Replacing The Backup Battery - Siemens SIMATIC Rack PC 840 Manual

4.3

Replacing the Backup Battery

Battery Power Supply for Real-Time Clock and Configuration
A backup battery (3.6 V-lithium battery) powers the the real-time clock even after
the Rack PC is switched off. In addition to the time of day, all the information about
the Rack PC (device configuration) is stored in RAM. If the backup battery fails or
is removed, all these data are lost.
The clock uses very little power and the lithium battery has a high capacity so that
the battery can provide backup power for the real-time clock for many years and
seldom needs to be replaced.
Battery Voltage too Low
If the battery voltage is too low, the time is lost, and a correct device configuration
can no longer be guaranteed.
In this case, you must replace the backup battery. The battery is in a battery holder
on the motherboard.
Replacing the Battery
To change the battery, proceed as follows:
1. Note down your own BIOS setup settings.
2. Separate the device from the mains and remove all cable connectors.
3. Open the unit as described in Section 4.1.
4. Pull the battery out of its holder.
5. Insert the new battery by slightly pushing it into its holder.
6. Close the unit.
7. Reenter your own BIOS settings.
SIMATIC Rack PC 840 Manual
A5E00104826-03
SIMATIC Rack PC 840 Expansions
4-9