How to build a lightweight 50A extension cord

mitch672 · Apr 17, 2013

I bought a CAMCO 30' 14-50 Male to Female extension cord on Amazon for $106.44 or so, I was not happy with it for a number of reasons, here is a link to the cord being discussed: Camco RV 55195 50 Amp 30 Extension Cord with Handle : Amazon.com : Automotive

It's way too heavy: since it's for a 14-50, it has an "extra" #6 AWG conductor in it (for the neutral), which is not needed for EV charging. Adds weight and bulk.

Its way too stiff: because of the (3) #6AWG (hot/hot/neutral) and the (1) #8AWG conductors, the cable is almost an inch in diameter, and is very stiff. It does not uncoil well, and it's difficult to get the full length out of it, without a helper to assist stretching it out.

I was unhappy with it, so I returned it to Amazon. Thinking about a solution, I started browsing eBay one day, and came up with a 25' length of 6/3 SOOW cord for $68, best of all this cord weighs 568 pound per thousand feet (or .568 pound per foot), this 25' cordage only weighed a little over 14 pounds. This is about 1/2 the weight of the above 30' 6/3+1/8 14-50 cord from Amazon. Good so far.

I decided to use 6-50 plugs and receptacles, because the UMC has that as an option, also when installing 6-50's in "the wild" at distant friends houses, 6/2 is much more economical to buy than 6/3, we only need 240V + ground, no need for a neutral. So I then bought 6-50 receptacles and plugs from Amazon, along with a 14-50 Male, this so I could make a short "adapter" cable from a 14-50 to a 6-50 receptacle, to use the extension cord, or plug the UMC directly in with the 6-50 adapter attached to it, this is so the cord can be used at RV Parks, if needed.

Here are the links:

25' 6/2 SOOW cordage from eBay, $68 with shipping included:
6 3 SOOW So Cord 25 ft HD USA Portable Outdoor Indoor 600 V Flexible Wire Cable | eBay

I also bought 2' from the same seller for the 14-50 Male to 6-50 Female adapter cord
6 3 SOOW So Cord per Foot USA Portable Outdoor Indoor 600 V Flexible Wire Cable | eBay

Then buy (2) 6-50 Receptaces: $11.65 each
Leviton 5378 50 Amp, 250 Volt, Surface Mounting Receptacle, Straight Blade, Industrial Grade, Grounding, Black - Amazon.com

One 6-50 Plug: $16.55 (Home Depot has it for about $15 as well)
Leviton 931 30/50 Amp, 250 Volt, Plug, Angle, Grounding, Black - Amazon.com

The add in one 14-50 for the adapter (think RV parks, you might need an extension), $14.42
Camco 55255 RV 50 Amp PowerGrip Replacement Plug : Amazon.com : Automotive

Here is the cord, l put together, 14-50 to 6-50 adapter in the 2nd picture. You might not save much money on building this extension cord, but it's lighter and far easier to unroll and use than the CAMCO 14-50 extension cord...

ElSupreme · Apr 18, 2013

I'm planning on doing the same but sticking with 30A. My grandparents and brother both will be offering up 14-30 or 10-30 dryer outlets. I save a bunch of money buying 8/3 SOOW cord. I'll buy a 6-30 outlet, and plug. And then make up a 14-30 adapter piece like you have.

Still trying to see if I can get my employer to buy the SOOW cord for me, and I pay them back somehow. Much cheaper that way.

Glad someone did it before I go all in. I have my Amazon cart full ready to pull the trigger but haven't yet. Mostly because I still don't have the 10-30 adapter from Tesla.

mitch672 · Apr 18, 2013

You could also build it as I did, the make adapters for the 30A receptacles and outlets on each end, you have more flexibility that way, but it is pricier for sure. The advantage is you would be "RV Park" ready, and you could in theory use the 50A 6-50 UMC adapter and turn the current down to 24A on it (until the 30A adapter comes in). It's not the best idea, but if it's for occasional use when visiting relatives, it will probably be ok... You just need to be vigilant in turning down the current to match the circuit ampacity (plus margin)

Now the "FlasherZ" warning: this could result in burning down your house, if you try and draw 40Amps on a 30A circuit and your circuit breaker fails to trip.

