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Choosing a Battery for Your Solar System | SolarKnowHow

Renogy Deep Cycle Battery

Choosing a battery for your solar power system can be confusing. There are numerous types of batteries on the market, and you need to make sure you choose the right type and storage amount.

This article reviews the types of batteries available, what criteria to consider, and how to determine how much storage your system needs.


Power Your Solar System With Confidence

Solar panel systems can provide inexpensive energy if installed correctly, enabling you to be more self-sufficient. However, while solar panels will power your system when the sun is out, you will need battery storage for the evenings and when clouds darken the sky.

Choosing the correct battery for your system will require planning and research. I’ll explain the different types of batteries and provide an overview so you can take the first steps in choosing the batteries you need. 

What is a Solar Battery?

A solar battery stores the solar energy collected by your solar panels for later energy consumption. When the sun’s rays hit your solar panel, electricity is produced, and the excess energy is sent to a solar battery, where it is stored. 

Solar batteries and solar battery banks can typically hold a charge for 1-5 days and store between 2kWh and 10kWh of electricity, depending on the size and number of batteries. This stored energy is then available to be used when the sun goes down, or weather conditions limit the amount of solar energy collected. A solar battery bank involves several connected batteries for additional storage. 

What Types of Solar Batteries Are Available?

Several types of solar batteries are available, each with pros and cons.

Lead-Acid Batteries

Lead-acid batteries have always been popular for solar batteries since they are affordable, require little maintenance, and tend to be reliable. However, they tend to be heavier than other batteries and may only last about three years. 

Lithium Batteries

Lithium (LifePo) batteries are becoming increasingly popular due to their lightweight design, compact size, and high capacity. In addition, they can last up to five years and require no maintenance. They are available as lithium-ion or polymer batteries (LiPo batteries).

Nickel-Cadmium Batteries

Nickel-based batteries are not as common as lithium batteries and lead-acid batteries, but they are known for durability and can operate at extreme temperatures. As a result, they are often used in large-scale operations. However, cadmium is highly toxic, limiting its use. 

Redox Flow Batteries

Redox flow batteries, or flow batteries, work by using a water-based electrolyte liquid that flows between multiple tanks to store energy. They are larger than other batteries and more expensive but may last up to 30 years. 

How Much Do Solar Batteries Cost?

The cost of solar batteries depends on the type of battery and brand. Lead-acid batteries cost between $5,000 to $15,000. Lithium-ion batteries cost an average of $7,000 to $30,000, including installation. The cost of flow batteries and lead cadmium batteries may vary, though some experts believe that the cost of flow batteries will continue to decrease. 

How to Calculate How Many Solar Batteries You Will Need?

Several factors go into determining how many batteries you will need.

  1. Determine your daily energy needs. You can use a calculator to add up your energy use by appliance or get the monthly kilowatt-hour output off your utility bill. Divide this amount by 30 for your daily usage. Divide this number by 1,000, and you have your watt-hours.
  2. Determine how many days you will not have sun. You will need to use your battery bank these days. This information can be found online.
  3. Temperatures affect batteries, so determine your high and low temperatures.

Solar Battery Criteria

When choosing a solar battery, there are many factors to consider. These include power rating, battery size and usable storage capacity, roundtrip efficiency, battery life, safety, and solar battery quality.

Power Rating

The power rating of your battery refers to how many kilowatts can be used at once. Therefore, if you require a large amount of power, you will need a higher power rating. 

Battery Size and Usable Storage Capacity

This refers to how much energy your battery can hold. Your needs will depend on how long your battery will be used to produce power and can vary depending on the amount of sunlight available or usage requirements. 

Roundtrip Efficiency

Roundtrip efficiency determines how efficiently your battery converts the energy collected into useable energy. The more efficient your unit, the less sunlight energy you will need. 

Solar Battery Life 

Your battery’s life will depend on its age and how many throughput cycles are used. If you are using your battery consistently, it may reduce the number of years it is useable. 


Each type of battery offers different safety concerns. You will want a battery certified by major safety organizations that exceed the federal safety standards. 

Battery Quality

All batteries in the United States meet rigorous safety and quality standards, but some manufacturers go above and beyond. That is why it is good to compare models to determine which offers the best value. 

What Certifications Should a Consumer Look For?

When choosing a solar battery, you want to ensure that it is certified by national and international safety organizations, including the UL, the UN, and the IEEE. These certifications indicate that your battery has met national and international safety standards.

Using Reviews and Forum Feedback to Choose

In addition to consulting installation experts in your area, ensure you do your research. Most installation experts will recommend their brands, so knowing what is available is essential.

Reviews on sites like Amazon can provide good information, but the quality and validity of these reviews have been questioned in recent years.

Solar forums provide a good source of information and allow you to ask questions from knowledgeable people that have probably used the batteries you are considering. 

Make an Informed Choice Before Purchasing Your Battery

Make an informed decision when choosing your solar batteries. Batteries are expensive, and there are several different types to choose from for your needs. However, selecting the correct battery and using it correctly will last you for years.

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