Absorbed Glass-mat, Enhanced Flooded Battery, What s The Difference. Agm battery repair

The Complete Guide to AGM Batteries

You’ve heard the term AGM battery before and may even know that it stands for Absorbent Glass Mat. But, what does Absorbent Glass Mat (AGM) actually mean and how does that enhance the battery’s performance over standard lead acid batteries?

Let’s review some basics of the SLA (sealed lead acid) battery construction. All SLA batteries are comprised of lead plates (positive and negative) and electrolyte that are then arranged into “cells” and placed into a battery case. Some of these batteries are also valve-regulated, which allows for the escape of minor amounts of gas that occurs during the recombination process during charging. Although these batteries allow gases to escape, they are spill-proof batteries (sometimes called valve regulated lead acid or VRLA), and allow for safe operation in almost any position (the only limitation is they are not recommended to be used upside down). Because they are sealed, you don’t need to add electrolyte after the manufacturing process, and any gases that are generated go into a recombination cycle.


In AGM type batteries, the construction follows the same basics as standard SLA, with the addition of a fiberglass mat that is placed between each negative and positive plate to absorb the electrolyte. Since the mat acts like a sponge with the electrolyte, the battery becomes non-spillable.

The AGM battery holds the electrolyte in place and works by allowing the electrolyte to be passed through the fiberglass mat, creating maximum surface area for the electrolyte to touch the plates without it flooding the battery with too much fluid. AGM batteries contain only enough electrolyte to keep the mat wet and if the battery is broken no free liquid is available to leak out. This allows for less electrolyte in the battery while still providing the same energy as traditional SLA batteries.


When most people think of AGM batteries, they likely think of deep cycle battery applications. However, not all AGM batteries are deep cycle. While a popular choice for deep cycling, as an AGM battery has a depth of discharge (DoD) of 80% versus a standard flooded battery which has a DoD of 50%, it is also a popular choice for starter batteries. This is because it has low internal resistance and can provide high current loads quickly. AGM batteries are also being used as start-stop batteries in modern cars, this is due to flooded batteries not being robust enough to handle the repeated cycling in start-stop applications which can cause the battery to fail after only a couple of years use.

For example, at Power Sonic we offer our AGM technology in both deep cycle AGM batteries (the PDC line) and as a popular option in our PowerSport family (Super Sport, Ultra Sport AGM, and our Stop-Start AGM lines). However, AGM is also the technology we use in our general purpose (PS) and long life (PG) families of products as the Absorbent Glass Mat separator maximizes the surface area of the electrolyte improving battery performance.

Each cell in an AGM battery has 2 volts so AGM batteries are available in a variety of voltages including popular 6V and 12V models.


One of the advantages of an AGM battery is they can be charged up to five times faster than a standard flooded battery. As with all sealed lead acid batteries, AGM are sensitive to over-charging, we recommend this guide to charging sealed lead acid batteries to ensure get the most out of your AGM battery.


Yes AGM batteries are recyclable. than 98% of an AGM battery can be recycled. We in the battery industry are very proud of the fact that lead acid batteries are one of the most highly recycled products on the planet. AGM batteries are environmentally friendly and easy to recycle, they can be recycled at almost all recycling centers, along with many automotive outlets and thousands of other locations.


There are many benefits of AGM technology over its older flooded battery construction. One big benefit of the fiberglass mat is that since the mat holds the acid, the battery is less likely to sulfate. This characteristic is what allows it to reach a deeper DoD than it’s flooded equivalent.

The lower internal resistance of the AGM battery also has a lower self-discharge rate and therefore doesn’t require a topping charge as frequently as a flooded battery would in long term storage conditions. It is important to note that AGM batteries still must be charged before storing and will require maintenance charging while in long term storage but will charge faster than a flooded battery.

Some advantages that AGM has over flooded batteries (as well as faster charging) are increased cycle life and vibration resistance. This is because the combination of the tightly packed AGM battery and the mat inside act as a damper, which are characteristics that lend nicely to power sport applications. Another benefit of the mat is that the battery requires less electrolyte than flooded batteries, which decreases its weight.

However, one of the down sides to the AGM battery is its cost – at slightly higher than flooded, you will pay more for a battery that doesn’t need to be maintained in the same way a flooded battery does. In fact, cost is one of the reasons flooded batteries are still commonplace (usually seen more in motorsport applications).


