AGM VS Lead Acid Battery: 12 Differences + 7 FAQs

Your car’s starter battery is most likely either a flooded lead acid or an AGM battery, both of which are rechargeable battery types. However, how do a flooded lead acid and AGM battery differ from one another? We’ll compare AGM and lead acid battery to see how they compare. Then, we’ll move to FAQs for more information on the car battery in this passage.

AGM VS Lead Acid Battery: 12 Differences + 7 FAQs

AGM VS Lead Acid Battery: 12 Main Differences

It’s significant to know that the AGM battery has its source in the conventional lead-acid battery before we start comparing so that there are some similarities between them.

Let’s now compare each battery type, starting with how it operates internally.

Firstly, How Do AGM VS Lead Acid Battery Work?

Technically speaking, the base chemistry of an AGM battery and a regular lead-acid battery is identical. Both of them use lead plates and a sulfuric acid and water electrolyte, which causes a chemical reaction that resulting in the production of hydrogen and oxygen as a byproduct. They begin to diverge, from where they stand. This is how:

Flooded Lead Acid Battery

In flooded lead acid batteries, the lead plates are immersed in liquid electrolyte (FLA batteries). Gas is released to the atmosphere for the reason that the chemical reaction cause water to be lost. Therefore, periodic replenishing of the electrolyte levels is necessary.

AGM Battery

In the AGM battery, fiberglass mats are positioned in between lead plates. This is where the name of the battery, Absorbent Glass Mat, comes from (AGM). The AGM separator absorbs the sulfation, keeping it stopped, making it free of freely flowing.

It hardly gets off-gassing because the AGM battery is encapsulated. The chemical reaction’s gases and electrolytes recombined. A vent also releases additional gas when necessary to maintain internal pressure (for instance, when the battery is overcharged).

Secondly, Maintenance Needs.

The Absorbent Glass Mat battery hardly needs maintenance and can be installed in less spaces for the reason that there is no off-gassing other than brief venting. It is best used in vehicles with batteries in the trunk and behind the seats, as well as in places where maintenance may be challenging.

The flooded battery, on the other aspect, needs frequent electrolyte maintenance and must be placed in a well-ventilated area because it emits fumes and steam.

Why do we need to replace lead-acid batteries?

Thirdly, Durability, Vibration and Shock Resistance.

Due to its history in the military and aircraft, AGM batteries are often more durable than flooded lead acid batteries.

The glass mat and battery plates of the AGM battery are sandwiched, which results in parts that don’t disintegrate readily. These features produce a battery that is resistant to vibration and stress, let them famous in motorbikes and race car. Flooded battery plates can be harmed by jarring motions and strong vibrations, thus it’s important to mount them safely.

Fourthly, Mounting Flexibility and Spillage.

The AGM battery is position-insensitive and spill-proof thanks to its glass mat technology. It can be made up in a variety of ways, but never upside down. However, the flooded cell battery must always remain upright because it contains a liquid electrolyte. If leakage electrolyte is not clear, corrosion may result.

AGM VS Lead Acid Battery: 12 Differences + 7 FAQs

Fifthly, Internal Resistance and Power Output.

Among the numerous lead acid batteries, the AGM battery has one of the lowest internal resistances. A fresh AGM battery can have an internal resistance of around 2%, compared to the 10-15% of a new flooded lead acid battery.

Low internal resistance of battery boosts battery voltage output. Additionally, it means that less heat will be lost when the system’s electricity flows. In comparison to a flooded lead acid battery or gel, an AGM battery reacts to loading better. Lead acid variants for start-stop cars are preferred due to their ability to regulate high power demands.  

Sixthly, Charging Time.

Faster charging periods are another benefit of the AGM battery’s low internal resistance. When using the same power source, the speed of a flooded lead acid battery can be up to 5 times faster than that of a lithium battery. 

Seventhly, Depth of Discharge.

The depth of discharge (DoD) of AGM batteries is 80%, which is higher than the 50% DoD of flooded cell batteries. The AGM battery is therefore a good choice for deep cycle applications.

But not like the lithium-ion battery. It can be completely discharged, neither battery type should be depleted below 50% of its capacity. 

Eighthly, Temperature Tolerance.

In general, the AGM battery performs better across the board and has a propensity for good Cold Cranking Amp (CCA) ratings. When frozen, the electrolyte contained in the glass mat does not expand like a liquid. AGM battery is prevented to be harmful from low temperatures. Therefore, even though the battery is unlikely to function in a cold environment, it won’t break. For another, flooded lead acid batteries will freeze in the cold. The accessories can leak and expand, and the battery plates can ruin.

