Stupid charged 2013 Volt's A/C, overcharged, car shook and a little smoke/smell came

Yep, I also read that you can't use the small cans of 134a at the auto parts store either since they contain a small amount of oil, and that you must fill with a 30# cylinder. I have a fair bit of automotive a/c experience, including complete rebuilds but the warnings on the Volt system have left me to just decide any work will get done with the dealer.

I don't think 55 out of the vent is an unreasonable figure. With 134a you generally won't see less than about 37 inside the evaporator. By the time the temperature is exchanged through the evaporator to the air, and to the vent opening you'll have even more loss of temperature. Granted this is normally on a 80-90 degree day. 100+ likely won't see less than about 65 out of the vent, possibly higher if the battery is also drawing from the A/C system. Truth be told though, most modern day A/C systems are VERY particular about charge quantity. a couple ounces over or under results in severe loss of cooling capacity. Most modern systems use 2 pounds or less. Not like the old R-12 systems that held 4 pounds and were much more forgiving with over or under charged systems.

Some are more efficient than others. Of course system size plays a big role but keep in mind, the size of the system also impacts how much energy is used to operate it. A luxury car doesn't exactly strive to be efficient like a Volt.