current = 215,000W / 307V = 700A
     

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