Smart Batteries; Smart Battery Operation - GE GFK-2741C Manual

Batteries

Smart Batteries

2.4
2.4.1

Smart Battery Operation

The battery output voltage is > 2.5 V when the battery is operating in its good state. At the end of the battery good
period, the battery output drops to <2.5 V for the battery low state. The period for the battery low state is 15 days
for all CPU models. Once battery output voltage drops to <2.5V, compatible PACSystems CPUs detect this as a
battery low condition; a Low Battery fault is logged in the Controller fault table and the red Battery LED on the CPU
starts blinking.
Once the low battery state is active, the user has 15 days of accumulative battery backed energy left for CPU RAM
retention during power loss. Since the low battery period may start while the PLC is powered down and faults
cannot be logged in this state, the low battery fault date is unlikely to indicate the starting point of the 15 day count
down. System power downs should not exceed 15 days as the battery voltage may drop to 0V, resulting in the loss
of CPU RAM memory contents.
Consider the following example:
Controller
State
Controller Power Down
Battery Output
Voltage
Battery Good
2.5V
Battery Low period starts
The Battery Low period of 15 days starts at Point T1, but the low battery fault is logged at Point T2, when the
controller is powered ON. The user should be aware that the Low Battery fault timestamp does not indicate the
start of the 15 day Battery Low period.
6
T1 T2
Battery Low fault logged
PACSystems* Controllers Battery and Energy Pack Manual
Controller Power Up
Battery Low
Battery output
voltage goes to 0
15 days
T3
Time
GFK-2741C