Samlex America MSK-10A User Manual

Page 14

14 | SAMLEX AMERICA INC.

SeCtIOn 4 |

Operation

voltage is compensated by raising the average current by raising the Duty Cycle. These
fast updates on battery voltage measurements and Duty Cycle corrections ensure charg-
ing of the battery at the specified Voltage regulation Set Point with minimum voltage
deviation.

optimum Pwm frequency: The PWM frequency can range from tens of Hz to around
1000 Hz. At higher frequencies, the time period between the cycles is lesser and is not
sufficient to complete the electro-chemical reactions. At lower frequencies, the rise
times of the charging pulses are lower which results in higher gas bubble formation
resulting in lowering of active surface area and increase of internal impedance. In
MSK-10A, frequency of 25 Hz is used for optimum charging performance.

benefits of pulsing nature of charging current during Pwm: During PWM voltage regu-
lated stages of Absorption (boost), float and equalization, Duty Cycle is lower and the
charging current is in the form of pulses. Pulsing charging current allows some oxygen
and Hydrogen generated during charging chemical reactions to be chemically combined
again and then absorbed. This eliminates concentration polarization and ohm polariza-
tion and reduces the internal pressure of the battery. Consequently, charging process is
smoother and more capacity is returned to the battery. further, pulsing current provides
more time to react, which reduces the gassing volume and improves the absorption rate
of charging current.

LeGenD:

Va - Absorption (boost) Stage PWM Voltage regulation Set Point
Ve - equalization Stage PWM Voltage regulation Set Point
Vf - float Stage PWM regulation Voltage Set Point

Please refer to figs 4.1A and 4.2b above
(Please note that these figures show curves for 12v flooded battery).

DAY

TIME

Fig 4.1A -
Normal Charging Cycle (12V, Flooded)
Bulk Absorption (Boost) Float

Fig 4.1B -
Equalization Charging Cycle (12V, Flooded)
Bulk Equalization Float

TIME

DAY

TER

Y V

STAGE 1

BULK

STAGE 2

ABSORPTION

(BOOST)

STAGE 3

FLOAT

NIGHT

NIGHT NIGHT