AGM, GEL and Wet Cell Batteries – What’s the difference?

Posted by on 22nd Feb 2019

AGM, GEL and Wet Cell Batteries - What's the difference?

The most common battery for marine, RV, solar installations as well as for many other home applications is the lead-acid battery. There are many different types. Let’s first look at what makes them similar: lead-acid batteries use an electrolyte consisting of sulfuric acid and lead-made plates to chemically store electrons. These batteries consist of cells connected together to provide an adequate amount of electrical energy storage for the needs. A lead acid battery stores a relatively large amount of energy, for a relatively long time, in a relatively small space. This portable power makes these batteries ideal for these applications.

What makes these batteries different?

AGM, GEL and WET Cell batteries – What’s the difference?

Although all AGM, GEL and flooded batteries contain lead acid, the internal battery construction divides them into the below categories.

Absorbed glass mats or " AGM" batteries are the newest and best in lead-acid batteries. An AGM battery uses a fiberglass separator between the plate and the wrappers to keep the electrolyte in place with capillary action. By combining lead plates, electrolytes, and fiber glass separation, AGM batteries create a "physical connection" through capillary action. This capillary action holds the liquid inside the glass mat, making the AGM battery "non-spillable" if ever exposed. Thanks to the AGM battery pack, it is the most impact-resistant and has the least internal resistance. Lower internal resistance increases output voltage, reduces charging time, and limits heat loss as power flows through the system. AGM Batteries has a huge advantage over the rest of the batteries - they do not require any special maintenance. Premium AGM batteries reorganize internally produced gases back into liquid. This recombination makes AGM battery maintenance free. There is no acid leakage, no mess while charging, no corrosion. AGM batteries can do everything that flooded, and GEL ones can do, just better.

"Wet cell" / Flooded batteries are the most commonly used batteries on the market today. These have the widest variety of shapes and sizes due to their wide use in many industries and applications. Rechargeable batteries re-use lead plates, sulfuric acid electrolyte and tile separators. Normally, flooded batteries are not sealed and do not recombine the gases to liquids internally. Instead, these gases are vented externally. The produced internal gases are released directly into the environment. Through the same ventilation holes, acid, steam and condensation can lead to maintenance. Flooded batteries require maintenance in the form of water to routinely load the lost electrolyte through the holes. Lead plates begin to deteriorate when they touch the atmosphere, so if you fail to maintain your batteries, they will corrode and get damaged. This type of batteries has very good prices but require more work. Unfortunately, due to the internal design, flooded batteries have the weakest internal design and very high internal resistance statistics.

GEL battery cells are also sealed exactly as indicated above in the AGM battery. That's where the similarities end up. A GEL battery uses silica to convert sulfuric acid to jelly. This jelly is then used as an electrolyte. You have to be careful with GEL batteries and avoid exposing them to high amperage situations. Such exposures may lead to formation of pockets inside the battery. These pockets allow the plates to become corroded, leading to premature failure. GEL batteries should not be used for fast charge / discharge or for high amplitude charging / discharging situations. Use the other types listed above for these high amperage situations. GEL batteries are slightly stronger with respect to the internal flood battery design, but weaker in terms of physical power compared to the AGM ones.