Zte Z557 User Manual page 17

If the battery is low, there will be a pop-up message on the
screen. As you charge your phone, the screen will show the
exact battery level on the status bar.
WARNING!
Use only ZTE-approved chargers and cables. The use of
unapproved accessories could damage your phone or cause
the battery to explode.
1. Connect the adapter to the charging jack. Ensure that the
adapter is oriented correctly. Do not use force.
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