The charger should correctly rated regarding AC in voltage, of course

Most chargers are multi-ranged, i.e. 100-240V. But if it is rated 110V for US, it will burn in EU.
i**-Chargers are non-standard!!!
A proper usb charger has to short-circuit USB data wires such that the device recognizes it as being a charger, not a computer device.
Have a look here for reference:
https://en.wikipedia.org/wiki/USB#Charging_ports
i**-Chargers are different...