AGM = Absorbed Glass Mat Batteries
These are the best lead-acid type battery for most Ham Radio use. They are sealed, won't leak, and can both deliver and charge at higher rates compared to Gel and Flooded batteries.
They are vibration resistant, can operate in any position, and are VRLA (Valve Regulated Lead Acid). They operate by quickly recombining the gases into water, so they don't outgass or lose water in normal operation.
AGM are good for solar systems because they capture more of the charge energy, up to 90%. Flooded and Gel batteries may only capture 70%.
AGM are good for dry camping with RV/Generator systems because they can be charged at very high rates and capture up to 90% of the charge energy. This is much faster and more efficient than flooded or gel batteries.
- Absorbed Glass Mat Battery Technology∞ - This article is on the Northern Arizona Wind & Sun website so it's biased towards the products they sell, but it still has good basic info on AGM technology.
- The ABCs of AGMs∞ - An article that goes into some detail on the proper care and feeding of AGMs, including examples of overcharged batteries. Includes some good photos. (Originally published in 2004 on oceannavigator.com, but available on this site in PDF format.)