Huh. I'm going to have a list of questions/disagreements for this.
or make one yourself from off the shelf outlets and plugs and #6 3 wire cable from The Home Depot.
I am genuinely curious what you think this can do. The only mobile connector adapter plug that comes with the car is the 5-15. Are you suggesting that someone build a pigtail adapter from parts that can go into the 14-50 outlet on the wall and then convert that to a 5-15 receptacle that his only Tesla plug can go into? Do you realize what would happen with that? It would work, but the Tesla 5-15 plug would still signal 12A maximum that the car is allowed to pull. That would not at all be an effective use of a 14-50 outlet on a 50A circuit. Buying an official Tesla 14-50 plug will signal the 32A maximum that the mobile connector can provide.
I would not really call that "MUCH" cheaper. The adapters from Tesla are now $45. Buying the plugs and receptacles and cable and wire strippers are going to run at least $20. Plus this will take someone's time to do it, which is worth more than $0. So this is about something like $20 savings. I am one of the people on here that tries to caution about wasting hundreds of dollars that others think is no big deal, but for saving $20 to build a homemade thing? And as I mentioned above--for something that won't really even have the full capability of buying an official one? That just doesn't seem worth it.
Of course, you need to know things like how to tighten a screw, strip wires, use colored wires, etc. And don't listen to folks who run around like Chicken Little claiming, "Your house will burn! Your house will burn!" It won't.
Right. It's possible for someone to make something well enough that it's not inherently really dangerous if they do it right, but it's more than just that:
1. Homemade can't signal the amp limit correctly
2. The OEM ones have a temperature sensor in the plug head that is up against the outlet in the wall that can detect heat. This extra pigtail connection would not have that safety check there. (The Tesla 5-15 plug would still have that, but it would only be sensing heat in the pigtail receptacle it's plugged into.)
3. Going from 14-50 outlet to 5-15 outlet to 5-15 plug to UMC is adding an extra set of plug connections, which is more resistive and weak points in the chain. So that is a worse overall connection. But as mentioned, this couldn't run at more than 12A anyway, so it's not as bad as higher current with those extra connections.