Nokia Lumia 900 User Manual page 10

10 Get started
You do not need to charge the battery for a specific length of time, and you can use the
phone while it is charging.
If your phone is off when you start to charge the phone, it automatically switches on.
Make sure you use a compatible USB charger to charge your phone.
If the phone indicates a low charge, do the following:
Charge from a wall outlet
1 First connect the USB cable to the charger, plug the charger into a wall outlet, then
connect the micro-USB end of the USB cable to your phone.
2 When the battery is full, unplug the charger from the phone, then from the wall
outlet.
To avoid breaking the USB cable connector, be careful when connecting or disconnecting
the charger cable.