<P> As with lead - acid batteries to maximize the life of AGM battery is important to follow charging specifications and a voltage regulated charger is recommended . and also there is a correlation between the depth of discharge (DOD) and the Cycle life of the battery, with differences between 500 and 1300 cycles depending on depth of discharge . </P> <P> Originally a kind of gel cell was produced in the early 1930s for portable valve (tube) radio LT supply (2, 4 or 6V) by adding silica to the sulfuric acid . By this time the glass case was being replaced by celluloid and later in 1930s other plastics . Earlier "wet" cells in glass jars used special valves to allow tilt from vertical to one horizontal direction in 1927 to 1931 or 1932 . The gel cells were less likely to leak when the portable set was handled roughly . </P> <P> A modern gel battery (also known as a "gel cell") is a VRLA battery with a gelified electrolyte; the sulfuric acid is mixed with fumed silica, which makes the resulting mass gel - like and immobile . Unlike a flooded wet - cell lead - acid battery, these batteries do not need to be kept upright . Gel batteries reduce the electrolyte evaporation, spillage (and subsequent corrosion problems) common to the wet - cell battery, and boast greater resistance to shock and vibration . Chemically they are almost the same as wet (non-sealed) batteries except that the antimony in the lead plates is replaced by calcium, and gas recombination can take place . </P> <P> The modern gel formulation and large scale production was from Otto Jache's and Heinz Schroeder's U.S. Patent 4,414,302 assigned to the German company Accumulatorenfabrik Sonnenschein GmbH . With gel electrolyte the separator was no longer such a critical, hard - to - make component, and cycle life was increased, in some cases dramatically . Shedding of active material from the plates was reduced . </P>

What is the difference between vrla and lead acid battery