Liebert 610 - Manual (Page 52)

Operation
46
The Battery Time Remaining graph and the Calculated times are extremely helpful to the operator who
has the discretionary authority to order load-shedding activities. The Series 610 automatically samples
battery voltage and load current and recomputes every six seconds. This gives the operator fast and
accurate feedback on efforts to extend battery time remaining by shutting down non-critical loads.
Figure 37 Accuracy range of values for calculated battery times
The Series 610 dynamically adjusts the Battery Shutdown voltage based on battery characteristics
and the length of the current discharge event. If a discharge event extends past 15 minutes (i.e., the
load is less than the full design rating), the Battery Shutdown voltage setting is gradually and auto-
matically increased, to protect the batteries from deep discharge.
When the battery voltage decreases to a preset limit (see 3.2.6 - Alarm Limit Settings Screen), the
Low Battery Warning alarm message appears on the display screen. This warns the operator that the
battery voltage is approaching the Battery Shutdown level—about five minutes of time remaining at
full rated load.
If the battery discharges to the Battery Shutdown level, represented by the lower line on the Battery
Time screen, the battery and input circuit breakers trip open and the UPS module is shut down. This
protects the battery from being damaged by an extended deep discharge.
NOTE
While every effort has been made to make the Rated and Calculated Time Remaining values as
accurate as practical, these values must be regarded as approximations. At the beginning of the
discharge cycle, the Calculated times could be off by as much as ±20% due to such variables as
battery initial charge, age of battery and the subsequent load-shedding activities of the
operator. Within a few minutes, however, these calculations should settle into their design
accuracy of ±10%, with the end-of-discharge tolerance being +0, -10% of actual observed time.
In addition, the operator can adjust the settings affecting Rated Total Time after gaining
experience with the actual battery and connected load.
NOTE
The Low Battery alarm setting is designed to be most useful at full load battery discharge
rates. Unlike the Battery Shutdown voltage, the Low Battery alarm setting is not automatically
increased and gives proportionately less warning during discharge events lasting longer than
15 minutes. The operator should consult the Battery Time screen or Present Status screen to see
the Calculated Time Remaining based on actual usage during the discharge period.
!
CAUTION
When battery shutdown occurs, no power will be supplied to the critical load unless power is
available through the bypass line from the utility source (or from an engine generator set). If
you anticipate a battery shutdown (and an engine generator set is not available), either
transfer the load to bypass (if available) or perform a controlled shutdown of the critical load.
0
5
10
15
20
25
0 2.5 5 7.5 10 12.5 15 17.5 20 22.5 25
Elapsed Time (Minutes)
C
alculated Time R
emaining
Upper Limit Actual Lower Limit