[Dave at Pelican Parts]

The 2nd-gen cars without "comfort access" (where you don't have to put the key in the dash to start the car) do not have replaceable batteries. They would be re-charged by being plugged into the car. That said, the batteries can eventually wear out. I have read of people carefully opening the key fob, de-soldering the old battery, and soldering a new one in. I believe they opened up the fob by cutting it? Not a job I would like to do, myself...

If you do have comfort access, the battery is intended to be replaced.

Not sure how the 1st-gen cars work.

--DD