Another popular alternative to flooded and AGM type batteries is the Gel battery. A Gel battery is still maintenance-free, its cells are sealed, and it uses a recombination process to prevent the escape of its gasses. What varies with a Gel battery is the electrolyte itself is a thixotropic gelled sulfuric acid.

When comparing a Gel battery to an AGM battery, you will see that the Gel battery’s rated capacity will decline much faster than an AGM battery’s as the ambient temperature get colder (below 32 degrees F). A Gel battery is also does not perform as well in high rate or starter applications as an AGM, which is why you don’t see Gel power sport batteries. On the plus side for Gel, it is more acid limited, giving it a slightly longer service life in some applications. Power Sonic offers Gel batteries in our DCG (Deep Cycle Gel) and our 2-volt OPzV Tubular Gel lines.


There are many differences between AGM and lithium batteries. When it comes to choosing the right battery for your application, you need to understand exactly what you are looking to get out of the battery. Is it a deep cycling application, a high rate discharge application or a float standby application? Does the application already have a built in charger for a specific chemistry? What is your budget? etc.

We at Power Sonic have put together a comprehensive guide to the differences between sealed lead acid batteries and LiFePO4 batteries, this should be able to help you to see whether AGM is the better choice for your application.

To summarize, depending on the application and your budget, you will find the AGM battery to be the more superior battery over flooded battery types due to its lower weight, lower maintenance, and overall enhanced performance. You will also find AGM to be a popular choice over the Gel batteries as they are much more common and usually less expensive. The battle between AGM and lithium batteries will depend on your application and what you are looking to get out of the battery.

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If you have any questions about which battery is more suitable for your application, please feel free to call or email us.


Find the right battery for your application today. Many of Power Sonic’s wide range of sealed lead acid batteries utilize the latest in AGM technology.

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Manufactured using the latest technology and stringent quality control, our battery products are designed to exceed in performance and reliability.


Our focused approach to exceptional end to end customer experience sets us apart from the competition. From enquiry to delivery and everything in-between we regularly exceed our customers’ expectations.


Delivery on time, every time to customer specifications. We pride ourselves on offering tailored service solutions to meet our customers’ exact specifications.

Absorbed Glass-mat, Enhanced Flooded Battery, What’s The Difference?

Cars have changed over the years. There was a time when a car battery started your car and powered the radio. Many of today’s vehicles need a battery to meet increased power demands. Car accessory demand has tripled since 2009, with new bells and whistles added yearly.

Standard flooded batteries are the most common car battery on the market. They have advantages, but they come with some limitations. They provide power to start your car and support electrical accessories. Enhanced flooded batteries and absorbed glass-mat batteries are newer technologies that offer more power for modern vehicles.

AGM and EFB batteries are rechargeable and required for newer cars with greater power demands.

Finding the right replacement car battery can be overwhelming. Many options are available, but it’s essential that you get the right one.

Standard flooded batteries

A standard or traditional flooded battery is a lead-acid battery used to crank a car’s engine and support standard accessories while the engine is running. If your car requires more than the usual power load, this battery might not suit your vehicle.

Examples of cars that use a standard battery include the Toyota Tacoma, Toyota Corolla and Lexus RX.

Did you know that spring and fall are the best times to test your car battery?

It’s best to check your battery before extreme weather hits with a free battery test at any Interstate All Battery Center ® or select repair locations.

Enhanced flooded batteries EFB

An EFB is a wet-filled battery like a standard flooded battery, but it’s more durable, stores more energy and has a longer life.

The many benefits of EFBs include the following:

  • Durability
  • Energy storage
  • Battery life
  • Weatherproof
  • Start-stop friendly
  • affordable than AGM

Some examples of cars that use EFB batteries are the start-stop versions of the Fiat 500, Toyota Yaris and the Ford ECOnetic range.

Are you looking for an EFB or AGM battery for your car or truck? Are you still unsure? Check out our premium car and truck battery page now to ensure you get the right power for your vehicle.

Absorbed glass-mat batteries AGM

AGM batteries are becoming the standard for modern cars because they demand more power for entertainment and GPS systems, cameras, plug-in devices and more. This battery is a must for cars that already come with an AGM.

AGM batteries use glass mats to absorb 100 percent of the electrolyte, making it spill proof.

AGM batteries are made to meet or exceed original equipment specifications. They’re the Smart choice for many new cars with start-stop technology or power-hungry accessories.