jaysquyres · Apr 18, 2013

I needed a solution to drive to Austin from Dallas for the TX Franchise hearings. Solution? Talk with hotels. The manager said all hotels want to book you, even if you need a 220Volt plug to use. I built a 6-3 SOO cable that the Tesla cable plugs into, then you have 4 connector options for whatever the Hotel has. I used their 30Amp AC plug. My local electrical house was cheaper than Home Depot, and they had more parts. Make sure to get a weather-proof connector plug for your cable (or make sure both cables fit through your window.) Look at the attached adapter guide when shopping for parts. Show them these pictures and say you need the bottom 4 plugs. Here are my cables and how it looks coming out of the Hotel:

Robert.Boston · Apr 18, 2013

@jaysquyres: I like what you've done there, putting your UMC inside the car to secure the cables, both from vandals and weather. Very clever.

FlasherZ · Apr 18, 2013

Thanks mitch.

My second warning: using an extension cord with the Model S violates manufacturer's instructions, which is against the NEC and creates another situation in which you can be denied insurance coverage, or perhaps create liability. If the hotel burns while your model S is plugged in using such an extension cord, you may be liable for their damage, regardless of how the fire started, if the hotel's insurance company were to determine that you had done so.

vfx · Apr 21, 2013

Robert.Boston said:
@jaysquyres: I like what you've done there,..... Very clever.

Though leaving his suitcase out in the parking lot...not so much.

pbrulott · Apr 29, 2013

I need a quick way of building an extension cord to plug into an oven female wall plug and to the male NEMA 14-50 side of the UMC. Around 50 feet to charge my Model S.

Was thinking of buying a female NEMA 14-50 wall plug and connect a 8-3 cable to it and then create a junction box to plug the male connector (don't seem to find a simple NEMA 14-50 connector in-store, just a pre-stubbed version).

This is for very very very rare use. any electricical advice?

FlasherZ · Apr 29, 2013

pbrulott said:
This is for very very very rare use. any electricical advice?

Amazon.com: Camco® Power Cord Plugs with PowerGrip™: Automotive
There's a 50A plug.

If you're using NM-B (a/k/a Romex), use 6/3 instead, that way at least you'll have a legal 50A extension cord, even if using it with the Tesla isn't to code. Make sure your connections are tight! Make sure you use clamps properly as well.

Babylonfive · Apr 29, 2013

FlasherZ said:
Amazon.com: Camco® Power Cord Plugs with PowerGrip™: Automotive
There's a 50A plug.

If you're using NM-B (a/k/a Romex), use 6/3 instead, that way at least you'll have a legal 50A extension cord, even if using it with the Tesla isn't to code. Make sure your connections are tight! Make sure you use clamps properly as well.

I used that plug on three cords and they work well.

pbrulott · Apr 30, 2013

Thanks, that's exactly what I need. Thanks for the feedback

FlasherZ · Apr 30, 2013

pbrulott said:
Thanks, that's exactly what I need. Thanks for the feedback

One other thought - 6/3 Romex is going to be very, very stiff -- you *can* use it but the best thing to do is source some 6/4 type SOOW rubber cord.

mitch672 · Apr 30, 2013

The same eBay seller also has 6/4 SOOW, pick your length needed:
6/4 SOOW from temco_industrial_power | eBay

dwegmull · May 3, 2013

When we had our driveway re-done, we could not use it for almost two weeks. I dismantled a 14-30 Tesla adapter and replaced its short cord by 50' of SOOW cable. Worked like a charm!

The cord is rated 30A and the Roadster was pulling 24A for a couple of hours to recharge from my daily commute. Once I regained usage of my garage, I put the adapter back together without problems, as Tesla uses plugs that are screwed together.
I charged this way in the evening and then moved the car to my next door neighbor's driveway for the night.

tbleakne · May 11, 2013

jaysquyres said:
I needed a solution to drive to Austin from Dallas for the TX Franchise hearings. Solution? Talk with hotels.
>>>
I used their 30Amp AC plug.
Here are my cables and how it looks coming out of the Hotel:View attachment 20328

In California I and others have seen motel room A/C commonly using 6-20 20 amp receptacles, not 30 amp. Perhaps TX needs heavy-duty units. 20A 240V circuit can deliver a little over 3 kWh per hour into the battery, which is too slow to fill up a 85 kWh battery overnight. In the heat of the summer I would think going without A/C in the room all night could really be difficult. I am glad your solution worked for you, I am still struggling to find ways to charge a Tesla at motels.

jerry33 · May 12, 2013

tbleakne said:
In California I and others have seen motel room A/C commonly using 6-20 20 amp receptacles, not 30 amp. Perhaps TX needs heavy-duty units. 20A 240V circuit can deliver a little over 3 kWh per hour into the battery, which is too slow to fill up a 85 kWh battery overnight. In the heat of the summer I would think going without A/C in the room all night could really be difficult. I am glad your solution worked for you, I am still struggling to find ways to charge a Tesla at motels.

