Siemens S5-135U/155U System Manual page 227

Inserting or
Before the RAM submodule with battery backup is started for the first time,
Replacing the
you must insert the battery provided. This is delivered separately to protect it
Backup Battery from premature discharge. Proceed according to the following steps:
Step
Figure 5-10
Caution
!
Improper replacement of the battery can result in explosion hazard.
It should only be replaced by the same type or an equivalent one
recommended by the manufacturer. Used batteries should be disposed of
according to the manufacturer's instructions.
System Manual
C79000-G8576-C199-06
CPUs, Memory Cards, Memory Submodules, Interface Submodules
Action
1 Open the upper side of the cover by releasing the snap-on catch.
Grasp the cover within the clearance from the PCB and pull it up.
2 Insert the submodule battery and secure it with a screw on the left
and on the right. Ensure correct polarity (+/-).
3 Close the cover again.
Battery
M 2.5 Screw
Battery
Fault LED
Mounting Location for Backup Battery
Grip
5-87