Absorbent Glass Mat (AGM) – this is a technological advancement that permits the acid found in a lead acid battery to be contained in fine fiberglass mats placed in between the positive and negative plates. By doing so the acid is kept available to the plates and allows for a quick reaction time between acid and plate.
AGM exists in both Pure Lead batteries and Sealed Lead Acid batteries that do not use gel.
AGM technology transfers and takes in higher rates of amperage than standard batteries during discharge and charging making it a better performer when high rate discharges are required over long periods such as is required for larger programmable logic controller (PLC) backup applications.
AGM technology was originally developed for the military to provide a battery for more rugged and hostile conditions where the designs of the time failed due to the delicate nature of the internal plates and the ease in which they would leak corrosive acid.
The concept was commercialized in 1972 not only to offer a tougher battery but also as a way to maximize the purity of lead in lead acid batteries. Before this lead, a soft metal, needed to be mixed with other alloys to give it strength so the plates did not buckle but by doing so the efficiency of the cells was reduced.
The solution was to make the separators that were used to keep the negative and positive plates from touching each other part of the structure while also winding the plates into a spiral shape which lead to the Cyclon brand. These batteries are often referred to as Pure Lead.
This idea was later refined so that flat plates could be used and AGM technology found its way into larger square shaped batteries.
AGM batteries can be charged with any standard charging system. Many high performance brand names often times request that only AGM batteries be used with their products.
With electrolyte held in the fibreglass mat AGM batteries can be operated at any angle without risking leaks. Their sealed nature also means they are ideal for locations with limited ventilation such as emergency lights, PLCs and alarm systems.
Despite their many advantages AGM batteries come at a cost premium which is not seen as worthwhile in many industries and flooded lead acid remains popular, especially in the automotive industry.
Where AGM batteries fit in the lead acid chemistry.
The types of lead acid batteries are defined as:
- Flooded Lead Acid
- Sealed Lead Acid (aka Valve Regulated Lead Acid)
For more see the article What is a lead acid battery.
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