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Charging the Model S with the UMC on an extension cord

Discussion in 'Model S: Battery & Charging' started by jed-99aggie, Dec 3, 2012.

  1. jed-99aggie

    jed-99aggie Member

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    I searched and came up with a few extension cord topics, but they read specific to Roadster. Now that there are a few Model S on the road, I am looking for some voice of experience and practical advise.

    When I travel to family (parents/in-laws) I will travel min 300 round trip. Very likely more when considering local, in-town transit. This trip will occur on average at least 1x / month with the car. Sometimes as a "day" trip.

    At one house we have a 6-50 circuit at the "head of" the garage. The garage is tight (both short and narrow) and I will emulate the ungrateful son-in-law if I routinely displace their family car to charge mine overnight in the sole available bay.

    At the other house, I did some inspection of the current wiring system and calculation of existing load. Based on my estimate, the main service panel would need an upgrade to 200amp service to support a dedicated branch circuit for the a 14-50 install in the garage. In the utility room, immediately off the garage in a 14-30 receptacle with 10 awg wiring.

    As a result, I am looking into the feasibility of fabricating a ~25 foot extension cord. I am thinking of purchasing 6AWG or likely 4AWG 4 conductor (600 Volt SOOW) cable.

    * On one end wire a 14-50 female receptacle. On the other end of the 24' cable, wire a twist-lock (Hubbell) type male connector.
    * Then create two interchangeable terminating ends that would be a short ~12-18" run.
    • cord #1: 1st end matching twist-lock female connector; 2nd end 6-50 plug
    • cord #2: 1st end matching twist-lock female connector; 2nd end 14-30 plug

    Based on the current announced plans, the supercharger network is not apart of my charging solution (at least not for the foreseeable future). Additionally, I am sure I will be able to find a J1772 charge station in the town, however I am not yet sold on the convenience of dropping off my car at some public charge station for an extended period of time (over-night).

    My forum search found some roadsters guys in Europe have done something like this. However I am seeking some knowledge of doing this in the US with a Model S. It would be disappointing to go through all this effort only to find out that the Model S throws an error code that it doesn't like the extension cord and doesn't want to charge.

    So I am seeking input, guidance and other thoughts on how this project would prove most fruitful. I have inquired through my delivery contact and have been referred internally. No word back from Tesla, yet.

    Thanks in advance for your input.
     
  2. widodh

    widodh Model S R231 EU

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    Just make sure the cable is thick enough to prevent a large voltage drop.

    I'm European, so not sure about the cable specs in the US.

    The charging cord error comes from a big voltage drop when the charger starts to draw power. A thicker cable prevents that and makes the car unaware of the drop.

    Also try to limit the amount of connectors and adapters involved, they will all eat away a bit of voltage.
     
  3. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    #3 FlasherZ, Dec 4, 2012
    Last edited: Dec 4, 2012
    A couple of things:

    1. You really shouldn't put a 14-50R on the end of an extension cord that is served by a 6-50P, because you have to deal with a neutral that isn't there -- one way is to bond neutral to ground which makes the ground a return path for 120V loads used, or you leave the neutral floating which can blow out appliances if that cord is used with anything using 120V loads (RV). I explained this a few times on the NEMA 6-20 and 6-30 threads, if you want to search. I have seen way too many "temporary" cords made for a specific purpose get "re-purposed" later. If you want to do this, label your cord "FOR TESLA ELECTRIC CAR CHARGING ONLY -- WILL DAMAGE OTHER DEVICES" or something similar, and cut the pieces in half when you get rid of the car. The best solution here is to use a 6-50R and Tesla 6-50 adapter and keep the cord to a 240V-only application instead of 240V/120V. You could then even make a 14-50P version of your own "adapter" as well.

    2. Another reason to use a 240V-only application: type SOOW cable requires #4 AWG for 50A if you run 4 conductors, but only #6 AWG for 50A if you don't. If you stick to the 6-50R on the Tesla side, you can use 6/3 SOOW rather than 4/4 SOOW.

    3. It would be against code to do the L14-30 in a permanent install, so that means it's also dangerous in a temporary install. The car will assume it has a 50A circuit because of the 14-50 plug and will automatically attempt to charge at 40A, even when you're using the L14-30 adapter. You *should* be protected by your circuit breaker, but I have seen breaker will-not-trip failures. If you insist upon doing this, make sure the place you will use this adapter is not served by a Federal-Pacific Electric or Zinsco panel (where breakers fail to trip up to 80% of the time), because there is a high likelihood of burning the home down if you forget to dial down the charge current.

    4. 50A twist-locks (6364 and 6365's) are incredibly expensive. It would likely be less expensive to make two extension cords than use twist-locks to create a "universal" cord.
     
  4. jed-99aggie

    jed-99aggie Member

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    Thanks widodh for the inputs. Yes, I am looking at some "fat" cable for this extension cord, noting your prior posts about voltage drop sensitivity. Also thanks for the reminder about the adapters. Yes I hope to minimize their use, not only for voltage preservation, but also considering their cost.

