Lucent Technologies Lineage
®
2000 ECS Battery Plant H569-403
3 - 12 Engineering, Planning, and Ordering
Issue 4 February 1997
between batteries and load, the minimum load voltage may be
reached before the batteries reach their end voltage so that their
rated capacity is only partially used. In this second case,
additional battery capacity would be required.
The trade-off between battery size and wire size is an economic
one. For systems with long cabling runs, the cost of large
quantities of heavy wire should be balanced against the cost of
additional batteries. Finding the exact optimum combination of
cabling and batteries involves complex iterative calculations
which are beyond the scope of this discussion. Some using
systems, such as electronic switching systems or transmission
systems, dictate maximum allowable voltage drops, thus
simplifying the calculations. Lucent offers a computerized
service to optimize the selection of cable sizes and battery
capacity for any application. Contact your Lucent Energy
Systems Account Executive for details on this service.
Alternatively, various rules-of-thumb are used to specify
maximum voltage drops. During discharge, the critical voltage
drop is the total drop from the battery terminals to the load
equipment. Increasing the voltage drop from dc distribution to
load can potentially be compensated by decreasing the voltage
drop from batteries to dc distribution.
The voltage drop from the batteries to the distribution (0.25
volts) has been covered above, in the paragraph “Battery String
Voltage Drop and Balancing.” One rule-of-thumb specifies a
maximum voltage drop of 0.75 volts in the feeder loop from the
dc distribution to the load and back again, using the List 2 drain
for that circuit as listed in Table 3-B. Voltage drop calculation
methods are described in the paragraph “Calculating Voltage
Drop.”
Fill in the selected or calculated system voltage drops, below.
s. Maximum drop (batteries to dc distribution):
____ volts
t.
Maximum drop (dc distribution to load): ____ volts
u. Maximum drop (batteries to load): (v) + (w) =
____ volts
After the total drop from the batteries to the load is determined,
the actual end voltage of the batteries can be derived from the
minimum input voltage to the load (b).
