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Limit Supercharger rate?

Discussion in 'Model S: Battery & Charging' started by nlc, Apr 10, 2014.

  1. nlc

    nlc Member

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    Just one small question off topic, when charging on a supercharger, is it possible to set a current limit on the console screen, as for a standard charge ?
     
  2. gaswalla

    gaswalla P4201/85/airsusp/pano/19i

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    No...
     
  3. TexasEV

    TexasEV Active Member

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    Because there is no reason to. Kind of defeats the purpose of a supercharger. The car tapers the voltage and current itself as the state of charge increases, no human intervention required.
     
  4. wycolo

    wycolo Active Member

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    #4 wycolo, Apr 10, 2014
    Last edited: Apr 10, 2014
    > when charging on a supercharger, is it possible to set a current limit on the console screen, as for a standard charge? [nlc]

    But, the SuperCharger *will* stop the session when you reach your CHARGE LIMIT (in Miles*) as previously set on the Charge Screen. If this limit is set unusually low for some reason, your session will END prematurely while you are ordering a meal next door. So you have to remember to check the Charge Screen before you plug into the SC and run off.

    * or kilometers
    --
     
  5. nlc

    nlc Member

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    OK, asking that for the eventuality we need to charge often on supercharger, without charging too fast (if we have time), to not use prematurely the battery pack.
    But that's true it will be unfair for other users to stay a long time on the supercharger
     
  6. TexasEV

    TexasEV Active Member

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    Tesla says supercharging does not prematurely use the battery pack.
     
  7. dirkhh

    dirkhh Middle-aged Member

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    And the people waiting for their turn might not be amused...
     
  8. tga

    tga Active Member

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    IMHO, limiting the charge rate is completely unnecessary. If you charge an 85kWh pack at 90kW, you are charging the pack at 1.06C. That is a completely reasonable rate for charging Li-Ion cells.

    Yes, 90kw (or 120kw) seems like a lot in absolute terms, but split that across 7000 cells in an 85kW pack, and it's just not that big a deal. 9.6kW ([email protected]) is practically a trickle charge.
     
  9. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    Hear! Hear!

    Here are the order of magnitude numbers that I give people. When waiting for a charge, orders of magnitude make a difference, and 2 make a huge difference! :wink:

    • 120V 3-Prong Outlet - 1.44 kW, 3 MPH, 100 miles in 32 hours
    • 14-50, RV Outlet - 9.6 kW, 28 MPH, 100 miles in 3.6 hours or almost 10 times faster than a 3-Prong outlet.
    • Supercharger - 120 kW, 400 MPH, 100 miles in 15 minutes or almost 100 times faster than a 3-prong outlet

    We all know that the Supercharger 120 kW rate tapers after the first 100 miles or so, but it gets the idea across about charge speed. BTW, the 3-Prong, 120 Volt outlet is the trickle charge...
     
  10. kendallpb

    kendallpb Model S: P 8061

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    This makes me feel better about finally getting the fuse replaced on my HPWC so I can charge at 80a versus 60a. Not that I need it normally, really. ;-)
     
  11. nlc

    nlc Member

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    You cannot compare, 80A on 230VAC is 18kW, thus approx 46A on the battery pack, that nothing :D
    But 120kW is 1.4C, it's not very high thus it will not stress the battery pack too much (Approx 300A), but it will stress more than a 20kW AC charge.
    Thus for long term, I think that not a good a idea to do its daily charge on a supercharger
     
  12. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    I love having the 80 Amp AC charging at home for those occasional times that I want quicker charging, but normally I dial the current back to 57 Amps (80/sqrt[2]). At that level, resistive heating is reduced by a factor of 2 and all home charges use, and test, both onboard chargers.
     
  13. invisik

    invisik Member

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    If you supercharge the first 100 miles and then it starts ramping down... can you unplug the supercharger, then plug the supercharger back in and have it charge at full speed again for another 100 miles? or is it smarter then that?

    -m
     
  14. nlc

    nlc Member

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    It is smarter, with high current the cells reach their top voltage more quickly, thus the car enters the Constant Voltage charge phase quickly and it asks the supercharger to lower the current
     
  15. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    It's way more complex than that. Current and total power come way down before max Voltage is reached. On an 85, the pack Voltage only goes from about 360 Volts empty to just over 400 Volts full, but the power into the pack goes from 120 kW down to 40 kW or so from empty to max Voltage stage. It's much more than a constant current until constant Voltage algorithm; input power and current are throttled well before final Voltage.

    One thing to be very careful of is that all values reported during charging are instantaneous except for charge rate in MPH or KPH. Charge rate in MPH or KPH is reported as the average for the session, not instantaneous; this causes great confusion to many.
     
  16. kendallpb

    kendallpb Model S: P 8061

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    For someone paranoid like me, reading in the early days about how faster charging supposedly was bad, yeah, I'm still happy to read the above. ;-)

    - - - Updated - - -

    Whosajigawhaaaaa? Is this some new (to me) thing I should worry about, resistive heating?! :scared:
     
  17. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    Nothing to worry about, just a little extra margin when I don't need to charge fast. I do, and I recommend other do, check all parts of the charging setup for unwarranted heat buildup. I know my whole HPWC setup runs relatively cool at 80 Amps. However, even if it is cool, cooler is a little better. When I don't need to charge fast at home, it's an easy tradeoff to charge 30% slower, have most of the components run with half the heat load, and put slightly less stress on the local grid. Therefore, my default current setting at home is 57 Amps, but I have no qualms about turning it up to 80 Amps if needed.
     
  18. dirkhh

    dirkhh Middle-aged Member

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    Whenever I charge overnight on a trip I always do the math for the SOC I want the next morning. And then step down the current so it just finishes charging when I leave. Who knows what the electrician at the hotel / camp ground was thinking when he wired things up... At home I'm too lazy to do this every day, so I just charge at the default 40A (but on a timer so that the two EVs don't charge at the same time - we only have a 100A panel in the garage and there are a bunch of other consumers on it).
     

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