Samlex Solar SCC-30AB Mode D'emploi page 32

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IntroductIon & features
Normal charging of the battery can convert the sulfate back to the soft active
material if the battery is fully recharged. However, a solar battery is seldom completely
recharged, so the soft lead sulfate crystals harden over a period of time. Only a long
controlled overcharge, or equalization, at a higher voltage can reverse the hardening
sulfate crystals.
In addition to slowing or preventing lead sulfation, there are also other benefits of
equalization of the solar system battery. These include:
Balance the individual cell voltages
Over time, individual cell voltages can drift apart due to slight differences in the cells.
For example, in a 12 cell (24V) battery, one cell may be less efficient in recharging to
a final Absorption Voltage of 28.8 volts (2.4 V/cell). Over time, that cell only reaches
1.85 volts, while the other 11 cells charge to 2.45 volts per cell. The overall Absorption
Voltage is 28.8V, but the individual cells are higher or lower due to cell drift.
Equalization cycles help to bring all the cells to the same voltage.
Mix the electrolyte
In flooded batteries, especially tall cells, the heavier acid will fall to the bottom of the
cell over time. This stratification of the electrolyte causes loss of capacity and corrosion
of the lower portion of the plates. Gassing of the electrolyte from a controlled
overcharging (equalization) will stir and remix the acid into the battery electrolyte.
NOTE: Excessive overcharging and gassing too vigorously can damage the battery
plates and cause shedding of active material from the plates. An equalization that is
too high or for too long can be damaging. Review the requirements for the particular
battery being used in your system.
When to Equalize
The ideal frequency of equalizations depends on the battery type (Lead Calcium,
Lead-Antimony, etc.), the depth of discharging, battery age, temperature, and other
factors.
One very broad guide is to equalize flooded batteries every 1 to 3 months or every
5 to 10 deep discharges. Some batteries, such as the L-16 group, will need more
frequent equalizations.
The difference between the highest cell and lowest cell in a battery can also indicate
the need for equalization. Either the specific gravity or the cell voltage can be
measured. The battery manufacturer can recommend the specific gravity or voltage
values for your particular battery. Normally, if the cell voltage differential is > 0.2 V,
equalization may be necessary.
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