[Al Skierkiewicz]

AGM batteries actually may have slightly more lead than previous gel cell types. The glass mat allows for closer plate spacing which may allow manufacturers to add one more plate in the same space as previous designs. This gives a little higher energy density and/or available peak current. The reason FRC went to AGM batteries (namely the MK series) came from a donation by MK to supply batteries to every team that year. The AGM design also keeps maximum contact between electrolyte and full plate during the battery's lifetime. This AGM series also lightly reduced the weight of batteries. Previous gel types could be up to 14 lbs when new. As the electrolyte evaporated, the weight went down but so did the available current and energy density.
Batteries used in safety light service are designed to be on trickle charge 24/7 so they have a tendency to outgas and remain at higher temperatures. Many jurisdictions also require safety lighting to provide light for a specific minimum time period. Older batteries in this service will meet that spec. Many building maintenance managers will replace all batteries every three years or sooner, depending on environment.