What is the difference between a gel and an AGM battery?

A gel battery is powered by a gelled electrolyte in a sealed container, rated non-spillable by the IATA (Air Transport Association) and the DOT (Department of Transportation), making it possible to ship it by air without restrictions. A gel battery is rated for operation at over -40 to +60° C, making it an ideal battery for outdoor use. AGM (Absorbed Glass Mat) batteries run off of electrolytes absorbed in sponge-like mats between plates. They are typically rated for use between 0 to +40° C, which is not suitable for outdoor conditions.