This is straight out of the owner's manual:
page 33
TriStar MPPT Operator’s Manual
FLOAT Stage
After the battery is FULLY charged in the Absorption stage, the TriStar MPPT 150V reduces the battery voltage to the Float voltage set-point. 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 float stage provides a very low rate of maintenance charging while reducing the heating and gassing of a FULLY charged battery. The purpose of float is to protect the battery from long-term over charge. The green SOC LED will blink once every two (2) seconds during Float charging.
Once in Float stage, loads can continue to draw power from the battery. In the event that the system load(s) exceed the solar charge current, the controller will no longer be able to maintain the battery at the Float set-point. Should the battery voltage remain below the Float set-point for a cumulative 60 minute period, the controller will exit Float stage and return to Bulk charging.
The Float set-point is temperature compensated if the RTS is connected.
EQUALIZE Stage:
WARNING: Risk of Explosion; Equalizing vented batteries produces explosive gases. The battery bank must be properly ventilated.
CAUTION: Equipment Damage; Equalization increases the battery voltage to levels that may damage sensitive DC loads. Verify all system loads are rated for the temperature compensated Equalize voltage before beginning an Equalization charge.
CAUTION: Equipment Damage; 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.
page 34
Operation
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 gasses. 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 gassing 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.
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.
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 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.
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.
... context is everything. If the OP's bank is being chronically undercharged, doing a 14.9v abs charge every few days is not going to remove the sulfation buildup / stratification. If they are being fully charged regularly, then unequal SG readings and/or unequal individual battery voltage readings are an indication a proper EQ'ing is in order.
