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Speedometer notes

Discussion in 'Model S: User Interface' started by DriverOne, May 15, 2014.

  1. DriverOne

    DriverOne Member

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    It's more than a speedometer. What's it's proper name? Despite not knowing, I made some annotations. I was amazed to see how much power regen can supply!

    TeslaSpeedoExplained2.png
     

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  2. Johan

    Johan Took a TSLA bear test. Came back negative.

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    Energy meter?

    Did you get a Model S in Croatia now???
     
  3. LMB

    LMB Member

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    Ludicrous speed!
     
  4. DriverOne

    DriverOne Member

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    If regen can feed 60kW into the battery, why is plug-in charging limited to 10kW/charger? When is regen going through to exceed that charger limitation?

    If you had a device to spin the wheels backwards fast enough, you could charge quickly even without a Supercharger :)
     
  5. gavine

    gavine Petrol Head turned EV Enthusiast

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    Might have to do with regenerative being DC and home charging is AC.
     
  6. castor

    castor Member

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    +1, An aftermarket motor that you put on your garage and make the wheel spin really fast, I don't think needs to be backward, it just needs to spin faster than electricity feed into the motor to have regen, same as you go downhill (tires still spin forward :) ), Supercharger at home, I'm not sure the efficiency of the charger :)
     
  7. Todd Burch

    Todd Burch Electron Pilot

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    Correct. AC current must pass through an inverter to be converted to DC, which can then be fed to the battery. (Batteries neither consume nor produce AC power).

    It's this inverter hardware that's limited to 10kW each.

    Regen, Superchargers, and DC fast chargers all feed DC directly to the battery, which is why the limit can be surpassed.
     
  8. markb1

    markb1 Active Member

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    Wouldn't the A/C induction motor produce A/C regen?
     
  9. DriverOne

    DriverOne Member

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    Surely the motor would. The inverter works both ways? Converting the motor's A/C into DC? In that case, why not use it rather than the 10kW chargers?
     
  10. SCW-Greg

    SCW-Greg Active Member

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    Cool "info graphic".

    However your max (governed) speed indicator is a bit off. Should point to 125 and/or 130.
     
  11. KenN

    KenN Member

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    The motor runs on 3 phase AC, and produces 3 phase on regen. During regen the 3 phase AC is rectified to DC. Feeding single phase AC into the inverter would mean an imbalanced source and likely wouldn't work. Also, I'm not sure what the motor voltage is, but probably much higher than household 120/240 VAC.
     
  12. DriverOne

    DriverOne Member

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    Thanks!
    Well spotted. I was doing this thinking of the 60kWh version, which I thought could reach 100mph.
     
  13. Todd Burch

    Todd Burch Electron Pilot

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    #13 Todd Burch, May 16, 2014
    Last edited: May 17, 2014
    Yes I should have been more clear. The motor itself produces AC on regen, and as Ken indicated this is rectified into DC and then fed into the battery. All I meant was that the regen path does not go through the inverter that's used when plugged into the wall.
     
  14. mgboyes

    mgboyes Member

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    An inverter is a device that converts DC to AC. A rectifier is a device that converts AC to DC.

    The Model S has one or two "chargers" depending on spec. They include rectifiers to convert fixed low frequency mains AC electricity to DC to charge the battery. A supercharger station uses the exact same chargers; it just has about 10 of them inside it (and they're run at higher load than in the car i.e. 12kW each, 120kW total).

    The car also has a "drive inverter" which is actually both an inverter and a rectifier; i.e. it can convert DC to AC and also AC to DC. It is a much higher power device (up to 310kW in inverter mode) and has to deal with variable, higher frequency, AC on the motor side.

    They're completely different systems with different purposes and tolerances.
     
  15. scaesare

    scaesare Active Member

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    Doesn't even have to be backwards: Ad-hoc Fast Charging
     
  16. EarlyAdopter

    EarlyAdopter Active Member

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    Good explanation. One correction: a Supercharger has a stack of 12 of the car chargers inside, currently running at 10kW each. I've seen inside of one and counted. No room for a 13th though, so to get from 120kW to 135kW they'll have to overdrive them slightly to 11kW.
     
  17. cgiGuy

    cgiGuy Member

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    Who's gonna be first to try this with a MS? Where would the connect point be for a tow rope? If you could get back 5-10 miles in a few minutes of towing, this could make flat-bedding unnecessary in many cases.
     
  18. markb1

    markb1 Active Member

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    I believe the EU-spec onboard chargers are 11kw, so a 135kw supercharger would use 12 EU chargers.
     
  19. mgboyes

    mgboyes Member

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    Sorry you're right that there are 12 charge units in a supercharger - I must've misremembered. However the 10kW (or 11kW in the EU) ratings that Tesla give for the in-car chargers are measured on the AC (input) side, whereas the 120kW rating of a supercharger is measured on the DC (output) side.

    If they're 90% efficient then a 120kW DC supercharger is actually consuming 133kW on the AC side today. A 135kW supercharger would be drawing 150kW from the grid, i.e. 12.5kW per charge unit.

    I'm sure that in the tightly controlled, liquid cooled environment of a supercharger cabinet, fed by a high quality mains supply, the chargers can be considerably "overclocked" beyond what they're asked to do in a car.
     
  20. Doug_G

    Doug_G Lead Moderator

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    Actually the charger probably doesn't use actual rectifiers, but would use a switching power supply topography that would convert AC to DC at the desired voltage. On high efficiency converters it's often a MOSFET switching at the right times instead of an actual diode.
     

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