Thanks ... but my point is that whatever is coming from the inverter even three prong is NOT grounded. Car has rubber booths ... etc. so the "third" prong is basically the body of the inverter which could be at any level(potential) so can the frame of your fridge at that point..... remember the little sparks touching the car ??? I may misunderstand what you are saying, but this is still a potential hazard ... like in a kitchen or bathroom where the person may get in contact with 'REAL' ground ... while the "appliance" powered is not at all grounded. Of course this is not a permanent setup just want to understand the issue.