At the B&B I will be staying at next week, they installed a NEMA 14-50 for me. I suspect B&Bs will be more amenable to charging requirement then motels. (In addition to providing a much better experience). Assuming the experience is positive, I'll post about it when I get back.

DEinspanjer · May 23, 2013

mitch672 said:
along with a 14-50 Male, this so I could make a short "adapter" cable from a 14-50 to a 6-50 receptacle, to use the extension cord, or plug the UMC directly in with the 6-50 adapter attached to it, this is so the cord can be used at RV Parks, if needed.
...
The add in one 14-50 for the adapter (think RV parks, you might need an extension), $14.42
Camco 55255 RV 50 Amp PowerGrip Replacement Plug : Amazon.com : Automotive

Two questions..

1. How long of an extension can you safely run if you are wiring it as 6-50?

2. How come the 14-50 adapter shown in the second picture of the first post doesn't have a 4th prong? Was it cut off for some reason?

edit. I lied. a few more questions:

I found the difference between SOOW and Type W, but I've seen 6/4, 6/3 and 6/2 (gauge?) tossed around on this thread. If you are building a 6-50 cable, and you want to optimize for length of run (say 50'?) then weight then flexibility, which one is appropriate? And do you need a different cable gauge for the short 14-50 adapter?

Puyallup Bill · May 23, 2013

DEinspanjer said:
Two questions..

1. How long of an extension can you safely run if you are wiring it as 6-50?

2. How come the 14-50 adapter shown in the second picture of the first post doesn't have a 4th prong? Was it cut off for some reason?

edit. I lied. a few more questions:

I found the difference between SOOW and Type W, but I've seen 6/4, 6/3 and 6/2 (gauge?) tossed around on this thread. If you are building a 6-50 cable, and you want to optimize for length of run (say 50'?) then weight then flexibility, which one is appropriate? And do you need a different cable gauge for the short 14-50 adapter?

See FlasherZ's FAQ - a wealth of information.
http://www.teslamotorsclub.com/showthread.php/12615-FAQ-Home-Tesla-charging-infrastructure-Q-amp-A

In the second picture, it looks like it is a 14-50 plug with the neutral prong removed. If so, then it is also usable at a 14-30 dryer outlet.

efusco · May 23, 2013

In the second picture, it looks like it is a 14-50 plug with the neutral prong removed. If so, then it is also usable at a 14-30 dryer outlet.

Is there a downside/danger in doing that?

mitch672 · May 23, 2013

efusco said:
Is there a downside/danger in doing that?

On the CAMCO 14-50, I just did not insert the neutral blade, is has no purpose when used as an adapter on a 6-50, since a 6-50 is just 2 hots and the ground. I think you can get away with 50 feet or so, but you should probably build it as 2 cords, maybe (2) 25 footers, or a 15' and a 35', as it's always better to use the shortest possible extension that works.

To build a 6-50 extension cord, you only need 6/3 SOOW, if you are building a 14-50 extension cord, you would need 6/4. (For the neutral conductor).

Personally I wanted the lowest weight cord, that's why I went with the 6-50 and built the RV Park 14-50 to 6-50 short adapter cable; I can still use a 14-50 in the wild, I just don't need to carry %25 more weight on the extension cord cabling... I also bought the matching 6-50 UMC adapter as well, of course.

For the short adapters you make up, stay with 6/3 as well, you want to keep the same size wire, 6/3 SOOW I believe is rated for either 45 or 55 amps with 2 current carrying conductors, I seem to remember.

Edit: the eBay auction states 45A per conductor on the 6/3 SOOW link:
6 3 SOOW So Cord 25 ft HD USA Portable Outdoor Indoor 600 V Flexible Wire Cable | eBay

How to build a lightweight 50A extension cord

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