SamplexPower SAM Series, Owner'S Manual

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SAMLEX AMERICA INC. | 11
iii. The “Standing Voltage” of a battery is the terminal voltage of the battery after it has
“rested” for at least 4 hours (no charging or discharging during resting period of 4
hours). The Standing Voltages of 12V Lead Acid battery are as follows (See Fig 2.2):
- fully Charged: Around 12.8V
- fully discharged: Around 11.8V
iv. Before the charger is switched ON (before Point 1 in Fig 2.3), the battery is almost
completely discharged to “Standing Voltage” of around 11.8V (Fig 2.2) and its inter
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nal resistance is, say 16 milli ohm. Assuming 4 milli ohm of battery wire resistance, a
resistance of 20 milli ohm will be seen by the charger when it is initially switched oN.
When the charger is switched ON (Point 1 in Fig 2.3), 13.8 V from the charger is fed
to the battery. Voltage difference of 2.0V (13.8V-11.8V) will initially TRY to drive very
large charging current of around 100A into the battery (2.0V ÷ 20 milli Ohm = 100A).
However, the charger will limit the current to 15A will enter Current Limit Condition
as explained at paragraph (i) above and its voltage will be clamped to the actual bat
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tery voltage i.e. 11.8V. This is the start of the “bulk Charge Stage”
v. Continuous15A constant current charging in the “Bulk Charge Stage” (Points 1 to 2
of fig 2.3) will slowly raise the battery voltage. As the battery voltage rises, the volt-
age difference between the charger’s float Stage Voltage setting of 13.8V and the
battery’s actual voltage reduces. The internal resistance of the battery also reduces.
When the battery voltage rises to around 13.6V, the charging current will reduce
below 15A and the charger will exit Current Limit Condition - its voltage will rise
to constant, regulated Float Voltage of 13.8V (Point 2 in Fig 2.3). At this point, the
charger will exit the constant current “Bulk Charge Stage” and enter the constant
voltage “float Charge Stage”.
vi. During the “Float Charge Stage” (Points 2 to 3 in Fig 2.3), the battery is charged at
constant voltage of 13.8V. The charging current tapers from 15A to low steady state
Float Charge Current of around 0.25% of the Ampere Hour (Ah) capacity of the bat
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tery (Point 3 in Fig 2.3). At 13.8V, the battery is charged to around 80% of its rated
capacity at C/10 Charge Rate (Fig 2.2).
SeCTIOn 2 | Features, Applications &
Principle of Operation