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Wiring UMC for 110/120 volt operation?

Discussion in 'Roadster' started by smorgasbord, Aug 20, 2012.

  1. smorgasbord

    smorgasbord Active Member

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    Like many Roadster owners, I have both a UMC and the standard 120 volt "spare" mobile connector. The UMC can handle 120 volts via an ahttp://www.teslamotors.com/roadster/charging/universal-mobile-connector, but do I need to spend the $100?

    I've created adapters from dryer outlets to NEMA 14-50 for pretty cheap, since those are straightforward to wire. I then need to manually limit the current I draw.

    For 110/120 volt operation, however, what is the wiring like? If I pin the ground wire to ground, and neutral to neutral, then which of the two remaining wires gets the 110 volt "hot"? Or, is it that I pin ground to both ground and neutral and then connect the two 110 volt wires to the two usually 220 volt wires?

    I don't know that I'm actually going to do this, but it would make sense to not have to carry both the UMC and spare mobile connector when traveling in J1772-less areas.
     
  2. doug

    doug Administrator / Head Moderator

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    For 240V, the neutral prong of the UMC isn't actually connected to anything. So for a 120V adapter, the 120V hot goes to one 240V hot, and the 120V neutral goes to the other 240V hot. Not sure if it will actually work on the Roadster UMC, though. It might do a voltage check.
     
  3. dwegmull

    dwegmull 2013 Model S 85

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    I just modified one of my pigtails this weekend.
    I agree with Doug in terms of basic wiring. in addition, TM offers a 120V pigtail, so the UMC should be able to handle it.
    As far as I can tell, the UMC sets the current as follows: in the twist lock outlet there is a fourth wire (purple) that is wired diffrently.
    In the 50A (40A charge current) pigtail, the purple wire is shorted to ground.
    In the 30A (24A charge current) pigtail, the purple wire is connected to ground via a diode with its anode to ground

    I suspect that reversing the diode would give 40A (32A charge current) and leaving the purple wire disconnected would give 20A (16A charge current). I will try to make a working 120V adapter tonight and report back.

    By the way, the twist lock plugs and outlets are made by Home Page | Marinco and are available at boating supply places. look for shore power, 240V/50A.
     
  4. doug

    doug Administrator / Head Moderator

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    It sounded to me like smorgasbord is making adapters to connect to the NEMA 14-50 pigtail, so I'm not sure what the UMC will do in that case since it expects 240V. For 120V Tesla omits the pilot signal.
     
  5. smorgasbord

    smorgasbord Active Member

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    Right - and that's my concern. Right now I can make adapters for under $15, but Tesla wants $100 for the 120v pigtail. So, if I'm already carrying the UMC I then also might want to carry the spare mobile, but since space is so tight on Roadster I'd rather just carry a second pigtail. Like I said, this isn't anything urgent. Right now I'm finding that the J1772 is really all I need for traveling in CA, so if I were to stay at someone's house over the weekend, the spare mobile would take up less space than the UMC. But, if I knew I would be RV park charging, then I wouldn't to carry all 3 connectors.
     
  6. dwegmull

    dwegmull 2013 Model S 85

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    I did build a 120V pigtail last night. Using the twist lock outlet that came with my 50A pigtail. Now that I see doug's comment, I'm not so sure that my experiment will be of value...
    Leaving the fourth wire inside the twist lock unconnected results in the Roadster charging at 12A, regardless of input voltage. While it works from an electrical point of view, the small diameter of the 120V cable result in a very loose mechanical assembly...
    IMG_20120820_183226.jpg
    I will try building an "external" adapter for 120V tonight and report back.
     
  7. TEG

    TEG TMC Moderator

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  8. jaanton

    jaanton Roadster NA #1026

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    I don't think this is quite correct. The 'spare' connector omits the pilot signal, but if you have the UMC working off of 120v it still produces a pilot. The car, if it sees the pilot will honor it whatever the voltage. I remember a post, which I can't easily find with search, that someone made a UMC pigtail which got 120v @ 24A to charge a Roadster. I have the NEMA 6-20 pigtail I purchased and wired up a NEMA 5-20 onto it and got 120V @ 16A. What I do remember is that if you try 120V with the UMC, the neutral needs to be on a specific pin. If it doesn't work one way, try swapping the hot and neutral and try again. 240v is easier in the sense that you have two hots and ground and those hots can be in whatever order, 120v is harder because you have to get the neutral in the right place. If I remember I can check this out tonight.
     
  9. TEG

    TEG TMC Moderator

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    FWIW, I have a LEAF portable J1772 modified to output a 16A pilot signal and pass through 120V or 240V.
    If I plug into 120V, the LEAF always pulls 12A, and just ignores the 16A pilot signal.

    Not sure about the Roadster, though. Yes, I heard someone used a campground TT-30 ([email protected]) and was able to convince the Roadster to pull 24A from it. I think they had to use the VDS override though to convince it to charge at that rate.
     
  10. dwegmull

    dwegmull 2013 Model S 85

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    I just did some further tests.
    The Roadster will happily pull whatever current the UMC tells it to pull, regardless of voltage.
    I only tried with a dryer outlet pigtail, so in my experiment, it was about to pull 24A.
    I can confirm that the "polarity" of the 120V cord matters.
    If the neutral and hot wire are swapped the car will display an error message.
    I will post a picture showing the correct "polarity" later...

    One more thought: if you own a 14-50 pigtail and need to plug into a modern dryer outlet, just open the 14-50 plug and remove the unused neutral prong. This only takes a screwdriver and is reversible!
    Don't forget to set your current limit to 24A!
     

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