Most 10W (2.0 A) chargers with a USB-A port will charge at full speed. It takes about 1.5A max, but it will only charge at 500mA (0.5A) from some. There are now many standards.
A 2.5W is the realistic minimum, and 7.5W USB-A charger with the right compatibility will charge it at full speed. No matter what charger is used it only wants 5V and will take a maximum of 1.5A
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