Flooded lead-acid batteries are what you typically find in a gasoline powered car. An AGM battery is a 12-volt car battery that can be used as an alternative to traditional flooded lead-acid batteries. The Valve Regulated Lead-acid batteries include AGM and gel technology. These are also known as SLA.
AGM
AGM is an acronym for Absorbent Glass Material. AGM batteries hold and suspend the electrolyte mixture like a sponge with tiny glass fibers while maintaining evenly distributed contact with the active lead materials on the plates. The electrons flow in a series circuit through six cells, each of which runs at approximately 2 volts for a total of 12 volts.
Charging: The charging voltages are the same as for any standard battery, there is no need for any special adjustments or problems with incompatible chargers or charge controls. However, AGM batteries are sensitive to overcharging and undercharging and improper charging can reduce overall capacity. You can buy battery chargers with a AGM setting that is better suited to these batteries. It is recommended to use a battery charger designed for AGM batteries.
AGM batteries improve on a major flaw of flooded batteries, spillage.
The AGM lead-acid batteries will be labeled as AGM, or Absorbed Glass Mat, or dry cell, sealed regulated valve, non-spillable, or valve-regulated on the label. AGM batteries are also called starved electrolyte’, or membrane batteries.
Gel-Cell
Gel batteries use a different method to keep the electrolyte in place. Gel batteries typically use a chemical agent such as silica to create a gel-like substance that allows for less movement. Both gel and AGM batteries are considered Valve-Regulated Lead-Acid (VRLA) batteries. The electrolyte in Gel batteries have a look of jelly.
Charging: Never charge a gel cell battery with a conventional lead acid battery charger. These batteries are finicky and are easily destroyed by improper charging. They must be charged at a slower rate(C/20) to prevent excess gas from damaging the cells. These batteries are never to be "fast charged."
Gel-filled lead-acid batteries come with a Geld filled’ label on the battery.
Comparison
The gel batteries can work in warmer temperatures, while AGM batteries work efficiently in cold temperatures.
According to the depth of discharge, temperature, maintenance, and how often and how deep cycled, the lifespan of agm batteries is around 4 to 8 years and gelled deep cycle battery is around 2 to 5 years.