Car Batteries

AGM vs Flooded Battery: What Are The Differences?

Mike Cross
Updated Oct 28, 2021
AGM vs Flooded Battery What Are The Differences

There are a variety of subcategories when it comes to lead acid batteries. This article will look at two of those. We will discuss a flooded battery and an AGM battery. The third type that we will not cover here is the gel cell battery.

Once you are done reading this you will know the difference between a flooded battery and an AGM battery and know which one is a better option for you.

Battery Basics

Before getting into a flooded battery vs an AGM battery we will give a brief explanation of how a lead acid battery works. Knowing this is important to understand fully the differences between an AGM battery and a flooded battery.

A lead acid battery is made up of three main things. Those things are sulfuric acid, metal plates, and water. The sulfuric acid is normally 35% and the water is 65% and this mixture makes a fluid called electrolyte.

This electrolyte is what produces the electrons that produce the charge. The metal plates are what the electrons pass thru to discharge from the battery and give off the charge. This is a simple explanation, but is good enough for here.

AGM vs Flooded Battery What Are The Differences
AGM vs Flooded Battery What Are The Differences

Flooded Battery

The flooded battery is also known as the wet cell battery and it is the most simplest battery available. These batteries resemble the earliest batteries most closely.

Between each plate is called a cell and in a wet cell battery the electrolyte mixture is just held between the plates in a liquid form. Since the battery is full of liquid it makes them heavy

Flooded Battery

Pros of Flooded Battery

The good thing about a flooded battery is that they are simple, and that makes them cheap.  Affordability is one of the biggest reasons why they are so popular.

Another reason that wet cell batteries are good is that they come in the biggest variety of sizes. This means no matter what you are needing a battery for, there should be a wet cell one that works for your needs.

This is another reason why some people use them because they might not be able to find another type of battery is the capacity or size they need.

Cons of Flooded Battery

The downside to flooded batteries though is that they require a lot of work to maintain. Since they are filled with liquid, the liquid can evaporate or freeze.

This means that every so often you have to check to make sure that the right volume of liquid is inside of it. If it is too low, then you have to add water. This loss of liquid can also affect the charge of the battery.

Another downside to wet cell batteries is that they can be dangerous. The acid inside of the battery is very corrosive and bad for you to touch or for it to get on things. If the shell of the battery cracks or the liquid comes out, then it can cause damage to other things.

Wet cell batteries are also the most common to have exploding issues. This is because if you over fill them, then they can bust especially when they get warm because the liquid inside will expand. This can make them dangerous. However, if cared for properly and maintain well, they can last for a long time.

AGM Battery

Now we will cover the basics of an AGM Battery. In an AGM battery between the plates are thin glass matts. That is because AGM stands for absorbed glass matts.

These matts is what holds the electrolyte liquid and they are only wet enough to hold the proper amount of liquid. This makes AGM batteries light.

An AGM battery

Pros AGM Battery

Outside of being light they are also safe. You don’t have to worry about the liquid spilling out and the only maintenance that has to be done on them is recharging to break the sulfur off the plates.

They can go longer without having to be recharged to since the liquid isn’t being held on the plates. The fiberglass suspended the liquid making them have low resistance as well, so they can be used for anything.

Cons of AGM Battery

The downside to AGM batteries is that they cost more than other types. This is offset some though because of how long they last. Another negative about AGM batteries is that they can be sensitive when charging.

They should not be discharged below 50% and when charging you want to make sure you don’t undercharge them, but you don’t want to overcharge them either. These things can really affect the battery life.

When to use

So when should you use each one? Well, flooded batteries are good for backup batteries, utilities, and grid power. While AGM batteries can be used every including off grid power systems and even vehicles.

Both types of batteries have their place and can be good. AGM batteries hold a charge better and are safer since just the right amount of liquid is held in suspension in the fiberglass and it isn’t just floating around inside.

Wet cell batteries though are very versatile and are cost effective if you need a lot of batteries. Flooded batteries can last a long time to with proper maintenance and care.


So now you have a better understanding of what a flooded battery is and what an AGM Battery is. You should understand how both types work now and what makes them different from each other.

If you want to learn more about the third type of battery which is Gel, then we have articles for that and if you want a more in-depth understanding and uses of AGM batteries, then we have an article explaining that as well, so you can learn as much as you want about the different types of lead acid batteries and what makes them different from each other.

Mike Cross
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