Rockwell Automation 8520 9/Series CNC Integration Maintenance Manual Documentation Set - Manual (Page 216)

Section 4C
Connecting the 4-axis Servo Module
4C-18
To replace the servo module battery, turn all system power OFF and
disconnect the old batteries from connector P2 on the servo module.
Battery replacement instructions are included with the battery replacement
kit. Before installing new batteries, use a voltage meter to make sure that
new battery voltage is higher than 3.5V dc.
Figure 4C.13
Servo Module Battery Connector P2
TB1
P1
(CN1)
J1
J2
J3
P3
P2
TB2