AGM (Absorbed Glass Mat) and gel batteries are both examples of VRLA (Valve Regulated Lead-Acid) batteries. They are also known as SLA (Sealed Lead-Acid) batteries. These abbreviations refer to the safety valves in the battery’s lid. In common parlance, the term gel battery is used to indicate both AGM and Gel batteries. AGM batteries may also be called “membrane”, “starved electrolyte” or “dry” batteries.