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4
INTRODUCTION & FEATURES
Four Stages of Solar Charging
Fig. 4.1 represents the 4 stages of charging used in the SCC-30AB
V
O
LT
A
G
E
TIME
NIGHT NIGHT
4
FLOAT
3
EQUALIZE
2
PWM
ABSORPTION
1
BULK
CHARGING
Fig. 4.1 Solar Charging Stages
1. Bulk Charging: In this stage, the battery will accept all the current provided by the
solar array. The value of this current will be equal to the Short Circuit Current Isc of
the solar array
2. PWM Absorption: When the battery reaches the Absorption Voltage, the PWM
begins to hold the voltage constant. This is to avoid over-heating and over-gassing
the battery. The current will taper off to safe levels as the battery becomes more fully
charged.
3. Equalization : Many batteries benefit from a periodic boost charge to stir the
electrolyte, equalize the cell voltages, and complete the chemical reactions (See
additional details on Equalization given below)
4. Float : When a battery becomes fully charged, dropping down to the float stage
will provide a very low rate of maintenance charging while reducing the heating
and gassing of a fully charged battery. When the battery is fully recharged, there can
be no more chemical reactions and all the charging current is turned into heat and
gassing. The purpose of float is to protect the battery from long-term overcharge.
From the PWM absorption stage, charging is dropped to the float voltage. This is
typically 13.4V.