What Is An AGM Battery? – Battery Hint

In the battery industry, the conventional Lead-Acid battery has been ruling over 200 years. The AGM battery is the upgraded and more technologically advanced form of old lead-acid batteries. These batteries have become popular in a very short amount of time because of their effectiveness, warranty, run time, power supply, etc. But what is an AGM battery?

Absorbent Glass Matt battery or simply known as AGM battery is the next generation deep cycle battery. The engineering process of the AGM batteries has been in such a way that the automobiles get the maximum advantage.

More advanced electrode plates and electrolytes are used in building up the AGM battery. The battery casing, cell chambers, opening, compartments, and connectivity of the AGM batteries have advantageous features than other types of batteries.

What exactly is an AGM battery?

AGM battery is an electrochemical battery. It transforms chemical energy into electrical energy for supplying power. As this battery is small and handheld, it can be used as a portable power supplier in case of emergencies. But mostly the AGM batteries are used in automobiles.

It helps to ignite the engine of the vehicle by providing cranking amps in burst mode for a small amount of time. Besides, the electronics inside the vehicle are also run by the battery. Such as the windows, radio, headlight, internal lighting, wiper, etc run on AGM batteries nowadays.

In AGM batteries the free electrons pass through the electrodes and electrolytes to produce electrical energy. The working principle of the AGM battery is the same as the wet cell battery. But the assembly and physical nature of the electrolyte is quite different.

Is AGM battery technology different from others?

Even though the working principle of AGM batteries is similar to other batteries. But the internal technology used in the AGM battery is quite different from others. 

In a normal battery, liquid acid is used as the electrolyte. Most of the time the acid is Sulphuric Acid. There are six different cell chambers in the lead-acid batteries. Each cell chamber contains a specific amount of electrolyte and an electrode plate in it. All the cell chambers combined to form the overall battery.

On the other hand, in AGM batteries a glass matt is used between the cell chambers. The glass matt is made up of fiberglass. These are semipermeable and only a certain amount of electrolyte passing can take place in between them.

The electrolyte in AGM batteries gets absorbed by the fiberglass mats. As a result, there remains no liquid form of electrolyte in the AGM battery. Since electron flow takes place between the electrolytes only in any form. It does not matter the physical form of the electrolyte.

For this the AGM batteries are non-spillable. Electrolyte being trapped in the glass matt, it becomes easy to move and carry the battery. Moreover, due to the more stationary phase of the electrolyte, electrons flow without any resistance. As a result, a better power supply is seen in the AGM battery.

Apart from these, the lead plates used in the Absorbed Glass Matt(AGM) batteries are mostly pure. ANd thinner and numerous plates are used in the AGM batteries. This makes the AGM batteries more effective and long-lasting than normal batteries.

How does the AGM battery work?

An Absorbed Glass Mat battery(AGM) is an electrochemical battery. It works on the principle of electrolysis. Basically, the transformation of energy takes place inside an AGM battery. You will get current due to the electron flow inside the electrolyte and electrodes. When free electrons move from the electrodes to the electrolyte then chemical energy is converted to electric energy.

Inside the battery, the energy is stored in the form of chemical energy. It transforms to electrical energy at the time of requirement. In the AGM batteries, the electrolytes are absorbed fully by the fiberglass mats. Because of more stability and reduced surface area oxidation and reduction, chemical reactions occur easily and effectively.

There are normally six cells in the AGM battery. Each cell chamber has lead plates acting as cathode and anode. Besides, there are absorbed electrolytes inside the cell chambers as well. The voltage rating of each call is approximately 2.1V. All the cells are joined together in a series circuit connection.

After combining the cell voltage output, an average AGM battery can generate 12-12.6V of potential. These batteries are rechargeable. By reversing the chemical reaction the battery can be recharged for further use. In the vehicles, there is a device called an alternator. The alternators rotate to supply electric energy which comes from the kinetic energy of the vehicle.

The AGM batteries deliver electricity in the form of direct current otherwise known as DC. Small electronic appliances, vehicular ignition, and home appliances require AGM batteries to power them up.

Let’s see the construction

The construction of the AGM batteries makes the primary difference with the normal batteries. Basic foundation of the AGM battery is similar to others.

