The PA3X has two batteries. One, a small CR2032, is used for the clock. The second, a much larger battery, is used to hold samples and factory resources (voices and stuff). The battery was included to shorten start up time. The PA3X can work without the RAM battery. It just takes a lot more time to boot up.

Many Korg's use a small battery for the clock that time stamps files when they are saved.

The larger sample backup battery that was used on many early Pa3X's did not contain current limiting circuitry and they were subject to run away current and occasional explosion. Replacement batteries were sent to users by Korg, and instructions were provided for their replacement. A small sticker was provided with the replacement that has a green check mark so that it is obvious that the replacement has been installed (assuming the installer used the sticker).

If you go to the link that Zuki provided in his first post and scroll down you will see a red comment on the battery problem. Click on it for details.