Deep Cycle Battery Vs. AGM: Complete analysis

Nowadays, almost everyone is using some electronic devices, electric vehicles, and these devices require a battery as well. And most of them always check the battery of their devices in their daily life.

All batteries store energy, but there are some major differences, like how different types of batteries work and from those which are most favorable for different applications. Most businesses now use rechargeable batteries to power their vehicles, office equipment, and renewable energy systems.

The lead-acid battery is the most prevalent. This is a well-established technology that is recognized to be dependable, long-lasting, and cost-effective. However, there are several distinct types of lead-acid batteries to be aware of. 

At present, we have different technologies in the field of battery technology like Gel deep cycle batteries, Lithium batteries, AGM(Absorbent Glass Mat), etc. Each of them has its own pros and cons.

What is a Deep Cycle Battery?

The Deep Cycle Battery looks exactly like the conventional car batteries, but the mechanism behind this is completely different. Often the term Deep Cycle Battery is referred to as a Lead-acid battery, and it has the ability to discharge most of its capacity first (i.e., deep discharge) before it requires a recharge.

Deep cycle batteries run perfectly until they’re not utilized 80% or more energy, and after that, the batteries need to be recharged.

One crucial thing whenever you’ll go to buy a deep cycle battery, the owner will, or the manufacturers will suggest you not discharge it more than 45% to increase its lifespan.

What exactly is meant by Deep Cycle Battery in technical terms?

A deep cycle battery is designed in such a way that it produces steady power over a long period of time. For example, batteries used in marine vehicles are lead-acid or deep cycle batteries, which is why sometimes we call them marine batteries.

If we compare it with a car battery, it provides a momentary burst, and that’s enough to start a car. Another key difference is its inside structure. A deep cycle battery has thicker plates with a small surface area, and a separator with highly dense active material, and thus these thicker battery plates help resist corrosion.

Different Types of Deep Cycle Batteries:

Selecting the right battery for your requirement is very much important. And since the deep cycle battery is applicable for both lead-acid and lithium technology. If we divide deep cycle batteries at a basic level, we will get two options.

One is Lead-acid batteries, and another is lithium-ion batteries. Now, lead-acid batteries are further divided into two parts—the first one Flooded lead-acid battery, and the second Sealed lead-acid battery. And the Sealed lead-acid battery is further split into two parts, the first one Absorbent Glass Mat (AGM) battery and the second is Gel battery.

Each deep cycle battery has its own pros and cons. Before exploring, each battery is completely different depending on its technology and manufacturing, which means the materials for cathode and anode, the electrolyte, and other parts used to manufacture the battery. With that, let’s deep dive into it.

1. Flooded Lead-acid Battery

In the current era also, we are using flooded lead-acid batteries, and it is one of the oldest and most widely used batteries for cars. Sometimes we call it wet cell, and this is manufactured with lead plates that are fully submerged in an electrolyte mix of water and sulfuric acid.

During the charging and discharging of the battery, some chemical reactions happen, and hydrogen gases vent from the battery.

• The usable limit of this battery falls around 30% to 50%. It means how much this battery can be used before recharging. In this scenario, it should be 50% of the total capacity. On average, the charging efficiency of this type of battery is 70% to 85%. If you are charging this type of battery, it will happen in stages, which means there will always be some spaces for undercharging and overcharging.
• Though this type of battery is reliable, affordable, and tolerant of overcharging, these batteries still require some space for ventilation.
• The ventilation must be upright so that we can avoid electrolyte leakage. 
• Even though these batteries require the most maintenance, they have a short life span compared with other batteries.

2. Gel Battery

The Gel battery is another Valve Regulated Lead Acid (VRLA) or Sealed lead-acid battery. Since AGM battery uses an electrolyte absorbed matt while Gel battery uses gelled electrolyte.

The gel battery is manufactured similar to the AGM battery, and thus the chemical chore is also similar in both the batteries. The gelled electrolyte present in the Gel battery is formed from water present in a silica agent and sulfuric acid.

Thus, each Gel battery/cell is a sealed case. Let’s compare the Gel battery size with other lead-acid batteries. It has smaller in size with high performance. The charges efficiency of the Gel battery is around 80% to 90%, with much better off-gassing and heat tolerance, which increases the Gel battery’s overall performance.

