Solar Vs. Deep Cycle Batteries: Are they different?

Batteries are a great scientific invention. They make our lives easy, and batteries provide us with energy that keeps our day-to-day life going. 

You may think all batteries are similar then, just energy storage that gives out energy whenever we need it. But no! Batteries can be of different types, specifically made to serve other purposes.

The battery in your car does not exactly work like the battery in your tv remote! We can easily see how a battery works differently for various uses.  

The primary aim of any battery is to store energy and deliver it at times of need. Solar batteries are nothing exceptional.

The battery connected to your solar power system that works as a backup power supply is the Solar battery. It stores the excess energy of the system and gives it back when needed. 

Now, on the other hand, deep cycle batteries are particularly famous for providing a continuous power supply over a long period. 

Batteries are almost irreplaceable components of civilization. If you are one of those who are eager to know how different types of batteries work and if they have anything in common, this is where we start our journey. In this blog, we will find out if solar batteries are somehow related to deep cycle batteries or if they are completely different! 

What are Deep Cycle Batteries?

The phrase ‘deep cycle’ means the level of discharge of this type of battery. Deep cycle batteries are famous for their long run, and they provide sustainable energy over a long period, making them the best choice in some cases. They supply you with continuous power, deeply discharging the battery. 

Here you will surely appreciate some information. Depth of Discharge rating (DoD) is the amount of energy you can use from your battery before recharging. Usually, you should not discharge your batteries fully, and they need some energy left to function perfectly.

But in the case of deep cycle batteries, they have the highest DoD rate. You can safely use a deep cycle battery until it is almost 80%-100% discharged. Only then this type of batteries will need to be charged again. For this reason, they can generate a steady power supply for you for a long time. 

These are special kinds of batteries that are not used everywhere. Your car battery is not a deep cycle battery. To run a car, we need an instant burst of energy. For this reason, a starter battery is an optimal choice for your vehicle as it can provide a burst of energy for a short time.

What are Solar Batteries?

Solar Batteries are connected to any solar power system to store the excess energy produced by the system, and it is the main purpose of a solar battery. 

If you want your solar system to be self-sufficient, you have to consider installing a battery. Solar systems work properly under certain conditions.

Solar panels stop producing power when the sky is cloudy or even after sunset. But our need for a constant power supply just doesn’t stop anytime. At that time, you can satisfy your needs by drawing power from the battery.

The battery provides the backup electricity that keeps your life running. Without batteries, an off-grid solar system cannot run all time. You can draw power from the local grid in an on-grid system when you need it. But as we see in off-grid systems, solar batteries are essential.

These batteries follow a pretty simple principle. Solar panels produce massive power during the daytime, much more than our need; that excess DC power is stored in the solar battery. It is so satisfying to know no energy is being wasted. You’re using that extra power later according to your need. That is the function of a solar battery- elegant and essential!

In this blog post, we have also explained how many solar batteries you may need for your solar system.

It is the backup power supply for your house or workstation. 

Can you use Deep Cycle Batteries as Solar?

To get the best out of your solar, you need to use a battery with high capacity, reasonable DoD rate, and high Round Trip Efficiency. The Round Trip Efficiency is given by the ratio of how much energy a battery gives off to the energy stored within it.

If your battery has a round trip efficiency of 90%, i.e., you can use almost 90% of the stored energy. We need this kind of performance for a hassle-free experience for our solar system. 

You can find all these qualities in a deep-cycle battery. Hence, deep-cycle batteries can be fairly used for solar. They are the best type of batteries that one can use for their solar power system!

Deep cycle batteries can significantly change the power supply style, especially for those who have an off-grid or stand-alone solar system. 

Mechanism of Deep Cycle Batteries

Deep Cycle Batteries have a little complex but evolving technology. If the electric power produced by PV cells is not used up immediately, it gets stored in the collection of individual smaller 2-volt cells of the deep cycle battery.

The electrical energy changes into chemical energy in the battery cell and gets stored, and this chemical energy is then converted back to electrical energy when needed. 

Deep cycle batteries are secondary batteries as they go through a rapid continuous charge and discharge process. This is known as the charging cycle of the battery. The chemicals are one-time usable in the primary batteries, which means they are thrown away after full discharge.

For this reason, deep cycle batteries are known as secondary batteries, as the chemical reaction within the battery is entirely reversible. 

Deep cycle batteries generally have about 200 to 2500 ampere-hours capacity. The size of a deep cycle battery is much larger than a regular car battery due to the size of lead plates, and Lead-acid batteries are a typical example of a perfect deep cycle battery. 

A primary lead-acid deep cycle battery has a plate of lead as a negative electrode, and as a positive electrode, lead dioxide is used. These two electrodes are immersed in a sulfuric acid solution which reacts as the electrolyte in this battery. 

A potential difference is obtained between the two electrodes, which results in current flow through an external load. This is the basic mechanism of a deep cycle battery (Lead-acid). You need to know that the maximum current through the load depends on the mass and volume of the cell. 

How do Solar Batteries Work?

Solar Batteries are used to store excess solar energy. Their working principle is pretty simple.

