I'm surprised the OBD II port is capable of powering something like this. I hope they aren't cheating by running off the onboard battery while running and charging while the car is off.
My car's 12V system warns me to limit use to 120W. That's for the "cigarette lighter" ports, but the OBDII power pin is probably similar if not on the same circuit. That'll run a lot of crap.
