Question for those who charge outside with Mobile Connector + extension cord

Question for those who charge outside with Mobile Connector + extension cord

For those who charge outside with the Mobile Connector using an extension cord, do you use anything to protect the Mobile Connector's main body from the elements or at least elevate it off the ground (assuming there's nothing to hang it on nearby)?

jillalameda | June 15, 2013

I haven't so far, although I only got the extension cord a few weeks ago after the rainy season had pretty much ended. It's a 1430, and the connection with the mobile connector is pretty tight. I have been wondering about this, though, and will be interested to hear people's thoughts about it.

KendallPB | June 15, 2013

@Paul - the actual cable (versus the ends)? No. It's encased in rubber or whatever. It's made for outdoor use. :-)

Brian H | June 16, 2013

I doubt the connection would be too happy lying in a puddle.

mbergman | June 16, 2013

I have used an extension cord a few times and left the main body on the ground with no problems. In the rain, I placed it under the car.

Manta | June 16, 2013

@KendallPB - Thanks, but I'm actually more concerned about the box than the cable. I talked to Tesla, and they said the box shouldn't sit in water. (It's OK for it to get wet, but it's not waterpoof,) To Brian's point, it's probably also not a good idea to have the connection between the Mobile Connector and extension cord sitting in water either.

KendallPB | June 18, 2013

Oh...uh, yeah, I wouldn't want the end of any cable sitting in water....

JDPink | June 19, 2013

Personally I raise my suspension to very high and make the connection from the MC to the extension cord under the car.
When it was raining I put thin red bricks (1/2" thickness} on the ground (after I parked) and then put the cables on that. This way the cables were not only covered from the rain but they were also off the ground.

Brian H | June 19, 2013

Aren't you afraid your car will get "bricked"? (Just joking!)

diegova | June 19, 2013

Got my MS two days ago. ( New to forum) Question for the group. Do I read this thread correctly that some owners have used an extension cord along with the MS cable? I was told not do that. Or is it fine? If fine, what cord specs can you provide?

LMB | June 20, 2013


It's not "fine" in any generic way, and Tesla is right to tell people not to do it. I don't believe there is any commercially available extension cord that would work, although I could be wrong about that.

On the other hand, engineers are making their own - as my husband did. In fact, we were comparing home-made extension cords with another S owner at the Milford supercharger on Sunday. We used our cord successfully twice this weekend, on a trip from Boston to Philadelphia and back.

But this is fraught with hazard. To make or use such a cord, you HAVE to know what you're doing. For example, the plug and socket on our cord are rated for 40 amps, but the cord is only rated for 24 amps. So if I were to plug it in and fail to turn the charging rate on the car down to 24 amps from the default of 40, terrible things would happen.

Why is our cord that way? Because we felt that in order to be truly useful, it would need to be long. So it's thirty feet. The scenario is that maybe we are traveling far, and we're stuck without any charging opportunities other than 110, and we don't have that much time - we can use this cable to hook up to someone's dryer outlet and charge faster. But what are the chances that someone's dryer is close enough to the driveway without a very long cord to get to it?

The problem with cord rated for 40 amps is that it's huge, heavy, inflexible, and inconvenient. Thirty feet of it would be especially that way. So we traded faster charging for convenience, but along with that comes risk that the cord could be misused in a disastrous way.

So this is why, unless you have enough electrical engineering background in your pocket to fully understand the issues, you should never use an extension cord to charge your Model S. It's taken me some time to "get it," and I'm still worried about it. Tesla is right to tell people not to do this.

satyrias | June 20, 2013


"unless you have enough electrical engineering background in your pocket to fully understand the issues,"

That is an arrogant and obnoxious response to someone's inquiry. People ask questions to learn and understand from each other.

Your condescending personality doesn't go very well in a forum like this.

From reading your post, I can say you are not educated enough to understand this subject.


You can use extension cord with a higher ampere rating than required for the charger. When the length of the cord goes up, the resistance goes up that can produce heat on the cable if the cable is at the exact ampere rating as the target equipment what it draws. That means, if the charger requires 50A, then use a cable with higher ampere rating than 50A, if you are using a longer cord. Telsa says that don’t use it, because they don’t want to take liabilities of recommending an extension cord, if someone misuse it.

As for laying it on the ground, there is no problem as long as the ground is dry. Just for your observation, the electric connections to new housing developments are coming through underground cables.

As for the connector, which is just a connector and there is no wave inference there to shield it from anything.

PaceyWhitter | June 20, 2013

I would like to add that there are MANY commercially available extension cords that will work well with the model S. They are not cheap, and are very thick but they will definitly do the job.

