AGM Stands For Absorbed Glass Matt
AGM batteries differ from traditional flooded lead acid batteries in their construction, inside AGM batteries the battery acid (sulfuric acid) (electrolyte) is soaked or suspended in a thin fibreglass mat which is sandwiched between each plate. With the exception of Optima batteries, which use cylindrical cells.
AGM Battery Facts
- They are maintenance free
- They have exceptional tolerance to vibration
- They are spill proof
- Safer than flooded lead acid batteries
- Are not always deep cycle!
Some Background To How They Came About
The first AGM battery was patented by Gates Rubber Corporation of the USA in 1972, however, this is a little grey as Yuasa Battery Corporation of Japan had prior art and experience with glass fibre separators. Despite this the first VRLA AGM batteries were used in a large scale with BT (British Telecom) and the battery was greatly refined working with BT for UPS use.
For automotive use, VRLA AGM batteries were first put into production in Brisbane, Australia and had early success. Price was always a challenge and vehicles in the late 80’s didn’t require the benefits seen with using VRLA AGM batteries. From the mid 2000’s onwards would see a resurgence as cars had greater accessory load, costs came down and the birth of stop-start vehicles had begun.
AGM batteries today are used not only for automotive applications but also deep cycle. The benefits of glass separators with durability, lighter weight, improved service life, lower internal resistance, superior starting power and improved cycling performance over traditional flooded batteries means they have reached mainstream use with car manufacturers and as replacement batteries.
AGM batteries are not suitable for every environment or application, when your application requires:
- No fumes (inside a caravan)
- Vibration resistance
- Sideways mounting (no spills)
- Effective use below 0 degrees Celsius
Times when AGM batteries may not be practical is when the battery will be used in extreme heat and when cost is a factor. To a lesser degree when the battery may be subjected to over charging, AGM batteries are more sensitive to over charging compared with flooded lead acid or gel batteries.