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Tesla Semi Event -- November 16, 2017

Discussion in 'Semi' started by doug, Nov 16, 2017.

  1. dhanson865

    dhanson865 Active Member

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    So it's like 4 charging cables in one port (2 pins per pack, 4 packs)

     
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  2. T34ME

    T34ME Active Member

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    Very true. But someone has to be in the home office, tracking all these autonomous trucks on the computer, monitoring all the on-board systems, routing all the deliveries. Americans should not be afraid of changes and the future. If we embrace progressive ideals our future will be bright indeed1
     
  3. lux_cars

    lux_cars Member

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    Eventually, when AI gets to human level intelligence and beyond, wouldn’t it replace that job too?
     
  4. electracity

    electracity Active Member

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    I doubt it. Most likely the batteries power the motors on a parallel circuit.
     
  5. 3Victoria

    3Victoria Active Member

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    Well, Santa has to pick up some presents for us fanbois and gals. o_O
     
  6. SageBrush

    SageBrush REJECT Fascism

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    Yep, but that means 400 kW average to each ~ 250 kWh pack over the 30 minutes that 400 miles of range are accumulated.

    400 volts at 100 Amps average. Somewhere around 1.6c average
    Either batteries are going to get a lot better real soon, or the voltage is going up.
     
  7. JRP3

    JRP3 Hyperactive Member

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    Agree, you probably want motor draw coming from the whole pack, as well as regen going into the whole pack, since each motor can have different levels of power flowing through them at any point in time. You would end up with unbalanced packs if each motor was wired to a specific pack. Though I guess that's less of a concern if each pack is charged individually.
     
  8. T34ME

    T34ME Active Member

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    Exactly, and that is why we need more dedicated, educated, imaginative, inspired young people of both genders and in between in the science discipline.
     
  9. T34ME

    T34ME Active Member

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    I am just a simple "complete enthusiast", I would be happy with just an open configurator for my model 3!
     
  10. mongo

    mongo Well-Known Member

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    Disagree, since each motor is individually controllable, you can set them to draw the same power. Unless it is in a limited traction condition, all motors will draw the same due to SW control.

    While driving, the system can shift loading to balance the packs, if needed. But it wouldn't be needed since they would get balanced at the next charge.
     
  11. electracity

    electracity Active Member

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    Motors probably won't all be geared the same. One set will probably be optimized for highway speed.
     
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  12. mongo

    mongo Well-Known Member

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    I think it. If you have a common bus then a single inverter failure can stop the entire system. Same with a single pack failure. To have a common bus and fault tolerance, you would need 2 contactors for each motor and pack. 2x2x4 = 16, vs the 8 needed to isolate packs from a single motor.

    What functionality does the extra 8 contactors get you? And why do you want to have a buss that is carrying 4x the max current of one motor?

    For charging, doubling pins is not a reliable way of doubling current handling without lots of derating (let alone 4x pins), so charging each pack independently allows greater overall power while reusing existing mechanical and electrical components.
     
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  13. mongo

    mongo Well-Known Member

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    That's what I thought too, untill Elon said you could lose two motors and still out accelerate a normal tractor. I took from that, that all four are the same.
     
  14. mongo

    mongo Well-Known Member

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    I'm thinking 250kW each to 4x200kWh packs with a kWh/mile around 1.3 so 1.25C.
    When you say voltage going up, are you speaking of the cells themselves? Stacking the same cells doesn't help the C rate.
     
  15. SageBrush

    SageBrush REJECT Fascism

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    Yes, my mistake
     
  16. ohmman

    ohmman Plaid-ish Moderator

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    I'd like to point out that Semi reservations are only $5000, but Roadster reservations are $50k/$250k respectively. :rolleyes:
     
  17. mongo

    mongo Well-Known Member

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    Both refundable. Guessing less window shoppers on the truck side of things. Add easier to vet real buyers.
     
  18. SageBrush

    SageBrush REJECT Fascism

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    #318 SageBrush, Nov 17, 2017
    Last edited: Nov 17, 2017
    The Tesla website says 'under 2 kWh per mile'
    If range is 500 miles then the total capacity approaches 1000 kWh and each pack ~ 250 kWh

    Each pack is taking 400 kW on average
    I just don't see how this is possible at 400v.
    Even 800v is a mighty stretch.
    Are we looking at a 1600v charging system ??
     
  19. mongo

    mongo Well-Known Member

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    Yeah, I'm thinking its quite a bit under 2 kWh. A 40% diesel at 7 MPG is 2.17 kWh/mile and the Tesla is way smoother ~ half the drag, let's give it a 25% advantage. If we said 1.5 kWh/mile then it only needs to put 150kWh into the sub-packs. In 30 minutes that's a 300kW charge rate into a 250 kWh pack, ~1.2 C which lines up with putting 125kW into a 100 kWh pack. If the pack is 400V, that's 750 Amps.

    Lincoln welding says 3/0 cable is good for 650A at a 60% duty cycle. Add liquid cooling, and it's feasible. 8 of those is going to be HEAVY, maybe it has a spring loaded lift mechanism to reduce the effective weight?
    May have dropped a decimal somewhere...
    :rolleyes:
     
  20. JRP3

    JRP3 Hyperactive Member

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    Except that defeats the whole point of torque vectoring, which adjust the draw and regen of each motor in real time. This will be happening on each corner, not just low traction situations. Remember the S/X D models already use 2 motors on one pack, and the Rimac uses 4 motors and torque vectoring with one pack.
     

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