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Reserve power 53
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DC reserve power
Reserve power for DC systems can be provided simply by adding batteries to
the external distribution. The reserve battery capacity is determined by
multiplying the system current drain by the time that is needed for the reserve
power to operate. This will determine the total Ampere-Hour requirements of
the batteries. Refer to Worksheets A through D.
The following guidelines should be used in determining DC reserve power
requirements.
Current required
When considering battery backup you should know with reasonable accuracy
the total system power requirement.
For new installations, Northern Telecom provides the operating company
with data listing the total current drain for each configured system.
A
rectifier and distribution panel which has the capacity to meet these current
drain figures, and some added capacity to charge batteries can then be
selected. For existing instahations, the total current dram of an installed
system can be calculated in several ways. Refer to “Operating power
requirements” for more information.
The amount of reserve battery capacity depends on the system line size (load),
the time the reserve supply must last in the event of power failure, and the
battery end voltage.
Batteries
Reserve batteries for a DC powered SL- 1 system must meet the following
requirements as defined in Table 19.
Table 19
Battery requirements
Float
voltage Equalize voltage
w
09
Battery configuration cell String cell String
24 stationary cells -2.17 -52.08 -2.25 -54.08
23 sealed cells -2.25 -51.75 -2.35 -54.05
24 sealed cells -2.25 -54.00 -2.35 -56.40
Power engineering 553-3001-l 52