    FlasherZ, Thanks for another valuable and informative post. You raise a number of additional thoughts I had not yet fully absorbed. Could you provide a little clarification on the following:
    • Your item #1. I was struggling with how to make this extension cord more universal and was in effect going to leave the ground unconnected in the 6-50 plug end. I read somewhere on a forum post that Tesla does not utilize the ground even though it utilizes a 14-50 plug as "standard". Any further confirmation out there? That said, this would be a TESLA dedicated cord and I like your idea of labeling to avoid possible future doubt.
    • Your item #3. I am not sure I follow. The house has a 14-30 currently wired in the utility room (permanent in the wall dryer outlet). Could you please elaborate on your code compliance reference? Also the house's breakers are GE type. That said I would have to remember to set the charge draw at 24 amps when connecting to this outlet, via my extension cord.
    • Your item #4. Yes I came to that realization too regarding the 50A twist-locks pricing. You make a good point: I could build one 25" 6-50 cable with 4AWG/3 cable (and pick up Tesla's 6-50 adapter); and a second 25" 14-30 (with either 8AWG or 10AWG/4 cable). For the 14-30 what is your thought in terms of how to connect it to the Tesla UMC (get Tesla's 14-30 adapter too)?
     
  5. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    #5 FlasherZ, Dec 4, 2012
    Last edited: Dec 4, 2012
    No - you must have ground. It's the neutral that is unconnected. The car must have ground for safety reasons, and in fact the Roadster won't charge without a good ground. Without ground, if one of the hot leads ever shorted to the car's chassis, you could be the path for 120V to ground. With a ground, it flows and trips the circuit breaker.

    What you don't want to do is leave a neutral floating -- it must be connected to a neutral conductor if you use a NEMA 14 series receptacle (and it cannot be ground!). While this isn't an issue for the Tesla chargers (since they don't use the neutral), if someone uses your adapter for a 240V/120V application (like plugging an RV in, or an electric range, etc.) you could end up destroying the appliance(s) that get plugged in.

    Basically, everything on a 30-amp circuit (breaker, 10 AWG wiring, receptacle, etc.) is sized for 30 amps and devices that plug in using a 30A plug are UL-listed such that they draw no more than that during nominal operation. The protection beyond that is intended for safety only (e.g., short circuit), and it's not really intended to be used all that often. If you create an adapter cord that would permit a 50-amp device to connect to a 30-amp outlet, it is too easy to "forget" and the car will attempt to draw 40A. This *should* trip the breaker, but I've seen some cases in which this doesn't happen (including my own home in California that had a Federal-Pacific Electric panel, and the insulation on wiring in the wall burned completely off the wire). You really want to minimize the possibility that you would trip the breaker.

    Your 25' 6-50 extension could use SOOW 6/3 cable, saving you about $3/foot over 4/4 cable (!). Green ground, black hot1, white hot2. Put red or black electrical tape around the end of the white conductor insulation where it terminates.

    If it were mine, for the L14-30 case, I would build an L14-30 extension cord using 8/4 SOOW and get the Tesla adapter for 14-30.

    If you really insist upon using a single adapter on the UMC for both cases, you could build an L14-30P to 6-50R adapter and you can use SOOW 10/3 cable for this. L14-30P hot1 (brass) to 6-50R hot1 (brass), L14-30P hot2 (brass) to 6-50R hot2 (brass), L14-30P ground (green) to 6-50R ground (green). Leave the L14-30P's neutral (silver) unconnected. It will work -- this has the caveat I reference in the paragraph above as being improper and a bit dangerous if your circuit breaker fails to trip, but if you trust your circuit breakers, it won't leave safety issues with ground or neutral.
     
  6. mitch672

    mitch672 Active Member

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  7. Discoducky

    Discoducky Active Member

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  8. JakeP

    JakeP S P4996 / X P6028

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    I just got the 15-footer, and it should be perfect for my parents' garage, where the electrician installed the 14-50 way in the back of the garage by the panel, rather than up front near the door, to allow flexibility of charging in the driveway even if another car is parked in the garage. The 15-footer is BIG and HEAVY, the 30-footer must be absolutely gargantuan!
     
  9. SuperCoug

    SuperCoug Model S Res #7734

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    When the cord is described as " a 6 / 3+8 / 1 STW cord" what exactly does that mean? I'm assuming the first "6" is the gauge of the wire but I don't have a theory on what the "3+8 / 1" portion is telling us.
     
  10. ElSupreme

    ElSupreme Model S 03182

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    6 is guage of the conductors
    6 is the guage of the conductors
    3 is the number of conductors
    +8 is with an additional 8 guage ground wire
    1 Is a single combined cord (I am not 100% on this one)
     
  11. Robert.Boston

    Robert.Boston Model S VIN P01536

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    I'm reasonably certain "6/3 + 8/1" means three #6 cables (two positives and a neutral) and one #8 cable (ground). In any case, my 50' example of a 6/3+8/1 has worked without issue. And, yes, it's a big sucker -- about 1.5" diameter (from memory).
     
  12. Zextraterrestrial

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    Really?? all you need for the S for a 14-50 is 2 hot wires. that is all that is used. But to be 'safe' you should have all of them
     
  13. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    6/3 + 8/1 STW.