Theresa | June 20, 2013

satyrias, Wow I can't believe that you thought that LMB was being arrogant and/or obnoxious. I thought what she was saying was a simple "You better understand what you are doing before attempting this". It was just a comment that if you don't know what you are doing you could hurt someone or even yourself.

satyrias | June 20, 2013


Don't say to someone, "engineering background in your "POCKET".

That is an arrogant superfluous comment.

GReese | June 20, 2013

There's nothing arrogant about telling people that a lack of understanding on a particular subject matter can result in their death or loss of property.

satyrias | June 20, 2013


"There's nothing arrogant about telling people that a lack of understanding on a particular subject matter can result in their death or loss of property."

Who said it is arrogant?

Can you comprehend the context?

Brian H | June 20, 2013

"That is an arrogant and obnoxious response "

Kinda sounds like you did. Regardless of "context".

DTL | December 16, 2014

also you can use this... just bought... will let you know if it fits but seems to accommodate up to over an inch... tesla cord is just over half an inch I believe...

Ive been using this cord for almost a year without problems...

dglauz | December 16, 2014

I have a place in San Francisco without 240 to my parking space. I have 120. I bought the heaviest 25 ft extension cord at home Depot; don't remember the gage. It runs from an outlet inside, through a vent and along the top of a fence. I plug in and let the box hang from the fence. When it rains I try to remember to put a plastic bag over the connection. Over the last year there has been a bit of corrosion on the inside of the plug at the receptor end of the extension cord. Last month the adapter failed and the SC replaced it. I need to clean the inside of the extension cord and get something to plug into the cord when it is not in use to prevent corrosion. Being close to the ocean is definitely a negative on this account.

The first time I used the cord I checked for voltage drop and cord warmth. Both were fine and I do not worry about those things.

DTsea | December 16, 2014

Satyrias, get off your high horse.

AoneOne | December 16, 2014

On a recent trip away from supercharger access I used both a 25-foot 12 gauge NEMA 5-15 120V extension cord at 12 amps, and a 25-foot 6 gauge NEMA 6-50 240 extension cord at 25 amps.

I did watch the voltage as the car ramped up the current at each site and saw little loss, confirming my (and my car's) opinion that the wiring was adequate, which was confirmed by the lack of substantial heating of the connectors or cable.

This isn't rocket science and doesn't require a degree from MIT. Use approved cords and connectors, check for hot spots, and use common sense regarding weather. You'll be fine.


The 5-15 cord allowed me to top off at the Sheraton Louisville Riverside hotel (kudos) with no problems at 12 amps. When rain threatened, I carefully draped the cords so the connectors and the UMC were off the ground and higher than the rest of the cord, so water would drain away from them. Also, as the cord crossed a sidewalk I notified hotel security who posted some orange cones to warn people of the trip hazard.

(If you intend to charge there, note that the closest parking spots are for handicapped parking. I'm "lucky" enough to have a handicapped parking permit, so the 25-foot cable was long enough. Without the permit, I'd have needed a 50-foor or longer extension.)

The 6-50 cord was my brother-in-law's, which he had made for his welder on a 50-amp circuit. I dialed the charging current back to 25 amps out of caution, and had no problems. I used Cord Depot's adapter from my 14-50 to the 6-50, and I was impressed with its rugged construction. Only the Tesla end of the cable was out of doors, so weather wasn't a factor there.

sbeggs | December 16, 2014


"Also, as the cord crossed a sidewalk I notified hotel security who posted some orange cones to warn people of the trip hazard."

Bravo. We hereby bestow upon you the rank of "AoneCone".


DTL | March 2, 2015

I bought the same extension cord as noted above [ ] and love it. Can handle anything and you can buy many adapters to fit it. I had bought the Tesla adapters for a drying machine but now I cant use an extension cord with it. Now I just buy adapters that fit this extension cord.

I tried using this product mentioned above [ ] but it was too small. The above cord is a gigantic 6 gauge.

Do you think this item [ ] would keep the connection between the Tesla and the extension cord safe from rain. I wonder if I should buy another one for the Mobile Connector's main body. Does anyone have the dimensions? Or you think you just need to elevate the main body from getting in a puddle.

Manta | March 2, 2015

If it (the Socket Box) can close over the cables, it should work. I didn't measure my Mobile Connector, but the main body may fit in there too (with a 15A extension cord, probably not with the Camco extension cord). If not, elevating the main body off the ground should be fine. I found this on the website.

Dimensions: Interior: 11.2" x 6.2" x 4.3" Max. Outer (with cover): 13.4" x 9.5" x 5"