For those that are unaware of the latest improvements in battery technology, "AGM" stands for "Absorbed Glass Mat". These are still lead/acid batteries, but their method of construction is different. Specifically, the fiberglass mesh mats. They are the GM in AGM batteries. Ultra-thin glass fibers soak up all the electrolyte (water and sulfuric acid) into thin pillows cushioning the lead plates. Instead of the free-flowing liquid inside of a regular car battery, an AGM battery carries its electrical charge in soaked sponges — and those mesh sponges are coating the lead plates.
The fiberglass mesh on the lead plates gives the electrical current a shorter, easier path to follow than in a regular battery with free-flowing liquid.
That’s called low internal resistance, and that’s how an AGM battery’s design that expand what car batteries can fundamentally do. Obviously, the Optima's everyone is mentioning are AGM's.