Lucent Technologies Lineage
®
2000 ECS Battery Plant H569-403
3 - 4 Engineering, Planning, and Ordering
Issue 4 February 1997
Multiply the number of cells per string (j) by the voltages (f), (g)
and (h) to find the values for (k), (l) and (m), respectively.
k. Float voltage per string: _____ volts
l.
Minimum string voltage at end of discharge: ____
volts
m. Maximum charging voltage per string: ____ volts
Compare these three calculated voltages, (k), (l) and (m), against
the steady-state load equipment voltages (a), (b) and (c).
If (l) is a higher voltage than (b), it may be desirable to provide
the low-voltage battery disconnect/reconnect feature to prevent
battery damage from deep discharge. A more complete
comparison of battery and load voltage ranges, involving dc
voltage drops in the cabling system, is provided in the following
sections.
Load Drain and
Growth
Under normal conditions with a constant load, battery plant
voltage to the load equipment is essentially constant. During an
ac power outage, however, as the batteries deliver power, the
voltage drops steadily. Most types of load equipment do not
draw a constant current over their input voltage range. Therefore
the current drain on the plant may change as the batteries
discharge.
Some types of load equipment are purely resistive, in that their
current drain decreases as the plant voltage decreases. Other
types of loads are characterized as constant power equipment, in
that the current increases as the plant voltage drops. Load
equipment may have a combination of resistive and constant
power characteristics.
In the telecommunications industry, List 1 and List 2 are the
designations of the load current drains which have historically
been used to size various elements of the battery plant. These
values are normally provided for each load circuit or group of
load circuits through engineering of the load equipment, a topic
not covered in this manual. These terms may be briefly defined
as follows:
LIST 1 drain: The average busy-hour current during normal
plant operation (i.e., at float voltage). This value is used to size
batteries and rectifiers.
