the ambient temperature. When the temperature is
higher, the charging voltage should be lower and
conversely when the temperature is lower, the
charging voltage should be higher. For specific
recommendations, please refer to the section on
Temperature Compensation. Similarly, charged
volume (measured in ampere hours) realized over a
given time will vary in direct relation to the ambient
temperature; the higher the ambient temperature,
the higher the charged volume in a given period of
time and the lower the ambient temperature, the
lower the charged volume in the same given period
of time. Figure 20 shows the relationship between
charged volume and temperature.
I
nitial Charge Current Limit
A discharged battery will accept a high charging
current at the initial stage of charging. High
charging current can cause abnormal internal
heating which may damage the battery. Therefore,
when applying a suitable voltage to recharge a
battery that is being used in a recycling application it
is necessary to limit the charging current to a value
of 0.30C Amps(max.). However, in float/standby use,
Powerline SC are designed so that even if the
available charging current is higher than the
recommended limit, they will not accept more than
2C Amps and the charging current will fall to a
relatively small value in a very brief period of time.
Normally, therefore, in the majority of float/standby
applications no current limit is required. Figure 21
shows current acceptance in Powerline SC charged
at a constant voltage of 2.30 Vpc without
current limit.
When designing a charger, it is recommended that
suitable circuitry is employed to prevent damage to
the charger caused by short circuiting the charger
output or connecting it in reverse polarity to the
battery. The use of current limiting and heat sensing
circuits fitted within the charger are normally
sufficient for the purpose.
To ensure the correct voltage is set accurately, when
adjusting the output voltage of a constant voltage
charger, all adjustments must be made with the
charger "ON LOAD" Adjusting the output voltage with
the charger in an"OFF LOAD" condition may result in
undercharging. The constant voltage range required
by a battery is always defined as the voltage range
applied to a battery which is fully charged. Therefore,
a charger having the output characteristics illustrated
in Figure 22, should be adjusted with the output
voltage based on point A. The most important factor in
adjusting charger output voltage is the accuracy at
point A, which should be in the range of
2.275vpc
0.005 volts per cell; however this accuracy
is not normally required over the entire range of the
load. A charger adjusted in accordance with Figure 22
will never damage a battery, even if the charger has the
characteristics Shown by the broken line in Figure 22.
As the temperature rises, electrochemical activity in a
battery increases and conversely decreases as
temperature falls. Therefore, as the temperature
rises, the charging voltage should be reduced to
prevent overcharge and increased, as the
temperature falls, to avoid undercharge. In general,
in order to attain optimum service life, the use of a
temperature compensated charger is recommended.
The recommended compensation factor for Powerline
SC is -3mV/ C/Cell (for float/standby) and -4mV / C
/Cell (cyclic use). The standard centre point for
temperature compensation is 20 C. Figure 23 shows
the relationship between temperatures and charging
voltages in both cyclic and float/standby applications.
Charge Output Regulation and Accuracy
Temperature Compensation
o
o
o
POWERLINE
SC
SERIES
09
Charge
Figure 20. Charging characteristics at
different temperatures
(%) (xCA) (V)
0.1CA-6.825V(13.65V)CONSTANT
VOLTAGE CHARGING
CHARGED
VOLUME
CHARGING
CURRENT
CHARGE
VOL
T
AGE
FOR
6V
BA
T
T
ER
Y
CHARGED VOLUME
CHARGE
VOL
TAGE
CHARGING CURRENT
CHARGE
VOL
T
AGE
FOR
12V
B
A
T
TER
Y
120
100
80
60
40
20
0
0.02
0.08
0.1
0
5
10
15
20
25
30
35
40
11.0
12.0
13.0
14.0
CHARGING TIME (HOUSE)
0
(V)
0.04
0.06
7.00
6.50
6.00
5.50
AT 0 C(32 F)
o
o
AT 20 C(68 F)
o
o
AT 40 C(104 F)
o
o
Figure21. Constant voltage charge
characteristics with no
current limit
CHARGE VOLTAGE:2.30V/C
TEMPERATURE:20 C (68 F)
o
o
CHARGING TIME (SECONDS)
CHARGING
C
URRENT
0.5
1.0
1.5
2.0
(xCA)
0
2
4
6
8
10
20
30
40
50
60
Figure 22. Output voltage adjustment
CHARGING CHARACTERISTICS
OUTPUT CHARACTERISTICS
A
CHARGING TIME
OUTPUT CURRENT
OUTPUT
VOL
T
AGE
CHARGING
CURRENT
A
