The Garmin Nuvi AC charger comes with adapters for various voltages. It works as you would expect. I think it should have been included with the unit as standard.
I bought this for my wife who travels every month. She often has to stay in hotels, so this lets her to charge her GPS in her room
Works fine, not a thing wrong with it. But if this is your first GPS purchase and your box doesn't include an A/C cable, don't jump to buy one. You don't really need it!