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Request for info: Taper on new "Urban Superchargers"

Discussion in 'Model S: Battery & Charging' started by Polly Wog, Sep 11, 2017.

  1. Polly Wog

    Polly Wog Member

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    With Tesla announcing today their new "Urban Supercharger", with the first two on-line stations in Chicago and Boston, I'm hoping that somebody on the forum will post what the taper is for their particular model. What I'm really wondering, since Tesla is saying that they are a dedicated 72 kWh charger, just how long you might get the maximum rate for a given SOC. So...anybody in Chicago or Boston that wants to share the information, please do here. Thanks!
     
  2. Akikiki

    Akikiki A'-Lo-HA ! y'all

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    Good question. I too had one. Will these Urban Superchargers be DC or AC? Because 72 amp coincides with the high amp chargers.
     
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  3. Veritas1980

    Veritas1980 Electric Viking

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    DC, it’s 72 kW, not amps. So since 22 kW on AC is the highest on a Tesla, it has to be DC.

    I don’t have specific knowledge on this, but why should the tapering be different on this compared to regular super charging?
    Battery is the same, and so I assume would be the limitations.
     
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  4. Polly Wog

    Polly Wog Member

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    Tesla could have theoretically designed it to maintain 72 kWh until the point at which a normal Supercharger would taper below 72 kWh, based upon SOC. Or, it could have a completely different taper. I'm just curious.
     
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  5. apacheguy

    apacheguy S Sig #255

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    Taper is controlled by the vehicle, not the charger. Whether you are connecting to Chaedmo or a supercharger, the vehicle doesn't care. It will attempt to pull the maximum amps dictated by the BMS.
     
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  6. Cosmacelf

    Cosmacelf Active Member

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    Presumably the taper is the same, but would be interesting to confirm. Btw, it is kW, not kWh. The unit kW is instantaneous power. kWh is power over time which is total energy.

    What I wonder is if this is what all new Superchargers will be. Tesla seems to have a problem with the older Superchargers overheating when in constant use and only being able to supply 60 kW or less.
     
    • Informative x 1
  7. Polly Wog

    Polly Wog Member

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    Thanks, @Cosmacelf. I know better, and yet I still made the mistake!
     
  8. FlyingCookie

    FlyingCookie Member

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    The goal of these is to draw load away from the high-speed superchargers, Which should HOPEFULLY lower their duty cycle. In theory these urban superchargers are cheaper to build, so they can have many more of them. Then we can go back to the high-speed superchargers being used for road trips, like they’re supposed to be, which should hopefully give them some time to chill between uses.

    Gonna stop for dinner for an hour or two? Plug into an urban supercharger and the car should finish charging for the week’s drives in an hour or two. On a road trip? Stop at a supercharger and be back on your way in 40 minutes.

    These bridge the gap between L2 and Superchargers nicely. At 40 amps and 208 volts (common in parking garages), L2 chargers only give you 8kw. If you spend all day shopping, that’s great. But 16kwh (a nice long dinner’s charge) isn’t going to get you terribly far. An Urban Supercharger could have you at 60kwh within an hour of grocery shopping and such, and not tie up the real Superchargers for people passing though.
     
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  9. apacheguy

    apacheguy S Sig #255

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    Why are the urban superchargers cheaper to build? With dedicated 72 kw output at each stall, you still need the same number of chargers as a pair splitting 145 kw.
     
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  10. ShockOnT

    ShockOnT ⚡️⚡️⚡️⚡️⚡️

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    I would think the taper is battery-limited, so whatever state of charge gets you 72kW on a normal supercharger will probable be the start of the taper on the Urban Supercharger too.
     
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  11. ItsNotAboutTheMoney

    ItsNotAboutTheMoney Well-Known Member

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    I'd guess it's because it's bundling stuff into a single unit and any cabling only has to handle 72kW.
     
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  12. apacheguy

    apacheguy S Sig #255

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    True, they can use higher gauge wires. I wonder if the low gauge wiring adds a lot to the cost of traditional supercharger installations.
     
  13. brkaus

    brkaus Active Member

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    It is possible that it wouldn't taper quite as fast, because there wouldn't as much heat buildup during the first part of a charge. Charging at 100kW+ is going to build heat possibly faster than it can be dissipated. So when you start at 100kW and it starts tapering, as it goes through 72kW there may be a higher internal battery temp compared to charging at 72kW for the same amount of time.

    So, starting at a lower level *may* end up not tapering as fast as it starts dropping from 72kW.
     
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  14. ShockOnT

    ShockOnT ⚡️⚡️⚡️⚡️⚡️

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    That makes an interesting point that Tesla could change supercharger behaviour to minimise total time to target charge percentage by give less than max speed.
     
  15. spottyq

    spottyq Member

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    I also have some trouble understanding that.

    Maybe the aim is more to have a consistent, long-ish* time to charge rather than pure speed ? And to differentiate them from the normal superchargers so that people on road trips won't confuse them.

    Also, just a quick question for anyone who might know : are urban superchargers shown differently on the car's map ? (I do not have a car so can't check it myself.)

    * Long-ish as in it seems to be spot on the time one would spend in a paying garage in the city while shopping/having a good meal.

    [Edit :] An other benefit is that you do not have to check if you are pulling into a paired stall. Many users do not know about it or worse, they do know about it but get it wrong and systematically pick a paired stall.
     
  16. FlyingCookie

    FlyingCookie Member

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    The wire gauge to 72kw should be less than half that to handle 145kw, which can be a difference of over $10 PER FOOT in price for the wiring. That, coupled with likely newer/cheaper chargers in the cabinets, potentially less heat generated in the cabinet meaning a smaller cooling system, it should work out to be significantly cheaper.

    Some of the Supercharger stalls may be located more than 200ft from the equipment. When you’re saving $2000/Stall in wiring alone, it adds up quickly. (These are precise numbers. The savings could be more or less)
     
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  17. brkaus

    brkaus Active Member

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    I'm pretty sure this is the primary savings, along with the removal of the high power switching electronics. Sharing chargers requires high power switches.

    Look at the charge pedestals - it appears that the cable to the car is now longer. So they have a bit more flexibility in placement (and parking skills) :rolleyes:
     

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