Off-grid charging: Critique my extension cord plan

[Pandalus]

I recently got a model S and live in Newfoundland, which is among the worst jurisdictions in North America for charging EVs. I'm planning some road trips and intend to do a lot of charging with NEMA 14-30 dryer plugs.

So, my question: If I bought one of these: Heavy-duty NEMA 14-50R extension cord for Tesla, 20 ft., it looks like I could plug into both dryer outlets and NEMA 14-50 RV outlets. HOWEVER, I also understand that this would enable me to draw too much from the NEMA 14-30 and trip a breaker or something.

Am I good using this, so long as I always keep the amperage to 24 amps or lower? Or do I need to buy the Tesla NEMA 14-30 adapter, and then also get a specific extension cord for that type of outlet?

 

[Feathermerchan]

If you buy a 50A extension cord and charge at 40A you'll be fine.
If you use an adapter and charge at 24A on a 30A circuit you'll be fine.
Like you said just watch it and remember where you are charging.

 

[Ostrichsak]

Also keep in mind that anytime you use an extension cord, even if one that has enough overhead for the draw you plan to pull, there is little to no thermal protection from the UMC. When pull up directly into the outlet that UMC can sense heat and will keep you from melting things down. If you use an extension cord, unless it's the cord itself that's heating up, you will affectively be negating your UMC's thermal protection. As long as you understand all of that then you're good to go with what you're describing.

 

[Pandalus]

Also keep in mind that anytime you use an extension cord, even if one that has enough overhead for the draw you plan to pull, there is little to no thermal protection from the UMC. When pull up directly into the outlet that UMC can sense heat and will keep you from melting things down. If you use an extension cord, unless it's the cord itself that's heating up, you will affectively be negating your UMC's thermal protection. As long as you understand all of that then you're good to go with what you're describing.

So basically if I do something stupid (like try to draw 40 amps when plugged into a NEMA 14-30) I'd risk a fire?

Other than trying to draw too many amps, can you think of anything else that would cause it to heat up or catch fire? I really don't want to burn cabins down but I also want to electric road trip lol

 

[murphyS90D]

Even with low current a bad connection will heat up. Monitor all of the connections to make sure they are not getting hot. They should never get hot enough to make it uncomfortable to wrap your hand around the connection.

If you tried to draw 40 amps from a 14-30 the fuse / circuit breaker should trip immediately.

 

[ReddykwRun]

And after you follow the a fore mention specs of amperage draw just remember the "German" rule of torque and this will apply to all your connections in the extension cord chain, they have to be
"Good 'n Tight", loose connections heat up and get looser (is that a word) and the looser they get the hotter they get till all hell breaks loose. Got it, get it, good.

 

[idoco]

Also don't forget 30A/120V adapters that can be used at RV parks and campgrounds that don't have 50A service. Here are two examples. There are others.

AC WORKS™ [EVTT30MS] EVSE RV/Generator TT-30 Plug to 50A Electric Vehicle Adapter for Tesla
TT-30P to NEMA 14-50R Adapter for EV Charging at Campgrounds

We're taking the ferry over to Newfoundland in a few days and will be there for July and August. The majority of our charging will be using 30A/120V from campground to campground.

 

[Feathermerchan]

Your UMC will still offer protection if you are using a 50A extension cord. The sensors are in the adapter part and so if that gets too hot then current will be reduced or charging will stop. It cannot know the temperature of the other end of the extension cord so that will not be protected. Also be sure none of the connections get wet. AFAIK they are not weatherproof.

 

[Big Toys]

I recently got a model S and live in Newfoundland, which is among the worst jurisdictions in North America for charging EVs. I'm planning some road trips and intend to do a lot of charging with NEMA 14-30 dryer plugs.

So, my question: If I bought one of these: Heavy-duty NEMA 14-50R extension cord for Tesla, 20 ft., it looks like I could plug into both dryer outlets and NEMA 14-50 RV outlets. HOWEVER, I also understand that this would enable me to draw too much from the NEMA 14-30 and trip a breaker or something.

Am I good using this, so long as I always keep the amperage to 24 amps or lower? Or do I need to buy the Tesla NEMA 14-30 adapter, and then also get a specific extension cord for that type of outlet?

Just for educational purposes, fuses protect wire that is downstream from the fuse, which is why fuses are placed as close as possible to the power source. Wire that is upstream or before the fuse is not well protected.

 

[solman244]

Also keep in mind that anytime you use an extension cord, even if one that has enough overhead for the draw you plan to pull, there is little to no thermal protection from the UMC. When pull up directly into the outlet that UMC can sense heat and will keep you from melting things down. If you use an extension cord, unless it's the cord itself that's heating up, you will affectively be negating your UMC's thermal protection. As long as you understand all of that then you're good to go with what you're describing.

UMC has thermal protection? Where?

I've had a NEMA 14-50 socket catch fire and melt my UMC adapter plug at Road Atlanta. Looked fine when I plugged in, but turned out to be super sketchy wiring and breaker setup. If my UMC was supposed to catch the overheat and shutdown, I'd love to know how that works, and why mine didn't...

 

[Feathermerchan]

All of the V2 UMC have thermal protection. The original V1 did not (as I understand) the adapters were recalled and replaced with ones that do.

 

[solman244]

Interesting. The UMC I was given with my 2014 Model S (purchased used from Tesla in 2017) is definitely V1. This warrants a call into service to ask about the recall.

 

[D.E.]

I recently got a model S and live in Newfoundland, which is among the worst jurisdictions in North America for charging EVs. I'm planning some road trips and intend to do a lot of charging with NEMA 14-30 dryer plugs.

So, my question: If I bought one of these: Heavy-duty NEMA 14-50R extension cord for Tesla, 20 ft., it looks like I could plug into both dryer outlets and NEMA 14-50 RV outlets. HOWEVER, I also understand that this would enable me to draw too much from the NEMA 14-30 and trip a breaker or something.

Am I good using this, so long as I always keep the amperage to 24 amps or lower? Or do I need to buy the Tesla NEMA 14-30 adapter, and then also get a specific extension cord for that type of outlet?

I’ve got s 30 foot 50A extension cord that I’ve used with dryer plugs. The cord is a beast, very heavy. It’s easy to set the maximum current draw when charging. At 24A, you’re way under the rating of the cord. You’ll be fine.

 

[Pandalus]

All of the V2 UMC have thermal protection. The original V1 did not (as I understand) the adapters were recalled and replaced with ones that do.

Is this the recall you're referring to? NEMA 14-30, 10-30, 6-50 Adapter Recall

 

[Feathermerchan]

I think so.

 

[whitex]

Best rule of thumb when charging from any plugs, is never charge above 80% of the circuit breaker value. If properly installed the circuit breaker matches the wiring, while the actual outlet may be rated higher. There are NEMA 14-50's out there installed on a 40A circuits with 40A breakers, so if you draw 40A sustained load you are risking fires. Max on a 40A breaker is 32A, which by the way is why Tesla switched to 32A chargers - there were a couple of fires in Canada with 40A chargers plugged into NEMA 14-50 on 40A circuits.