Absorbed Glass Mat batteries are constructed differently than the traditional flooded battery. This write-up covers mainly the Concorde Sun-Xtender AGM's, but also applies to most other brands of deep cycle AGM batteries. In AGM batteries (also called starved electrolyte), there is a thin ultra-fine fiberglass mat sandwiched between the plates that are saturated with battery acid to about 95% of what they can hold. This mat is then packed in between the plates and slightly compressed, then welded/soldered in place. Because the plates and mats are packed fairly tight, they are almost immune to vibration