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AGM Vs Lead Acid – What’s The Differences?

Right now, the most popular choice from a car battery is the traditional lead-acid battery which provides highly reliable and durable performance.

Although, there are multiple types of lead-acid batteries available in the market. Out of which, the most preferred options are absorbed glass mat (AGM) batteries or the older flooded batteries. Both of these options contain the electrolyte solution, which undergoes a chemical reaction and supplies charged electrons in the system.

While both of these batteries might look similar in application, each of them has certain advantages and limitations, which you must know before selecting one. Thus, we have come with this helpful guide where we will walk you through the important differences between an AGM and a lead-acid battery.

In this guide, we will be looking at different aspects of both batteries such as working principle, durability, internal resistance, power output, etc and find out the ideal option for your application.

Hence, we will recommend you to read the article until the end to find out the best option for yourself. But before we take a look at the pros and cons of both options, let’s try to understand these options and how they differ in construction and working.

What is an AGM Battery?

An AGM battery is named after the material which is used in its construction. These batteries are made with absorbed glass mat material and have gained a lot of popularity since 1980. These batteries used to be the most preferred option for high powered vehicles such as off-road motorcycles, military vehicles, and even aircraft. Nowadays, AGM batteries are highly simplified and are available for commercial as well as personal vehicles like cars and trucks.

An AGM battery is a completely sealed battery. This means that these batteries are leak-proof and completely maintenance free for the user. Thus, it is a great alternative choice for traditional options available in the market.  Because of its high power capacity, AGM batteries provide large amounts of starting current to the vehicle and offer a comparatively longer working period.

Pros and Cons of AGM Batteries

As the AGM batteries are also known as maintenance-free batteries, it offers certain advantages over other options. Here are some benefits of the AGM batteries:

  • AGM batteries are factory sealed and offered as maintenance-free batteries so that you won’t have to monitor the battery health from time to time.
  • You will not have to provide watering service to the AGM batteries.
  • Because there is a minimal amount of liquid inside the battery, the AGM batteries are free from spillage or leakage, even in case of an incident.
  • In comparison, AGM batteries perform much better than flooded lead-acid batteries.

Although, even AGM batteries have certain limitations, which might be a deal-breaker for most users. Here are some limitations that you will have to face with AGM batteries:

  • AGM batteries are easily affected in case of overcharging and undercharging. Thus, additional care needs to be taken while charging AGM batteries.
  • The best performance from AGM batteries is obtained when these batteries are above 50% of their capacity.
  • AGM batteries are best suited for powering renewable energy sourced equipment such as off-grid power systems.

What is a Flooded Lead Acid Battery

If you have any prior experience with batteries, there is a good chance that you already know about flooded lead-acid batteries. The flooded lead-acid car batteries have been highly popular for vehicles and high power stationary equipment for decades now.

Flooded lead-acid batteries are primarily powered by the liquid electrolyte solutions. Thus, it is necessary to keep track of the liquid present inside the battery to get optimal performance from flooded lead-acid batteries.

Pros And Cons of Flooded Lead Acid Batteries

Similar to AGM batteries, flooded lead-acid batteries also feature a handful of pros and cons, which you should know. Here are some advantages of a flooded lead-acid battery:

  • Flooded lead-acid batteries are considered the best selection for a backup power system.
  • These batteries are highly cost-effective and available under a cheaper price range compared to AGM batteries for the same power capacity.
  • Flooded lead-acid batteries are highly reliable as they offer a deep charging cycle.

While the advantages of a flooded lead-acid battery might be great, there are some limitations that affect its performance and applications.

  • The major flaw in the flooded lead-acid battery design is the free liquid present inside the casing. Because of that, these batteries are prone to problems like leakage and require constant maintenance.
  • Flooded lead-acid batteries can easily get damaged in case of an incident.
  • Environmental factors such as temperature have a great effect on the performance of lead-acid batteries.

Differences Between AGM vs Flooded Lead Acid Batteries

Now that you understand what AGM and flooded lead-acid batteries are, it is time to understand the major differences between these options so you can choose better. As batteries are highly complicated peripherals, it is not possible to simply differ between both choices.

