I found the Vision Spinner II at the warehouse today and tested several VB skillets. The skillets fired up at all 4 settings: 3.3v, 3.8v, 4.3v, 4.8v.
I did a full button cycle (approx 12 seconds) at each setting. At the 4.8v setting, I did 4 cycles on the same skillet and it didn't burn out...