Samsung GALAXY S4 Quick Reference Manual page 7

IMPORTANT: Verify that the battery is installed prior to connecting the wall charger. If
3. Insert the USB cable into the device's Power/USB connector.
The device turns on with the screen locked and indicates
both its charge state and percent of charge.
4. Once complete, unplug the charging head from the power
outlet and remove the USB cable from the device.
6
both the wall charger is connected and the battery is not installed, the
handset will power cycle continuously and prevent proper operation. Failure
to unplug the wall charger before you remove the battery, can cause the
device to become damaged.