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How to Tell if Battery is AGM (Differences)

AGM stands for Absorbed Glass Mat, and these batteries are designed for high performance and better longevity than traditional flooded lead-acid batteries. Curious about how to identify them?

Quick Summary – Identifying them involves checking for “AGM” or related terms on the label, observing a flat top and sealed appearance, or performing a wiggle and shake test. These batteries are maintenance-free, spill-proof, vibration-resistant, and have a low self-discharge rate, leading to longer lifespan and performance.

In this article, we’ll dive deeper into identifying AGM batteries and discuss some of their unique benefits. Stick with me, and you’ll be able to spot an AGM battery with confidence!

Why AGM Batteries are Different

mechanic installing an AGM battery to a car
Video | Counterman

AGM batteries are a type of lead-acid battery that has some unique characteristics compared to other battery types. Here’s how they are different:

  • Construction: AGM batteries use a special absorbent glass mat (AGM) that wicks the electrolyte solution between the battery plates. This makes them less susceptible to vibration, more compact and allows them to be used in any position.
  • No Free Liquid: In AGM batteries, the electrolyte (sulfuric acid) is held in the glass mats, unlike a flooded lead-acid battery where the electrolyte is free. This makes them non-spillable and safer to use.
  • Maintenance-Free: AGM batteries are sealed, so they’re maintenance-free. This means you don’t have to add water or electrolyte, which is necessary for flooded lead-acid batteries.
  • High Discharge and Recharge Efficiency: AGM batteries can deliver high currents, have a low internal resistance, and can be charged quickly compared to other types of batteries.
  • Deep Discharge Recovery: AGM batteries have a good tolerance for deep discharge and can be recharged back to full capacity repeatedly without damaging the battery, which makes them ideal for applications such as solar panels, RVs, and boats.
  • Lower Self-Discharge: The rate of self-discharge in an AGM battery is lower than in other types of lead-acid batteries, which helps extend its lifespan.
  • Vibration Resistance: The tightly packed construction of an AGM battery makes it highly resistant to vibration, which adds to its durability.

Remember, every type of battery technology has advantages and disadvantages, and the best choice will depend on the specific use case.

AGM batteries, with their unique features, are often a good fit for high-performance and heavy-duty applications.

Identifying an AGM Battery

Quick Guide to Identify an AGM Battery

CharacteristicsHow to Identify
Label and Model NumberCheck for “AGM” or related terms on the label. If unclear, search for the battery’s model number online or contact the manufacturer.
Battery Top and Removable CapsAGM batteries have a flat top with no removable caps.
Wiggle and Shake TestIf the battery doesn’t leak or make sloshing sounds when shaken, it’s likely an AGM battery.

Label and Model Number

Alright, guys, the first thing I usually do when checking if a battery is AGM is to look for the label. Keep your eyes peeled for any mention of “AGM” directly on the battery.

Sometimes, it’s unclear, so you’ll want to check the model number. Go ahead and search for the battery’s model number online, or simply contact the manufacturer to get the details.

Battery Top and Removable Caps

Now let’s talk about the battery top. AGM batteries are designed to be maintenance-free, so they typically have a flat top without any removable caps.

Unlike other batteries, you don’t need to worry about topping off the electrolyte in an AGM.

Appearance and Orientation

What you’ll notice about AGM batteries is that they have a distinct appearance. Not only is the top flat but the separator is made of fiberglass, separating the lead plates inside.

This fiberglass separator gives the battery flexibility and can be placed in different orientations without problems. So, if the battery looks sealed and versatile, it’s probably an AGM battery.

Wiggle and Shake Test

mechanic installing an AGM battery to a car
Video | Counterman

Here’s a fun little test I love to do with AGM batteries – the wiggle and shake test.

Because of the fiberglass separator and no free liquid in the battery, AGMs won’t spill or leak if you give them a good shake.

So give that battery a wiggle and a shake; if it doesn’t leak or make any sloshing sounds, you might have an AGM battery.

Comparison of AGM vs. Traditional Flooded Lead-Acid Batteries

CharacteristicsAGM BatteriesTraditional Flooded Lead-Acid Batteries
MaintenanceNo regular maintenance neededRequires periodic topping off of electrolyte
Vibration ResistanceHighLow
Self-Discharge RateLowHigh
Life Cycle and Service LifeLongShorter compared to AGM
Performance in Cold TemperaturesHighLow
Resistance to SulfationHighLow

Performance and Lifespan Advantages

Vibration Resistance

Let me tell you, AGM batteries have a fantastic feature in that they’re highly resistant to vibrations.

The unique construction with the absorbent glass mat between the lead plates keeps things tight and secure inside the battery.

This is great news for folks using AGM batteries in their motorbikes, boats, or off-road vehicles, where vibrations are a fact of life. Trust me, a stable battery equals a happy vehicle.

Self-Discharge Rate

Now, I know we all have those moments when we don’t use our vehicles or devices for a while, and this is where AGM batteries shine, my friends! These batteries have impressively low self-discharge rates.

In comparison, traditional flooded lead-acid batteries can’t boast the same. Remember, a lower self-discharge rate means the battery retains its charge longer when not in use.

Also, the maintenance aspect is minimal because of its non-spill, dry-cell design.

Life Cycle and Service Life

AGM batteries love to show off with their longer life cycle and overall service life, especially when we’re talking about the Renogy deep cycle batteries!

Typically, AGM batteries last longer than conventional flooded lead-acid batteries. This is due to their impressive ability to resist sulfation, that pesky chemical process that hinders battery performance over time.

Your golf carts and electric vehicles will surely appreciate the longevity of AGM batteries; I know I do!

So there you have it! AGM batteries are all about performance, power, and safety. Plus, they’re spill-proof and withstand cold temperatures with ease.




  • “Batteries in a Portable World: A Handbook on Rechargeable Batteries for Non-Engineers” by Isidor Buchmann.


Video References


Canbat Technologies Inc.

The Battery Shop

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About Alex Robertson

AvatarCertifications: B.M.E.
Education: University Of Denver - Mechanical Engineering
Lives In: Denver Colorado

Hi, I’m Alex! I’m a co-founder, content strategist, and writer and a close friend of our co-owner, Sam Orlovsky. I received my Bachelor of Mechanical Engineering (B.M.E.) degree from Denver, where we studied together. My passion for technical and creative writing has led me to help Sam with this project.

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