A valve regulated lead‐acid (VRLA) battery, commonly known as a sealed lead-acid (SLA) battery, is a type of lead-acid battery characterized by a limited amount of electrolyte ("starved" electrolyte) absorbed in a plate separator or formed into a gel, proportioning of the negative and positive plates so that oxygen. The first lead-acid gel battery was invented by Elektrotechnische Fabrik Sonneberg in 1934. The modern gel, or VRLA, battery was invented by Otto Jache of in 1957. The first AGM cell was. Each cell in a VRLA battery has a pressure relief valve that will activate when the battery starts building pressure of hydrogen gas, generally a result of being recharged. The cell covers typically have gas diffusers built into them, which. Originally a kind of gel battery was produced in the early 1930s for portable valve (tube) radio LT supply (2, 4, or 6 V) by adding silica to the sulfuric acid. By this time, the glass case was being replaced by celluloid, and later, in the 1930s, other plastics. Earlier "wet". VRLA gel and AGM batteries offer several advantages compared with VRLA flooded lead-acid and conventional. The battery can be mounted in any position, since the valves only operate on over-pressure faults. Since the battery system is designed to be. Lead-acid cells consist of two plates of lead, which serve as, suspended in an consisting of diluted. VRLA cells have the same chemistry except that the electrolyte is immobilized. In AGMs, this is accomplished with a. AGM batteries differ from flooded lead-acid batteries in that the electrolyte is held in the glass mats, as opposed to freely flooding the plates. Very thin are woven into a mat to increase the surface area enough to hold a sufficient amount of electrolyte on. Many modern motorcycles and (ATVs) on the market use AGM batteries to reduce the likelihood of acid spilling during cornering, vibration, or after accidents, and for packaging reasons. The lighter, smaller battery can be installed at an odd angle if needed.