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Discussion in 'Supercharging & Charging Infrastructure' started by TomB985, Aug 11, 2019.

  1. Evoforce

    Evoforce Active Member

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    MY question to you is... Why did you do it? I mean, just why?? :D
     
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  2. Tz00

    Tz00 3 LR AWD

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    I thought so as well, but my charge rate went down. I moved, and it was higher after. TeslaFi showed it going down as well and higher on the standalone charger after.

    I was at another charger yesterday and it was 50% full. I was sitting in the car watching the kW rate as someone pulled in to the other shared charger and my kW immediately went down.
     
  3. K3Man

    K3Man Member

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    Regarding the issue with sharing etiquette- I’m a relatively new Tesla owner but know about the sharing a charger (that is not an “urban” nor a V3) thing, but have now met several other Tesla owners that had no idea that most chargers are shared. I show them the pedestal numbers and use that to help cement the concept, hoping that they can use that as a helpful mnemonic for future supercharging. :)
     
  4. NoMoGas

    NoMoGas Supporting Member

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    I don't see the harm as it's far from full.
     
  5. mociaf9

    mociaf9 Active Member

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    #25 mociaf9, Aug 12, 2019
    Last edited: Aug 12, 2019
    It does actually have an impact on your charging rate IF you're getting more than 108 kW when the second car plugs in. If you've plugged in relatively recently and had a low enough SOC so that you are getting over 108 kW, your charging rate will drop to ~108. This happens due to the way that traditional superchargers dynamically switch power. The superchargers are made of 12 AC to DC chargers (rectifiers) just like what you have in the car for charging at home. Each is capable of the same ~12kW. So, when all are working there's ~144 kW available. But, in order to be balanced on the 3 phase AC power that's being drawn from the grid, the architecture of the superchargers bundles them in groups of 3 (one per phase). In effect, the 12 are really more like 4 groups of 3 each. Any car plugging in is guaranteed the power from 1 group of 3, which is why the second car to plug in will only get around 36 kW if the first car has a high charge rate. But since the new car is getting 1 group that only leaves 3 groups (9 chargers) for the first car, hence the limit of ~108 kW. If the first car's charging rate has already dropped below that point then they won't be affected, but if they're still above it then their charging rate will drop to there. Subsequent group shift--giving access to additional power in blocks of 36 kW--will happen once the first car's rate drops below 72 kW, then 36 kW.

    The above is assuming that the supercharger is in perfect working order. However, if one or more of the individual chargers within the supercharger is faulty, you could still be minorly affected even below 108 kW.
     
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  6. Tz00

    Tz00 3 LR AWD

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    Interesting... Both of my shared sessions dropped by almost exactly 1/4 kW when the other person plugged in. ~120kW down to ~90kW. That must be the current limit on the rectifier at the required voltage. So you basically loose 1/4 of the your charging kW, not 144kW - 36kW.
     
  7. mongo

    mongo Well-Known Member

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    If the line voltage was low, or it was hot out, then each unit may have been limited to 10kW. Ideally each would be 12kW.
     
  8. mociaf9

    mociaf9 Active Member

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    #28 mociaf9, Aug 12, 2019
    Last edited: Aug 12, 2019
    Yeah, that's more or less true if you're getting the max output of a fully working supercharger. Or the supercharger may not be upgraded to 150 kW yet. In which case each of the 12 chargers are only putting out ~10 or 11 kW, and the switching will then be in groups of 30-33 kW. But thinking of it only as a 1/4 drop will potentially obscure some of the nuance that will let you understand what's happening if you're not getting the max output due to the car's SOC or if the supercharger isn't working perfectly. For example, let's say that one of the 12 chargers in the supercharger stack is faulty. They will fail individually without stopping the rest from performing properly. Based on SoC, you're charging at 110 kW when a second car plugs into the paired stall. Car #2 gets one group of 3, but the faulty charger isn't in that group. So, they end up with their 36 kW. On a perfectly working supercharger, you'd only drop from 110 kW to 108 kW, a negligible drop of 2 kW. But since one of the 3 charger groups you're left with has a bad charger in it, your rate will actually drop to ~96 kW. Neither of those is a 1/4 drop.
     
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  9. Tz00

    Tz00 3 LR AWD

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    Wouldn't the rectifier be limited by current? So if you were at 110kW, and 1/3 of the charges "go away", then you aren't going to be able to get 108kW, but rather ~82kW? They can't increase the voltage, as that would be limited to the car's battery voltage, so the kW can't increase on each of the remaining chargers.
     
