Change the batteries in a car remote by purchasing a new battery, opening the remote, and replacing the dead battery. New car remote batteries can be purchased from auto parts dealers, including Auto Zone and Advance Auto Parts.
To remove the old battery, examine the back of the back of the car remote for small screws. Many car remotes use two screws to hold the back and front plates together, though this number can vary based on make and model. Remove the screws to detach the back cover of the remote, and disconnect the old battery from the metal contacts. Do not touch the battery contacts or any of the circuitry. Insert a fresh battery in the correct orientation, and screw the back plate into place.
Alternatively, some car remotes utilize plastic tabs rather than screws. To open this type of car remote, look for a small notch, often located on the side of remote near the seam. Use a flat head screwdriver or a coin to pry apart the front and back panels of the remote. Replace the dead battery with a new battery, ensuring to insert the new battery in the same orientation as the old. Firmly push the two halves of the remote back together until the plastic latch clicks.