Rockwell Automation 8520 9/Series CNC Integration Maintenance Manual Documentation Set - Manual (Page 215)

Section 4C
Connecting the 4-axis Servo Module
4C-17
The Digital Servo Module, 8520-ENC4, provides battery backup for the
absolute encoder position register. This register retains position data
during power loss. The battery backup power originates from the batteries
plugged into the servo board at connector P2.
Important: Battery backup is required for absolute encoders only.
Incremental encoders do not require battery backup.
Even if battery backup fails, or the encoder cable is temporarily
disconnected, the encoder will still maintain position data for up to 24
hours. This also allows for battery replacement without loss of data.
The battery backup is tested at power up, and at four hour intervals while
system power is on. If battery voltage drops to 2.8V during the battery
test, the control automatically displays the warning message “REPLACE
ABSOLUTE FEEDBACK BATTERY” on the operator panel.
Important: Once the “REPLACE ABSOLUTE FEEDBACK BATTERY”
message is displayed, it is essential that the batteries be replaced to avoid
loss of absolute position data.
The lithium battery contains heavy metals and
must be collected separately from other waste.
4C.5.4
Digital Servo Module Battery
Replacement