Expected
S
ervice
Lif
e
of
P
o
werline
S
C
10
POWERLINE
SC
SERIES
In practice where there are short term temperature
fluctuations between 5 C and 40 C, temperature
compensation is not absolutely essential. However,
it is desirable to set the voltage at a value shown in
Figure 23 which, as closely as possible, corresponds
to the average ambient temperature of the battery
during its service life. When designing a charger
equipped with temperature compensation, the
temperature sensor must sense only the
temperature of the battery. Therefore, consideration
should be given to thermally isolating the battery
and temperature sensor from other heat generating
components in the system.
o
o
Charging Efficiency
cyclic service life
Figure 26. Cycle service life in relation to depth
of discharge
Float Service Life
The charging efficiency
of a battery is expressed
by the following formula:
The charging efficiency varies depending upon the
state of charge of the battery, temperatures and
charging rates. Figure 24 illustrates the concept of
the state of charge and charging efficiency. As
shown in Figure 25, Powerline SC exhibit very high
charging efficiency, even at low charging rates,
unlike some nickel cadmium batteries.
There are a number of factors that will affect 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 26 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. If an extended cycle life is required then it
is common practice to select a battery with a larger
capacity than the one that is required to carry the
load. Thus, at the specified discharge rate over the
specified time, the depth of discharge will be
shallower and cyclic service life will be longer.
Powerline SC are designed to operate in
float/standby service for approximately 5 yrs based
upon a normal service condition in which float
charge voltage is maintained between
2.275vpc
0.005 volts per cell in an ambient
temperature of approximately 20 C. Figure 27 shows
the float service life characteristics of Powerline SC
when discharged once every three months to 100%
depth of discharge.
η
Expected Service Life of
Powerline SC
o
(Ah)Ampere hours Discharged
(Ah)Ampere hours Charged
η
=
Figure 24. Charging efficiency vs
state of charge
CHARGE
EFFICIENCY
STATE OF CHARGE(%)
(%)
100
50
0
50
100
Figure25. Charging efficiency
CHARGE
E
FFICIENCY
(
)
η
AT 40 C
o
AT 25 C
o
AT 0 C
o
70
80
90
100
0.001
0.002
0.005
0.01
0.02
0.05
0.1
CHARGING CURRENT(xCA)
0
13.2
13.8
14.4
15.0
15.6
6.6
6.9
7.2
7.5
7.8
2.2
2.3
2.4
2.5
2.6
14
32
50
68
86
104
122
140( F)
o
-10
0
10
20
30
40
50
60( C)
o
AMBIENT TEMPERATURE
CHARGING
V
OL
T
A
GE
Figure 23. Relationship between charging
voltage and temperature
(V)12V
BA
TTER
Y
(V)6V
B
A
T
TER
Y
(V/CELL)
0
CYCLE
USE
STAND-BY
USE
100%
80%
60%
40%
20%
0%
0
0 . 1
0 . 2
0 . 3
0 . 4
0 . 5
0 . 6
0 . 7
0 . 8
0 . 9
Thousand cycles
D.O D. in%
.
