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How does a Supercharger work?

Discussion in 'Technical' started by deckofficer, Feb 11, 2015.

  1. deckofficer

    deckofficer Member

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    I know it is charging DC but how does it get enough power from a typical pole transformer that is shared with other energy users? A 6 bay charger station filled with cars needing a charge, even derated 50% and 100% efficient (which it isn't) would be pulling 360 kW from a distribution transformer that is shared. Since it is DC charging, are they using batteries as a buffer so that they can pull a smaller load for a long time during non use to have say the equivalent of 12 Tesla battery banks charged and ready to dump their charge into the cars?

    I just can't find any info on how it is done, could someone point out a link for me?
     
  2. Chris TX

    Chris TX Active Member

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    #2 Chris TX, Feb 11, 2015
    Last edited: Feb 11, 2015
    FWIR, multiple 480VAC 400A feeds (192kW)
    Split into the three phases
    208VAC 40A feeds each of the 12 chargers in the cabinet
    12 chargers are ganged together for 120kWh of charging.
    Chargers produce lots of DC, which is bypassed through the car's onboard chargers to the battery.

    Oh, and it's never been a "typical pole transformer". It's going to be a pad mounted beast of a transformer.
     
  3. deckofficer

    deckofficer Member

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    #3 deckofficer, Feb 11, 2015
    Last edited: Feb 11, 2015
    So does that mean you would only see 120 kW charge if both your bank is low enough and your the only one using one of those 6 bays?
     
  4. Saghost

    Saghost Active Member

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    Pretty much. It actually isn't that you have to be the only one charging - you just have to be the only one (or at least the first one) using a given set of charger modules, which are shared between two stalls.

    If there are 12 bays, six of them can have 120 kW at any given time if the cars are in the right 6 slots and the state of charge and battery temperature permits it.
    Walter
     
  5. Chris TX

    Chris TX Active Member

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    Each 120kWh Supercharger cab should have an A and a B station. The B station is a slave to A. If there is a greater need in the A station, it gets the power from B. If two dead cars show up and plug into the same cabinet's A and B station, the A car will get full power until it starts to throttle. Once it throttles, the "leftover" power goes to the B side.
     
  6. Saghost

    Saghost Active Member

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    I was under the impression that it was pure FIFO - as in, if a car plugs into B when there's no car in A, it gets the 120 kW - and if a car later plugs into A while the B car is still charging, the B car continues to have priority and full power, while the new A car waits. Is this not the case?
    Walter
     
  7. deckofficer

    deckofficer Member

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    #7 deckofficer, Feb 11, 2015
    Last edited: Feb 11, 2015
    This gets me back to the original question, and that is how does existing infrastructure in a typical parking lot support this amount of power draw without some kind of buffer like 500 kWhr of batteries at the station.

    I did some research and answered my own question. Tesla uses (12) of their 10 kW in a ganged network, so the draw from the mains is always a manageable 120 kW. I just couldn't see typical power in restaurant parking lots being able to go much higher than 120 kW, like if on a 12 bay station, 6 could pull 120 kW, which is way more than the mains could provide. So it is 120 kW only if your the only one charging, no matter how many stations are there unless special mains were provided.

    How Tesla Superchargers Outsmart the Electric Car Industry | PluginCars.com
     
  8. Saghost

    Saghost Active Member

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    The existing infrastructure in the typical parking lot doesn't support that kind of power. Tesla works with the lot owners and utility companies and has their own dedicated transformers installed from the utility mains. There are lots of construction photos scattered around the forum.
    Walter
     
  9. Chris TX

    Chris TX Active Member

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    It isn't FIFO like some people believe. I followed a Supercharger tech from Colorado to Kansas and chatted with him along the way. B is indeed a slave to the A side and it will give up most of its power if the need is on the A side. If you're plugged into B and someone plugs their car into A and it needs more than is leftover from your car charging, it will take it. The only way the B side would get almost no power is if someone pulled into the A slot with an almost dead battery ("Charge Now")
     
  10. Saghost

    Saghost Active Member

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    Interesting. This is the first time I've seen that described.
     
  11. SUN_Spot

    SUN_Spot Member

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    Are the A and B sides marked in some way? Sounds like you want to select the A side whenever possible to avoid reduced charge rate when someone else arrives.
     
  12. ggr

    ggr Roadster R80 537, SigS P85 29

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    That's not at all how I thought it worked, but it's a very easy experiment if sometwo want to perform it.
     
  13. TEG

    TEG TMC Moderator

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    The big transformers, and other charging equipment is usually in a little "pen" off to the side of the actual supercharger connecting posts.

    Check out the little fenced rooms in these pictures:
    36.jpg
    tesla-100th-supercharger-hamiltion-NJ-10.jpg

    I think they could have a "trickle charge" (of sorts) to a battery bank for locations that don't have sufficient primary power, but I don't think they have done much of that yet (if at all.)
    Some locations do have battery banks but I think that is more about grid balancing (to avoid peak demand charges, and capture cheaper power at night when rates are lower.)

    Many places don't have sufficient extra power available for this sort of thing. They have to research and find only suitable locations. I suppose if they wanted a location badly enough, they could work with the power company to upgrade the main power distribution coming to the site. (But that could get very expensive and time consuming.)
     
  14. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    Yes. They are clearly marked 1A, 1B. Sometimes the A and B are next to each other and sometimes all the A and all the B pedestals are grouped together.
     
  15. deckofficer

    deckofficer Member

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    Thank you for taking the time to post, your text and pictures answers a lot of my questions.
     
  16. miimura

    miimura Active Member

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    In the background of the second picture (with Tesla logos painted on the tarmac) you can see a huge green pad-mounted utility transformer. For a site with 6-8 stalls, it would typically be a dedicated 500kVA transformer outputting 277Y480V power. There is some disagreement in this community about whether Tesla uses the Euro-style 3-phase on-board chargers, or they use the 40A single phase chargers, but allow them to go up to 277VAC at full current. In the car, the charger will decrease the current to limit the power to 10kW when you go over 250VAC.
     
  17. TEG

    TEG TMC Moderator

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    Some more Supercharge stations with supporting equipment cabinets showing:
    null-5.jpg
    tesla-supercharging-station.jpg

    I think not all locations are the same. There are different vintages/versions of supercharging, and different equipment requirements for some sites.
     
  18. stevezzzz

    stevezzzz R;SigS;P85D;SigX

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    I have never seen a charging session of mine throttled by another S plugging into the other pedestal of a paired Supercharger. That doesn't rule out the possibility that I've just been lucky and always have been plugged into the A side when someone else plugs into the B side; but I've never heard anyone else claim that A is always the Master and B is always the Slave. And aren't there some SpCs that dispense with the A/B markings entirely?

    @Chris TX: FWIW the people who work for Tesla have not always proven to be a reliable source of information...and that's an understatement. :wink:

    As others have noted, the sharing of charging power is done at 10kW granularity: each 10kW charger in an SpC cabinet is dedicated to one or the other of its two pedestals at any given time.
     
  19. Chris TX

    Chris TX Active Member

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    When the guy opens up a Supercharger cabinet and shows me how everything works, and he's been responsible for commissioning many of them, I tend to believe him ;)
     
  20. nwdiver

    nwdiver Active Member

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    Most transformers I've seen at SCs are 500kVA. That's up to 500kW depending on power factor...
     

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