Samlex America SAM-1500C-12 - Manual (Page 9)

6 | SAMLEX AMERICA INC. SAMLEX AMERICA INC. | 7
SECTION 2 | Features, Applications &
Principle of Operation
SECTION 2 | Features, Applications &
Principle of Operation
Fig. 2.2 Battery Charger Stages and Voltage/Current Curves
2 Stage charging
Working of a 2 Stage Charger is explained below. Please refer to Fig 2.2.
2 Stages of Charging are bulk and float Stages. A 2-Stage Charger is able to recharge a
battery to around 80% capacity. This type of charger is used in Backup / UPS applications
where the battery remains charged, is floating most of the times and will discharge at
lesser frequency only during power outages. Charging details are given below:
• The charger’s output voltage will be 13.8V for charging current < the Bulk Charge Current
of 15A.
• If the battery was discharged to a level that draws higher current > the Bulk charge Current
of 15A, the charger will limit the charging current to 15A, its voltage will drop and will be
clamped at the actual battery voltage when charging was started (Points 1 to 2, fig 2.1).
Charging will take place at constant current limit of 15A, the battery voltage will start rising
and the current demand will start reducing. When the current reduces to less than 15A, the
charger will exit current limit / Bulk Charge Stage (Point 2, Fig 2.1) and will output a fixed
float Voltage of 13.8V thereafter (Points 2 to 3 on the Voltage Curve in fig 2.2). battery’s in-
trinsic voltage will continue to rise towards 13.8V and charging current will start to taper off
(Points 2 to 3 on the Current Curve in fig 2.2). When the battery voltage has reached almost
13.8V, it would have charged to around 80% capacity and the current draw will be reduced
to few hundred milliamps (around 0.1% of battery Ah capacity) to compensate self discharge
(Point 3 on the Current Curve in fig 2.2).
• If the discharged level at the time of switching ON was such that the charging current drawn
was < 15A, the charger will not be under current limit and will output Float Voltage of 13.8V
(Points 2 to 3 on the Voltage Curve in fig 3.2). battery’s intrinsic voltage will continue to rise
towards 13.8V and charging current will start to taper off (Points 2 to 3 on the Current Curve
in fig 2.2). When the battery voltage has reached almost 13.8V, it would have charged to
around 80% capacity and the current draw will be reduced to few hundred milliamps (around
0.1% of battery Ah capacity) to compensate self discharge (Point 3 on the Current Curve in
fig 2.2)
Bulk Charge
Stage
Float Charge
Stage
Charger Current Curve
Charger Voltage Curve
Time
Voltage
Curr
en
t
9
10
11
12
13
14
1
1
2
2
3
3
15A
0A
LEGEND
1.
Charging Starts
1 to 2. Bulk Charge Stage: Constant Current = 15A
2.
Exits Bulk & Enters Float
2 to 3. Foat Stage: Constant Voltage = 13.8V
Current Tapers to 0.1% of Ah Capacity
13.8V
5A
10A
20A