14 | SAMLEX AMERICA INC.
SAMLEX AMERICA INC. | 15
SECTION 4 |
Operation
4.4.1.1 Stage 1 - Bulk Stage
Please refer to Fig 4.1
This is almost a constant current stage. During this stage, the Mosfet Switch is kept at 100%
Duty Cycle (
ON continuously
) and hence, maximum current equal to the available instantaneous
Short Circuit Current "Isc" of the solar panel(s) / sola array is fed to the battery and the battery
voltage starts rising. When the voltage rises to the Absorption Voltage “Va”, the controller tran-
sitions to Absorption Stage. 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 Absorption Stage.
4.4.1.2 Stage 2 - Absorption Stage
Please refer to Fig 4.1
The controller enters this stage from the previous Bulk Stage when the battery voltage rises to the
Absorption Stage Voltage “Va” which is internally set as follows:
- “Va” for 12V battery: 14.4V for Sealed Lead Acid (
AGM - Absorbed Glass Mat
)
- “Va” for 24 V battery: 28.8V for Sealed Lead Acid (
AGM - Absorbed Glass Mat
)
This stage is timed for 2 Hrs - either continuous or cumulative.
This is a constant voltage stage and the Mosfet Switch operates under PWM control by feeding
pulsing Short Circuit Current “Isc” with constantly reducing Duty Cycle (< 100% to > 0%) /
average current to keep the battery voltage constant at the Absorption Stage Voltage “Va”. This
is an intentional, controlled over voltage condition for the battery for 2 Hrs. This is necessary to
return the balance 20% of the capacity. At this voltage, the battery starts gassing (
evolution of
Hydrogen and Oxygen due to electrolysis of water in the electrolyte
) and hence, it is necessary to
exit this stage as soon as 100% capacity is restored. If this over voltage condition is allowed to
continue after 100% recharging, the battery will be damaged due to effects of overcharging like
overheating, loss of water (
Flooded Batteries
), corrosion of the Positive plates and excessive build
up of pressure resulting in acid spillage due to opening of pressure activated relief valves (S
ealed
Batteries
). The balance of 20% of the battery capacity is restored in this stage. As the battery
capacity rises from 80% to 100%, the PWM control tapers the current by continuously reducing
the Duty Cycle from < 100% to > 0%.
Change over to the next Float Stage Voltage “Vf” (
13.8V for 12 V battery and 27.6V for 24V
battery
) is possible only after the battery voltage is held at the selected Absorption Stage Voltage
“Va” for continuous or cumulative period of 2 Hours. If Absorption Stage Voltage “Va” cannot be
maintained continuously / cumulatively for 2 Hr, transition to Float Stage
WILL NOT
take place.
4.4.1.3 Stage 3 - Float stage
Please refer to Fig 4.1
The controller enters this stage from the previous Absorption Stage after the battery voltage is held
at the selected Absorption Stage Voltage “Va” for continuous or cumulative period of 2 Hours.
This is also a constant voltage stage and the Mosfet Switch operates under PWM control by
feeding pulsing, instantaneous Short Circuit Current “Isc” with very low Duty Cycle of > 0%
to < 10% to keep the battery voltage constant at the Float Stage Voltage “Vf” (
13.8V for 12V
battery and 27.6V for 24V battery
). During this stage, the battery is 100% charged and a very
low “Trickle Charge” of around 0.1% of the Ah Capacity is required to be fed to the battery to
compensate for self-discharge. The battery can be left at this stage for prolonged period of time.
Содержание MSK-20A
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