Not all AGMs are the same

Pure lead AGMs are 99 percent pure lead and offer advanced power and superior battery life. Alloy AGMs are made from mixed metals and are less refined than pure lead AGMs.

Pure Lead AGM Batteries

  • 99.9% pure lead
  • Up to 2x battery cycle life vs. flooded batteries
  • Fastest recharge times
  • Slowest self-discharge/shelf life
  • Sealed. zero water loss

Alloy AGM Batteries

  • Recycled lead alloy metal
  • Similar to pure lead AGM, but not as powerful
  • Less expensive than pure lead AGM

Some examples of cars that use an AGM battery include the Buick Encore, Jeep Compass and the Ford F-150.

Are you looking for a particular battery, battery accessory or something more?

Find all your battery and power accessory must-haves at an Interstate All Battery Center ®.

Find the right battery for you

When it’s time to replace your car battery, finding the correct one is critical. Deciding which is best for you can be overwhelming. The good news is that we are always here to help you find the right battery for your vehicle.

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How Do I Know if My Battery is AGM?

If your vehicle is about to undergo repair, and the mechanic is suggesting a battery replacement, do you know how to choose the right battery for your vehicle? Since it’s something that we don’t do often, most people don’t know much about it. Actually, there are various types of batteries used in different vehicles.

For instance, usually, boats and cars support lead-acid batteries. However, the batteries which come with lead-acid in liquid form have plenty of shortcomings and do not last much longer.

In contrast, AGM batteries are now being used more often since they do not contain any liquid acid, and are more efficient. AGM basically stands for Absorbed Glass Mat Battery, in which a thin mat made of fiberglass is placed between the electrolyte plates, and packed tightly. These mats are basically saturated with acid, and since they are packed so well, there’s almost no chance of acid spillage like the wet cell batteries.

Hence, the AGM batteries are much safer, and usually last longer. That said, if you are looking for a battery replacement for your car, substituting the old wet cell batteries with AGM batteries is quite a good decision. But, you should know that the handling methods of both kinds of batteries are quite different from each other. So, how would you know if the currently installed battery in your car is AGM or not? We’ll tell you!

How to Make Sure the Battery is AGM?

Whenever you think of repairing or replacing the battery, you should be aware of the handling methods and be careful at all times. It’s important because wet cell batteries and dry cell batteries (AGM batteries) have different handling methods. So, before proceeding with any repair or replacement, you should verify what type of battery you are going to deal with. Actually, to know if the battery is an AGM type or a wet cell, there are three simple ways you can use to find out.

Method 1. Check the Manufacturer’s Label on the Battery

Usually, all the batteries have labels and other information about the battery provided by the manufacturer. Hence, if the label on the battery is still in good condition, you will be easily able to figure out the type of battery. In the case of AGM batteries, it’s usually mentioned on the label. However, if you don’t see AGM written anywhere on the label, you can look for the model number of the battery and check for its information online, or contact the manufacturer and ask for it.

Method 2. Look at the Top of the Battery

If the label is not in good condition, and not helping you much, you can know about the type of battery by looking at its design and construction. Basically, an AGM battery will always have a flat top, and only the negative and positive terminals of the battery will be sticking out. On the other hand, the liquid acid batteries have a removable top which is not the case with AGM batteries as they are properly sealed.

Method 3. Shaking the Battery

As we said earlier, AGM batteries are a better substitute for liquid acid batteries because there’s no risk of acid spillage. This means you can check for the battery type just by shaking it. Simply unplug the battery and take it out of the vehicle. Now, shake the battery and notice if you feel any liquid wiggling inside it. If yes, then it’s a conventional wet cell battery. On the other hand, in case you don’t feel any wiggle, it’s an AGM battery since they have acid trapped between the mesh as absorbed by the fiberglass mats.


If you have read this article until now, we can assume that now you will be able to figure out the battery type very easily. Finding out if the battery is AGM is quite simple, but still, we would suggest you consult the manufacturer to confirm if the battery is AGM or not. If you are thinking of a battery replacement, then replacing the old liquid lead acid battery with a new AGM battery is a good decision any day.

Because AGM batteries are easy to handle and have less maintenance, unlike other types of batteries. over, they are much safer and have a longer life too. That said, if any information from this article helped you in any way, do let us know about your experiences in the Комментарии и мнения владельцев section below.

