AGM vs GEL Batteries: Capacity, Charging, Battery Life & Discharge

AGM vs GEL Batteries: Capacity, Charging, Battery Life & Discharge


When looking for the right lead-acid battery, AGM and Gel are the two options to consider. These two types of batteries are the most common sealed lead-acid (SLA) batteries, and if they have a one-way blow-off valve, they are known as valve-regulated lead-acid (VRLA) batteries.

AGM and Gel batteries have a few things in common, such as lead plates with the same chemistry and the ability to deep discharge. However, the design and overall performance differ, with the main difference being the type of membrane that separates the plates and holds the electrolyte.

AGM batteries have an absorbent glass mat between the lead plates that acts as a sponge for the electrolyte, while Gel batteries have silica added to the electrolyte to form a thick mixture that keeps the electrolyte between the lead plates. Both AGM and Gel batteries are non-spillable as the electrolyte is contained in the separator, not flooded like in flooded lead-acid batteries.

In this article, we provide a detailed explanation of AGM and Gel batteries’ chemistry, and compare AGM vs. Gel batteries to help you make an informed decision and choose the best fit for your needs.

Sealed Lead-Acid Batteries: AGM And Gel

AGM vs GEL Batteries: Capacity, Charging, Battery Life & Discharge

Let’s first clarify the difference between starter batteries and deep cycle batteries before proceeding to the comparison of AGM and Gel batteries. There are two types of lead-acid batteries.

Starter Battery

Starter lead-acid batteries play a crucial role in starting vehicles and other machinery. They are designed to provide a high surge of current, typically in excess of 100 Amps, for a brief period of time, typically a few seconds or less. The purpose of this high surge of current is to provide the energy required to start the internal combustion engine of a vehicle or other machinery.

Once the engine is started, it no longer requires the battery’s power, and the battery’s output drops significantly. As a result, starter lead-acid batteries are optimized for quick, high-current delivery, rather than sustained energy output. They are commonly used in vehicles and other equipment that requires a quick burst of power to start, but not much energy thereafter.

Deep Cycle Battery

Deep cycle lead-acid batteries are designed for a different purpose than starter batteries. Instead of providing a quick, high-current burst, deep cycle batteries deliver a steady, low-current output over a prolonged period. This type of battery is optimized for devices and appliances that require a consistent, low-level power supply for several hours.

The term “deep cycle” refers to the ability of these batteries to be discharged to a significant extent – typically 50% to 80% of their total capacity – without being damaged. This makes them well-suited for use in solar battery systems, where they are used to store energy produced by solar panels and deliver it as needed. Because they can withstand delivering a continuous current for an extended period, deep cycle batteries are ideal for this application.

Structural Differences Between AGM and Gel Batteries

The reason for the difference in current delivery between deep cycle and starter batteries is the thickness of their lead plates. Deep cycle batteries have thicker lead plates, making them more durable and better able to handle extended periods of low current delivery. On the other hand, starter batteries have thinner lead plates, making them more suited for short bursts of high current. If a starter battery was used as a deep cycle battery, the thin plates would bend or lose shape, impacting performance and reducing its lifespan.

Structural Differences Between AGM and Gel Batteries

Additionally, the type of separator between the lead plates in deep cycle batteries also contributes to their ability to handle a greater depth of discharge. There are two types of lead-acid batteries designed for improved durability and performance: AGM and Gel. In this article, we compare AGM and Gel batteries for deep cycle use.

Why Should You Buy An AGM Battery?

The AGM battery is capable of delivering a high surge of current because it has a low internal resistance. This makes it ideal as a starter battery. On the other hand, Gel batteries are better suited for off-grid systems, as they work well as deep cycle batteries.

One advantage of AGM batteries is that they can be charged quickly, while Gel batteries cannot. AGM batteries are also more durable, making them a good choice for use in sports vehicles that are exposed to vibration.

For stationary solar systems, either AGM or Gel will perform well. However, if you need to power high-demand devices, AGM batteries are the better option. Although AGM batteries have a slightly shorter lifespan than Gel batteries, they are more affordable. If you’re on a budget, AGM is a good choice.

Why Should You Buy A Gel Battery?

Gel batteries are ideal for applications that require frequent deep discharge. Even if you discharge a gel battery up to 90% regularly, it can still perform for about 700 cycles, which is more than an AGM battery that is frequently discharged at only 50% of its total capacity.

So, if you’re planning to discharge your battery more than 50% of its capacity, it is best to choose a gel battery to extend its lifespan. In addition, gel batteries are more resistant to low temperatures, so if you plan to use or store them in colder environments, a gel battery is the best option.

What is the difference between GEL and AGM batteries?

AGM vs GEL Batteries: Capacity, Charging, Battery Life & Discharge

The AGM vs gel batteries have a clear difference between them. They are different in electrolytes, made for different uses. Let’s have a glance at the key differences between these two types of batteries.

Features AGM Battery Gel Battery
Power Suitable for high amp with a very slow self-discharge rate Suitable for lower high amp
Charging Easy Delicate and needs caution
Lifespan 4 to 8 years 2 to 5 years
Current Suitable for higher currents Warmer weather
Temperature Colder weather Warmer weather

Vibration Resistance

The AGM battery’s tight assembly of lead plates and electrolyte-soaked glass mats, which act as shock absorbers, make it highly resistant to vibrations. Furthermore, its fast recharge rate and high number of cycles enhance its overall performance. Although gel batteries also provide good vibration resistance, it is not as high as AGM batteries.


AGM batteries work efficiently at optimal capacity across a wide range of temperatures and can handle high amp with a low self-discharge rate. This means less energy is lost even when left plugged in. The AGM battery is capable of starting a car engine more than 60,000 times, which is three times more than traditional batteries. On the other hand, gel batteries have lower power capacity and are ideal for low-amp burst applications.


AGM vs GEL Batteries: Capacity, Charging, Battery Life & Discharge

AGM batteries charge quickly and retain the charge well, making them ideal for demanding applications. They are compatible with standard chargers and do not require any special adjustments. AGM batteries have a low internal resistance, so they do not heat up even under heavy charging and discharging currents. In contrast, gel batteries are delicate and can be easily damaged if not charged correctly. Gel batteries need to be charged at a slower rate (C/20) to prevent damage to the cells and cannot be fast-charged using conventional automotive chargers.

Battery Lifespan

The lifespan of AGM batteries is 4 to 8 years, while gel deep cycle batteries last 2 to 5 years, depending on the depth of discharge, temperature, maintenance, and frequency and depth of cycling. The actual lifespan varies greatly depending on usage, charging practices, and other factors.


AGM batteries have no limits on charge or discharge current and have a low self-discharge rate, from 1% to 3% per month. This allows them to be stored for extended periods without charging, unlike standard batteries. Gel batteries are best suited for deep discharge as they are less affected by acid starvation.


  • Bayram Sarıkaya

    I am very curious about batteries, devices that charge batteries and these topics. I share reviews, comparisons and news for people who are curious about these issues.

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