- May 07, 2018 -
Valve Regulated Lead Acid (VRLA) Batteries | Also called Sealed Lead Acid (SLA) batteries.
This construction is designed to prevent electrolyte loss through evaporation, spillage and gassing and this in turn prolongs the life of the battery and eases maintenance. Instead of simple vent caps on the cells to let gas escape, VRLA have pressure valves that open only under extreme conditions. Valve-regulated batteries also need an electrolyte design that reduces gassing by impeding the release to the atmosphere of the oxygen and hydrogen generated by the galvanic action of the battery during charging. This usually involves a catalyst that causes the hydrogen and oxygen to recombine into water and is called a recombinant system. Because spillage of the acid electrolyte is eliminated the batteries are also safer.
AGM Absorbed Glass Mat Battery | Also known as Absorptive Glass Micro-Fibre
Used in VRLA batteries the Boron Silicate fibreglass mat which acts as the separator between the electrodes and absorbs the free electrolyte acting like a sponge. Its purpose is to promote recombination of the hydrogen and oxygen given off during the charging process. No silica gel is necessary. The fibreglass matt absorbs and immobilises the acid in the matt but keeps it in a liquid rather than a gel form. In this way the acid is more readily available to the plates allowing faster reactions between the acid and the plate material allowing higher charge/discharge rates as well as deep cycling.
This construction is very robust and able to withstand severe shock and vibration and the cells will not leak even if the case is cracked.
AGM batteries are also sometimes called “starved electrolyte” or “dry”, because the fibreglass mat is only 95% saturated with Sulfuric acid and there is no excess liquid.