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6.7
OB 129: Battery State
Function
How the BAU signal is
formed
Jumper setting in the power
supply
Jumper MB-NB Jumper MA-NA
open
open
closed
closed
Parameters
Result
CPU 948 Programming Guide
C79000-G8576-C848-04
With OB 129, you can check the state of the back-up battery with a
STEP 5 program (OB 129 scans the BAU signal). Depending on the
result, you could, for example, set a fault indicator (lamp).
The power supply contains two back-up batteries, a lithium cell (MB
for main battery) and an accumulator (RB for reserve battery). The
BAU signal is formed by ANDing the battery monitoring signals.
In the power supply of the PLC, there are two jumpers with which the
monitoring of the batteries can be influenced. Jumper MB-NB
determines when the BAU signal is generated (if this jumper is not
inserted, BAU is generated once following POWER UP). Otherwise
the signal is monitored cyclically during operation. The monitoring
signal of the accumulator can be disabled with the jumper MA-NA.
The possible combinations of jumper settings and the resulting battery
monitoring by OB 129 are illustrated in the following table:
Time when BAU signal
generated
open
after POWER UP
closed
after POWER UP
open
cyclic
closed
cyclic
none
RLO = '0':
battery OK
RLO = '1': battery run down
OB 129: Battery State
BAU signal generated from
monitoring signal of ...
lithium cell
lithium cell and accu
lithium cell
lithium cell and accu
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