The flooded lead acid battery will consume more acid in high temperatures, putting the battery grids at risk of exposure to the atmosphere (the lead plates need to stay submerged). 

Ninthly, Sensitivity to Overcharging.

AGM battery is substantially less tolerant of overcharging than flooded lead acid batteries. As for thermal runaway, overcharging makes sealed design AGM battery is more pregnable. Even if thermal runaway is ignored, overcharging will reduce the lifespan of an AGM battery more quickly. Therefore, to regulate the voltage and current entering the battery when charging an AGM battery, utilize a controlled battery charger.

Tenthly, Lifespan and Self-Discharge.

AGM batteries often have a longer use life than normal lead acid batteries. AGM batteries have longer use life than flooded batteries but are not in use for the reason that their low self-discharge rates.

AGM batteries can last up to seven years with proper maintenance, but a flooded battery lasts three to five years. If your automobile struggles to start, your battery may need repair.

Eleventhly, Corrosion and Sulfation.

Because it can exhaust acidic gas and is more likely to leak than an AGM battery, flooded batteries are more susceptible to corrosion than AGM batteries.

However, if both batteries are kept in a discharged state for too long, sulfation will occur, but AGM batteries are slightly more elastic, to some degree because of their slower self-discharge rate. It’s probably time to get in touch with your mechanic for a replacement battery if you see significant corrosion on your battery terminals.

Twelfthly, Cost-Effectiveness.

As a starter battery for regular autos, the flooded battery is affordable and dependable. AGM batteries can cost high to 2-3 times as much as a normal battery.

Let’s review some frequently asked questions now that we’ve known how the flooded lead acid battery and AGM battery comparison.

Battery FAQs

Here are answers to some questions on car battery:

What Are AGM Batteries?

Early in the 1980s, the Absorbent Glass Mat (AGM) battery was created as a substitute for NiCd batteries. This kind of sealed lead acid battery (SLA battery) is spill-proof and needs no maintenance.

It is utilized in a wide range of applications, including maritime, off-grid, and high-powered sophisticated vehicles.

What’s A Flooded Lead Acid Battery?

The flooded lead acid battery (FLA battery), which has been used for more than 150 years in a variety of applications, is the most widely used type of lead acid battery.

Another name for it is a typical or conventional lead acid battery. The traditional battery is frequently referred to as a flooded battery because of the liquid acid inside. In a typical car, there’s a good chance that the battery is a wet cell.

What Is SLA Battery?

A subset of lead acid batteries is the sealed lead acid battery (SLA battery). A VRLA battery is another name for it.

The sealed battery does not allow access to its internal compartment, unlike wet cell batteries. Instead, it controls the pressure brought on by internal chemical processes via a one-way valve.

Are Gel Batteries AGM Battery?


Since both AGM and gel batteries are sealed battery types, they are frequently confused with one another.

The electrolyte of the gel battery is silica gel, in contrast to the AGM battery, which uses a glass mat to keep its electrolyte. Due to their poor performance as starter batteries, gel cell batteries are rarely utilized in automobiles. Additionally, the gel may be harmed if overcharging occurs because of how sensitive it is to doing so.

Are EFB Batteries AGM Battery?


Enhanced Flooded Lead Acid Battery is referred to as EFB.

The EFB batteries are flooded batteries created to be more affordable than an AGM battery while also being an upgrade over ordinary batteries. Basic start-stop vehicles employ it.

Are There Lithium Car Starter Batteries?

Yes. And no.

Electric car usually uses lithium-ion battery as their power source (EVs). It functions differently from a standard lead acid battery and cannot be sufficiently recharged by the alternator found on a typical automobile engine, but lithium starting batteries are used in racing due to their lighter weight and smaller size. In addition, the lithium-ion battery can maintain its power output at any rate of discharge.

Are ordinary car starter batteries made of lithium any time soon?

Most likely not, given their high cost.

Can AGM or Lead Acid Battery Be Used as Battery Bank?


Both flooded lead acid batteries and AGM batteries can function as battery banks as well as be charged by a solar panel.

It will be less expensive to use as a flooded lead acid battery bank.

However, because the batteries must be positioned upright, they may require more maintenance and take up more room.

Because AGM batteries may rest on their sides, configuring an AGM battery bank would be simpler.

They require no upkeep as well. They will cost more than a flooded battery bank, though.

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