Remove the battery from the midframe.

Do not reuse the battery after it has been removed. The stress of removal can cause hidden damage to the battery cell, creating 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 entire area under the battery with isopropyl alcohol.

Apply a few new strips of pre-cut adhesive or Tesa tape.

If you are attaching the battery with a custom-cut adhesive, follow this guide.

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