My car is parked outdoors, and I charge at a 14-50 outlet I had installed, also outdoors. A few safety questions: 1) Is it safe to leave the UMC plugged into the car in the rain? That seems like an obvious yes. But I want to double check. 2) Is it safe to to leave the UMC plugged into the outlet, but the Tesla-end hanging on a hanger, unplugged, in the rain? Or just in general to leave it that way, rain or no? 3) If the UMC is plugged into the outlet, with the Tesla-end not plugged in, how worried should I be if my 2-year old were somehow to get the Tesla-end and play with it? Is it impossible to get shocked from the Tesla-end?
The coupling connection is protected fairly well against weather elements. The Tesla end can hang on a hanger without problem, because the UMC meets NEC 625's interlock requirements to energize only when the car is attached. If the NEMA 14-50 is outdoor it should be protected by a weather resistant cover. As mentioned, the NEC 625 requirement for interlock makes it safe. You should be more concerned if your 2-year-old were to play with the 14-50 and touch the exposed blades.
My four year old, who has successfully spidered the windshield on a car with his head (just stood up and boom), torn the door off of a fridge (climbed it to get to some leftover birthday cake) and also managed to pop out a window from a casing that doesn't allow popping out (luckily it was a ground level window over the porch - he wanted to "eat snow" that had recently fallen), is yet to damage the UMC or himself in nearly six months. If it passes the Eli test, it probably can handle a whole hell of a lot! For the record, he is an otherwise well behaved, sweet, wonderful kid. He just has a special ability to break things around the house. It is strange really... he even broke the Roombah, that was a collaboration with his cousin, so I don't hold him accountable for that.
When the UMC is inserted into the charge port, it's weather resistant. If you unplug it during rain the port blinks a bit if there was water on the UMC plug (the water drips into the port and confuses the system). Solutions: 1) Wipe off the UMC before unplugging so that it's fairly dry. 2) Cover the UMC plug and port to keep the rain off. I envision a cover that velcros around the UMC cable and has a flat part to protect the port from most of the rain.
Don't do that. Rain will get in anyway, and you'll just end up creating a water pouch instead of a rain protector. That will cause rust after a while. (Anybody who has done outdoor Christmas lights in a rainy climate quickly learns this one the hard way...). If a plug is rated for outdoor use, just leave it uncovered - don't put it in a bag. It will still get wet, but that way at least it has a hope of drying again.