Operation
ProStar MPPT Operator’s Manual
41
40
4.0
the battery voltage above the standard absorption voltage
so that the electrolyte gases. The green SOC LED will blink
rapidly two (2) times per second during equalization charg-
ing. The duration of the equalize charge is determined by
the selected battery type. See table 4-1 in this section for
more details. The
Equalization Time
is defined as time spent
at the equalization set-point. If there is insufficient charge
current to reach the equalization voltage, the EQ will termi-
nate after an additional 60 minutes to avoid over gassing
or heating of the battery. If the battery requires more time
in equalization, with non-metered versions, manual EQ can
be activated using the push-button (see Section 4.5) to
continue for one or more additional EQ cycles. The Prostar
MPPT meter, or MSView software, can also be used to
program EQ timing and duration.
The Equalization set-point is temperature compensated
through either the on-board local temperature sensor, or an
optional Remote Temperature Sensor (RTS), if connected.
Why Equalize?
Routine equalization cycles are often vital to the perfor-
mance 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 bat-
tery 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.
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 of sulfate crystals.
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 an 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.
Preparation for Equalization
First, confirm that all of the system loads are rated for the
equalization voltage. Consider that at 0°C (32°F) the equal-
ization voltage will reach 16.75 volts for L-16 batteries with
a temperature sensor installed. Disconnect any loads at risk
of damage due to the high input voltage.
If Hydrocaps are used, be sure to remove them before start-
ing an equalization. Replace the Hydrocaps with standard
battery cell caps. The Hydrocaps can get very hot during an
equalization. Also, if Hydrocaps are used, the equalization
should be set for manual only (DIP switch #7 is Off).
After the equalization is finished, add distilled water to each
cell to replace gassing losses. Check that the battery plates
are covered.
Equalize a Sealed Battery?
The
Battery Charging Settings
table (see table 4-1 in this
section) shows two sealed battery settings with an Equal-
ization cycles. These are minimal “boost” cycles to level
individual cells. This is not an equalization, and will not vent
gas from sealed batteries that require up to 14.4V charg-
ing (12V battery). Many VRLA batteries, including AGM and
