I just verified this with MacTracker, the iBook never had a separate backup battery. As I recall the iBook relied on residual charge in the main battery to retain the data stored in PRAM. So if the main battery is dead anything stored in PRAM would be lost any time the iBook was powered down. However, assuming external power, the PRAM contents would be reconstricted on booting up but the date/time would have to be reset each time. IIRC an incorrect date/time could cause mischief but I don't remember what form that took.
More recent and expensive MacBooks use a different type of chip that is not dependent on power to retain its contents for PRAM and the backup battery has become extinct. Magnetic media such as the HD will deteriorate over time and the data becomes unreliable, but that should not effect the startup chime.