An AGM battery is assembled on a strong plastic case. There are six cell chambers inside the battery casing. Each cell of the battery is composed of positive and negative Lead plates. These are the electrodes of the battery which act as anodes and cathodes individually inside the chamber.

In between the electrodes inside the cell, there is an absorbed glass mat separator. It contains the electrolytes in the gel type of formation. This glass mat makes the electrolytes being absorbed and makes the entire battery free of liquid electrolytes.

The lead plates in the AGM batteries are tightly compressed to paste on the grids. It helps in improving the cycling ratio of the battery. Besides, the battery can withstand more external vibration than a flooded battery cannot do. Therefore overall battery life is extended drastically.

There is a safety valve located at each cell of the battery. These valves open when the internal pressure arises due to gas production. While charging the battery Hydrogen gases are performed. These valves slowly and separately expel the gases to the atmosphere. Because the accumulation of hydrogen gas is very dangerous due to its flammability.

Another form of AGM battery is available in the market. These batteries are known as spiral cell batteries. Because each cell of these batteries is composed of the lead plates in positive and negative forms, the grids, and the absorbed glass mats. Being highly compressed these materials are constructed in spiral cylindrical form. 

These types of batteries are more vibration resistant than normal batteries. Apart from that, the durability, strong build-up of the battery is ensured. That is why this battery is mostly used in extreme vehicles such as ATVs, motocross bikes, offroad trucks, and cars, etc. In the marketplace, Optima batteries bring the most effective spiral AGM batteries.

Are there any special benefits of AGM batteries?

The unique assembly of the AGM batteries and premium materials used in them makes it more advantageous than others. In this section, we shall learn about the distinctive features and the benefits of AGM batteries.

Non-Spill Assembly

Each cell of an AGM battery is made of sandwiched electrodes, an AGM separator with absorbed electrolyte, and grids. This cell makes the battery completely liquid-free. Because the glass matt actively absorbs the electrolytes which reduces the surface area and increases conduction.

Moreover, in spiral AGM batteries, cells are made of spiral cylindrical shape which makes the construction more spill-free. That is why handling AGM batteries is risk-free and convenient.

Vibration Resistance

One of the best features of the AGM batteries is the anti-vibration construction. Every material of the battery is packed very closely. Moreover, the use of a fiberglass mat acting as the AGM separator absorbs the liquid electrolytes. And so there remains no free liquid inside the cell chambers.

For all these reasons, AGM batteries are highly vibration repellent. If you are an adventure enthusiast and love offroad driving, then this battery is suitable for your vehicle. Rally cars, ATVs, and dirt bikes use AGM batteries nowadays.

Very Short Charging Time

The electrolytes in the AGM battery do not reside in the liquid form. It gets completely absorbed by the glass mats in between the cell plates. Therefore, the effective surface area of the electrolytes is reduced. That is why it takes very little time to charge the AGM battery than other wet cell batteries.

Maintenance Free

The construction of the AGM battery makes it a maintenance-free battery. The cells and the battery casing are completely sealed. Since no liquid electrolyte is active inside the AGM battery. There is no requirement of filling the cell chambers with distilled water to keep the electron on track.

More Power Supply

AGM batteries can generate more energy than flooded batteries. The loss of energy production in AGM batteries is very negligible. The use of pure lead plates as electrodes and high-quality electrolytes ensures maximum productivity. 

Ultimately, the internal resistance that hinders the electron flow is much lower than in flooded batteries. Therefore, you do not have to worry about the sudden discharge of the battery.

Sulfation Free

Sulphation is the process of accumulation of free Sulfur from the sulphuric acid used in the electrolyte in the electrochemical cells. It is a common phenomenon in wet cell batteries. One of the good reasons for batteries showing underperformance is sulfation.

But in the AGM batteries, there are no liquid electrolytes used. Therefore, sulfation does not happen. Even if it happens, it happens very negligibly. Therefore, AGM batteries perform longer than normal batteries.

Advanced Water Retention technology

During the charging process of batteries, hydrogen gas is evolved. It is an extremely flammable gas. That is why charging of batteries is done in very well ventilated areas to avoid dangers of explosion.

