My wife has just bought a used coffe maker for travel use.
It made perfectly fine coffee when plugged into an AC power outlet.
But then she tells me it also works with an adapter to a 12V car cigarette lighter socket.
At first I didn't believ this, particularly since I was born in a 240V AC country.
But it's true and a bit of googling didn't find out how it works but did find something similar.
Just google for: Vintage Empire Kar-N-Home Car Travel Coffee Maker Percolator 12volt and 110volt
The power cord has a conventional connector for an AC outlet and it comes with an adapter for 12V which is no bigger than a usb charger adapter.
The instructions do say that it will make coffee in about 12 minutes on AC and 25 to 40 minutes on DC.
My guess is that there's a diode somewhere so it's using half wave rectified AC. I also guess that there's no such thing in a 230/240V country.
Are my guesses correct and if not how does it know it's on AC or DC?