Lead Acid battery downsides

It is typically considered wise to use just 30% – 50% of the rated capacity of typical lead acid “Deep Cycle” batteries. This means that a 600 amp hour battery bank in practice only provides, at best, 300 amp hours of real capacity. If you even occasionally drain the batteries more than this their life will be drastically cut short.

2/ Limited Cycle Life

Even if you are going easy on your batteries and are careful to never overly drain them, even the best deep cycle lead acid batteries are typically only good for 500-1000 cycles. If you are frequently tapping into your battery bank, this could mean that your batteries may need replacement after less than 2 years use.

3/ Slow Inefficient Charging

The final 20% of lead acid battery capacity can not be “fast” charged. The first 80% can be “Bulk Charged” by a Smart three-stage charger quickly (particularly AGM batteries can handle a high bulk charging current), but then the “Absorption” phase begins and the charging current drops off dramatically.

Just like a software development project, the final 20% of the work can end up taking 80% of the time.

This isn’t a big deal if you are charging plugged in overnight, but it is a huge issue if you have to leave your generator running for hours (which can be rather noisy and expensive to run). And if you are depending on solar and the sun sets before that final 20% has been topped off, you can easily end up with batteries that never actually get fully charged.

Not fully charging the final few percent would not be much of a problem in practice, if it wasn’t for the fact that a failure to regularly fully charge lead acid batteries prematurely ages them.

4/ Wasted Energy

In addition to all that wasted generator time, lead acid batteries suffer another efficiency issue – they waste as much as 15% of the energy put into them via inherent charging inefficiency. So if you provide 100 amps of power, you’ve only storing 85 amp hours.

This can be especially frustrating when charging via solar, when you are trying to squeeze as much efficiency out of every amp as possible before the sun goes down or gets covered up by clouds.

5/ Peukert’s Losses

The faster that you discharge a lead acid battery of any type, the less energy you can get out of it. This effect can be calculated by applying Peukert’s Law (named after German scientist W. Peukert), and in practice this means that high current loads like an air conditioner, a microwave or an induction cooktop can result in a lead acid battery bank being able to actually deliver as little as 60% of its normal capacity. This is a huge loss in capacity when you need it most…

The above example shows specification of Concord AGM battery : this spec states that the battery can provide 100% of it’s rated capacity if discharged in 20 hours (C/20). If discharged in one hour (C/1), only 60% of rated capacity will be delivered by the battery. This is direct effect of Peukert losses.

At the end of the day, an AGM battery rated for 100Ah at C/20 will provide a 30Ah usable capacity when discharged in one hour as 30Ah = 100Ah x 50% DoD x 60% (Peukert losses).

6/ Placement issues

Flooded lead acid batteries release noxious acidic gas while they are charging, and must be contained in a sealed battery box that is vented to the outside. They also must be stored upright, to avoid battery acid spills.

AGM batteries do not have these constraints, and can be placed in unventilated areas – even inside your living space. This is one of the reasons that AGM batteries have become so popular with sailors.

6/ Maintenance Requirements

Flooded lead acid batteries must be periodically topped off with distilled water, which can be a cumbersome maintenance chore if your battery bays are difficult to get to.

AGM and gel cells though are truly maintenance free. Being maintenance free comes with a downside though – a flooded cell battery that is accidentally overcharged can often be salvaged by replacing the water that boiled off. A gel or AGM battery that is overcharged is often irreversibly destroyed.

7/ Voltage Sag

A fully charged 12-volt lead acid battery starts off around 12.8 volts, but as it is drained the voltage drops steadily. The voltage drops below 12 volts when the battery still has 35% of its total capacity remaining, but some electronics may fail to operate with less than a full 12 volt supply. This “sag” effect can also lead to lights dimming.

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8/ Size Weight

A typical 8D sized battery that is commonly used for large battery banks is 20.5″ x 10.5″ x 9.5″. To pick a specific 8D example, Trojan’s 8D-AGM weighs 167lbs, and provides just 230 amp-hours of total capacity – which leaves you with 115 amp hours truly usable, and only 70 for a high discharge applications!

If you are designing for extensive boon docking, you will want at least four 8D’s, or as many as eight. That is a LOT of weight to be carting around that impacts your fuel economy.

And, if you have limited space for batteries on your rig – size alone of the batteries will limit your capacity.

This article is the exclusive property of PowerTech Systems. Reproduction prohibited without permission.

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