reviewed_by: Quality Department AGM Battery: Absorbent Glass Mat Car Batteries Explained An AGM (Absorbent Glass Mat) battery is a valve-regulated lead-acid (VRLA) battery in which the sulfuric acid electrolyte is absorbed into a compressed borosilicate glass-fiber mat between the plates. The acid is immobilized, so the battery is sealed, spill-proof, and mountable in any orientation…