A Guide to Solar Batteries: Working, Types, Advantages, and Disadvantages

Solar Batteries are photovoltaic (PV) devices that store the electrical energy generated by solar panels for future usage.

These types of batteries are one of the core working components in solar power storage systems as several individuals prefer converting the renewable energy sources to satisfy their electricity demands.

Solar batteries enhance the efficiency and versatility of solar setups by allowing you to store excess energy produced by the array during non-usage hours, thereby reducing the dependence on the grid and lowering your electricity bills.

Understanding energy storage systems benefits solar power users by enhancing home value, reducing their dependence on fossil fuels and minimizing their carbon footprint, gaining knowledge about efficient usage of solar energy, reducing financial savings, and many others.

Even the best solar battery brands in the market have their own advantages and disadvantages. To find out its worth, you need to consider certain important factors while selecting. This includes the number of batteries required, the possibility of adding existing batteries to the solar system on your own, and the difference between AC and DC Coupled voltage.

What are Solar Batteries?

Solar batteries are devices that stores the extra electricity converted from sunlight by solar panels for future use. They are manufactured by obtaining raw materials and essential components based on different types used.

The chemical reactions take place inside the solar battery when the sunlight strikes the solar panels and converts them into electricity through the photovoltaic effect, to store additional electricity as reserved energy. DC electricity from the solar panels flows directly into the battery in a DC-coupled system and is converted into AC electricity by a solar inverter, which is then transferred into a solar battery.

Solar batteries play a crucial role in enabling the use of solar energy at night, on cloudy days, or during power outages by storing excess energy during sunny periods. This can be used at any time only in an off-grid solar system. If you’re considering purchasing a home battery system, it’s important to understand the various options available and find the one that best suits your needs.

How do Solar Batteries Work?

The lithium-ion solar battery works on the oxidation-reduction (known as Redox) reactions. There are four main components inside a lithium-ion battery namely the cathode, anode, a separator, and electrolytes. The reduction reaction takes place at the positively charged cathode and the oxidation reaction at the negatively charged Anode.

A chemical reaction involves lithium iron phosphate (LiFePO4) on the cathode when the battery is connected to a charger. Compounds get broken into electrons with the positively charged Lithium ions (Li+) and negatively charged iron phosphate (FePO4 -) as remainders.

A charger assists the electrons flow to the anode and the positively charged lithium ions flow through the electrolyte to merge with the graphite as Anode. Finally, these two elements are combined to form a compound known as lithiated graphite. The lithium-ion battery gets completely charged when all the lithium ions and electrons have gone through this movement.

Anode, Cathode, and lithium-salt electrolyte play an important role in facilitating the entire process:

1. Anode: It is an important element of lithium-ion batteries which is made up of graphite due to its special characteristics such as layered structures, huge electrical conductivity, and consistency. The movement of lithium ions from the cathode to the anode makes them hold in spaces between the graphite layers during the charging process and the high energy density of the battery acts as an effective storage method.

2. Cathode: The Cathode is made up of lithium metal oxides such as lithium-ion phosphate to provide thermal stability.

3. Lithium-Salt Electrolyte: The electrolyte present in lithium-ion batteries enhances the lithium ions transfer from anode to cathode.

Lithium-ion technology is suitable for solar energy storage due to its higher depth of discharge (DOD), longer lifespan, higher energy density and efficiency, and lower maintenance costs. Mainly, reversible chemical reactions allow power absorption and discharging.

Advantages of Installing a Solar Battery

These are the following benefits of installing a solar battery:

1. Energy Independence: The additional batteries in a solar system make homeowners more independent and can generate excess energy during sunny days for future use when there is limited sunlight or during huge demand seasons. As a result, the dependence on the standard power grid is minimized and gives more control over electricity usage, thereby promoting renewable energy and long-term financial savings.

2. Reducing Electricity Bills: Solar battery helps you to save money by using more electricity generated from solar panels during peak demands. For instance, the average household uses 75% to 85% of solar electricity with a battery when compared to 50% of power consumption without any storage.

