Samlexpower SEC-1280UL Guide D'utilisation page 12

SECTION 4 |
(c) Please also note that the output voltage at the two banks may differ between
0.2 to 0.8V depending upon the different values of the charging current being
delivered through each as a result of different values of voltage drops Vf and Vb
across the isolating Schottky Diodes.
2. Standard Temperature Conditions: The charging voltages shown pertain to bat-
tery electrolyte temperature of 77°F (25°C)
3. Charger / Battery Voltage / Current Values:
(a) During Constant Current "Stage 1 - Bulk Stage" (See Section 4.3.1), the output
voltage of the charger will be clamped to the actual battery voltage corre-
sponding to the intrinsic (internal) State of Charge of the battery. However,
during (i) Constant Voltage "Stage 2 - Absorption Stage" (Section 4.3.2) and (ii)
Constant Voltage "Stage 3 - Float Stage" (Section 4.3.3), the charger will output
constant voltage. During these stages, the intrinsic (internal) voltage of the bat-
tery will be lower than the rated Absorption and Float Voltages of the charger
and the charging current will taper down as the Stage of Charge of the battery
rises under constant voltage charging.
(b) The voltage curve shows the voltage at the charger Output Connectors, which
will be the same as the voltage at the battery terminals (assuming that there is
no voltage drop along the wires connecting the charger to the batteries)
(c) The Current Curve shows the current being drawn by the battery
4.3.1 Stage 1 - Bulk Stage
4.3.1.1 The Bulk Stage is a Constant Current Stage where the battery is charged at "Bulk
Stage Current" rating of (i) 80A for SEC-1280UL or, (ii) 40A for SEC-2440UL. During this
stage, the charger's open circuit voltage will be (i) 13.5V for SEC-1280UL or, (ii) 27.0V for
SEC-2440UL. However, when discharged battery is connected and charging is initiated
under this stage, the terminal voltage of the charger will get clamped to the battery
voltage - see Section 4.3.1.2 for details.
4.3.1.2 Let us assume that SEC-1280UL is being used to charge a 12V battery bank that
has been discharged to 10.5V. When the charger is switched on, the 12V battery will
initially try to draw very large current = (13.5V - 10.5V) " Internal Resistance of dis-
charged battery (say 0.02 Ohm) = 150A. As the Bulk Current rating of SEC-1280UL is 80A,
the charger will enter current limit condition at 80A (Point A2 in Fig 4.1) and its voltage
will drop but will get clamped at the initial battery voltage of 10.5V (Point A1 in Fig 4.1).
The battery will start charging at constant current of 80A (Section A2-B2 in Fig 4.1) and
its intrinsic (internal) voltage will ramp up almost linearly (Section A1-B1 in Fig 4.1). When
the battery's intrinsic voltage approaches 13.5V (Point B1 in Fig 4.1) and the current
drawn by the battery reduces to < 80A (Point B2 in Fig 4.1), the charger will exit Constant
Current Bulk Stage and enter Constant Voltage Absorption Stage described further at
Section 4.3.2.
12 | SAMLEX AMERICA INC.
Principles of Operation