Progress Solar/Wind SLT 700 Series Operator's Manual page 114

Certain battery types benefit from a periodic boost charge to stir the electrolyte, level the cell
voltages, and complete the chemical reactions. Equalize charging raises 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 charging.
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 equalize set-point. If
there is insufficient charge current to reach the equalization voltage, the equalization will terminate
after an additional 60 minutes to avoid over gasing or heating the battery. If the battery requires more
time in equalization, an equalize can be requested using the TriStar Meter or push-button to continue
for one or more additional equalization cycles.
The Equalize set-point is temperature compensated if the RTS is connected; otherwise, voltages set-
points are based on the reference of 25ºC.
.
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 manufac-
turer can recommend the specific gravity or voltage values for your particular battery.
Why Equalize?
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
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
charging 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
to lead sulfation.
Normal charging of the battery can convert the sulfate back to the soft active material if the
is fully recharged. However, a solar charged 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.
38 Operation
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 equalization voltage will reach 16.75 Volts for 12 Volt L-16 batteries (67.0 Volts for 48 Volt
systems) 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 starting an equalization. Replace the Hydro-
caps 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 gasing 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 Equalization 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 charging (12V bat-
tery). Many VRLA batteries, including AGM and gel, have charging requirements up to 14.4V (12V
battery). Depending on the battery manufacturer's recommendation, the "boost" cycle for sealed cells
can be disabled by setting the equalize setting switch to manual, if required.
Battery Charging Settings
Preset TriStar MPPT 150V battery charging options are shown in tables 4-1 and 4-2 below. All voltage
settings listed are for nominal 12 Volt batteries. Multiply the voltage settings by two (2) for 24 Volt bat-
teries or by four (4) for 48 Volt systems.
NOTE: These settings are general guidelines for use at the operator's discretion. The
TriStar MPPT 150V can be set or programmed to charge to virtually any specific
crystals
requirements, but only the battery manufacturer can recommend optimal settings for
their products.
Settings
Switches
4 - 5 - 6
off-off-off
susceptible
off-off-on
off-on-off
off-on-on
battery
on-off-off
on-off-on
on-on-off
on-on-on
1 "Sealed" battery type includes gel and AGM batteries
Battery Absorp. Float Equalize
Type Stage Stage Stage
(Volts) (Volts) (Volts)
1 - Gel 14.00 13.70
2 - Sealed 14.15 13.70 14.40
1
3 - Sealed 14.30 13.70 14.60
1
4 - AGM/Flooded 14.40 13.70 15.10
5 - Flooded 14.60 13.50 15.30
6 - Flooded 14.70 13.50 15.40
7 - L-16 15.40 13.40 16.00
8 - Custom Custom Custom Custom
Table 4-1. Battery charging settings for each selectable battery type
TriStar MPPT Operator's Manual
Absorp. Equalize Equalize
Time Time Interval
(Minutes) (Minutes) (Days)
150
150 60 28
150 60 28
180 120 28
180 120 28
180 180 28
180 180 14
Custom Custom Custom
39