But in AGM batteries, the evolution of Hydrogen gas is very negligible. With new technology, the amount of gas evolves actively combines with oxygen to produce water. This reduces the danger of flames and explosions.

Anti-thermal activity

Most of the batteries degrade their power output performance in low temperatures. Because, in low temperature, the electron flow is immobilized and as a result, minimal voltage is being seen.

But, in AGM batteries, the closely packed cells reduce the impact of temperature on the power output. No matter if the temperature is hot or cold, the AGM battery performs continuously.

Will there be any drawbacks?

Like every other thing, AGM batteries also have some drawbacks. But compared to the advantages proposed by the AGM batteries, the disadvantages are quite negligible.

Sensitive to Overcharging

In the AGM batteries, the cells have close and compactly packed plates in glass mats with electrolytes. Unlike the liquid electrolytes, there is very little surface area in the AGM batteries. Therefore, it cannot handle overcharging.

You have to continuously monitor the voltage in the battery while charging is in progress. It is imperative you stop charging the AGM battery when the state of charge is above 90%.

Cost Ineffective

Construction of the AGM batteries is very costly. Because it used almost pure and thinner lead plates as electrodes. Moreover, the fiberglass mat comes expensive as well. The assembly cost of the AGM battery is not budget-friendly. That is why in the retail market you will find the AGM batteries cost higher than those of normal wet cell batteries.

Reduced Charge Capacity

AGM batteries can hold a charge for a long period of time. But, with regular uses, the charge holding capacity of the AGM battery is reduced significantly. The cycle life remains prominent but the degradation makes the battery vulnerable in a certain period of time.

Charger Specific

Being highly sensitive due to high voltage. AGM batteries cannot be charged using conventional battery chargers. It requires a specific automated smart battery charger that possesses the AGM charging profile. These chargers are way too expensive and make the overall cost of the battery package higher than average.

How do you know if your battery is AGM or not?

Nowadays, most modern vehicles use AGM batteries. But many vehicles still use lead-acid deep cycle batteries. If your car requires some sort of maintenance and repairing it is imperative for you to know the type of battery in your car.

Normally, AGM batteries are lighter than Lead-Acid batteries. AGM batteries remain completely sealed. You cannot find any sort of opening way on top of the lid. But in lead-acid batteries, there are 6 caps to fill the cells with acid. This also differentiates the AGM batteries from the normal battery. Because in AGM batteries you do not have to refill the cell chambers with acid.

To confirm that your battery is an AGM battery, you can check on the manufacturer’s label on the top or side. It will clearly state the battery details in depth.

Do AGM batteries have different applications?

Absorbed Glass mAt or AGM batteries are formerly designed and manufactured for vehicles only. Because of its extreme durability, vibration resistance, and spill-proof technology, the AGM batteries were used in vehicles only. But, at the present time, there are many wide ranges of applications for the AGM batteries.

In recreational vehicles

In recreational vehicles, AGM batteries are used to supply power to portable home appliances. Portable electronic devices, small refrigerators, induction stoves, lights, fans, etc can be powered using AGM batteries.

Extreme offroad vehicles

The AGM batteries are widely used in off road vehicles. Vehicles such as rally cars, ATVs, motocross dirt bikes, speed boats, etc use the AGM battery for starting up the engine. Its spillproof and anti-vibration technology makes the battery well suited for these vehicles.

Household Inverter

AGM batteries can also be used for powering up household electronics at the time of power outbreak. The investors can easily invert the power output from the battery to lighten up the devices for emergencies.


The sump pumps in the basement of the house use AGM batteries. During an emergency the pump fails to drive the extra water and the basement becomes flooded. That is why AGM batteries are installed to deliver emergency power to the sump pumps to prevent flood and water clogging in harsh weather conditions.

Are there any Differences between AGM and normal batteries?

By normal batteries we mean the conventional wet cell flooded batteries. There is a huge difference between flooded lead-acid batteries and AGM batteries. Though the basic principle of power generation is the same. The difference lies within the materials used for constructing the batteries and the ways of construction.

AGM batteries use sealed compartments with only the connecting terminals whereas flooded batteries have cell openings on top. The cells are made of thin lead plates packed tightly with the glass mat and the grids. Electrolytes are absorbed by the glass mats.

