Nokia Lumia 521 User Manual page 13

2. When the battery is full, disconnect the charger from the phone, then from the wall outlet.
You don't need to charge the battery for a specific length of time, and you can use the phone while
it's charging.
If the battery is completely discharged, it may need to charge for up to 20 minutes before you can
use your phone. The charging indicator may not be displayed in this time.
Tip: You can use USB charging when a wall outlet is not available. Data can be transferred while
charging the device. The efficiency of USB charging power varies significantly, and it may take
a long time for charging to start and the device to start functioning.
First connect the USB cable to the computer, then to your phone. When the battery is full, first
disconnect the USB cable from your phone, then from the computer.
The battery can be charged and discharged hundreds of times, but it will eventually wear out. When
the talk and standby times are noticeably shorter than normal, replace the battery.
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