Join The Community

240 Extension Cords

Sorry if this is a duplicate, but I searched this forum and didn't find a thread like this.

I know that Tesla says not to use extension cords, but I just returned from my first road trip (90 mi each way) and I almost got stranded. the place I stayed had a great 240 plug near a parking spot, but it was just about 15' beyond the standard charger that comes with the car. So, I moved to another spot where I could use their 110. that worked fine, but at only 3 mi per hour, I needed over 24 hours to recharge the "90 miles" that I had driven which drained my engine 140 mi equivalent (4 guys in the car and it was cold).

I don't want to have that "range anxiety" again, so I would like to find a 15' - 30' extension cable that will get me closer to the 20-25 mi/hr charge rates that I get at home.

I saw that one guy bought this RV extension cord on Amazon, but he didn't say if it actually worked and charged in that low 20 mi range.

Anyone have experience with this or another RV extension cord and if they will work for occasional (5x per year) travel?

Actually you can just use one extension cord if you make a 5-15 adapter (regular household plug). I've got my bulky 30' nema 14-50 extension cord plug the mobile charger 20' cord equals 50' reach. Again I know this works if you use the 14-50 as the base adapter, and frankly it should work with the 6-50 too, you just have to test it since I haven't seen anyone on these forums say it work with 120v.

OK, I see from your document that you did make a 120 V adapter for your 14-50 cord -- it's a NEMA 5-20. Any you say you haven't tried it out yet?

I have tried it out - the nema 5-20 and 5-15 work just fine, as does the TT-30 (also a 120V source). I said I haven't tried these out on a NEMA 6-50 Tesla plug instead of the NEMA 14-50 that I used.

@DouglasR and shop

Haven't considered making a 5-15 to 6-50 adapter but I assume it would behave then same as a 5-15 to 14-50 as I am pretty sure the Model S adapter delivers the same three conductors to the charger plug in both 14-50 and 6-50 UMC adapters (ignoring neutral with the 14-50).

Does your 14-50 to 5-15 work? I assume you are connecting hot to hot and neutral to the other hot and ground to ground. I may try it out. I will send a picture later but am pretty happy with the 6-50 receiver I used. Seems solid and has good connections both mechanically and electrically. I will send a picture next chance I get.

Yes my 14-50 to 5-15 works. The UMC is picky, however, as to which hot the 120v hot goes to and which one gets the neutral. My document describes how to wire it for a 14-50, and my guess would be you would use the same polarity for the 6-50. The other useful 120v adapters are a tt-30 ( for a derated 24amps), and a 5-20 which you do find in commercial garages from time to time. You can of course just plug a 5-15 adapter into a 5-20 socket, but then you would be pulling slightly more amps than what the plug is rated for.

Btw, the one time I used my TT-30 adapter, I was only able to draw 20amps from it. Couldn't make it draw 24amps. I suspect that is an artificial software or hardware limitation in the UMC - they probably didn't envision a 120v source that was capable of delivering more than 20amps.

I'd argue there's no problem using a 100-foot 12-gauge extension cord to charge at 120V 12A. It's the same wire gauge that's most commonly used to connect the wall outlet to the breaker panel. It has 1.6 ohms of resistance per 1000' feet, so unless the total run from the breaker panel to the car exceeds 350 feet, you'll still see at least 113V, which works (if you don't like it, you can always cut the current to 6A and the voltage will rise to 116-117V). Finally, there's no increased risk of fire hazard with the extension cord in that situation, because the heat generated per foot of wire is about a quarter watt - no different than what happens to the wire between the panel and the outlet when you plug in a hair dryer and run it on high.


@Jack, on your long trip, did you have any occasion to use a 100' cord? It's a lot to lug around, and I'm thinking 50' (+the UMC) ought to be long enough for most any occasion.

Am I going to be okay to plug my Tesla 14 50 adapter into a Camco 30' 50 amp cord and then use a 14 50 to 14 30 adapter on the other end to plug into a dryer receptacle? I would first dial the car back to a 24 amp charge.

Is there a power loss when two adapters are involved like that on each end of an extension cord?

@cathy - your setup is exactly what I created. I tested it with a 10-30 connector and it worked with no measurable loss.

Cathy - that should work fine. Dialing back amperage to 24 amps should be all that is needed.

