eprosenx
Active Member
I would not use any adapter other than the ones that Tesla sells. The adapter that plugs into the UMC tells it how much current to draw. A NEMA 14-50 should have a 50A breaker (except in parts of Canada where it is 40A). A NEMA 14-30 has a 30A breaker and is safe to draw 24A. If you use an add on adapter to plug NEMA 14-50 into a NEMA 14-30 plug, the UMC will attempt to draw 32A which should trip the breaker. If it doesn't trip the breaker, you could be creating a dangerous situation.
The reality is that I think use of the UMC in the wild is going to be very rare.
Yes, this is a good callout. I should have been more specific about the critical need to set charging amperage properly if using these kinds of adapters. The issue I have run into is that the UMC cable by itself is often not long enough to get to the receptacles I need, so the adapters that you can buy from Tesla (which auto limit the current) won't get you far enough.
I'm pretty much in the same camp as eprosenx, above, with a few differences. I guess I'm a boy scout at heart and like to be prepared.
If you're in the other camp & want to travel light, I'd suggest to just carry the UMC and the 3 adapters that come with the car, and add a 50' standard 12 gauge extension cord.
First, absolutely no reason to not carry the J-1772 adapter that the M3 comes with. It's tiny, fits in the glove box, and gives you many Level 2 charging sites. I signed up for a ChargePoint account, which charges for free at some places, and for reasonable $$ at many other locations. There are many other EV charging providers, but ChargePoint has the most charging locations.
That 50' 14-50 extension cord that eprosenx bought weighs a ton, so I opted for this one instead:
Heavy-duty NEMA 14-50R extension cord for Tesla, 20 ft.
It's only 20 feet instead of 50, but it only weighs 10 lbs instead of 23 lbs and it plugs in directly to 14-50, 14-30, and 14-60 receptacles. I added 10-30 to 14-50 and TT-30 to 14-50 adapters. The 20 feet of this cord plus the 20 feet of the UMC gets me 40 feet total.
I added the 6-20 Tesla adapter, specifically because my brother has this 240V outlet in his garage. I built a 25' - 12 awg 240V extension cord to go with it, at a cost of about $30. I also added simple molded L6-20 and L6-30 (locking) adapters that output to the straight plug 6-20 and that will also work with this same 6-20 extension cord. These adapters are pretty cheap and very small. After I built this 240V extension cord, I discovered that evseadapters.com sells one.
I got the 5-20 Tesla adapter, for the reason quoted above by eprosenx. Pretty widespread availability of this outlet and 16 amps is a lot better than 12 at 120 volts. Added a simple molded 5-15 to 5-20 adapter, about $7. Some 20 amp circuits only have standard 120V duplex 5-15 outlets and this adapter gets you the 16 amps out of the circuit. You do have to check the breaker to verify the circuit has a 20 amp breaker before you use this adapter in a standard house duplex outlet. I have one of these outlets in my garage, the only thing on the circuit is the built-in house vac.
Lastly, I carry a 50' 12 awg standard 120V extension cord. Super slow, but plug in anywhere.
There are a handful of other possibles, mainly industrial type 6-50 and 10-50 used for welders and heavy shop equipment. I'm going to forego these adapters, as they are about $75 each and have limited charging possibilities in most situations.
Ack! I messed up and linked to the wrong cord. I have the 20' one you linked to. The 50' one actually does have a neutral and it can't plug into a 14-30 receptacle (which is likely the most common use case). Even the 20' one though is crazy heavy. I wish it was a lower gauge (since the UMC can only do 32a and not 40 I think this would be fine).
SgtTortuga is spot on.
Don't do any of this customized adapter stuff unless you fully understand exactly what you are doing! One additional BIG gotcha is that when using some of these adapters, DON'T use standard RV style adapters & extension cords, as the wiring for Tesla and other EVs is significantly different from RV wiring, and you can cause very serious electrical problems, including fires. You could also blow up the electrical system in your RV using Tesla/EV adapters.
And, you do have to manually set charging amps to no more than 24 amps whenever you are using -any- of the 30 amp to 14-50 adapters. Set the charging current before you plug in!
Yes, to do all this custom adapter stuff you really should understand what you are doing. Without the right knowledge this could be somewhat dangerous (though there are supposed to be breakers and such, but they are not foolproof). The Tesla factory adapters I think also have thermal sensors in them so they increase safety that way as well but using additional adapters or extension cords may negate some of that protection.
Note that using a standard RV extension cord would be just fine on a Tesla (assuming sufficient ampacity), just the other way around is NOT ok. I am not aware of any RV adapters that would cause a problem for a Tesla, but some just won't work (like a TT-30 to a 14-50 RV adapter for instance).