Choosing the correct USB adaptor is very important for your safety and the
function of the battery pack.
Charging by cable: As a minimum you need to use an USB adapter with the
following output: 5V / 2A.
Wireless charging: You will need a 10W wireless charger and an adapter that
fits it.
The battery pack on 5,200 mAh will fully charge in 6 hours, while 3-5 hours is
enough the first time. Never charge the battery in or near water!
Operating temperature: -20°C to 60°C 
Charging temperature: 10°C to 45°C