Zte OPTUS X MAX User Manual page 19

WARNING!
Do not remove the back cover. The battery is not removable.
Removal may cause fire or explosion.
1. Connect the adapter to the charging jack. Do not force the
connector into the jack.
2. Connect the charger to a standard AC power outlet. If the
phone is on, you'll see a charging icon such as
appear on the status bar.
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