What you need:
-Flat screwdriver,
-CR2032 battery.
For the new type of keychain:
-push the button to jump the key,
-there's a square plate in the middle of the middle, and it's a screwdriver,
-replace the battery.
For the old type of strap:
-push the button to jump the key,
-insert a screwdriver in the transverse hole in the middle,
-turn the screwdriver by 90 degrees,
-to separate the halves of the strap,
-arrange half a piece of beams with the buttons upward,
-use the screwdriver to open the battery compartment with the buttons up (the screwdriver is inserted into the gap between the halves, in the ear),
-replace the battery.
