Lucent Technologies 1200A 24V ECS Battery Plant J85500E-2
3 - 4 Engineering, Planning, and Ordering
Issue 7 October 1998
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, the batteries deliver power, and their
voltage drops steadily since 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. 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.
List 2 Drain. The peak current under worst case conditions of
voltage, traffic, etc. This current is used to size load feeder
cables, plant discharge capacity and overcurrent protectors.
The summations of List 1 and List 2 drains for all the individual
load circuits provide the List 1 and List 2 drains, respectively, for
the entire battery plant.
Initial List 1 drains are used to size initial rectifiers and batteries
since these components may be added relatively easily to
