The Ultimate Guide for AGM (Absorbent Glass Mat) Battery

AGM Battery

Absorbent Glass Mat batteries are used as an efficient solution to save and use energy.

This article will discuss what actually AGM batteries are, their difference from traditional versions, and where you can use them. We’ll also discuss how to properly maintain and charge them.

What is AGM Battery?

AGM batteries are one variety of battery technology. It works in lead-acid batteries, like those in automotive usage. Plus, they are manufactured to be more efficient than other traditional types.

Thin mats composed of fiberglass material are used in producing these batteries. Then, this thin mat absorbs the electrolyte. As a result, it allows the battery to be sealed and watertight.



AGM battery is composed of a separator, electrolyte, casing, and lastly negative plates & positive plates.

– The separator is the absorbent glass mat that separates the positive and negative plates.

– The electrolyte is a sulfuric acid and water mixture. It supplies the electrical charge needed to power up the battery.

– The casing is made of plastic or metal. It is designed to protect the battery from the environment.

–  The negative plates and positive plates are made up of thin lead sheets. These plates are then connected to the terminals of the battery.

AGM Batteries Characteristics

Observe the following characteristics to determine if a battery type is AGM.

  • First, check if the battery has a heavier plate design. The reason why heavier is because the plates are being tightly packed.
  • Another characteristic is they are typically sealed and don’t require regular maintenance.
  • Then, its housing is made of plastic. AGM batteries also have a lower profile design compared to traditional batteries.
  • Finally, they have superior cold-cranking amps. This makes them ideal for applications in colder climates.

AGM Differences from Standard Batteries

Totally sealed. Meaning, they are maintenance-free and can be installed in any position. Standard batteries must be filled with electrolytes and must be kept upright.
Spill-proof and can be used in enclosed spaces. Standard batteries are prone to leaking.
Designed with greater power density. Therefore AGM batteries can bring more power in smaller sizes. Standard batteries need to be larger to achieve the same power output.
More expensive but they are also more reliable and have a longer life. Cheaper compared to AGM types.
Can be recharged quickly and can tolerate deep discharge cycles. While standard batteries cannot.

Where Does Absorbed Glass Mat Batteries Applicable?

Where Does Absorbed Glass Mat Batteries Applicable

They are increasingly popular choices for applications such as:

Automotive. Typically used in cars and light-duty vehicles. It provides power to the starter, lights, and other electrical components.

Marine. Used particularly in boats and other marine vessels.  The batteries supply energy to the starter, lights, and more.

Industrial. Used for various tasks including providing standby power for machinery and equipment. They also provide power for forklifts and other material-handling equipment.

Solar. Stores energy from photovoltaic panels and provide power to electrical systems.

Backup Power. Applied in uninterruptible power supplies (UPS) and other backup power systems. This provides emergency power when utility power fails.

Telecommunications. AGM types are the right batteries for sustaining telecom equipment’s power. It supplies standby and backup power for switching systems or base stations.

Mobility. Used in providing power for operating electric wheelchairs and mobility scooters.

Trolling Motor. AGM battery provides consistent power over an extended period of time. That’s why they are suitable for trolling motors.

Four Types of AGM Battery

Below is a list of the different types available in the market.

  1. Flooded Lead Acid (FLA): This is the most common type of AGM battery. It is often used in automotive applications. This type consists of lead plates suspended in a liquid electrolyte solution.
  2. Gel Cell: This type uses a gel electrolyte instead of a liquid. The gel is more resistant to vibration and shocks. Therefore, this type finds suitable for applications where the battery will experience movements.
  3. Carbon Foam AGM: It uses carbon foam to provide increased cycle life and reduce weight. You can find them commonly used in Electric Vehicles and stationary storage applications.
  4. Valve Regulated Lead Acid (VRLA): Sealed type and does not require electrolyte addition. It is designed to be maintenance-free. And known to provide consistent output over long periods.

Pros & Cons of Using AGM-Type Battery

Like other batteries, using an absorbent glass mat battery has both pros and cons.


-Low maintenance: AGM batteries require minimal maintenance.

