SamplexPower SEC-1250UL Guide D'utilisation page 9

SECTION 4 |
4.2 BATTERY IMPEDANCE AND CHARGING CURRENT
The internal impedance of a healthy battery is very low - in tens of milli Ohms. The
impedance is higher in discharged condition. Average impedance may be assumed as 20
milli Ohm or 0.02 Ohm.
When the charger is delivering a constant voltage under Absorption/ Float Stages (is
supplying current < its Bulk Stage Current value), the charging current drawn by the bat-
tery can be roughly calculated as follows:
Charging current = (Charger Voltage - Intrinsic battery voltage) ÷ Internal resistance (0.02 Ohm)
For example, when SEC-1250UL is in the Bulk Charge Stage 1 (Fig 4.1), its output voltage
is set at 13.5 VDC. When a battery discharged to say 10.5V is charged, it will try to draw
very large current = (13.5V - 10.5V) ÷ Internal resistance (0.02 Ω) = 150A. SEC-1250UL
will, however, limit this current to 50A.
4.3 CHARGING STAGES AND CHARGING CURVES
These chargers are designed to provide the following 3-Stage / 2-Stage charging algo-
rithms for Lead Acid Batteries (Flooded / AGM / Gel Cell types)
• 3-Stage Charging Algorithm: Bulk Stage " absorption Stage " Float Stage for Lead
Acid Batteries
• 2-Stage Charging Algorithm: Bulk Stage " Float Stage. When 2-Stage Charging
Algorithm is selected (Section 7.4), the Absorption Stage of the 3-Stage Charging
Algorithm is bypassed. This algorithm is suitable for operation as a Power Supply
(Section 8.3) or as a DC UPS (Uninterruptible Power Supply) in conjunction with a
battery (Section 8.4)
The type of Lead Acid Battery and the desired charging algorithm can be selected with
the help of DIP Switches S1 and S2 (7 in Fig 3). For details, please refer to Sections 7.4
Charging Curves for 3-Stage Charging Algorithm are given at Fig 4.1 for SEC-1250UL and
at Fig 4.2 for SEC-2425UL
Details of the 3 stages of charging operation are explained at Sections 4.3.1 to 4.3.3
Principles of Operation
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