What Is An AGM Deep Cycle Battery?

The Absorbed Glass Mat battery is the newly formed deep cycle battery. It is otherwise known as the AGM battery. This battery works on the principle of electrochemical reactions. It is basically a technologically advanced form of Lead-Acid batteries.

Considering you want to make an update to the battery or replace it with your current battery. Then it is imperative you should know what is an AGM deep cycle battery. Deep cycle batteries have a better tendency to deliver a higher burst of power to the vehicles.

The power production of AGM deep cycle batteries is similar to other lead-acid batteries. But the difference between AGM batteries and other batteries lies in the construction of the battery.

What exactly is an AGM deep cycle battery?

For this, firstly we need to understand what a deep cycle battery is. Deep cycle batteries have a higher capacity for power production. This battery can discharge up to 80% or more. During its discharge process, the power delivery process is never interrupted. It makes the difference between a deep cycle battery and a regular battery.

Regular batteries can’t sustain a high discharge rate. Besides, they fail to produce higher bursts of cranking amps required for vehicles. The AGM batteries can produce the high cranking power required for starting up the vehicles.

Especially in cold regions, regular batteries fail to perform. Whereas, AGM batteries can easily produce high cold-cranking amps. As a result, your vehicle never sits idle or requires jump-starting. Moreover, the AGM batteries are very different from those of regular batteries or other deep cycle batteries.

Standard flooded batteries, Gel batteries are Lead-acid batteries. But, an AGM battery has a special formation of buildup that differentiates between the batteries. In an AGM battery, there are six separate cells.

In each of the AGM batteries, lead plates are used as electrodes. These plates are quite thinner compared to electrodes of the lead-Acid batteries. That is why more plates can be used for making up the cell.

In between the positive and negative electrodes, an AGM separator is installed. This AGM separator is made up of glass mats. They have a liquid absorbing power such as a sponge. These Glass mats are used to absorb the liquid electrolyte.

The AGM batteries use slightly concentrated sulphuric acid as the electrolyte. Being absorbed by the AGM separator, their electron transfer increases. As a result, AGM batteries have a higher power output capacity. Moreover, they have a low self-discharge rate and quick-charging capability.

In each cell of the AGM batteries, grids, electrode pilates, and fiber-glass mats are highly compressed. This makes a closely packed structure of the cell. Besides, the battery cells are placed very securely inside the cell chambers.

For this type of engineered design, the AGM batteries are very durable and spillproof. Its lid is completely sealed except for the pressure valve. This makes the battery vibration resistive as well.

Is AGM different from other deep cycle batteries?

There are mainly four major types of deep cycle batteries available in the market. These are the wet cell batteries, sealed batteries(AGM), gel-filled batteries, and Li-ion batteries. Except for the Li-ion battery, all other batteries are Lead-acid batteries.

Those work on a similar electrochemical oxidation-reduction reaction. The prime difference lies in the construction engineering of the batteries. The Absorbed  Glass Mat or AGM batteries are very different from the other types of deep cycle batteries.

AGM battery is spill-proof. It is because of the sealed battery compartment. This battery is vibration resistive. Because the cells of AGM batteries are closely packed to each other with no presence of a liquid electrolyte.

In the AGM batteries, electrolytes are absorbed by the fiberglass mat. Unlike the other deep cycle batteries, AGM batteries do not possess free liquid Sulfuric acid inside the chamber. Therefore, a higher rate of electron transfer is seen which escalates the power delivery from the battery.

Like all other things, AGM batteries have some drawbacks as well. This battery is very sensitive to overcharging. High voltage input damages the internals of the AGM batteries. Besides, the depth of charge of the battery is 50% only. Whereas, other deep cycle batteries have an of discharge up to 80%.

Are AGM batteries and deep cycle batteries different from each other?

Though all the deep cycle batteries have similar types of working principles. But there are huge differences in the construction and performance of the batteries. 

Comparison between AGM battery and  Standard battery

By standard Battery, it is meant about the conventional flooded battery used as a lead-acid battery. The main difference between AGM batteries and wet cell batteries is the state of electrolyte they use. 

In the AGM battery, the sulfuric acid used as an electrolyte is completely absorbed by the AGM separator. Therefore, in the cell chambers of the AGM battery, no liquid form is found. On the other hand, in wet cell batteries, the Lead plates are directly poured into the liquid electrolyte.

Moreover, standard flooded batteries require regular refilling of distilled waters through the cell opening caps. This is done to maintain the balance of free electrons in the electrolyte. But, in AGM batteries, it is not required to refill the battery.

Again, sulfation occurs massively in the flooded batteries. Because in the wet cell batteries the Lead and sulfate ions are actively found. This phenomenon is negligible for AGM batteries. That is why very little sulfation occurs in AGM batteries.

You have to regularly equalize the flooded batteries to keep the battery life stable. AGM batteries being maintenance-free does not require frequent equalization. Equalizing on a regular basis would get the job done.

The AGM batteries are completely sealed shut. There are no openings of any sort in the entire battery. This makes the battery spillproof and leakproof as well. Standard batteries on the other hand are not spillproof. It is tough to handle and the standard lead-acid batteries.

