I just did one of these conversions for Waidy:
The cool thing is Tesla's inclusion of a handy 3.3v source which is normally used for the charge door release transmitter. This enabled easy addition of a bright LED for nighttime, something not even Tesla thought of!
I opened one of the UMC's up, but it's a pretty destructive process due to the housing overmold and it being glued shut. If not for this "one way trip", I'd have simply replaced the thin (too thin?) Tesla cable.
Tesla is really pushing the limits! They use two 2.5mm wires for each side, (Equivalent to #13AWG) and inside the box they use the exact same relay ClipperCreek uses on the LCS25, a single 30A rated relay. (at 40A!) It's arguable that splitting the high-current between 2 smaller conductors is better for heat-dissipation, but then you have the pesky termination issues. Inside the UMC, Tesla welds the 2 conductors to a little square terminal, then screws this to a PCB terminal. So this is a good termination and it looked well-done by my assessment. Having 4 smaller wires instead of 2 larger ones definitely makes for a smaller, more flexible cable overall, so regardless of any potential current handling gain, it's good ergonomically.
I definitely don't like their interchangeable right-angle plug connector design. First off, if you are going to do right-angle, why not make it symmetrical? That way you could flip it 180 degrees if your outlet is installed upside-down. (Patent-Pending! =)
Their "dongle" design makes for compact and simple plug adapters, but it ends up being a really big blob, especially when used on smaller outlets (NEMA 5-15). I think I prefer having a short length of cable for each adapter, as this makes the final plug smaller, more compact, more flexible, and spreads out heat.
Ok, onto my conversion. Sorry, I didn't think to take pictures of the pin connection detail until it was already all assembled. Here's the best I can do:
Since the "no-name" Chinese handle pins are made for much larger wire, you cannot crimp it by itself and get a reliable 40A connection. I took a crimp ferrule from a yellow butt-splice connector, and crimped the 2 Tesla wires into that, which were very well crimped, then crimped and soldered that into the no-name pin. I believe this is as good as I can make it.
I would not trust solder alone, there must be a solid mechanical bond first at these current levels with the relatively tiny wires. If you are soldering anything, it absolutely must not be allowed to move, as you will have stress-concentrations where the solder wicking inside the wire strands ends.
Needless to say, I'm not doing another one of these. It's a lot of work to do properly, I'm not sure I like the "no-name" Chinese handle, and the UMC itself isn't the hardiest design to begin with, though it is sexy!