Samlex Solar SCC-30AB Mode D'emploi page 31

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 for a 12V battery.
Equalization
Caution!
• Equalization is carried out only for non-sealed / vented / flooded / well cell lead acid
batteries.
• Do not equalize sealed / VRLA type of AGM / Gel cell batteries.
• Top up the electrolyte with distilled water after completion of equalization.
Routine equalization cycles are often vital to the performance and life of a battery
— particularly in a solar system. During battery discharge, sulfuric acid is consumed
and soft lead sulfate crystals form on the plates. If the battery remains in a partially
discharged condition, the soft crystals will turn into hard crystals over time. This
process, called "lead sulfation," causes the crystals to become harder over time and
more difficult to convert back to soft active materials.
Sulfation from chronic undercharging of the battery is the leading cause of battery
failures in solar systems. In addition to reducing the battery capacity, sulfate build-up
is the most common cause of buckling plates and cracked grids. Deep cycle batteries
are particularly susceptible to lead sulfation.
IntroductIon & features
4
31