Kia K4 key fob battery

Flip key

1. Open the flip blade. Never force the hinge sideways, since the spring and pin are the weak part of a flip key.
2. Some flip keys have a screw on the back; others just clip. Remove the screw if there is one, then pry gently at the seam.
3. Take out the old cell, noting which side faced you, and fit the new one the same way.
4. Clip the body closed, fold the blade, and test the buttons from a few steps away.

A CR2032 is 20 mm across and 3.2 mm thick. CR2032, CR2025 and CR2016 share the same width but not the same thickness, so a swap between them can leave a loose contact or a case that will not close.

Smart key (push-button start)

1. Find the small release on the edge or back of the fob and hold it while you pull out the metal emergency key.
2. Look inside the empty key slot for a notch. Put the tip of the metal key or a small flat screwdriver wrapped in tape there and twist gently until the shell splits.
3. Note which side of the old coin cell faces up (usually the side with the writing), lift it out with a plastic tool, and press the new one in the same way.
4. Snap the halves back together, slide the metal key home, and press each button, then try the start button from the driver's seat.

Kia smart keys usually free the mechanical key with a button, and the case opens at the gap it leaves.

A CR2450 is 24.5 mm across and 5.0 mm thick, much fatter than a CR2032. A thinner cell will rattle and lose contact, so buy the exact size.