In case of overpressure, open the safety valve, and if we open it, gases will be released. Still, if the Gel battery is charged correctly, there won’t be any gas leakage and thus not be required to open any safety value.

Though Gel battery has many advantages, since it is a sealed case battery, it is entirely spill-proof, leak-free, vibration-resistant, and shock-resistant. Even though it has many benefits, there are some disadvantages of Gel battery as well.

The electrolyte present in the silica gel cannot withstand high temperatures for a more extended period, and thus it can be quickly burned even if the Gel battery is new.

The Gel battery cannot be charged using a fast charger, and it requires a special type of regulator or charger. The Gel battery is costlier than any flooded or AGM battery as well. If we charge and discharge the Gel battery properly, we can increase its lifespan. These batteries are perfect for wheel-chair, boats, personal vehicles, etc.

We have covered all the lead-acid batteries and now let us talk about the Lithium-Ion battery, which is also a category of Deep cycle battery.

3. Lithium-Ion Battery 

Lithium-ion batteries may be the future of deep-cycle batteries, and it is the latest in technology in the battery segment. The anode is made out of graphite carbon; electrolytes are lithium salts.

And on the other side is the cathode, which is made up of the combination of lithium manganese oxide (LiMn2O4) or lithium cobalt dioxide (LiCoO2)and lithium iron phosphate (LiFePO4). Now, if we charge or discharge the lithium-ion battery, these substances will be helping there.

If we deep dive more, we will find that lithium-ion batteries use LiMn2O4 or LiCoO2 as a cathode and thus have much higher energy than other batteries. Lithium-ion batteries are mostly used for small devices, and one of the most used devices is a smartphone which we use daily. Lithium-ion batteries should be avoided for larger devices because they risk thermal runaway.

In the lithium-ion battery, if we use LiFePO4 as a cathode and different lithium salt variations for its electrolyte, it would be a much better and safer option because it can provide a long lifespan to the battery-less cost than other lithium-ion batteries.

When we compare the lithium-ion battery with other batteries, almost no maintenance cost is required, and it has the highest energy density.

Lithium-ion batteries are almost 30% lightweight compared to other lead-acid batteries, and it has a usable capacity of 80% to 100%, which is the best in this segment. These batteries support fast-charging and long life-cycle 2000 to 5000 charge cycles.

The lithium-ion batteries have a constant voltage over any discharge rate. It means if the battery is discharging, the power light would not be dim, and in the case of full discharge, the lights will go off.

While it has many advantages, there are a few disadvantages as well, one of them is its price. Lithium-ion batteries are costlier than lead-acid batteries, and it requires a particular type of battery management system.

But since the last few years, as the manufacturing of lithium-ion batteries is increasing, its price has been falling too. 

When we talk about AGM batteries, most people think about Deep Cycle battery applications. But not all AGM batteries are Deep Cycle batteries. The depth of discharge (DoD) of AGM battery is 80% and when compared with a flooded lead-acid battery whose DoD is just 50%.

What is an Absorbent Glass Mat (AGM) Battery?

AGM also stands for absorbent glass mat; it is a type of sealed lead-acid battery (or you can say Valve Regulated Lead Acid VRLA battery). It is one of the most used VRLA batteries.

AGM deep cycle battery is very similar to the flooded lead-acid battery, and the only difference is that it is specially designed fiberglass mats that are very thin in nature. These fiberglass mats are placed between lead plates. Between the lead plates, electrolyte solutions are present.

Here, the fiberglass mats act as a damper between those lead plates.

This damping action helps to withstand even cold temperatures because it makes AGM deep cycle batteries vibrant and shock-resistant. 

And when the batter is ON or in the working stage, the electrolyte moves from the fiberglass mats to the battery plates and back as the battery is discharged or charged.

If the system requires a high load current, the Absorbent Glass Mat battery provides it easily. And since AGM batteries have a fiberglass design, these batteries can be charged faster than other batteries with the help of an AGM battery charger.

If you have a capacity from 30Ah up to 200Ah, then it is a good choice to select an AGM battery.

The Absorbent Glass Mat deep cycle battery has a faster charging option and very low internal resistance than other batteries like Gel batteries or Flooded lead-acid batteries.

