Does the 5300 have an internal (PRAM or clock) battery?

Yes. The 5300 takes a pair or VL2330 coin-type 3V lithium rechargeable batteries wired in series. The batteries are connected to the PowerBook via a three wire cable that plugs into the Power Management Unit. The batteries are rechargeable and generally have a lifespan of several years. As long as you plug in your PowerBook from time to time, it is unlikely that the battery will go dead due to being completely discharged.  more