Absorbed glass mat (AGM) Battery is a class of VRLA battery in which the electrolyte is held on the glass mat separator by way of capillary action.

AGM batteries are just like flooded lead acid batteries, except the electrolyte is being held in the glass mats, as opposed to freely flooding the plates. Very thin glass fibers are woven into a mat to increase surface area enough to hold sufficient electrolyte on the cells for their lifetime. The fibers that comprise the fine glass fibers glass mat do not absorb nor are affected by the acidic electrolyte they reside in. These mats are wrung out 2-5% after being soaked in acids, prior to manufacture completion and sealing. The AGM battery can now accumulate more acid than is available, and never spill a drop.

The plates in an AGM battery may be any shape. Some are flat, others are bent or wound. AGM batteries, both deep cycle and starting, are built in a rectangular case to BCI battery code specifications. Optima Battery builds a patented cylindrical AGM series of batteries that are fashioned to fit the same BCI battery size specifications as any other battery.

Advantages of AGM VRLA Battery

All AGM batteries boast some significant performance enhancement over traditional flooded lead acid cells:

  • AGM construction allows purer lead in the plates as each plate no longer needs to support its own weight based on the sandwich construction with AGM matting. Traditional cells must support their own weight in the bath of acid.
  • AGM Batteries are un-spillable, keeping lead and acid out of the environment.
  • AGM Batteries have high specific power or Power Density, holding more roughly 1.5x the AH capacity as flooded batteries based on purer lead.
  • AGM Batteries have very low internal resistance allowing them to be charged and discharged quite rapidly without creating heat based on construction and pure lead.
  • AGM Batteries are maintenance free, never requiring a watering over the life of the battery.
  • AGM Batteries will not corrode their surroundings as the acid is encapsulated in the matting.
  • AGM Batteries will not freeze and crack, operating well below 0°F or C.
  • AGM Batteries can be UL, DOT, CE, Coast Guard, and Mil-Spec approved to isolate HAZ-MAT.
  • AGM Batteries are exceptionally vibration resistant based on the sandwich construction.

Disadvantages of AGM VRLA Battery

  • Cost. AGM automobile batteries for example, are typically about twice the price of flooded-cell batteries in a given BCI size group.
  • AGM Batteries boast up to a 10 year lifespan, but must be sized to discharged less deeply than the traditional flooded batteries.
  • AGM Battery depth of discharge for optimal performance 50% Flooded Battery depth of discharge for optimal performance 80%
  • AGM Batteries do not tolerate overcharging. Overcharging burns electrolyte, which is unable to be replaced, leading to premature failure.