General info about Gel and AGM deep cycle batteries

VRLA Technology

Valve-regulated lead-acid (VRLA) technology encompasses both gelled electrolyte and absorbed glass mat (AGM) batteries. Both types are valve-regulated and have significant advantages over flooded lead- acid products.

What is a gel battery?

A gel battery is a lead-acid electric storage battery that:
• is sealed using special pressure valves and should never be opened.
• is completely maintenance-free.*
• uses thixotropic gelled electrolyte.
• uses a recombination reaction to prevent the escape of hydrogen and oxygen gases normally lost in a flooded lead-acid battery (particularly in deep cycle applications).
• is non-spillable,andthereforecanbeoperatedinvirtuallyany position. However, upside-down installation is not recommended.

* Connections must be retorqued and the batteries should be cleaned periodically.

What is an AGM battery?

An AGM battery is a lead-acid electric storage battery that:
• is sealed using special pressure valves and should never be opened.
• is completely maintenance-free.*
• has all of its electrolyte absorbed in separators consisting of a sponge-like mass of matted glass fibers.
• uses are combination reaction to prevent the escape of hydrogen and oxygen gases normally lost in a flooded lead-acid battery (particularly in deep cycle applications).
• is non-spillable,and therefore can be operated invirtually any position. However, upside-down installation is not recommended.

* Connections must be retorqued and the batteries should be cleaned periodically.

What are the differences between gel batteries and absorbed glass mat (AGM) batteries?

Both are recombinant batteries. Both are sealed valve-regulated (SVR) – also called valve-regulated lead-acid (VRLA). AGM batteries and gel batteries are both considered “acid-starved”. In a gel battery, the electrolyte does not flow like a normal liquid. The electrolyte has the consistency and appearance of petroleum jelly. Like gelled electrolyte batteries, absorbed electrolyte batteries are also considered non-spillable – all of the liquid electrolyte is trapped in the sponge-like matted glass fiber separator material.

The “acid-starved” condition of gel and AGM batteries protects the plates during heavy deep-discharges. The gel battery is more starved, giving more protection to the plate; therefore, it is better suited for super-deep discharge applications.

Due to the physical properties of the gelled electrolyte, gel battery power declines faster than an AGM battery’s as the temperature drops below 32oF. AGM batteries excel for high current, high power applications and in extremely cold & hot environments.

What is the difference between VRLA batteries and traditional wet batteries?

Wet batteries do not have special pressurized sealing vents, as they do not work on the recombination principle. They contain liquid electrolyte that can spill and cause corrosion if tipped or punctured. Therefore, they are not air transportable without special containers. They cannot be shipped via UPS or Parcel Post or used near sensitive electronic equipment. They can only be installed “upright.”

Wet batteries lose capacity and become permanently damaged if:
• left in a discharged condition for any length of time (due to sulfation). This is especially true of antimony and hybrid types.
• continually over-discharged, due to active material shedding. This is especially true of automotive starting types.
Gel cells have triple the deep cycle life of wet cell antimony alloy deep cycle batteries, due to our unique design. The shelf life of a VRLA battery is seven times higher than the shelf life of a deep cycle antimony battery.

How do VRLA batteries recharge? Are there any special precautions?

While our VRLA batteries accept a charge extremely well due to their low internal resistance, any battery will be damaged by continual under- or overcharging. Capacity is reduced and life is shortened.

Overcharging is especially harmful to any VRLA battery because of the sealed design. Overcharging dries out the electrolyte by driving the oxygen and hydrogen out of the battery through the pressure relief valves. Performance and life are reduced.
If a battery is continually undercharged, a power-robbing layer of sulfate will build up on the positive plate, which acts as a barrier to recharging. Premature plate shedding can also occur. Performance is reduced and life is shortened. Therefore, it is critical that a charger be used that limits voltage. The charger must be temperature-compensated to prevent under- or overcharging due to ambient temperature changes.

 

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