What is a Gel battery?
A gel battery is a lead-acid electric storage battery with below features:
• It is sealed using special pressure valves and should never be opened.
• It is completely maintenance-free.*
• It uses thixotropic gelled electrolyte.
• It 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).
• It is non-spill able, and therefore can be operated in virtually any position. However, upside-down installation is not recommended.
What is an AGM battery?
An AGM battery is a lead-acid electric storage battery with below features:
• It is sealed using special pressure valves and should never be opened.
• It is completely maintenance-free.*
• It has its entire electrolyte absorbed in separators consisting of a sponge-like mass of matted glass fibers.
• It 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).
• It is non-spill able, and therefore can be operated in virtually any position. However, upside-down installation is not recommended.
How does a VRLA battery work?
A VRLA battery is a “recombinant” battery. This means that the oxygen normally produced on the positive plates of all lead-acid batteries is absorbed by the negative plate. This suppresses the production of hydrogen at the negative plate. Water (H2O) is produced instead, retaining the moisture within the battery.
It never needs watering, and should never be opened as this would “poison” the battery with additional oxygen from the air. Opening the battery will void the warranty.
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-spill able – the entire 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 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:
• Its left in a discharged condition for any length of time (due to sulfation). This is especially true of antimony and hybrid types.
• It continually over-discharged, due to active material shedding. This is especially true of automotive starting types.
Gel cells have tripled the deep cycle life of wet cell antimony alloy deep cycle batteries, due to their unique design. The shelf life of a VRLA battery is seven times higher than the shelf life of a deep cycle antimony battery.
Can VRLA batteries be installed in sealed battery boxes?
NO! Never install any type of battery in a completely sealed container. Although most of the normal gasses (oxygen and hydrogen) produced in a VRLA battery will be recombined as described above, and not escape, oxygen and hydrogen will escape from the battery in an overcharge condition (as is typical of any type battery).
For safety’s sake, these potentially explosive gasses must be allowed to vent to the atmosphere and must never be trapped in a sealed battery box or tightly enclosed space!
Why can’t VRLA batteries be opened?
VRLA (Valve-Regulated Lead-Acid) batteries, sometimes called SLA (Sealed Lead-Acid) batteries or SVR (Sealed Valve-Regulated) batteries work on a recombination principle. Oxygen gas is produced at the positive plates during charge. The charged negative plates react first with this oxygen and subsequently with the electrolyte.
Water is produced and the negative plates are very slightly discharged. Additional charging recharges the negative plates instead of producing hydrogen gas. Since very little hydrogen and oxygen is lost and the water (H2O) is retained, we say that the gasses have recombined. To work properly, the oxygen produced must be retained in the battery until the reaction is completed.
Positive pressure allows the gas to be retained. If any VRLA (gelled or absorbed electrolyte) battery is overcharged, gas will be vented from the valves. Hydrogen as well as oxygen will be released. If continued, the electrolyte will eventually dry out and the battery will fail prematurely. This is why charging limits are so critical.
In a sealed battery a balance is maintained between the hydrogen, oxygen and charge. If a VRLA battery is opened, or leaks, the negative plates are exposed to extra oxygen from the atmosphere. This excess oxygen upsets the balance. The negative plates become discharged. The positive plates may be subsequently severely overcharged. The battery will fail prematurely, and the warranty will be voided.
What do the ratings and specifications signify?
All ratings are after 15 cycles and conform to BCI specifications.
CCA = Cold Cranking Amperes at 0°F (–17.8°C)
Cold cranking amperes equal the number of amperes a new, fully charged battery will deliver at 0°F (–17.8°C) for thirty seconds of discharge and maintain at least 1.2 volts per cell (7.2 volts for a 12-volt battery).
CA = Cranking Amperes at 32°F (0°C)
Same as above tested at 32°F (0°C).
RC = Reserve Capacity at 80°F (27°C)
The reserve capacity is the time in minutes that a new, fully charged battery can be continuously is charged at 25 amperes and maintain at least 1.75 volts per cell (10.5 volts for a 12-volt battery)
