Translations:Fonctionnement, entretien et régénération de batteries au plomb/44/en

AGM batteries are a type of sealed/VRLA battery, in which the electrolyte is a liquid but it is held in place in a fiberglass blotter, and hence its name: Absorbed Glass Material.
View the inside of an AGM battery

Advantages Disadvantages
Maintenance-free with minimal release of gas They do not perform well in hot conditions (loss of electrolyte in the form of gas at higher temperatures) A temperature above 49°C (120°F) is very dangerous for the battery life.
They maintain the electrolyte homogeneity well. They are sensitive to overcharging and high voltages (loss of electrolyte in the form of gas) /
Withstand colder temperatures well because of their homogeneous electrolyte (Since the electrolyte is held in the glass mat separators, it won't expand when frozen like it will in a flooded battery Limited lifespan (high acidity level required)
Allows high peak currents (CCA) to pass
Shock-resistant (Vibration-resistant) (Because of the fibre glass mats are woven tightly and the plates are packed tightly, making them immune to vibrations)
Low self-discharge (1-3% per month)