And the car should remember the amperage setting by location. So you should only have to dial back once. IIRC


"Am I going to be okay to plug my Tesla 14 50 adapter into a Camco 30' 50 amp cord and then use a 14 50 to 14 30 adapter on the other end to plug into a dryer receptacle?"

I would like to do this as well, I have not been able to locate 14 50 to 14 30 adapter, have you?

@DJay - most of the people who are doing this have made their own 14-50R => 14-30P/10-30P adapters. It isn't hard if you know what you are doing.

jat- Thanks for the follow up. I was just reading the great instructions published by "shop" earlier in this thread and will give it a try. It certainly looks easy enough.

Boy... Think how much easier this would all be if Tesla sold a much longer version of the UMC... You know, like one that might actually reach a dryer outlet from a driveway? Then we wouldn't be buying/fabricating adapters to go to extension cords to connect to their tesla adapters.

Has anybody just spliced in a 50' extension to the UMC cable itself? Yes, I know, some voltage drop. But like several above have noted, use the right gauge wire and this can be minimized. Charge with a little less current if you have to. It just seems like an spliced-in-extension between the module and the adapter that takes all the different tesla plug heads would be less hassle than a 14-50 extension cord plus a bunch more adapters for THAT.

@Zain, that seems a bit crazy given the reported successes with

If you are going to the trouble of splicing a cord, then installing a closer 240V receptacle isn't that much more work. I'm not even sure HOW to splice a cord that carries 50 amps/240V. That is a DIY job I would not want to do. The home made adapters may look like a lot of work, but they aren't really. And when done right, you aren't going to be wondering if the cord/receptacle/adapter is going to catch fire.

Yes, Tesla could sell a 50' UMC, and that might be nice (or not, see below).

In the meantime, the home made adapters work fine, and you get the added bonus of being to plug into all sorts of power sources should you get into a tight spot, or even a routine spot. People have charged from work using a TT-30, for example. Or from a marina using an SS-50 50A connection.

The reality is that electric cars need relatively close by power sources. Stringing 50' of 240V/50A power through a house might be fine for occasional use, but if you think about it, it isn't very safe. It is a trip hazard. Accidentally yanking such a cord so that the plug comes partially out of a socket isn't likely to be very safe.

Thanks Shop.. I think, that splice can be done. Though there's a lot to do to make sure it's right. And I do worry it'd be more work the what you did.

It wouldn't be for regular use, obliviously if you go to that kind of trouble you might as well put the outlet or high power wall charger where you need it I the garage. Which we did.

But for road trips and taking the car out at the edges of the charging network, I'm looking for the handiest solution that can be tossed in my "frunk." One that'll let me use various dryer outlets, RV camp outlets and the occasional twist lock style one you encounter. I started down the path you already tread with your excellent note on buying and making adapters. But then thought: you know, if this stupid cord was just longer, then I could use the tesla provided adapters, not carry an extension cord and not have a box of extra adapters.

I get the safety thing. But if it's going to be a moble adapter, then it does need to work in moble situations. There isn't always a nice wide parking stall a short distance from the outlet you want. Even stopping in with the in-laws you have the driveway to dryer scenario. Pulling into an RV area and borrowing shore power you'd need even longer.

I got a camco 15' and 30' and chained them together and gave that a try and it works perfectly fine, it charges at full 40A (per the webservices read-out)
like 237V/39 or 237V/40 readings. zero issues. if anyone needs an easy way to extend the reach, these cords do the job well.

Does anyone know if the adaptors sold by EVSEadapters (link below)will work (link below)? They appear to be similar to the homemade ones by shop but they use a 10 gauge cable for the NEMA 14-50 to NEMA 14-30 connector, wheras shop used 4 wire. Is this a problem?

10 gauge for 30 amps is the right gauge. It should work fine.

Thanks shop.

Why would you need an adapter for a 5-20 you can plug a regular household appliance into a 5-20 outlet and it will not fry so why not just use the 5-15 adapter for the tesla

Because the tesla 5-15 adapter has a pilot signal in it that tells the Model S to limit max amps to 12 amps. But if you had a 5-20 plug, then you can safely draw 16 amps, 33% more. So an official Tesla 5-20 adapter would be nice, or failing that, a home made one.

X Deutschland Site Besuchen