Lucent Technologies 1200A 24V ECS Battery Plant J85500E-2
3 - 12 Engineering, Planning, and Ordering
Issue 7 October 1998
additional batteries. Finding the exact optimum combination of
cabling and batteries involves iterative calculations. Some using
systems, such as electronic switching systems or transmission
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.
The voltage drop from the batteries to the distribution has been
covered above in 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 paragraph “Calculating Voltage Drop.”
Fill in the selected or calculated system voltage drops below.
v. Maximum drop (batteries to dc distribution): ___ volts
w. Maximum drop (dc distribution to load): ____ volts
x. 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).
y. Actual battery string end voltage: ____ volts
z. Actual battery cell end voltage: ____ volts
Since most battery vendors provide capacity information as a
function of end voltage, item (z) is important in the selection of
a specific battery. If (z) 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
