Samlexpower SEC - 1215A Owner's manual - page 5
CHARGING STAGES
NOTE ! –
VOLTAGE READINGS ON NO LOAD
The output has one common negative terminal and three positive terminals for charging 3
banks of batteries. Each positive terminal has an internal isolating diode in series which has a
forward voltage drop of 0.8 to 1.1 V. On no load ( that is when no battery or other dc load is
connected to any of the 3 terminals ) , the voltage reading will read 0.8 to 1.1 V higher than
the specified float voltage. Note that the specified float voltage is at a load of 1 A. Also, the
voltage on the terminals not connected to the load ( for example, when one bank of battery is
connected to one positive terminal, the other 2 positive terminals will remain disconnected )
will read 0.8 to 1.1 Volt higher than the voltage of the loaded terminal.
These chargers can be manually selected to operate in 3 stage or 2 stage modes ( Please see
“Selecting the Type of Battery and Charging Stages” at page 7) . The charging stages are
described below :
STAGE 1 -CONSTANT CURRENT OR BULK CHARGE STAGE
When the battery is low, it will try to draw larger charging current. The charger senses the current
draw and limits this to the maximum permissible value (15A for SEC-1215A / SEC-2415A and 30A
for SEC-1230A). Bulk charging takes place at this constant current. In this condition of constant
current, the voltage measured at the charger or battery terminals will be the battery’s own voltage.
The constant current injected into the battery starts restoring the battery capacity and it’s voltage
starts rising. When this voltage approaches the threshold of battery “gassing”, termed “boost or
absorption voltage”, the charger automatically switches over to Stage 2 - “Boost or Absorption
Stage”. The value of this voltage depends upon the type of battery being charged (See Dip Switch
Settings). By this time, approximately 80% of the battery capacity will normally have been restored
(Note: The percentage capacity restored till the point the battery reaches the boost or
absorption voltage is inversely proportional to the value of the bulk charge current.)
STAGE 2 - CONSTANT VOLTAGE BOOST OR ABSORPTION STAGE
As explained above, when the battery voltage approaches the point where battery “gassing” can
begin, the charger automatically switches over to the “Boost or Absorption Stage”. The charger
applies a constant voltage whose value depends upon the type of battery selected ( See Dip Switch
Settings ). This controlled overcharge restores the balance 20% of the capacity in a minimum
amount of time. As the capacity is fully restored, the charging current starts reducing. When the
current reduces below the preset threshold, the charger automatically switches to the “Float or
Maintenance Stage”.
STAGE 3 – CONSTANT VOLTAGE , FLOAT OR MAINTENANCE CHARGING
STAGE
As explained above, as the charging current drops below the preset threshold ( 1.5 to 2 amps for
SEC-1215A / SEC-2415A and 2.5 A to 3 A for SEC-1230A ), it signals that the battery is 100%
charged. In this “Float or Maintenance Charging Stage”, the charger outputs a constant voltage of
13.5 V for 12 V system and 27 V for 24 V system. This helps in maintaining 100% capacity of the
battery and also compensates for self discharge. The battery can remain connected in this stage
indefinitely without the risk of overcharging or excessive loss of electrolyte.
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