The Color LaserWriter 12/600 PS uses a 3.6 volt lithium battery at location BT1 on the I/O controller to retain the page count and other parameters when the printer is powered off. If the battery voltage drops, or it is removed from the I/O controller, then the page count information will no longer be retained. Service Source contains additional information on battery testing and replacement procedures.
Replacement batteries are available as a service part using part number 742-0011.