Hence, we will be considering different aspects of a battery and comparing these options simultaneously. This should give you a good idea about a certain aspect of the battery and how an AGM or a flooded lead-acid battery performs under certain conditions.

Here are some important characteristics of AGM and flooded lead-acid batteries:

1. Working Principle

AGM Batteries

The absorbed glass mat material present in AGM batteries is a special element that reacts with the electrolyte solution, which is available between the battery plates inside the battery. Due to its unique design aspect, the material saturates with the electrolyte to produce current. Thus, it is capable of storing the power in rather a suspended state compared to the liquid form technology used in other batteries.

When the battery is activated, the ionized electrolyte is transferred from the glass mat material towards the battery plates. The mat material contains sufficient amounts of electrolytes to provide high capacity output from the battery. Even if the battery’s outer casing is damaged, it is designed in such a way that it does not cause any hazardous leakage.

Flooded Lead Acid batteries

Flooded lead-acid batteries are much simpler in construction and usage compared to lead-acid batteries, as these are older models. These batteries also consist of a liquid electrolyte solution that triggers the chemical reaction within the battery. The charge is drawn from the battery, the solution bonds with the lead plates present inside the batteries. Thus, causing a chemical reaction inside the battery and supplying current throughout the circuit.

2. Maintenance

AGM Batteries

As mentioned earlier, AGM batteries are completely free from maintenance and do not require any special care. That being said, it is still not the most ideal option as you will still need to pay attention while charging the battery. But being completely maintenance-free, you do not necessarily need to look at the battery every now and then and can be placed in an enclosed space with ease.

Flooded Lead Acid Batteries

Due to the free liquid content inside the battery, the flooded lead-acid batteries need constant care and maintenance. You will have to periodically check these batteries for potential problems and repair them if necessary. Thus, the batteries must be installed in an easily accessible place which might make them an unsuitable choice for some vehicles. These batteries also release gases and require a ventilated installation space.

3. Durability and Resistance

AGM Batteries

AGM batteries are comparatively tougher than the flooded lead-acid battery. They have great durability and resistance to unnecessary shock and vibration. Because of the unique internal design, the parts of the AGM batteries do not get damaged easily, thus providing a resilient structure for heavy applications.

Flooded Lead Acid Batteries

Flooded batteries are best suited for stationary applications as these devices can get damaged easily. Even after slight impact or excessive vibration, flooded lead-acid batteries can generate leakage problems which will further cause a lot of trouble to the user.

4. Mounting Flexibility

AGM Batteries

AGM batteries have great flexibility for mounting. Due to its design, it can be stored at any location. Given that the battery is not mounted reverse, it should work just fine in any mounting position.

Flooded Lead Acid Batteries

Because of the liquid electrolyte present in the flooded lead-acid batteries, you have to pay extra care while installing it. You need to make sure that the mounting is secured and stable and will not tilt the battery at any point. If the electrolyte is spilled over the surface of the battery, it can cause sulfation and corrosion.

5. Internal Resistance

AGM Batteries

The internal resistance in a battery causes loss of power due to excess heat generation. Fortunately, AGM batteries offer a very low internal resistance which is around 2%. Thus, you can get an increased voltage output from these batteries for a longer period of time. This feature makes AGM batteries a perfect choice for start/stop type engines.

Flooded Lead Acid Batteries

Flooded lead-acid batteries have a comparatively higher internal resistance which dampens their performance by a considerable margin. Generally, a standard flooded lead-acid battery has around 10 to 15% internal resistance. Thus, you can expect higher internal heat generation in these batteries, which also creates the need for proper ventilation.

6. Charging Time

AGM Batteries

Because of the low internal resistance, AGM batteries also carry a great advantage which is faster charging time. As there is barely any power being wasted while charging these batteries, you can expect quicker charging sessions which will also prevent your battery from going below 50% capacity.

