Here's a quick how-to: (WARNING: This may void warranties, set fire to your cat, and cause the end of the world. The whole time pissing off the lawyers, so DO NOT perform this modification unless you are FULLY QUALIFIED!)
Order 2 of these
Take out your J1772 inlet on your car, remove the weather boot, and ziptie one of the above thermostats to each of the two main AC wires with the tab end as close to the inlet as practical. The AC lines are the top 2 heavy connections on the inlet. Use high-quality (3M) electrical tape
wrapped all around these and it's associated wire such to insure heat is conducted into the thermostat. (Use at least 8 layers of tape) The copper wiring will conduct heat quite well to the thermostats if done in this manner.
Locate the proximity line, it is the one connected the small pin on the lower right if viewing the inlet from the front side where you would connect to it. Cut it at a suitable location at least a few inches away from the inlet and install a 330 ohm 1 watt resistor
across the break. I recommend 1 watt not because of the power, but because of it's mechanical robustness. Wire both of the thermostats in series with each other, and then connect them across the 330 ohm resistor (the two series thermostats will be wired like an "M" and then the two ends of the "M" will be connected to each end of the resistor which is where the proximity line is also connected.) I recommend soldered connections covered using high-quality glue-flow type heatshrink. Plan the heatshrink in advance before doing any soldering.
Now if either of the current-carrying connectors get much over 70C, charging will halt until they cool off, at which time it will resume. This will protect your inlet from catastrophic failure. The resistor insures the car still "sees" the J-plug inserted, but will disable current flow.