Absorbed Glass Matte or "AGM" batteries are the latest and greatest in lead-acid batteries. An AGM battery uses a separator consisting of fiberglass between the plate and wrappers to hold the electrolyte in its place with capillary action. Combining the lead plates, electrolyte, and fiber glass separation fibers in a confined space, AGM batteries create a "physical bond" by way of capillary action. Similar to how water creeps up a towel when it is put in a bathtub. This capillary action holds the liquid inside the glass matting, making the AGM Battery "spill proof" if it is ever exposed. Due to the tight packing of an AGM battery, it is also the most impact resistant, and boasts the least internal resistance. The lower internal resistance increases the output voltage, decreases charging time, and reduces losses to heat as power flows through the system. AGM Batteries then bring the trump card to the table, they are maintenance free. Premium AGM batteries recombine the gases produced internally, back into liquid. This recombination makes the AGM battery maintenance free. No acid leaks, no mess while charging, no corrosion on surrounding parts. You plug in these batteries and walk away. AGM batteries can do anything that flooded and GEL batteries can do, just better.
GelGEL cell batteries are also sealed just like the AGM battery listed above. That is where the similarities end. A GEL battery uses a silica (sand) to turn the sulphuric acid into a jelly like substance. This jelly is then used as the electrolyte. Great care must be taken with GEL batteries not to expose them to high amperage situations. High amperage situations can literally 'SCAR' the jelly inside of a GEL battery, creating a pocket. These pockets allow the plates to begin corroding, leading to premature failure. GEL batteries should not be used for fast charging/discharging, or high amperage charging/discharging situations. Use the other types listed above for these high amperage situations. GEL Batteries are slightly stronger in regards to internal construction than a flooded battery, but pale in comparison to the physical strength of an AGM battery.
Flood AcidFlooded or "wet cell" batteries are the most commonly used batteries on the market today. Flooded batteries come in the widest variety of shapes and sizes due to their widespread usage in a multitude of industries and applications. Flooded batteries again use lead plates, a sulphuric acid electrolyte, and plate separators but that is where it stops. Usually flooded batteries are not sealed, and do not recombine the gases to liquids internally. Instead, these gases are vented externally. Internal gases produced are released directly to the environment. Through these same vents can flow acid, steam, and condensation, leading to maintenance. Flooded batteries do require maintenance, in the form of water, to routinely replenish lost electrolyte through the vents. Lead plates start to deteriorate when they touch the atmosphere, so if you fail to maintain your batteries, they will corrode and fail. Flooded batteries hold very good rates of charge for the price, but require more work. Unfortunately due to the internal construction, flooded batteries have the weakest internal construction, and some very high internal resistance statistics.