Remove the battery.

Do not reuse the battery after it has been removed, as doing so is a potential safety hazard. Replace it with a new battery.

To install a new battery:

Remove any remaining adhesive from the phone, and clean the glued areas with isopropyl alcohol and a lint-free cloth.

Apply pre-cut adhesive strips or double-sided tape to the exposed, silver part of the battery compartment, not on the black foam layer.

Press the battery firmly into place for 5-10 seconds.