Lift the battery out of the phone case.

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

Before installing your new battery, peel up all the old adhesive and remove it from the phone.

For best results, clean the area underneath the battery with isopropyl alcohol and a lint-free cloth or coffee filter. This helps prep the surface so the new battery can adhere more strongly. Replace old adhesive with stretch release adhesive strips, double-sided tape, or pre-cut adhesive strips.

If you're also replacing the screen assembly, which includes the midframe, the new midframe may have battery adhesive pre-installed. In that case, don't apply any more adhesive—just peel the backing off the preinstalled adhesive and install the battery.