Deep Cycle Flooded Battery vs AGM: The Pros and Cons of Each

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Growing demand in South Korea, Malaysia, Indonesia, and India are responsible for rapid growth in the Asia Pacific battery market. This industry is poised to post growth of 9.2%

Two significant categories within the deep cycle market that are driving this growth are hybrid and pollution-free electric vehicles. But these batteries have so many more uses. 

The most common type of batteries bought are AGM and flooded batteries. They each excel in specific applications and have their pros and cons. 

Not sure which one is right for your needs? Use this guide to help you decide. 

Deep Cycle Flooded Batteries

These are the traditional batteries that were first used in applications that required a battery. They work by using lead plates that are surrounded by a sulfuric acid electrolyte solution. There are plate separators, but they only separate, the fluid is free to move about the plates. 

Unlike AGM and other types of batteries, flood batteries are not sealed. They do not recombine the gas produced into a liquid. Instead, the gas vents out externally. 

Because these are open vents that allow for internal gas and fluid to flow out, everything can escape through the vents. This includes condensation, steam, and acid.

Because of this, you’ll need to clean the outside of the battery around the vents. Be careful though; acid is extremely harmful to you. 

Flooded batteries do require regular maintenance. You’ll need to add water regularly to replenish the lost electrolytes. 


Typical uses of this type are grid energy storage, and utility. They work best in an application with little vibration or shaking. They are also used in golf carts and forklifts. 


These are the most reliable for applications that need a backup power supply. 

They come in the widest variety of shapes and sizes. This makes them ideal for fitting into a wide range of applications that may not accommodate other types of batteries. 

Of all the battery types on the market, they have impressive charge rates for their price. So if you’re looking for an affordable, well-performing battery, then this is it. 


The biggest con is they required regular maintenance. The lead plates deteriorate when they come into contact with the atmosphere. So as the battery works, the fluid level inside drops and the plates become exposed to air. 

When exposed to air, the plates begin to deteriorate. Once this happens, your battery will corrode and fail. You’ll need to buy a new battery after this happens. 

Because these batteries are vented, they are susceptible to the environment they are in. Extreme climates can cause the water to freeze or evaporate faster. This will increase the maintenance needs and shorten the useful life of the battery. 

This design gives them the weakest internal construction of all battery types on the market. They also have very high internal resistance statistics. 

Finally, there is no getting around the fact that these batteries have the potential to create a hazardous environment. Be sure to place yours in well-ventilated location so that there isn’t a buildup of hydrogen gas

Deep Cycle Absorbed Glass Matte or “AGM” Batteries 

These batteries have a special glass mat in them that separates the battery plates. It wicks the electrolyte solution away. As it works the fibreglass mat becomes soaked with electrolyte liquid. 

This way, the solution is stored in a “dry” state. Otherwise, the electrolyte solution would be in a free liquid state to slosh around. If the battery gets damaged or tipped over, the solution won’t pour out. 

There is plenty of solution in the fibreglass to run the battery at full capacity. As the battery works, the electrolytes transfer from the glass mat to the battery plates as necessary.


AGM batteries are often used in renewable energy applications. Think environmentally friendly systems such as solar or wind power. 

They are also commonly used in electric cars, robotics, or uninterrupted power supply systems. Then finally, they are ideal for certain motorcycles and ATVs. 


You will often here these batteries referred to as maintenance-free. This is because they don’t require the regular addition of water. 

They tend to perform better than flooded batteries because there is no free liquid. There is also no gassing. 

If you have an application where maintenance is tough, then these batteries are a great solution. You can place the battery and not have to worry about regularly accessing it. 

Because these batteries are packed so tightly inside, they are the most impact resistant. They also have the least internal resistance of your battery options. 


One downfall to these batteries is that they are temperamental when it comes to charging. If you over or under-charge the battery, you will negatively affect the performance and life of your battery. 

They perform at their peak when they are used in an application that doesn’t require more than 50% of their capacity. 

Which Is Right for Your Needs?

Before you decide whether or not a flooded battery or an AGM battery is right for you, consider all of the pros and cons. Think about your intended application and if your battery of choice will work well in that environment.  

Think about the size and shape of the space for the battery; you need it to fit securely. Also, consider your ability to maintain the battery. Think about if you are going to add water to the flooded battery or properly charge the AGM battery. 

Once you make your decision and buy your new battery, be sure to care for it properly. This will ensure that your battery lasts for its entire expected lifespan. 

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