What Is The Difference Between AGM and Lead Acid Batteries

When talking of conventional types of 12v batteries we always hear of AGM and Lead Acid batteries. I have had the experience of being asked which type I wanted when I was once shopping for a new battery. Not knowing the difference can be quite confusing. Especially if the sales person simply wants to make the sale and not really interested in wasting their time trying to educating the customer. So in this article I will explain the difference, keeping it as simple as possible and with a minimum of technical jargon.I will also explain which type, I feel, is more suitable for use in offroad vehicles. 

agm battery


AGM (Absorbent Glass Mat) batteries are a type of lead-acid battery. The main difference lies in their construction and electrolyte management. The key distinctions between the two are:

  1. Electrolyte Management:

    • AGM Battery: AGM batteries use a highly porous glass mat separator soaked in electrolyte. The electrolyte is absorbed and held within the glass mat, providing a stable environment for the chemical reactions to occur. This design eliminates the need for free-flowing liquid electrolyte, making AGM batteries spill-proof, maintenance-free, and resistant to vibration.

    • Flooded Lead-Acid Battery: Flooded lead-acid batteries have liquid electrolyte that freely flows around the lead plates. The electrolyte level needs to be regularly monitored and replenished with distilled water to compensate for evaporation or electrolyte loss. These batteries can be more prone to spills, require ventilation, and can be sensitive to orientation during operation.

  2. Construction:

    • AGM Battery: AGM batteries consist of lead plates, a glass mat separator, and a tightly packed cell configuration. The absorbed electrolyte provides intimate contact between the plates, allowing for efficient charge and discharge cycles. The sealed design of AGM batteries ensures there is no free electrolyte to spill, making them more versatile in terms of installation and usage.

    • Flooded Lead-Acid Battery: Flooded lead-acid batteries also contain lead plates, but they are immersed in a liquid electrolyte solution, usually sulfuric acid diluted with water. The plates are often suspended in the electrolyte, and the battery requires ventilation to dissipate any gasses produced during charging.

  3. Maintenance:

    • AGM Battery: AGM batteries are generally maintenance-free. They do not require regular electrolyte checks or refills, as the absorbed electrolyte remains stable within the glass mat. 

    • Flooded Lead-Acid Battery: Flooded lead-acid batteries require periodic maintenance. The electrolyte level needs to be checked regularly, and distilled water may need to be added to compensate for evaporation or loss. Additionally, the battery terminals may need cleaning or occasional equalization charging to mitigate sulfation and stratification.

  4. Application:

    • AGM Battery: AGM batteries are commonly used in various applications where maintenance-free operation, durability, and vibration resistance are crucial. They are popular in automotive, marine, RV, and off-grid energy systems. AGM batteries are known for their ability to deliver high currents and handle deep discharges without significant capacity loss.

    • Flooded Lead-Acid Battery: Flooded lead-acid batteries have been widely used for decades, particularly in automotive applications. They are known for their affordability and good all-around performance. These batteries are often used in traditional vehicles, boats, industrial applications, and backup power systems where maintenance is manageable and spillage is not a concern.



When it comes to deep cycle batteries, both AGM (Absorbent Glass Mat) and traditional flooded lead-acid batteries can be suitable and both types will deliver the same level of performance. Deciding on which types is more suitable depends on the specific requirements and preferences.



 In my opinion I would recommend AGM over Lead Acid for use in offroad vehicles for the following reasons:

-Vibration Resistance:

Offroad 4x4 vehicles often encounter rough terrain and vibrations. AGM batteries are known for their excellent vibration resistance due to their construction with absorbent glass mat separators. They can better withstand the rigors of offroading and are less prone to internal damage from vibrations compared to traditional flooded lead-acid batteries.


AGM batteries are maintenance-free, meaning they do not require regular electrolyte checks or refills. This can be advantageous for offroad enthusiasts who prefer a hassle-free and low-maintenance battery solution.

-Deep Cycling:

Offroad 4x4 vehicles often require batteries that can handle deep cycling, as they may encounter situations where the battery is discharged and recharged frequently. Both AGM and flooded lead-acid batteries can handle deep cycling, but AGM batteries tend to have a slight advantage in terms of depth of discharge and recovery. They can recover more efficiently from deep discharges, making them suitable for demanding offroad applications. 

-Durability and Safety:

AGM batteries have a sealed design, making them spill-proof and resistant to acid leaks. This can be beneficial in offroad environments where the battery may be exposed to vibrations, impacts, or inclines. Traditional flooded lead-acid batteries, although less resistant to vibration, can still be used in offroad vehicles, but extra precautions may be necessary to secure and protect them.

Ultimately, the suitability of AGM or flooded lead-acid batteries for offroad 4x4 vehicles depends on your specific needs and priorities. Consider factors such as vibration resistance, maintenance requirements, deep cycling capabilities, durability, and budget when making your decision. It's recommended to choose batteries from reputable manufacturers and select the battery type that best aligns with your  requirements.

I hope this has been of use to you. If you have any questions (or comments) please write to me 


Duncan Udawatta


This article is in a series of related articles which can be found in the EDUCATIONAL section of the website. These are:

-Why a DC-DC Charger is a Must-Have for Deep Cycle Batteries

-Understanding Usable Power Capacity of a Deep Cycle Battery 

-How to chose a deep cycle battery for your consumption.

-How to maintain batteries when parked for a prolonged period of time.



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