Here are some pros and cons of the ADM deep cycle battery:

• The Absorbent Glass Mat deep cycle battery has been specially designed for the Aircraft industry because it has shocks and resistance to vibrations.
• ADM battery has 80% depth of discharge and 95% efficiency in charging.
• ADM batteries have very minimal maintenance costs, are durable insensitive, and have fast charging.
• ADM batteries are very expensive compared to other batteries like flooded lead-acid and gel batteries.
• ADM batteries are very sensitive to overcharging and thus require a regulated charge.
• ADM batteries do not long-lasting as compared to flooded lead-acid batteries in demanding applications

AGM batteries vs. different Deep cycle Batteries

AGM Battery vs. Flooded Battery

Since AGM is based on new technology, it has many advantages over flooded batteries. One of the major benefits is that the AGM battery has a fiberglass mat, and this fiberglass mat holds the acid and thus very less chance to sulfate; due to this, the AGM battery has more DoD compared to the flooded battery.

However, there are a few disadvantages of the ADM battery. One of them is that it is costlier than a flooded lead-acid battery. Due to this reason, flooded lead-acid batteries are still in use in motor-sport applications.

A few benefits that AGM has over flooded batteries (as well as quicker charging) are its expanded cycle life and vibration resistance. The reason behind this is that the combination of mat and tight sealed AGM battery act as a damper, which is the quality to start motor-sport applications.

AGM Battery vs. Gel Battery

Both AGM batteries and Gel batteries are types of Sealed lead-acid batteries, but there are differences as well.

The rated capacity of the Gel battery is decreased much faster than the AGM battery’s rated capacity because the ambient temperature gets colder (less than 32 degrees F). The AGM batteries perform well in starter applications or high rate, while Gel batteries do not perform well.

AGM Battery vs. Lithium Battery

AGM battery is a type of Lead-acid battery while Lithium battery is not. So, when you are selecting a battery, you first decide for what application you will be using this battery.

Are you going to use it for a deep cycle application, afloat standby, or a high-rate discharging application? And do you want the battery with a built-in charger or not? And most important, what is your budget for this?

Let’s conclude this, so depending on your application or system and your budget, you will get to know that overall AGM battery is a good option. Because it is higher-ranking than flooded lead-acid batteries, and no maintenance, lightweight, great performance are other benefits as well.

You will find that an AGM battery is a better option than a Gel battery because these batteries are very less expensive and common. And last but not least, the final fight between AGM battery and Lithium battery is that it completely depends on your system or application and what you want with that battery.

Conclusion

A deep cycle battery is a lead battery designed to provide sustained power over a long time, and it can work fine until up to approximately 80% of the discharge. After that, they needed to be charged again to restore their normal functionality.

The “deep cycle” discharge level is in contrast to other types of batteries, which only give short bursts of energy before needing to be recharged. A starter battery, for example, discharges only a small percentage — usually 2 to 5% — each time it is used.

Usually, they come with a variety of types like flooded deep cycle batteries, maintenance-free lithium batteries, Gel batteries, etc. The flooded lead-acid batteries have a high energy requirement of the system.

However, they are cheaper than the other deep cycle batteries. They have significantly less lifespan compared to others(only 300-500 cycles). The Gel batteries have a good lifespan, have low discharge rates, and have a good discharge cycle of about 70%. However, they are expensive to use.

Lithium batteries have a very high energy density, and the batteries have much higher capacitive rates and need much lesser maintenance costs. These are very lightweight and hence easier to use.

The battery has a good lifespan of about 2000-5000 charges per cycle, and it also has a better depth of discharge of approximately 80%-95%. However, they are extremely costly among all types of batteries. Another disadvantage of this battery is that its performance decreases rapidly with decreasing temperature.

AGM(Absorbent Glass Mat) almost needs no maintenance to use. These batteries support fast charging at a faster rate, and thus quicker response gives a very high load current on the requirement.

It has a thick separator, and it helps to reduce the spilling and has high discharge efficiency of about 80%. It is costlier than flooded lead-acid batteries but less than Gel and Lithium-ion batteries. It has very low potential. And if overcharged, the battery might get damaged.