My original 04 KJ key fob is now 17 years old, still working, yet it was time to inspect the batteries! There are two 3 volt batteries on top of each other. The owner's manual states Panasonic CR 2016 required & use a dime to open the case gently. These definitely are the original batteries! Removing the first top battery was interesting. Look at the plastic clips first. ^^ You don't want to break them. What I did is use my thumb, move one of the clips slightly outward, while using the flat blade jewelers screwdriver, to pry the battery upwards. Wear eye protection, it popped out at a rapid pace! 2nd battery repeat... ^ I used a bit of fine emery cloth to clean terminals. Alcohol used to clean batteries. Then inspected batteries for leaks, they were fine & took a voltage reading on each battery. Each battery read 3.27v for a total of 6.54v combined, just like new !! Installing the batteries back in place was much easier. Move clip slightly outwards & they drop into place. Expect them to be rotational (not completely tight) which seems to be normal. Cleaned the rubber seal, then reassembled the split case together. FOb still works perfectly. These fobs are quality, yet I would have preferred, metal battery clips instead of plastic. It really is amazing after all these years, that these batteries last so long !