User manual

www.enersys.com
Publication No: US-NP-AM-003 • January 2011 13
 Cyclic Service Life
There are a number of factors that will effect the length
of cyclic service of a battery. The most significant are
ambient operating temperature, discharge rate, depth of
discharge, and the manner in which the battery is recharged.
Generally speaking, the most important factor is depth of
discharge. Figure 11 illustrates the effects of depth of
discharge on cyclic life.
The relationship between the number of cycles which can be
expected, and the depth of discharge is readily apparent. In
relation to a specified discharge rate, if the application
requires a longer cyclic life than is obtainable by selecting the
battery capacity according to common practice, select a bat-
tery with larger capacity. Thus, at the specified discharge rate
over the specified time, the depth of discharge will be
shallower and cyclic service life will be longer.
 Float Service Life
Genesis
®
NP batteries are designed to operate in standby
(float) service for approximately 3 years, based upon a normal
service condition in which float charge voltage is maintained
between 2.25 and 2.30 volts per cell in an ambient
temperature of approximately 25
0
C (77
0
F).
In normal float service, where charging voltage is maintained
2.25 to 2.30 volts per cell, the gases generated inside Genesis
NP battery are continually recombined, and return to the
water content of the electrolyte. Therefore, electrical capacity
is not lost due to “drying up” of the electrolyte. Actually,
through the gradual and very slow corrosion of the elec-
trodes, the battery will eventually lose capacity and come to
the end of service life. It should be noted that the corrosive
process will be accelerated by high ambient operating
temperatures and/or high charging voltage. When designing
a float service system, always consider the following:
LENGTH OF SERVICE LIFE WILL BE DIRECTLY
AFFECTED BY THE NUMBER OF DISCHARGE CYCLES,
DEPTH OF DISCHARGE, AMBIENT TEMPERATURE, AND
CHARGING VOLTAGE.
Expected Service Life of Genesis
NP Batteries
Figure 11. Cyclic Service Life in Relation to Depth of Discharge
Genesis
®
NP Series
TESTING CONDITIONS: DISCHARGE CURRENT: 0.17C AMP. (F.V. 1.7V/CELL)
CHARGING CURRENT: 0.09C AMP.
CHARGING VOLUME: 125% OF DISCHARGED CAPACITY
AMBIENT TEMPERATURE: 20°C TO 25°C (68°F TO 77°F)
PERCENTAGE OF CAPACITY AVAILABLE
(AH%)
120
100
200
400
600
800
1000
100%D.O.D.
50% D.O.D.
30% DEPTH OF DISCHARGE
1200
1400
80
60
40
20
0
NUMBER OF CYCLES (CYCLES)
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