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Infrastructure for multiple electric vehicles at home

Discussion in 'Technical' started by smorgasbord, Jun 5, 2011.

  1. smorgasbord

    smorgasbord Active Member

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    I was thinking about a "success problem": Suppose EVs become popular and mainstream. Cool! Now, mentally raise your hand if you currently have 3 or more vehicles AND 3 or more drivers at home. Now imagine you need to charge 3 or 4 vehicles in one evening. What's the current draw?

    I just installed a 50 amp outlet for my upcoming Roadster (can't wait!). I have a Model S on order. I'll probably want something along the lines of the HPC for the Model S, which puts me at 140 amps total. My whole house is only 200 amps. Many homes in the US are only 100 amps service.

    So, what's the future going to be for families with 3 or more vehicles?

    I'm thinking they all get plugged in to a single charger unit, which communicates with the cars to figure out which cars need what to get fully charged, and spreads the load amongst the cars and/or sequences which cars get charged when. It might be good to have a way to enter priorities for which vehicles to charge first, and/or enter anticipated mileage for the following day for each car, but that's probably more input than most people will want to give. Another possibility is that many people charge at work, which has the benefit of reducing charge times at home, but has the disadvantage of pulling electricity during prime use hours, which could be a drain on the system (I'm in CA, so we're familiar with rolling blackouts).

    What I can't see happening is that all homes in the US get upgraded to 400 amp service. Any other ideas or thoughts here for a many EV future?
     
  2. dpeilow

    dpeilow Moderator

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    Well, to do average mileage (at least in the UK which is 10000 per annum) you only need to charge at 1kW overnight. So in theory, it shouldn't be a problem.
     
  3. EV_de

    EV_de Model SP10/XP9 EU ZOE#47

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    no Problem in EU ... IF all cars supporting 3 phase charging ...

    US 240V * 50 A = 12 KW
    EU 400V * 16 A = 11 KW ... Fuses - 63A / phase ... 3 cars each 3p 16 A + Power left for the House ..
     
  4. vfx

    vfx Well-Known Member

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    If they are all empty at by night, that's a lot of driving.
     
  5. smorgasbord

    smorgasbord Active Member

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    Yes, not every car is going to need the full 3-4 hour charge each night, but it's easy to imagine a family where one person commutes to work, another runs errands, and another goes to school. Even if they're not all empty at night, you still have the simultaneous charging load issue for the hour or so they each need to be charged. I suppose you could program one car to start at midnight, the next to start at 2am, etc., but that assumes the each car is finished within its 2 hour window - and if it's not it's going to overload the circuit while you're sleeping. So, I think you need to do the sequencing in the charger, in which case you might as well have a smart charger that knows when each car is done, and/or reduces power to each so that the total is not more than the incoming circuit can handle.
     
  6. LASpark

    LASpark Member

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    #6 LASpark, Sep 8, 2013
    Last edited: Sep 8, 2013
    I think you are correct. Eventually Tesla will probably come out with a Dual HPWC that has two charging cords. Each will communicate with the two cars to charge them serially overnight, so the circuit would not have to be upgraded. "Port A" could always start first, and when the car reaches the desired state of charge, the Dual HPWC would automatically begin charging "Port B". The fight among the spouses would be who gets / needs to use Port A!
     
  7. dirkhh

    dirkhh Middle-aged Member

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    Interestingly enough this has been a recent conversation in my home. So if we get that second Tesla, how will we deal with charging it? Our driveway / garage doesn't allow to park both cars there (well, we could put one in the garage and one in the driveway but then one car would block in the other one). So we not only wouldn't be able to use the Dual HPWC that you envision, we'd even have to come up with a solution where one of us can charge on the street in front of the house. Which adds permitting issues. And of course there'd be no place left on the panel and if those both were 100A circuits. And I'm reasonably certain that we'd have to upgrade the drop to our house!
    So yes, two (or more) Teslas in a family do create a bunch more problems...
     
  8. jerry33

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

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    This is what we do now. Unfortunately, both aren't Teslas.
     
