Samlex America MSK-10A - Manual (Page 16)

16 | SAMLEX AMERICA INC.
SeCtIOn 4 | Operation
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
Transition Voltage Set Point “Va”. This is an intentional, controlled over voltage condi-
tion 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 continues
after 100% recharging, the battery will be damaged due to effects of overcharging
like overheating, loss of water, corrosion of the Positive plates and excessive build up
of pressure resulting in acid spillage due to opening of pressure activated relief valves
(sealed 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 Transition Voltage Set Point “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 (boost) Transition Voltage Set Point “Va” for continuous or
cumulative period of 2 Hours. If Absorption (boost) Transition Voltage Set Point “Va”
cannot be maintained continuously / cumulatively for 2 Hr, transition to float Stage
WiLL not take place.
STATUS LeD “bATT” is steady Green during this stage
NoTe: During Absorption (boost) Stage, if the load current is more than the current
from the Pv Panel(s), the battery voltage will drop. If the battery voltage drops to 13.2v
for 12v battery and 26.4v for 24v battery, the controller reverts to Stage 1: bulk Stage.
Pwm DuTy Cycle is changed to 100% and STATuS leD “bATT” changes to steady Green
thereafter.
Stage 3 - float stage
The controller enters this stage from the previous Absorption (boost) Stage after the
battery voltage is held at the selected Absorption (boost) Transition Voltage Set Point
“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 Transition Voltage
Set Point “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 Ca-
pacity 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.
STATUS LeD “bATT” is steady Green during this stage