On the other hand, flooded batteries have blocks of lead plates in each cell submerged in liquid electrolytes. It makes the effectiveness, performance, durability, and long-lasting activity of the AGM battery better than the lead-acid battery.

Are AGM batteries and EFB the same?

EFB stands for the Enhanced Flooded Battery whereas AGM stands for Absorbed Glass Mat batteries. The EFB batteries and AGM batteries are not the same. EFB batteries are simply an upgraded version of the old flooded lead-acid batteries. The following chart shows the difference between the AGM and EFB batteries.

AGM BatteryEFB Battery
Uses tightly packed cells with gridsUses only the Lead plate as an electrode
Absorbed Glass Mat is used to carry the electrolytesDirect flooding of electrolytes is used in the liquid form
Spiral forms of cells are availableThe only block forms of cells are available
Charges very quicklyCharging takes time
Sealed compartment for spill-proofNot spill proof and vibration resistance

What are the differences between AGM battery vs gel?

The main difference between the AGM battery and Gel battery lies in the electrolyte type. In the following comparison chart, the differences are highlighted.

AGM BatteryGEL Battery
Electrolytes used in the AGM is absorbed by the glass matIn the gel battery, the electrolytes are used in the form of a gel.
The depth of discharge of the AGM battery is higherThe depth of the Discharge in the gel battery is lower.
Two forms of cells are found in the AGM batteryThe block form of cells are found in the GEL battery

Do AGM batteries and lithium have the same mechanism?

AGM batteries and Lithium-ion batteries have different forms of mechanism. In AGM batteries the electrons flow from the electrodes and electrolytes to generate voltage and electricity. But in the lithium-ion battery, electricity is generated due to the flow of free ions in the electrolytes.

AGM BatteryLithium-ion Battery
Sensitive to overchargingNot sensitive to overcharging
Can not be discharged below 50% SoCAllowed to get discharged further below 50%
Cost per life cycle is averageThe cost per cycle is very higher
The good charge holding capacityThe excellent charge holding capacity

Is the AGM battery the standard battery?

AGM batteries and Standard batteries differ from each other on the basis of construction and assembly. Buy standard battery we mean the Lead-Acid battery

AGM BatteryLead-Acid Battery
Uses sealed compartmentPossesses cell chamber openings 
Sulfation doesn’t occurSulfation occurs frequently
Doesn’t require refilling with acidRequires regular refilling with acid/distilled water

Does AGM battery differ from optima battery?

Optima battery is a form of AGM battery. AGM batteries have two types of cells. The block type of cell and spiral form of cells. In the optima batteries, the cells are formed in a cylindrical manner with a highly closed pack of lead plates and the glass mat containing the electrolyte. Optima batteries are more spill-proof and vibration resistive than other types of batteries.

How is an AGM battery different from calcium?

Calcium batteries are the upgraded form of the former lead-acid batteries. It has better efficiency and starting power than the lead-acid battery.

AGM BatteryCalcium-Battery
Electrodes are made of pure lead platesIn the electrode, the calcium is added for better efficiency 
More conductiveLess conductive
The good charge holding capacityThe average charge holding capacity

Comparison between AGM battery vs deep cycle

Deep cycle batteries need to be deeply discharged over the use of time. But you cannot deeply discharge an AGM battery. The AGM battery cannot be discharged under 50% of the state of charge. 

It will not be possible to restore the battery health as it degrades when discharged deeply for AGM batteries. But, on the other hand, deep cycle batteries can be restored completely from a deeply discharged condition.

Is the AGM battery flooded?

AGM batteries are quite different from flooded batteries. These are completely different in respect of the construction and assembly of the battery.

AGM BatteryFlooded Battery
Glass mat is used as a separatorNo separation grid is in the cell chamber
Electrolyte remains in the absorbed formElectrolytes remain in liquid form
Does not require regular filling of the acidNeed to be filled with acid on a regular basis
Non-spillable sealed compartmentNot spill proof and may cause leakage of electrolyte

Are AGM batteries and wet cells the same?

AGM batteries are very different from wet cell batteries. In the AGM battery there remains no liquid electrolytes available in the battery. But, in the wet cell battery, the cell chambers are flooded with liquid electrolytes.

