Valve-Regulated Lead-Acid Batteries (VRLA) Batteries are a type of rechargeable battery commonly known as Sealed Lead Acid (SLA) Battery.The main difference between VRLA and Flooded lead batteries is that the electrolyte in the VRLA batteries is immobilized. This has made the VRLA battery the most popular reserve power battery because the electrolyte is captive, which prevents it from spilling even when the casing is punctured.In VRLA batteries the electrolyte is made captive using Absorbed Glass Mat separators