We can store Solar energy in electrochemical batteries as chemical energy. When Direct Current is sent to batteries, it reacts with the battery components. When current is drawn from the battery, the reverse reaction happens.

Lithium-ion batteries can also be used for this purpose. The new technology has developed varieties of batteries from traditional lead-acid batteries. Most modern kinds of batteries are modular systems that have made energy storage more flexible. For example, flow batteries are a new technology that is progressing fast. 

Types of deep cycle batteries

Four types of deep cycle batteries are typically used for our solar. They are: 

• Flooded Lead-acid battery: These types of batteries are heavy. It consists of lead plates filled with a liquid electrolyte. Usually, sulfuric acid (concentrated) is used.
• Lithium-ion batteries: These are the most expensive type of deep cycle batteries. A traditional lithium-ion battery has a cathode, and an anode dipped in lithium salt. 
• Sealed AGM: AGM stands for Absorbed Glass Mat. A positive and negative plate separated by an absorbed glass mat is what we see in an AGM battery. The glass mat absorbs the acid in the battery and restricts its flow inside the battery. These batteries are vibration-resistant and maintenance-free.
• Sealed Gel: Sealed Gel Batteries are small, slowly self-discharging, maintenance-free batteries. These are other lead-acid batteries with a ‘gel’ electrolyte. Like AGM batteries, they can be used in any orientation as we don’t need to worry about leakage. 

In the below table a thorough comparison of different types of Deep Cycle Battery is given:

Types of Solar Batteries: 

You will be amazed if you take a few minutes and try to see the different types of Solar Batteries! There are so many! We have many different types of Solar Batteries to fulfill your particular need perfectly. Some are expensive, and some are not.

Some batteries use harsh chemicals, whereas some solar batteries are bio-friendly. We also have varieties of mechanisms in different batteries. 

Some types are:

• Lithium-ion battery: Higher DoD rating, proper size but expensive, sensitive to fire.
• Lead-acid battery: Cheap, most used, but low DoD rating and not a good lifespan. 
• Nickel-cadmium battery: cadmium is an extremely harsh chemical, but this battery can survive in extreme temperatures.
• Tubular battery
• Flow battery

Check out this post to learn more about different types of batteries

Solar and Deep Cycle Batteries: Are they the same?

If I try to give you an answer in words, then yes! Solar batteries and deep cycle batteries are the same. In most cases, the batteries we use for our solar system are deep cycle batteries. Or should I say in every case?!

Our solar power system provides us with the electricity to run our house or workplace. In our solar system, the solar panels contain PV cells (photovoltaic cells) which absorb the sun rays and produce DC power. When solar panels produce excess power, we store it in the battery.

Later on, when solar panels stop producing power due to weather conditions or at night, we use that stored energy. This is how our self-sufficient green energy source works. When we draw energy from the solar battery, we need to run our house using that.

It will help if you run the necessary electronic appliances at home using that energy. Most of our home appliances need a continuous power supply. For this purpose, deep cycle batteries are the game-changers. Deep cycle batteries are experts at providing a steady, consistent flow of relatively low energy over a long period. 

So, the batteries we use for our solar system are deep-cycle batteries. Don’t be confused any longer! Whether your solar battery is lithium-ion, lead-acid, or anything else, it is likely a deep cycle battery. 

Cons: 

Although deep cycle batteries are very useful, they have some disadvantages too. For our solar system, we mainly need deep cycle batteries. We intend to power our house for a long time. At this stage, now we know this can be done using a deep cycle battery.

Theoretically, deep cycle batteries have an 80% to 100% DoD rating, but this range lies between 50% and 60%. And also, you should not discharge your battery more than 45% if you want to keep it working correctly year after year. If not disadvantages, this is one issue that asks for your concern. 

Deep cycle batteries are mainly flooded deep lead-acid cycle, lithium-ion, sealed AGM batteries. All of these kids are very well-known and trusted batteries worldwide. Yet they have some disadvantages too. 

• Flooded lead-acid batteries emit explosive hydrogen gas during charging. You need good ventilation to avoid any unwanted situations.
• AGM batteries are expensive and sensitive to overcharging. 
• Lithium-ion batteries are a very agreeable choice but at a high price. They are expensive and hard to recycle. 
• Although these batteries are the Power House of your solar system, this can also be the most dangerous part because the acid and chemicals used can cause a burning sensation to our skin.

Well, this is not the end. There are other kinds of deep cycle batteries with different pros and cons. 

But don’t worry; with proper precautions and care, any deep cycle battery will give you a long undisputed service in your solar system.

Check out my other post on Solar vs. car batteries here.

Conclusion

Today most solar batteries are deep cycle batteries. Deep Cycle batteries are energy storage with a specific mechanism. For that particular mechanism of providing power continuously over a long time, they fit the best as the solar batteries.

We mainly expect a steady flow of charge from our solar batteries to run our household. Generally, we don’t need any burst of charge to kick start our electronic appliances at home. Instead, we need a lower but consistent power supply.

Deep cycle batteries deeply discharge themselves to harness the stored power creating a low but continuous flow of charge. So, Solar batteries are deep cycle batteries in short. They are not different.