AGM (Absorbed Glass Mat) sealed battery technology was originally invented in 1980 and developed and introduced in 1985 for military aircraft where power, weight, safety, and reliability are paramount considerations.
AGM batteries are NOT gelled electrolyte. The active lead alloy plates are packed in with a fiberglass mat. This glass mat absorbs and immobilizes the acid while still keeping the acid available to the plates. This allows a fast reaction between acid and plate material. Even if the battery is broken, no electrolyte is spilled.
Damage due to plate movement that might occur due to vehicle vibration or impact is greatly reduced.
In the AGM battery gasses recombine almost 100% within the battery, reducing hydrogen emissions far below most battery types, and less than half the lower explosive limit for hydrogen. Low gassing also cuts water loss by up to 98%.
Batteries using AGM technology also have a much lower (about 1/2) self-discharge rate which allows them to maintain their charge longer when not in use. However, they seem to be more easly damaged when they are allowed to sit in a discharged or partial-discharged state.
Batteries using AGM technology have lower internal resistance than traditional flooded lead-acid batteries. Approximately 2%, versus 25% for flooded batteries and 16% for gell batteries.
Internal resistance of a battery denotes its ability to deliver high cranking currents without significant drop in voltage. This means higher cranking amps. Increased efficiency also means that more efficient charging. Less charge current is required to charge the battery because less current is being wasted and the battery produces less heat during charge.