  9. andrewket

    andrewket 2014 S P85DL, 2016 X P90DL (soon 100)

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    I have two EVs right now. The S and a volt. I have an HPWC on a 100A circuit and a 14-50 on a 50A circuit. The volt only uses 240V/16A. I bought a clipper creek EVSE and wired a 14-50 plug to it. This way I can use the 14-50 for other things. We have an X on order. If we end up with three EVs (two Teslas) my plan is to share the HPWC and charge each car every other day. With the battery capacity of the Teslas charging every day is not required for our usage pattern. The position of the HPWC in the garage should make it possible to reach both cars.

    If I was doing this over, I would run lower gauge wire from my main panels to the sub in the garage. I used aluminum cable and I've already hit the max. Also, instead of buying the clipper creek evse I would have bought an extra tesla mobile adapter and changed the end to a J1772. The mobile adapter does 240 and 120V, and up to 40A/240v for only ~$200 more than the clipper creek that I bought that maxes out at 20A.

    A
     
  10. dirkhh

    dirkhh Middle-aged Member

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    The text under your user name might give the impression that at least one of them is :)
    For us it's currently the Model S below VVVVV in the garage and a Toyota Sienna on the street in front of the house ;-(
    I'm trying to convince my wife to add a Model X reservation. No luck so far, in large part because​ of the charging infrastructure issue.
     
  11. jerry33

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

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    That's right both are not Teslas, meaning that one is and the other is not. What you are thinking of is "Neither are Teslas" :)
     
  12. dirkhh

    dirkhh Middle-aged Member

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    Man... that's mean... poking fun at the non-native speaker here.
    Both... are... not Teslas. :tongue:

    :biggrin:

    But I know how to fix this. You simply need to buy a second Tesla and then go back to fix your post to say "both are Teslas" and we'll both think it means the same thing. Easy! :)
     
  13. Kaivball

    Kaivball Member

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    I upgraded to a 400 amp panel so I can have two NEMA outlets when the time comes.
     
  14. jerry33

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

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    Sorry, that wasn't the intent.


    I wish my wallet would agree with you. Donations to help fix this anyone? :)
     
  15. drees

    drees Active Member

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    Chargepoint just came out with a product (CT4000) that lets 2 cars share a single 40A circuit. If only one car is drawing current, it gets 30A allocated to it (limit of J1772 plug). If two cars are drawing current, each car gets 16A (16*2=32A, limit of 40A circuit).

    The same thing could be done with a dual-plug HPWC but with the limits raised appropriately.

    There will definitely be demand for this type of product as more households go to dual-plug-in vehicles.
     
  16. Zythryn

    Zythryn MS 70D, MX 90D

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    Another solution is simply to charge at lower amps.
    We have two and one 60 amp breaker with two NEMA 14-50 plugs.
    Each car is set to charge at 24 amps. Works great and gives us plenty of charge.
    I suppose if the pair, or trio of family members drive move than 400 or 600 miles a day you may need another solution.
     
  17. dirkhh

    dirkhh Middle-aged Member

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    And here I thought it was obvious that I was just kidding. No offense. None whatsoever. I was just joking around.
    Good luck with that :)
     
  18. brianman

    brianman Burrito Founder

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    A doesn't imply B here. B is allowed by A, but not implied by it.
     
  19. Chris TX

    Chris TX Active Member

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    I've been thinking about the possibility of having two OpenEVSE chargers (EMW JuiceBox) where one is the "master" and the other is "slave". The Master EVSE sees what is plugged in and can juggle the charging between the two. You can even prioritize the vehicle that gets charged. I know with the Tesla API you can see the battery level and modulate the amp draw. I don't know about the Leaf or other vehicles, though.

    Or, if you have two Teslas, you could just have a service running on a home computer (or Linux powered router) that can see when the cars are plugged in at home (WiFi local network) that sends commands directly to the cars to balance their amp load. You can even grab the live data from your eMeter depending on the manufacturer. If the house's load starts to reach 80%, it would throttle down the amp draw on the car(s).
     

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