Harness Power


Posted On: July 21, 2020

Choosing the Best Solar Batteries

best solar batteries

To find the best solar batteries you must understand the important specifications that need to be evaluated when shopping for a storage solution. If you do not have a battery bank, you will not be able to store the energy that is collected by your solar panels to use when you need it during an outage or your utility’s peak cost periods. Choosing your battery bank should not be taken lightly. There are many things you will need to consider such as how long the solar battery will last, and how much power it can provide. In this guide, we will discuss everything you need to know about choosing energy storage for your residential solar system

Understanding How a Solar Battery Works

A solar battery is designed to store excess energy that is collected by your panels. Grid-tie systems use battery storage for electricity when there is a power outage. Off-grid systems need a battery bank to even work and provide you with electricity.

When panels produce more energy than you need, this energy can go towards charging up your batteries. For those times when solar panels are not actively producing any electricity, you will be able to draw from your battery bank. For grid-tie systems, energy would only go back to the grid if your batteries are completely full. If the batteries are low, they can be programmed to draw from grid power to recharge. 

Different Types of Batteries

Lead-acid or lithium-ion batteries are the typical choice for solar energy storage. However, to find the best batteries for your system you must understand what the difference is between these types of batteries – including flooded lead-acid, sealed lead-acid, and lithium batteries. 

Flooded Lead-Acid Batteries

Flooded lead-acid (FLA) batteries have been around the longest and by far the most common battery type to use for off-grid solar. They are the least expensive battery choice, 99% recyclable, and easy to dispose of once they have reached their end of life. 

Flooded lead-acid are the best batteries for solar when comparing the price tag. However, they do require maintenance and must be monitored. Here are some things you should know about flooded lead-acid batteries before you invest in them as your solar storage solution:

  • These batteries can handle daily charge cycling. They will emit gas as a byproduct, so proper ventilation is needed. 
  • FLA batteries are for those who want to be more hands-on with their storage and solar system. While these batteries are the most affordable option, they will require upkeep. 
  • Maintenance of the batteries will include making sure that every cell is submerged in water. Therefore, they will need a top up with water ranging between one to three months. To be cautious, it is best to check your batteries once a month. 

Sealed Lead-Acid Batteries

Sealed lead-acid batteries are a great option for those who do not want to worry about regular maintenance. 

  • SLA batteries are spill-proof and non-hazardous. There are two different types of sealed lead-acid batteries: absorbent glass mat (AMG) and gel. 
  • SLA batteries are self-contained. They will not have to be topped up with water as flooded batteries do. Because you do not have to worry about upkeep, they are the perfect solution for places that are not occupied all the time, such as off-grid vacation cabins. 
  • SLA batteries can handle the temperature better. These batteries will not self-discharge fast, which means they can sit idle for extended periods of time. 

Lithium Batteries

Lithium batteries happen to be one of the newest storage solutions in the industry. These batteries made their debut in the 1970s. They are very common in laptops and cellphones. However, they have become increasingly popular in the solar energy industry. While lithium batteries are more expensive, they do have many benefits that cannot be found in other batteries. 

  • Longer lifespan than other battery types
  • No maintenance
  • Efficient power source
  • Large storage capacity
  • No gas emissions or ventilation needed (making them the cleanest energy solution for  battery storage)

Comparing Solar Batteries

The factors that you want to look at when considering each type of battery option include capacity, depth of discharge (DoD), round trip efficiency, and the life span. Looking at these specifications will help you determine which are the best solar batteries for your system. 


The capacity of a battery is the total amount of electricity that a solar battery can store. It is measured in kilowatt-hours (kWh). You will find that solar batteries are designed to be stackable, which allows you to use multiple batteries for your energy bank. This will expand your capacity and give you more storage for the energy your panels are generating. 

Capacity can tell you how big a battery is, but it does not give you an indication of how much electricity the battery can provide at any given time. To get a full picture of what a battery is capable of, you will need to also look at the battery’s power rating. For solar batteries, the power rating will be the amount of electricity that the battery will be able to deliver at any point in time. This is measured in kilowatts (kW).

Batteries that have a high capacity and low power rating would provide a low amount of energy. It would only be enough to run a few appliances for a short period of time. For batteries that have a low capacity and high-power rating, you would be able to run your entire home for a few hours. 

Depth of Discharge (DoD)

The depth of discharge will provide the amount of battery capacity that can be used. The higher the DoD the more usage you can get from the battery’s capacity. You will want to make sure that your depth of discharge is 40% or more. 

Solar batteries typically need to retain some charge because of their chemical composition. When you use 100% of the battery’s charge it will shorten its lifespan. Most manufactures will list a maximum DoD for optimal performance of the battery. When a battery has a higher DoD, it will be able to utilize more of its capacity. 

Round Trip Efficiency

The round-trip efficiency will be the difference between the amount of energy that it takes to charge it versus the available amount of energy. The higher the amount of round-trip efficiency, generally the more economic value from the battery. You will want your round-trip efficiency to be around 80%.

Life Span and Warranty

The performance of the battery will decline as it ages. You will find the warranty will guarantee that the battery will perform at a specific level for a certain amount of years or cycles. It will also ensure the battery maintains a certain capacity. 

Solar batteries used for home energy will typically cycle each day. Its ability to hold a charge will gradually decrease the more that it is used. If you are wondering how long your solar battery will last, the answer will depend on the brand of battery and its capacity. 


Various manufacturers are creating solar batteries including automotive companies and tech startups. There will be loads of reviews you can read to help you decide which brand of battery is best for your solar system. The brand of the battery will highly depend on your preference. Make sure that you understand the warranties that are offered by each manufacturer.  

How Long Will A Solar Battery Last?

There are two ways that this question can be answered. You must first determine how long the battery will be able to power your home. Most batteries will run overnight while the panels are not producing energy. 

To make an exact calculation, you need to know how much energy your home consumes, capacity, and power rating. The answer is somewhat complicated. Your panels will be producing energy for 6 to 7 hours during peak sunlight hours. You have to keep in mind that most batteries do not run at their maximum capacity, and peak at 90% DoD. So, your 10kWh battery will actually have 9 kWh of useful capacity. 

The Lifespan of a Solar Battery 

The solar battery typically has a useful lifespan of 5 to 15 years. Therefore, you can expect to replace your batteries at least one time during the 25 to 30-year lifespan of your solar system. With new technologies becoming available, the offerings in the energy storage industry will continue to grow. 

Providing proper maintenance can help enhance your battery’s lifespan. Most solar batteries are affected by temperature, so it will be vital that you protect them from freezing or sweltering temperatures. 

Getting Started

If you are ready to invest in a solar system with energy storage but do not know where to start, give us a call at 949-478-5597 or fill out our online contact form. We can offer you guidance when it comes to designing a system that suits your needs.

Check out our blog to learn more about solar panels for garages.

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