Remove the mechanical key by pressing the release button on the back of the fob
Locate the seam around the key fob case
Insert a small flathead screwdriver or coin into the seam
Gently twist to separate the two halves of the fob
Work around the edge if needed until the case opens
Lift out the battery or internal components as needed
Refit the two halves by aligning them and pressing them together
Reinsert the mechanical key into the fob until it clicks