Making a UMC extension cord

trbeals · Apr 20, 2014

I'd like to create a UMC extension cord that would connect to the UMC on one end, and the UMC adapters on the other end. The cable would pass the pilot and other signaling necessary for the UMC to deduce the correct charging rate based on the attached adapter. This seems like a safer (although still not "official") option than a NEMA 14-50 50 AMP extension with "dumb" adapters that then connect to other (potentially <50 amp) plugs.

Anyone know where I could find the necessary male and female connectors to mate to the UMC to build this, short of cannibalizing a UMC and adapter?

FlasherZ · Apr 20, 2014

Custom Tesla part. You'd probably have to have something manufactured for you.

qwk · Apr 20, 2014

I really don't know why one would go through the expense and trouble of making something like this, when a properly sized extension cord would work just fine for a fraction of the cost.

mitch672 · Apr 20, 2014

25' of the proper 8/3 SEOOW 40A cable costs $60 from Amazon:
Coleman Cable 096040008 SEOOW SEOPRENE, 8/3, 25-Foot - Electrical Wires - Amazon.com

This is $2.40 per foot. The same cable that Tesla uses for the UMC with control wires costs $5/foot (plus shipping)

I don't see the need to use it, and, the connectors tesla uses are proprietary, so you would have to have it custom made, it's just not worthwhile from almost every perspective.

If you want the same cable Tesla uses for the UMC, it is availble here:
J1772 Cable

Cosmacelf · Apr 20, 2014

No one has done it, probably can't be done safely. The UMC end is a Tesla proprietary connector. Tesla itself doesn't even have a generic connector that plugs into the UMC - all Tesla parts are integrated with an electrical male plug. I suppose if you were really handy with a 3D printer and a lot of trial and error you could make a part, but your guess is as good as mine whether it would reliably work with 40A currents running through it.

FlasherZ · Apr 20, 2014

mitch672 said:
25' of the proper 8/3 SEOOW 40A cable costs $60 from Amazon:

NEC Table 400.5, column B: 8/3 is limited to 40A interactive duty or 32A continuous duty for 240V-only use - (EV charging is always considered continuous duty). 6/3 is required.

mitch672 · Apr 20, 2014

FlasherZ said:
NEC Table 400.5, column B: 8/3 is limited to 40A interactive duty or 32A continuous duty for 240V-only use - (EV charging is always considered continuous duty). 6/3 is required.

Yes, strictly following code that's true. You might want to look at the high temperature insulation on the SEOOW cable I specified.
You do know that Tesla is using (2) #12 wires paralleled for the UMC cable (per leg). Also high temp insulation.

You can also get 6/3 SEOOW, it's overkill considering what tesla is using on the UMC itself.
Coleman Cable 096030008 SEOOW SEOPRENE, 6/3, 25-Foot - Electrical Cables - Amazon.com

Here is the spec on the 105 degree C insulation and 40A ampacity rating for the 8/3 SEOOW cable
https://www.ccixpress.com/wcsstore/CCIxpress/images/catalog/catalogPDFs/2-/22316.pdf

FlasherZ · Apr 20, 2014

Yes, I'm not a fan of Tesla's setup in the UMC, I understand it makes things a bit more flexible but it leaves more failure points IMO. 400.5 doesn't make any distinction for insulation temperature or even service type on the cord (J vs. standard vs. E).

Of course, just by using an extension cord, you break code anyway, if we accept that we're going to use one we've decided to go out of bounds anyway.

mitch672 · Apr 20, 2014

Yes, I agree. I know 2 wrongs don't make a right, but we can't re-engineer the existing UMC.
It's why the HPWC is always a better choice for a fixed location installation.

rdrcrmatt · Apr 21, 2014

I also got a NEMA 14-50 25' extension cord from Amazon. Its a proven and safe way to lengthen your UMC.

linkster · Jun 10, 2014

Might the combination of these two gizmos be a slight variant solution to the op's request in seeking a "smart" mid-stream Tesla UMC extension cord that provides proper signaling from QuickChargePower.com?

Cosmacelf · Jun 10, 2014

Yes. But at a cost of $1450.

TonyWilliams · Jun 12, 2014

Cosmacelf said:
Yes. But at a cost of $1450.

Converting an existing Model S UMC would save about $700 from that cost. Another option is to use our standard JLong J1772 extension cord, drawing power from a J1772 converted UMC, and then use the existing J1772 to Tesla adaptor.

Also, we can just lengthen the UMC cable (we buy that cable in 1500 foot rolls).

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