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Thread: Design for Large Quantity of EV Chargers

  1. #1

    Design for Large Quantity of EV Chargers

    Has anyone done any designs for large amount of EV chargers in a parking lot? I have done many designs for EV charging, but the quantities have usually been small (2-8 chargers). I guess here in California these are turning from curiosities to expected public infrastructure. I have a client that wants me to put together a design for 12 Level II chargers and to make provisions for expansion to FIFTY!! total Level II chargers. The issue is that all these loads have to be considered continuous and no real diversity factor can really be applied to it. Each Level II charger is 32A, 208V, 1PH or 6.7KVA. 50 chargers = 332.8 KVA!

    The facility has the capacity but I know that the facility manager is not expecting to run that much power out to a parking lot. He was asking me in the kickoff meeting whether we can take care of all this with a 2-section (84 circuit) panelboard and picking up all the loads off of that. Now I have to tell him that he needs to put a 1,200A (or two 600A) distribution board out in the middle of his corporate campus parking lot.

    I guess my question is has anyone had any direct experience with EV chargers? Do they really draw 32A while charging? Can any load factor be applied to this load?


  2. #2
    Join Date
    Apr 2007
    Berkeley, CA
    Quote Originally Posted by Machiavelli999 View Post
    I guess my question is has anyone had any direct experience with EV chargers? Do they really draw 32A while charging?
    As a user, yes, not a designer. The EVSE will advertise its maximum current capability via a pilot signal in the J1772 connection from EVSE to EV, and then the AC-to-DC charger on the EV is allowed to draw any current up to the maximum advertised by the EV. So if you install a 32A EVSE and plug any car into it that can draw 32A (many current models), the load can be 32A continuous for well over 3 hours.

    I believe that there are smart EVSEs available that will talk to each other and reduce their advertised capacity to obey an overall current limit. Definitely you can get two EVSEs that share a 40A circuit (32A continuous) and if cars are plugged into both of them, each EVSE advertises only 16A. Not sure if there are larger scale solutions, e.g. 10 EVSEs sharing a 200A circuit (160A continuous).

    Cheers, Wayne

  3. #3
    Join Date
    Jul 2005
    At my age, I'm accustomed to restaurants asking me to pay in advance, but now my bank has started sending me their calendar one month at a time.

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