I'm traveling to my son's home to visit for Easter.....and will do some slow charging via 110V plug in his garage. I had never charged with 110V, so tested out in my garage outlet today. Plugged in, at 108V was getting 12A charging and 4 miles/hr. I was using a 25' orange extension cord from my outlet to the Tesla cord and adaptor. After letting it charge for about 4 hrs, I unplugged it and both ends of my extension cord were warm.....not hot, but definitely warm.
My extension cord is just a standard orange 3-prong outdoor rated cord you can buy in Home Depot. Is this warmth normal....or should I be using a certain higher rated extension cord.....and if so, what type? Just want to make sure I don't burn down my son's house.....that would not be a good thing.
There has been a lot of good advice in this thread already.
I will underscore that Tesla does not recommend charging on extension cords for lots of the reasons already mentioned. It is not that it will not work, but that many people use poor quality parts and it is just inherently more dangerous due to all the added factors (more connection points, potentially damaged cords, lack of thermal monitoring, etc...)
With that being said, I personally do use an extension cord sometimes when traveling, but only when I have to (and I typically do some real safety checks when doing it to include even using my thermal camera to identify hotspots). Note that my solution has been to use this extension cord:
Heavy-duty NEMA 14-50R extension cord for EV, 30 ft. with this adapter:
NEMA 5-15P/5-20P to 14-50R 120V Adapter for EV, 3 ft. Now it does require carefully setting how many amps to draw (12a on a 15a circuit, 16a on a 20a circuit), but the cord is so crazy thick and it is built for EV charging that I have zero concerns about the actual cord being an issue (it is designed for 40a continuous!).
To my comment above, one of the added risk factors of using an extension cord is that the receptacle the cord is plugged into is not monitored for overheating like it would be if you plugged the UMC Gen 2 directly into it. The UMC Gen 2 has a thermal probe in the plug end that is an added safety feature to make sure the plug/receptacle is not overheating (say due to loose spring tension on the receptacle, etc...)
I’ve used this cord from Home Depot for 20A outlets:
Yellow Jacket 50 ft. 10/3 SJTW Outdoor Heavy-Duty Extension Cord with T-Blade Power Light Plug-2991 - The Home Depot
Again this is for occasional use when traveling, not a long term solution for routine use.
That is a good quality looking cord! Thanks for the link!
I would also add to this thread that folks should utilize the shortest cord that gets them the required results. Less distance is always better (lower resistance). Note that the UMC is 20 feet long, so with a 30 foot extension cord you have 50' of reach.
Do note that with that extension cord, it won't plug into a 15a receptacle (one without the sideways notch on the left prong). Even if your son has a 20a circuit, there is a good chance the receptacles are only 15a (allowed in US electrical code). So if I was going to get an extension cord like that, I would probably also get one of these:
https://www.amazon.com/gp/product/B017EUTHC0/ref=oh_aui_search_asin_title?ie=UTF8&psc=1
That would allow you to plug into a NEMA 5-15 receptacle even if using that really heavy duty extension cord.
Then you also should purchase the Tesla UMC adapter for a 5-20 receptacle which will allow you to pull down up to 16a instead of only 12a. You must be careful though to only draw 12a on 15a circuit though. The combination of that adapter I linked to above plus that Tesla UMC adapter would allow you to pull 16a on a 15a circuit if you are not careful, so please don't do that. ;-)
We should also touch on a topic I am somewhat hesitant to give advice on: In the situation where a circuit is 20a and you are positive the wiring in the wall is sufficient (at least 12 gauge), that adapter I linked to combined with the Tesla UMC adapter will let you pull 16a even on a 15a receptacle (on a 20a circuit). There is some evidence online that even 15a receptacles are fine with the full 20a. I would be lying if I said I had not drawn 16a on a 15a receptacle but connected to a 20a circuit before (using that adapter I linked to). This is certainly out of spec for the 15a receptacle, though 15a receptacles are required to handle passing through 20a through their backstab / screw connectors and folks have said they usually use the same guts as 20a circuits just with no sideways prong. I have only done it during the day when I could monitor things. No issues. The proper solution is actually to replace the 15a receptacle with a 20a receptacle (which is what I did in my garage just for fun since the circuit was already 20a). They only cost a few bucks...
Good luck! Let us know what you decide to do! Being able to charge over a weekend while staying with someone is nice since it means less time on the road spent charging (superchargers, etc...)
