Remove the battery.

To install a new battery:

Use tweezers and a spudger to remove all the old adhesive from the battery recess.

If your replacement battery doesn't have adhesive pre-installed, put strips of thin, double-sided tape on the logic board (not directly on the battery) where the old adhesive was.

Insert the battery cable into its connector on the battery and lower the locking flap.

Remove any liners from the battery adhesive or double-sided tape.

Position the battery so the side with the cable connector is on the left edge of the watch.

Firmly press the battery into place to secure it with the adhesive.