Maintaining AGM batteries is easier than maintaining flooded cell batteries. The one thing that AGM batteries do not like is high voltage charging. Things like "equalizing", "conditioning", or lots of other labels for raising the voltage causes venting. Venting causes a permanent loss of capacity.
The preferred charging profile is the same for flooded and AGM. Many of even the simplest high quality chargers automatically provide the optimum profile. WFCO chargers are simple to operate. There are no complected settings, but they provide a precise microprocessor controlled charge.
For deeply discharged lead acid batteries, supply up to 14.4 volts. For batteries with limited SoC to start with, use 13.6 volts. Maybe 70% SoC should start at 13.6
As charging progresses, current decreases. Decrease voltage to prevent excessive production of hydrogen gas. 13.6 volts is typical after maybe 4 hours.
Both AGM and Flooded batteries produce more hydrogen from the water at high voltages. You can add water to flooded, but not AGM. If your AGM batteries show signs of venting, the voltage is too high for too long.
Higher voltage in late stages produce higher current flow. Many people monitor this and try to "fool" their chargers to increase flow. The batteries do not absorb the extra current, they only produce hydrogen from the excess.
AGM batteries are often designed to absorb current faster than many flooded designs. Four hours at 14.4 volts will often supply power to bring deeply discharged batteries up to 90% Soc.
Periodically you must continue charging at 13.6 volts for another 10 to 14 hours. This is necessary to redissolve all the sulfate produced when discharging. If you left the batteries discharged for a while, more hours are required. The longer the sulfate is left in place, the harder it is to remove it.
Leaving lead acid batteries discharged for 3 months may make the sulfate impossible to redissolve.
Battery University https://batteryuniversity.com/articles
How does the Lead Acid Battery Work?
https://batteryuniversity.com/articl...d-battery-work
How do battery chargers work
https://batteryuniversity.com/articl...-chargers-work
How to Charge and When to Charge?
https://batteryuniversity.com/articl...when-to-charge
Measuring State of Charge (SoC)
There are basically 3 voltage profiles for lead acid batteries. They are Charging, Discharging, and Static.
Static voltage is measured when there is no charging or discharging for a while. Usually 3 hour rest is good for highly accurate measurement. See table below.
Charging profile depends on the charger. Voltage starts at the static level and rises to the preset voltage from the charger. It is always higher than static.
Discharging is always lower than static. The faster the discharge, the lower the voltage. Voltage will rise to static level when discharge stops.
After 3 hours rest.
Lead Acid Batteries SoC
100% 12.7
90% 12.5
80% 12.42
70% 12.32
60% 12.2
50% 12.06
40% 11.9
30% 11.75
20% 11.58
10% 11.31
0% 10.5
This is a typical table. My AGM batteries hold 13.0 volts for weeks when fully charged and disconnected.
Linear Mode