  10. Need

    Need Active Member

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    The driver could have ran out of juice and called for a tow in the middle of the night. He/she called the tow truck and ask the driver to tow it to the nearest supercharger and plug it in. He/She will pick up the car the next day!
     
  11. VT_EE

    VT_EE Active Member

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    That must be a rental :-D
     
  12. Big Earl

    Big Earl Supporting Member

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    #32 Big Earl, Aug 12, 2019
    Last edited: Aug 12, 2019
    Not the case. Cabinets are setup with four groups of three ~12 kW chargers (each charger is on a phase for even load distribution, since the grid provides three-phase power). First car has access to all four groups for 144 kW. Second car comes along and gets access to one group for 36 kW, leaving the first car with three groups for 108 kW. When the first car’s charge rate drops below 72 kW, the second car will get a second group, for 72 kW.

    An urban Supercharger is locked at two groups (72 kW) for each car.

    Numbers can be less if the charger if it’s in need of service. The numbers above are assuming perfectly functioning equipment. Numbers can also be slightly higher if the grid is supplying slightly higher than normal voltage.
     
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  13. SSonnentag

    SSonnentag Active Member

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    The second car can take away from your charge rate. If you're charging at more than 105 kW or so, they will knock your rate down to 105 kW or less. Each pair of plugs is made up of 4 individual chargers. The first car to plug in gets all 4. The second car gets at least 1. So if car 1 is charging using all 4, it will get knocked back to 3 when the second car plugs in. If the first car's charge rate is already at or below what 3 of the 4 chargers can provide, then the first car shouldn't see any change in charge rate when the second car plugs in.
     
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  14. mociaf9

    mociaf9 Active Member

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    No. The current increase isn't an issue for the rectifiers. The supercharger can put out more current to get the remaining rectifiers up to 12 kW each. And the car/battery doesn't care. If it can take 108 kW, it can take 108 kW. It doesn't "see" each charger individually. The pack voltage is constant and the amps at the charging port don't change whether they are split over 12 rectifiers or over 9 of them. That only matters to the supercharger, the amount of current coming down the wire is the same.

    Of course, underlying this thought and your question is the belief that, when charging a single car, the supercharger cabinets divide the power output equally between all 12 chargers in the stack. I.e. that when you're plugged in alone, charging at 110 kW, that each of them is putting out ~9.2 kW. But this may not be so. Maybe it uses 3 groups of 3 at full power giving 108 kW (12 kW/charger), and the final group of 3 is only putting out 2 kW (0.66.. kW/charger). There might be efficiency reasons for doing so. Who knows?
     
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  15. EVDRVN

    EVDRVN Member

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    I've seen this before, usually a tow situation. If not you know you are at the Palo Alto, Redondo Beach, or San Mateo Cross Roads SC. Yahoo central.
     
  16. Tz00

    Tz00 3 LR AWD

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    Sure, but as I said, my charging rate dropped by 1/4... so that would imply that the 3 sets of charger did not increase their output when another car connected. The total output kW was less than the 3 could output in theory. But they can't dump in a higher voltage than the battery pack will accept, so the limit of the current remains.
     
  17. ALSET YXES

    ALSET YXES Member

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    Yup, and those stupid people wonder their cars get vandalized... Don't be that douche bag.
     
  18. ALSET YXES

    ALSET YXES Member

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    Good luck with the training... If they've made it this far then there is no hope for them.
     
  19. ALSET YXES

    ALSET YXES Member

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    Wrong... For V2 Superchargers both cars will receive slower charge rates depending on both car's SOCs. V1 & V2 posts share the full supercharger cabinet (no physical partition). The urban posts share a single supercharger cabinet but each has a dedicated 75kw partition capable of 72kw max regardless of the other common post is in use or not. (no rate of charge slow down)
     
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  20. mongo

    mongo Well-Known Member

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    V1 & V2 do physically/ electrically partition the charge units (4 groups of 3 units each). A battery's voltage varies with state of charge. You cannot connect two packs and a charger together unless they had the same SoC to begin with. A 75kWh and 100kWh pack are very incompatible (350V vs 400V) . Urban superchargers permanently tie half the charge units to one pedestal and half to the other.
     

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