-Safe to use: Since sealed, they are safer than other battery types. Another reason is that they don’t require regular refilling with electrolytes.

-Reliable energy source: AGM types are built to supply outstanding power. Therefore, they can handle a wide range of temperature conditions.


-High price: They can be pricey compared to other traditional batteries.

-Heavy: Also can be quite heavy, which makes them difficult to move around. And could potentially reduce the range of a vehicle.

-Vibration: The batteries are more sensitive to vibration, which can cause them to malfunction.

How to Tell When Absorbent Glass Mat Batteries are Bad

They have superior performance and a long lifespan. But like all batteries, they can degrade over time. To ensure your AGM battery is working properly, it’s important to know how to tell when they’re bad. Here are the signs.

  • Battery Will Not Hold a Charge
  • Diminished Performance
  • Overheating
  • Swelling or Bulging
  • Low Electrolyte Levels
  • Corrosion at Battery Terminals
  • Bad Smells
  • Excessive Vibrations
  • Unusual Noises
  • Battery Self-Discharge
  • High Internal Resistance

Charging Techniques for Standard AGM Batteries

Charging Techniques for Standard AGM Batteries

Batteries require special charging techniques to achieve optimal performance.

The first step is to determine the best charger for the battery. AGM batteries require a charger that is specifically designed for them. This should be noted on the battery or charger itself.

Once the proper charger has been identified, next is to check the charger’s voltage and current output. It is important to ensure they provide the correct voltage amount for the battery.

After that, this is the time to begin charging the battery. Read the instructions that come with the charger and adhere to them.

Most AGM chargers require the battery to be connected first before the power is turned on.

The Most Recommended Charger

You should choose a multi-stage charger for your AGM batteries. These chargers provide a steady voltage over a period of time. Which will then allow the battery to charge more efficiently.

Multi-stage chargers also help to reduce the risk of overcharging – which can damage the battery. This is because they are designed to provide the correct charge.

AMP Requirement

If you are going to charge an absorbent glass mat battery, you will need an amp specifically designed to meet its unique charging needs.

As mentioned, charging the AGM battery needs the right charger. Aside from that, you need to consider the charger amperage rating. AGM charger must deliver between 5 and 15 amps – depending on the battery size being charged.

A charger with a higher amperage rating is able to charge a larger battery in a shorter time. While a charger with a lower amperage rating is used to charge a smaller battery for a longer time.

Overcharging AGM Battery: What Will Happen?

Overcharging AGM Battery What Will Happen

Overcharging can cause serious damage to the battery. Or even worst, can be a safety hazard.

When the AGM battery is overcharged, the electrolyte heats up. Which then causes the separator to expand.  This expansion can cause the positive and negative plates to come into contact with each other – leading to a short circuit. If that happens, that can cause sparks and the potential of a fire.

To prevent overcharging, make sure your battery is properly maintained. Always consider using chargers specifically designed for AGM batteries.

How Long Can AGM Battery Sit Without Charging?

Generally speaking, Absorbent glass mat batteries can remain idle without charging for up to 2-3 months, without any significant loss of performance. However, keep in mind that battery performance will degrade over time. Especially if the battery is left without charging for periods longer than 3 months.

To ensure that your battery continues to perform optimally, you should recharge the battery every 3months. Even though it has not been used during that months.

Maintenance Guidelines

AGM batteries require regular maintenance to ensure they last as long as possible.

The most important step is keeping them charged regularly. Preferably once a month to ensure they remain healthy. If the battery is not regularly charged, it can become sulfated. Resulting in reduced capacity and a shorter lifespan.

Another important step is to frequently inspect battery condition. This includes checking the voltage, the electrolyte specific gravity, and the water amount in the cells. Check all of these at least once a month. But if it is in hot climates, do it more often.

In addition to monthly checks, it is also important to perform regular maintenance on an AGM battery. This includes regularly checking the terminals for cleanliness and tightness. As well as ensuring the battery is properly charged. If the battery is left in a discharged state for too long, it can be permanently damaged. This time you need them replaced.

Finally, make sure to keep them in a dry and cool setting. High temperatures can reduce the battery life and cause permanent damage. It is also important to ensure that the battery remains in an upright position.

