[extrashaky]

The correct battery size for a 2014 is CR1632. It costs $3 at Walmart or Best Buy.

To replace the battery in a 2014 remote:

Press the button on the side of the remote to release the mechanical key and pull it out. Where the head of the mechanical key usually sits, you'll see a slot. The end of the mechanical key is made to fit into that slot. Stick it in there and twist it to pop the case open.

The battery is on the back of the circuit board (the side facing away from the remote buttons). Sometimes the board will stick to the back half of the case and will have to be gently pried out with the end of the key. To remove the battery, gently pry away the tiny black tabs that hold it in place, then put a new one in the same direction (flat side facing you). Put the circuit board back where you found it, press the halves of the case back together and reinsert the mechanical key.

These batteries last about two years whether you use them or not. When mine went out, my never-used spare was dead also, which made me think there was a problem with the car. Changing both batteries brought both remotes back to life. If you're using the spare now, be prepared for it to die also.