AGM BatteryWet Cell Battery
AGM batteries use absorbed form of electrolytes in the glass matsWet cell batteries use the liquid form of electrolytes
The electrode plates, grids, and glass mats remain tightly packed in the conditionThe cell chamber has only electrodes and electrolytes present
Vibration resistance due to sealed compartmentNot vibration resistance or spill proof.

Is the charging method different for AGM Battery?

AGM batteries are very charge-sensitive. It cannot withstand overcharging. That is why a different approach is followed to charge the AGM batteries. A walk-through of how to charge the AGM batteries is proposed below.

  • Firstly, disconnect the battery from all the electronic appliances.
  • Clean up the battery terminals to make those corrosion-free.
  • Connect the battery properly using the connecting cables of the automatic smart battery charger.
  • If the battery charger does not have voltage reading technology then an additional voltmeter needs to be connected to the battery.
  • Select the amp setting. For the AGM battery, the amp input should not exceed 10 Amps. The range of amps is 2-10amps.
  • Select the “AGM” charging profile in the battery charger. And switch on the charger.
  • Keep eye on the voltage reading and soc reading on the charger display. Make sure you do not charge the battery over 90%.

Want to prolong the longevity of AGM batteries?

AGM batteries have a better cycle and charge holding and power delivery capacity. A new AGM battery has a lifespan of 4-5 years. With proper maintenance and regular checking, you can prolong the lifespan of the battery.

  • Keep the terminals of the battery clean using steel wool. It will help to remove the corrosion and promote better electricity flow.
  • You have to use the Automatic smart battery charger for the AGM batteries. A normal conventional charger may overcharge the battery which shall damage the battery life.
  • Charge the battery in a very well-ventilated area.
  • You can perform regular desulfation procedures on the battery to keep your electrolyte free of contamination.

Frequently Ask Question about AGM Battery

Here, we shall learn about the commonly asked question by the consumers of the AGM battery.

How Long Do AGM Batteries Last?

A new AGM battery can last up to 4-5 years at a stretch without any maintenance. You can easily prolong the life of the battery following some basic housekeeping rules. Dong those the life expectancy of the AGM battery can be extended up to 7 years.

Can I charge an AGM battery with a regular charger?

You can charge the AGM battery using a regular charger but you have to constantly keep an eye on the voltage output. Because the conventional battery chargers do not have any sort of controlling sequence installed. Therefore, overcharging the battery may reduce its longevity.

How long does it take for the AGM battery to fully charge?

A smart quick charger will fully charge an AGM battery in just 7-8 hours of uninterrupted charging. You can set up the profile to 20 amps for quick charging. But exceeding 10 Amps for an AGM battery can damage the internal materials of the battery.

What is the Maximum discharge of AGM batteries?

The maximum discharge limit of an AGM battery is 50% of the State of charge. Discharging the battery below 50% can damage and reduce the longevity of the battery. Overly discharged AGM batteries need permanent replacement and cannot be restored properly.


Production of Absorbed Glass Mat (AGM) batteries is a blessing for the automobile industry. It can withstand heavy vibrations. Therefore, driving your favorite adventurous vehicles offroad will keep you tension-free from getting your vehicle completely shut suddenly. For getting all the advantages you have to get to know what is an AGM battery, its uses, and its importance.

AGM batteries are made to be spill-proof. The sealed compartment makes sure of no leakage. Therefore handling of the AGM battery is danger-free. Proper usage, maintenance of the battery can give some extra years to live as well. Spiral AGM batteries are the best for extreme dirt bikes, ATVs, etc.

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Marcelo Araujo-Xavier

Hi, Marcelo Araujo-Xavier is here! I am the author of Batteryhint. I have been working in the battery industry for over 20 years and have a passion for helping people find the best battery for their needs. I have personally tested and reviewed hundreds of different batteries. I'm certified by the International Association of Automotive Battery Manufacturers. I have always been interested in batteries and how they work, so I decided to start this website to share my knowledge with others. I hope you find the information on this website helpful and informative. I will be regularly updating this website with new resources, If you have any questions or comments, please feel free to contact me. I would love to hear from you and help you find the best battery for your needs.

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