    Type is STW = (Service, Thermoplastic, Weather resistant} It's an outdoor type cord but is not oil-resistant (which would be STOW)
    6/3 + 8/1 = 3 conductors of AWG 6 (black, white, red) and 1 conductor of AWG 8 (green)

    - - - Updated - - -

    No, you also *need* an equipment grounding conductor (aka safety ground). Otherwise, a hot wire shorting to the car chassis can use you as a path to ground instead of shorting via the EGC and tripping a breaker.

    If you are building a 14-50 extension cable, you must also provide the neutral, or you could end up with a floating neutral if the cord were used for something else -- say, an RV. This will destroy a lot of 120V appliances in an RV if used with a floating neutral.
     
  14. efusco

    efusco Moderator - Model S & X forums

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    Mods, perhaps merge this thread with the previous one on the same subject (though this one's gone a bit off tangent): Extension Cords
    I'd posted other info and photos to support the viability of charging with an extension cord.
     
  15. Puyallup Bill

    Puyallup Bill Member

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    My charging situation is extremely limited, as I live in a ground floor apartment, attached garage, 100 Amp panel, no 240 volts in the garage, and management is not interested in such, even if I cover the costs. I do not anticipate moving.

    In order to charge my Nissan LEAF, I home brewed a quick 240 box, as I was fortunate to find two 120 volt circuits in the garage on separate phases. There is relay protection so that if one 120 volt plug is disconnected, the other 120 volt plug will not be hot. The quick 240 box receptacle is NEMA L6-20, X, Y, and GND. I charge at 12 Amps, as both 120 volt circuits are 15 Amp.

    I understand that the 14-50 UMC uses GND, X, Y, and does not connect neutral. That being the case, I plan to extend X, Y, and GND from the 240 box to a separate box with a 14-50R. Neutral will not be connected, and the box will be clearly labeled for Tesla charging only. Charge at 12 Amps.

    Am I OK with this set-up?

    When necessary for a little faster charging, I plan to use a 3 #6, 1 #8 14-50 extension cord from the electric stove outlet. Forty Amp breaker, 30 Amp charge.
     
  16. Lloyd

    Lloyd Active Member

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    I would wire a 6-50 because it has no neutral, label it for 12 amps only.
     
  17. Puyallup Bill

    Puyallup Bill Member

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    Good idea to prevent misuse.

    But, that wakes up some brain cells. The two neutral wires dead end unused in the quick 240 box, so I'll just carry them over to the 14-50R, and placard it for 12 Amps. That way, if someone plugs in a 120/240 volt device, it may pop a breaker, but not destroy the device.

    Thanks.
     
  18. dtich

    dtich #P708

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    ack, no, you need the ground wire! don't forget that one, goodness sake.

    and a properly wired 14-50 receptacle has a neutral even if the circuit doesn't use it in all circumstances.

    people should NOT be making their own power cables, esp. at this level of voltage and current, if they don't really understand electrical wiring. please let's not have any stupid disasters. and disasters can happen with this stuff.

    [no finger pointing, just sayin...]

    also, a MAJOR common area of wiring issues (fire hazards!) are the connections between cables: junction boxes, terminations (plugs, receptacles)... please pay particular attention here. solid, clean connections, nothing loose or in danger of loosening....

    now i'm all uptight about people messing with 40A circuits in their garages. lol.


    edit: ok. didn't scroll the page and see the responses before i jumped in....
     
  19. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    Doesn't quite work that way -- it's not about the current going through it, but rather the fact that neutral is floating. With a floating neutral, if you plug in a device that uses 120V appliances to both legs from neutral, you'll end up frying the 120V appliances by creating 240V potential through them. With a 14-50, it's entirely likely someone might try to plug an RV into it, and you'll blow up a lot of appliances in that RV.

    - - - Updated - - -

    Will it work? Yes.
    Will it be safe? If you can trust your breakers or have another current-protection device (like a fuse or breaker) on your quick 240 box.
    Will it be insured if your house burns, regardless of whether your device caused it? Likely not, because your device is not UL listed and violates express NEC rules on paralleling conductors.

    This is fine, although I wonder why you wouldn't just replace the breaker with a 50A if you have all 50A-capable wire (#8 THHN or 6/3 Romex) and a 50A receptacle, so you can charge at 40A.
     
  20. Puyallup Bill

    Puyallup Bill Member

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    #20 Puyallup Bill, Jan 4, 2013
    Last edited: Jan 4, 2013
    Appreciate your comments.

    Perhaps I was not clear - the 14-50R would have GND, X, Y, and neutral. But, on second thought, (actually, third thought) I'll probably just use the SAE J1772 that I currently use with the LEAF - providing I get a J1772 adapter with the S. My garage wiring will not support charging both at the same time.

    Well, as I indicated, I rent, and I am loath to change any installed wiring or devices, and management is not interested in doing so.

    Now, if Elon will install a Supercharger at the intersection of WA 512 and I5, I'll be in tall cotton and forget about all this Mickey Mouse stuff.:biggrin:
     

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