AGM (Absorbed Glass Mat) Technology; An absorbed glass mat (AGM) battery has the electrolyte absorbed in fiber-glass mat separators. After the battery is filled and sealed, AGM batteries do not require addition of electrolyte or water and vent less gas than flooded lead-acid batteries. The reduced venting is an advantage since they can be used in confined spaces. Premium AGM batteries are BEST because: - they have the slowest self discharge -they have improved life-cycle performance -they have extreme vibration resistance