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Stage - 1: Bulk Stage. Refer to Fig 4.2B. During the night of the 27th day, the battery
voltage will drop below the Float Transition Voltage Set Point “Vf” (Curve portion A1
to B1), as there is no sun and discharging takes place due to loads that are powered
during the night e.g. night lighting.
When the sun is available in the morning on the 28th day, Equalization is activated
and charging commences in Stage -1, Bulk Stage. During this stage (Curve portion B1
to C1), the Switch is kept at 100% Duty Cycle (ON continuously) and hence, maximum
current equal to the available Short Circuit Current “I
SC
” of the panel is fed to the
battery and the battery voltage starts rising. This is equivalent to Constant Current
Charging. When the battery voltage approaches the Absorption Transition Voltage
Set Point “Va”, it starts gassing. As the voltage rises further towards the Equalization
Voltage Regulation Set Point “Ve”, gassing increases. When the battery voltage
reaches the Equalization Voltage Regulation Set Point “Ve” and is sustained for a
minimum period of around 50 to 55 sec, the controller transitions to Equalization
Stage (Point C1). At the end of the Bulk Stage, the battery is charged to around 80%
capacity. The balance of 20% capacity is restored in the next Equalization Stage.
Stage - 2: Equalization Stage. Refer to Fig 4.2B. The controller enters this stage at point
“C1” from the previous Bulk Stage when the battery voltage reaches the Equalization
Voltage Regulation Set Point “Ve” and is sustained for a minimum period of around
50 to 55 sec. This stage is timed for continuous / cumulative period of 1/2/3 Hours
based on the programmed type of battery. During the Equalization period (Curve
portion C1 to D1), the battery is in overcharge condition, is gassing and bubbling
vigorously and the electrolyte gets stirred up resulting in removal of stratification.
Also, weaker cells are brought up to full charge (equalized).
In this stage, the Switch operates under PWM control by feeding pulsing Short Circuit
Current “Isc” with constantly reducing Duty Cycle (< 100% and > 0%) / average current
to keep the battery voltage constant at the Equalization Voltage Regulation Set Point
“Ve” (Curve portion C1 to D1). This is equivalent to Constant Voltage Charging. This is
an intentional, controlled over charge condition for the battery for 1/2/3 Hrs.
Change over to the next Float Voltage Regulation Set Point “Vf” is possible only after the
battery voltage is held at the selected Equalization Voltage Regulation Set Point “Ve” for
continuous or cumulative period of 1/2/3 Hours depending upon the programmed type of
battery. If “Ve” cannot be maintained continuously / cumulatively for 1/2/3 Hrs, the charger
will NOT exit out of Equalization Stage and transition to Float Stage will NOT take place.
Automatic Equalization
Automatic equalization after interval of 28 days or manual equalization can be selected
using DIP Switch 5 located at the back of the unit (Fig 5.2). Please refer to Fig 4.2B.
NOTE: During Equalization Stage, if the load current is more than the current from
the solar panel, the battery voltage will drop. If the battery voltage drops
around 1V below the Equalization Transition Voltage Set Point “Ve” for around
1 min, the controller reverts to Bulk Stage with 100% Duty Cycle. The front
SECTION 4 |
FEATURES & OPERATION
Summary of Contents for EVO-30AB
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