What is the part number or type of the batteries used in the remote?

Most sears remotes use a standard 9 volt transistor battery or AA . Have you opened the hand held remote to inspect?

Yes. This is a compact remore, about 7 years old. It's set-up to use a flat 3-V lithium battery, similar to the CR2032 in computers. I've tried that battery with no results. I trained my cars to open the door, but would like a spare if I change cars. Would that have any effect on the remote? Thanks