There is another form of AGM battery known as spiral AGM batteries. The Optima batteries are this type of Spiral AGM battery. The cells of the spiral AGM batteries are made in a cylindrical way. Its cell plates, separator, and grid together being highly compressed makes a cylindrical shape. 

Compared to the standard flooded batteries, spiral AGM batteries are very vibration resistive. They can easily sustain heavy movements without spilling the electrolytes or damaging the battery.

The depth of discharge of the AGM battery is quite higher than the standard battery. It is one of the main drawbacks of the AGM battery. Compared to the standard battery which has almost 80% depth of discharge. The AGM batteries only have a 50% depth of discharge. It means you have to remain extra careful about your battery being discharged deeply.

Overcharging can be a massive issue for the AGM battery but not for the standard battery. High voltage can cause damage to the AGM batteries in a great manner. Therefore, you have to only use a specified charger for charging the AGM battery. But for standard batteries, you can easily use all sorts of smart or conventional chargers. 

Comparison between AGM batteries and Gel-filled batteries

The name of the battery says it all. In the gel battery, silica is mixed with electrolytes to make it in a gel form. Whereas in AGM batteries, the electrolyte is absorbed by the presence of a glass mat in between the lead plates.

Both of these batteries are spillproof and vibration-resistant. It is because none of these batteries have the free liquid form of Electrolytes. Comparing the self-discharge rate, the gel-filled batteries have higher power-losing capability.

On the other hand, AGM batteries have a very slow self-discharge rate. But, the power consumption capacity of the Gel-filled battery is quite high. Coming to the depth of discharge, gel batteries perform better than AGM batteries. It can go up to 80% or more whereas the discharge limit of the Gel battery is limited to 50% only.

If you want instant cranking power then the AGM battery is better. The gel-filled battery cannot put up with a heavy burst of cranking amps. Therefore, gel-filled batteries perform better in warm conditions and AGM batteries work better in cold conditions.

Recharging the AGM battery is faster and easier than Gel-filled batteries. Recharging both the gel-filled battery and AGM battery is sensitive.

Can you understand if your battery is in a deep cycle or not?

It is important for you to understand the difference between the normal battery and the Deep Cycle battery. Because in case of upgrading or replacing the battery you must know the type of battery you are dealing with. You cannot replace a deep cycle battery with a normal one.

For knowing if your battery is a deep cycle or not, you can perform a series of actions. A deep cycle battery has higher cold-cranking amps. The regular battery cannot produce high bursts of electric current. Therefore, a standard load test using the compatible battery tester can be done to differentiate the battery type.

Moreover, the reserve capacity(RC) of deep cycle batteries is higher than the normal battery. A deep cycle battery can deliver constant 25 amps of cranking amps maintaining the minimum voltage limit. This cannot be done by the regular battery.

How to understand whether your battery is AGM deep cycle or not?

An AGM battery has several hundred or thousands of Cold Cranking Amps(CCA). If you want to confirm that your battery is an AGM deep cycle a physical test can be done. You can check for any cell opening caps available on the lid of the battery. Only AGM and gel-filled batteries have completely sealed battery compartments.

Again, you can shake the battery unit to check for any splashing noise from the cell chambers. AGM batteries do not have liquid electrolytes inside the cell chambers.

Performing the load test, identification of the battery can be done easily. Other deep cycle batteries than the AGM battery cannot show heavy load testing results.

Are AGM deep cycle batteries better than others?

AGM batteries have a technologically advanced build-up. This enhances the battery performance at the field level. 

AGM battery vs Standard battery 

AGM batteries show a very low discharge rate than other deep cycle batteries cannot perform. Moreover, AGM batteries have higher power developing capacity and a high CCA rating. This battery can get charged very quickly unlike other deep cycle batteries. To an extent, it can get charged up to 5 times faster than others.

Further going, you do not have to pour distilled water to keep the cell chambers flooded. Even the sulfation rate of AGM batteries is lower than other deep cycle batteries. Importantly, AGM batteries are completely spill-proof and vibration-resistant. This makes the battery maintenance free.

AGM battery vs Gel batteries

Both AGM battery and Gel-filled batteries can be used on extreme vehicular activities. But gel-filled batteries have high maintenance costs. Whereas, Gel batteries have high sensitivity to the recharging process.

The charge holding capacity of the AGM batteries is higher than Gel batteries. Moreover, AGM batteries can produce higher CCAs than gel batteries. Coming to durability, AGM batteries can easily withstand rough handling and movement. For all these reasons, AGM batteries are considered better than other deep cycle batteries.


The development of the AGM battery is a wonder in the field of batteries. It has significantly increased the safety of portable batteries. Besides, the dangers and accidents caused by the batteries have been reduced with the introduction of AGM batteries.

Out of several deep cycle batteries, the AGM batteries have topped with lots of new enhancements. Except for some drawbacks, the AGM batteries are compatible with most of the applications of emergency power delivery.

For some regular maintenance, replacement, or upgrading your current battery would need you to identify the battery. That is why you must know what is an AGM deep cycle battery.

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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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