Absorbed Glass Mat (AGM) Batteries 101

Written By: Randy Anderson Technical Sales & Training Manager

Our busy lives are driving the demand for low maintenance goods and services through the roof; batteries are no exception. AGM or Absorbed Glass Mat batteries fit this category perfectly. These batteries, like regular flooded batteries, contain a series of positive and negative plates. However, unlike regular flooded batteries, the electrolyte solution is absorbed into fine fiberglass mats that separate the positive and negative plates, the battery cover is sealed instead of being vented, and rubber safety relief valves are installed in the cover to prevent damage to the case if they are overcharged.  AGM batteries are now manufactured in a wide range of sizes and are available to replace almost all automotive, powersport and deep cycle footprints with very similar or greater performance.

Automotive applications are rapidly changing from flooded to AGM technology. This change is driven by the high electrical demand of today’s vehicles. They not only require battery power to start the engine multiple times during a normal drive but the battery must also supply power while the engine if off to operate all the normal 12 volt loads.  This has resulted in requirements for AGM batteries that are a hybrid of starting and deep cycle characteristics. This enables the battery to withstand the increased workload that it has to endure. Today’s vehicles are also more compact which means space under the hood is at a premium. This is perfect for an AGM battery because they can be buried within the engine compartment or installed in the trunk with no worries about maintenance, off-gassing or leak damage.

Many electric vehicles such as golf carts, floor scrubbers and remote electric vehicles have switched to AGM technology for many of the same reasons.  With the introduction of deep cycle and traction battery sizes to match those of flooded, we have seen a huge shift in the EV market moving towards no maintenance products.  Much of this demand is due to health and safety. With flooded batteries, many schools, hospitals and government institutions now require that only AGM batteries be used in floor care equipment since they poses no immediate health risk from hydrogen gas during charging or dangerous spills of sulfuric acid.

One of the markets to first adopt the use of AGM batteries is the UPS or Uninterruptable Power Supply market. AGM batteries are a natural fit in these applications as batteries are typically installed in small enclosures or cabinets where you would not normally be able to install traditional flooded batteries, due to the risk of corrosion to electronics and combustible hydrogen gas emitted during charge.  The internal components of AGM batteries designed for UPS applications are very similar in design to automotive starting batteries, plates are thinner than deep cycle batteries with heavy inter-cell lugs to withstand high amperage draws for short periods of time with the ability to recharge quickly.

When choosing an AGM battery for an application make sure that you’re getting the right battery for the job. These batteries all look similar but may not perform as expected or have shorter life if not designed for the application.  Charging AGM batteries should also be taken into consideration as they are much more sensitive to overcharge and higher voltage than flooded batteries. Charging these batteries with a charger designed for flooded or gel batteries will almost always shorten the life of the battery so always consult the manufacturers recommended charging specifications to ensure your AGM battery meets its performance requirements.

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