Flooded Lead Acid Batteries

Flooded lead-acid batteries are up to 5 times slower in terms of charging speed than an AGM battery. Even while using the same power source for charging the battery, you can observe a much slower charging period for flooded lead-acid batteries.

7. Discharge

AGM Batteries

Each battery has a particular depth of discharge rating, which represents the percentage of battery capacity drained with respect to the total capacity of the battery. A typical AGM battery has a depth of discharge of around 80%, which is quite higher than that of the flooded lead-acid battery. Thus, these batteries are perfect for deep cycle battery applications.

Flooded Lead Acid Batteries

The flooded lead-acid batteries, on the other hand, offer only 50% or lesser depth of discharge. Hence, you are bound to lose the performance and efficiency of the battery if it falls 50% of its capacity. Therefore, flooded lead-acid batteries require more frequent charging sessions.

8. Temperature Tolerance

AGM Batteries

AGM batteries have a decent tolerance against harsh temperatures and offer much better performance in comparison. The electrolyte in an AGM battery that is stored inside the glass mat does not get affected by sudden temperature changes and thus, does not expand or contract. Hence, even if the battery does not perform optimally in a colder or hotter environments, it does not fail completely.

Flooded Lead Acid Batteries

In the case of flooded lead-acid batteries, the liquid is free on the inside and can freeze over the surface of battery plates. This can damage the battery plates and cause the external casing to break. This might result in the leakage of the fluid. In the case of hot regions, flooded lead-acid batteries have a higher chance of failure due to quicker evaporation of the fluid.

9. Overcharging

AGM Batteries

Overcharging causes a lot of problems in batteries. However, AGM batteries are more prone to get damaged by overcharging. As these batteries are completely sealed, there is not enough room for excessive heat dissipation, which is caused by overcharging. Thus, frequent overcharging of AGM batteries causes them to degrade faster.

Flooded Lead Acid Batteries

Overcharging is not as big of an issue for flooded lead-acid batteries. These batteries have a high tolerance towards overcharging. Because of that, you do not need to monitor a flooded lead-acid battery constantly while it is charging.

10. Expected Lifespan

AGM Batteries

AGM batteries have proven to be more long-lasting than other options. Because of the low self-discharge rate, they do not lose power as quickly as other batteries when not in use. Thus, you will not have to recharge AGM batteries as often.

Flooded Lead Acid Batteries

While an AGM battery can last up to 7 years, a flooded lead-acid battery lasts nearly 3 to 4 years, depending on many other factors. Thus, you will start to notice problems with a flooded lead-acid battery much quicker than an AGM battery.

11. Corrosion and Other Problems

AGM Batteries

As there is no chance for liquid spillage, AGM batteries are safer from problems like corrosion and sulfation. That being said, the battery will still undergo sulfation problems if it is unused or discharged for a very long time. But, because the self-discharge rate is slower in AGM batteries, the sulfation problem will also be less severe.

Flooded Lead Acid Batteries

Problems like sulfation and corrosions are repeatedly observed with flooded lead-acid batteries. In most cases, it is caused by leakage of the electrolyte solution from the battery. In the case of a flooded lead-acid battery, if you see significant amounts of corrosion and sulfation on the surface, you will have to get the battery replaced.

12. Price Range

AGM Batteries

Probably the biggest limitation of an AGM battery is its expensive price range. While it does offer many great advantages over other options, it is not affordable for all. Generally, these options are almost twice as expensive as a traditional flooded car battery.

Flooded Lead Acid Batteries

The flooded lead-acid battery is the best choice if you are looking for a cheap and reliable option as a starter unit. Keep in mind that you can always replace the battery with an AGM battery later on with a higher budget for your next battery.


After going through our guide, you must have realized that AGM and lead-acid batteries are quite different. Whether you are looking at construction, working principles, or the performance of the battery, you will find these options distinct from one another.

The important thing to keep in mind is that you can always upgrade to an AGM battery from a flooded lead-acid battery. But it cannot be true the other way around if the manufacturer has decided to put an AGM battery in your car in the first place. Hence, we will recommend you always go for the AGM batteries if you can find a decent option in your budget.

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