Information to be added.
The absorbed glass mat (AGM) type uses a glass mat separator. AGM batteries differ from flooded lead acid batteries in that the electrolyte is held in the glass mats, as opposed to freely flooding the plates. Very thin glass fibers are woven into a mat to increase surface area enough to hold sufficient electrolyte on the cells for their lifetime. The fibers that compose the fine glass mat do not absorb nor are affected by the acidic electrolyte. These mats are wrung out 2–5% after being soaked in acids, prior to manufacture completion and sealing.
The plates in an AGM battery may be any shape. Some are flat, others are bent or rolled. AGM batteries, both deep cycle and starting, are built in a rectangular case to BCI battery code specifications.
AGM batteries will hold their charge very well and can still be 60% charged after 12 months.