Absorbed Glass Mat VS Lead Acid Battery

Absorbed Glass Mat VS Lead Acid Battery

AGM and Lead acid batteries have so many differences, especially in design. Other differences include:

AGM Lead Acid
-More efficient -Less efficient
-More expensive -Less expensive
-Sealed -Must be packed with electrolyte
-Long service life – Perform best in moderate temperatures
-More lightweight -Heavier in design
-Vibration-resistant -While lead-acid types are not


AGM VS Lead Acid Charging

When charging, the dissimilarities between AGM and lead acid batteries are their charging rate.

The AGM is able to have higher charge rates compared to lead acid types. Therefore they can be charged faster. Besides, lead acid batteries require a slower charging rate to prevent overcharging.

AGM Differences from Gel Battery

One major difference between the two batteries is the electrolyte used.

In an AGM battery, the electrolyte is a liquid. Compared to a Gel battery, it uses a gel-like substance. This difference in electrolytes results in a few other differences between the two.

This makes AGM types have higher cranking amps, while Gel batteries have higher amp-hour ratings.

In terms of which has a longer life span, AGM batteries win. Additionally, AGMs typically require lesser maintenance. Very different from Gel batteries since they require periodic maintenance.

Dissimilarities of Flooded Batteries and AGM

Flooded batteries and AGM batteries are both used in automotive and recreational vehicle applications. While both types of batteries may look similar, they have many differences to take into consideration.

Their most notable difference is the design. Flooded batteries are designed with a vent cap to release gases and a liquid electrolyte solution. While the AGM type has a solidified electrolyte solution plus sealed. That way they require no maintenance or ventilation.

Another difference is the cost. AGM batteries typically cost more than flooded batteries. AGM also has a much higher cranking power than flooded batteries.

Flooded batteries are more prone to corrosion plus sadly require more frequent maintenance. Like frequently adding distilled water and cleaning the battery terminals.

Are Absorbent Glass Mat Batteries Recyclable?

Yes. Lead-acid batteries, including AGM (Absorbed Glass Mat) batteries, are one of the most commonly recycled consumer products. This is due to their lead content.

The benefits of recycling AGM lead-acid battery can help conserve natural resources, reduces the need for mining, and reduces air and water pollution caused by the manufacturing process.

When recycling them, it is important to follow the manufacturer’s instructions and local laws. AGM batteries should be recycled according to EPA regulations. It is illegal to dispose of lead-acid batteries in the garbage. If you are unsure of how to dispose of the battery, contact your local waste management agency for more information.

Service Life

AGM battery lifespan can vary depending on the battery quality, the application, and the environment it is used in. Generally, they are assumed to last for about 3-5 years.

To get the most out of your battery, it is important to properly charge and maintain it.

Absorbed Glass Mat Battery Price

Its costs can vary depending on the capacity and other factors.

By Capacity: Prices:
2V $10-$400
12V $60 – $300
6V, 8V, 10V $100 – $1,000
24V, 48V $500 – $3,000

Is it Worth It to Purchase AGM Battery?

Yes. They are worth it if you’ve been looking for a maintenance-free battery.

AGM batteries typically last 2-3 times longer than other types of batteries. For various applications, they are proven more vibrate-resistant and shock-resistant.

Even though they are generally more expensive, they are worth it in the long run.

Will They Work in Any Car?

No, AGM batteries are intended to be used in a few vehicles. Like cars of BMW brand, Mercedes-Benz, and Audi.

Can AGM Battery Be Reconditioned?

Yes, the batteries can be reconditioned if they are not damaged beyond repair. However, it is important to note that reconditioning a battery can only be done by a professional. Reconditioning an AGM battery involves testing it, replacing any damaged cells, and recharging it.

Can AGM Batteries Be Jump Started?

No. This specific battery should not be jump-started.

AGM batteries are sealed and do not have the same tolerance level for high currents as standard lead-acid batteries. So attempting to jump-start could cause irreversible damage.

Are They Recommended to Use in Cold Environments?

Yes. All types of AGM batteries are generally recommended for cold environment use. They do not freeze and are more resilient to cold temperatures.

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