Lucent Technologies Lineage
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2000 ECS/GPS Battery Plant J85500G-2
Issue 6 May 1999 Engineering, Planning and Ordering 3 - 11
systems, dictate maximum allowable voltage drops, thus
simplifying the calculations. Lucent Technologies offers a
computerized service to optimize the selection of cable sizes and
battery capacity for any application. Contact your Lucent
Technologies 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, under 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 next section, Calculating voltage
drop.
Fill in the selected or calculated system voltage drops below.
19. Maximum drop (batteries to dc distribution): ____ volts
20. Maximum drop (dc distribution to load): ____ volts
21. Maximum drop (batteries to load): (19) + (20) = ____ 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 (2).
22. Actual battery string end voltage: ____ volts
23. Actual battery cell end voltage: ____ volts
Since most battery vendors provide capacity information as a
function of end voltage, item (23) is important in the selection of
a specific battery. If (23) is below the manufacturer’s
recommended discharge voltage, low-voltage battery
disconnect/reconnect may be helpful in preventing battery
damage from deep discharge. In attended locations with back-up
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