Gel cell batteries have many of the same advantages of an AGM. They are sealed, easy to transport and can be mounted in any position. The internal difference is in the electrolyte. The gelled electrolyte is highly viscous and recombination of the gases generated while charging occurs at a much slower rate. This means the charge rate is lower than either an AGM or flooded lead acid. If charged too rapidly, gas pockets form in the gel. These pockets keep the gel away from the lead plates, reducing capacity until the gas bubble can move to the top and recombine.
This can mean lost energy absorption when the renewable energy, solar, wind or hydro, is available. Unless you have a specific need for this type of battery or get a smoking deal, it would be hard to justify the cost.
Advantages
• No maintenance required
• Batteries can not spill if ruptured or overturned
• Minimal gassing
• Low Temperature tolerant
• High temperature tolerant
• More easily shipped
Disadvantages
• Higher cost
• Slightly lower capacity