3. Minimizing Environmental Impact: Using solar batteries to store additional energy in homes and business areas, helps to reduce carbon footprint and energy waste as well as avoids the effects of climate change.

4. Reliable Backup Power Source: Solar batteries are mainly used for stable backup power, by storing extra energy from solar panels. In other words, there is a continuous supply of power even if there is no sunlight or the grid is down. Also, a set of batteries can offer a long-term solution to power outages, particularly when the battery storage system is connected to a solar panel system.

Disadvantages of Using Solar Batteries

These are the drawbacks of using solar batteries:

1. High Cost: As of July 2024, solar batteries are expensive in the US with a price range between $6,000 to $23,000 approximately, which varies on the brand, type of battery used, power output capacity, installation charges, and several other factors. As a result, few battery systems might not be budget-friendly for homeowners.

2. Installation Complexity: Depending on the configuration of your solar panel system and existing hardware, the complexity of installing a solar battery varies. For example, AC-coupled batteries are easy to install within half a day, whereas, for Hybrid systems, the set-up takes more extended time.

3. Higher Maintenance: Solar battery requires frequent checking to ensure its working on a long-term basis. The maintenance process involves evaluating the battery’s operation at an accurate temperature range, determining the connections for any indications of corrosion or looseness, and tracking the battery’s charge levels to protect it from getting too high or too low.

4. Huge Space Requirements: The limited storage capacity of solar batteries can be a drawback for owners who might have a huge demand for energy storage. Also, the larger battery systems require more space.

5. Safety Risks: The improper installation or maintenance of solar batteries can cause safety concerns such as overheating or catching fire. This occurs if the batteries are not properly installed or ventilated.

Types of Solar Batteries

These are the four main types of solar batteries explained below with their applications, advantages, and disadvantages:

1. Lead-acid:

Lead-acid solar batteries are the oldest types of storage batteries used since 1859 that have sulfuric acid as their electrolyte and use lead electrodes.

Applications: Used in photovoltaic systems, vehicles, homes, mobile towers, etc.
Advantages: Cost-effective, high surge capabilities, proven track record of performance.
Disadvantages: Discharging below a specified voltage can result in a lower lifespan, requires regular maintenance, and is heavy and bulky compared to other solar batteries.

2. Lithium-ion:

Lithium-ion solar batteries have made a huge revolution in energy storage technology, particularly for residential solar systems.

Applications: Used in emergency power backup systems such as the UPS, consumer electronics like smartphones and other devices, aiding powered devices for disabled individuals such as electric wheelchairs and electric vehicles like cars.
Advantages: Faster charging and Long-lasting, Higher energy density which is ideal for storing thousands of watts of solar production.
Disadvantages: Chances to get overheated and not safe operating at higher temperatures.

3. Nickel Cadmium:

Nickel-cadmium solar batteries use nickel hydroxide and metallic cadmium electrodes.

Applications: Used in consumer electronics such as smartphones, televisions, flashlights, or computers.
Advantages: Higher temperature resistance, higher power density, and longer lifecycle of 15 to 20 years.
Disadvantages: Insufficient charging efficiency and requires high-voltage charger which is highly expensive, increased initial costs due to safe disposal restrictions.

4. Flow Batteries:

Flow batteries are new competitors in the battery storage market that are made up of silicon solar cells integrated with advanced solid elements.

Applications: Large-scale storage applications
Advantages: Long-term performance, improved safety, and capacity for extended operation.
Disadvantages: Huge initial costs and lower power density.

AC Coupled Storage vs DC Coupled Storage

It is possible to link a solar panel to a battery either through AC (Alternating Current) coupling or DC (Direct Current) coupling. Let’s draw a comparison between these two storage systems highlighted by the pros and cons:

AC Coupled Systems:

The AC-coupled systems consist of a separate inverter for solar panels and battery modules that can be discharged at their maximum potential and released independently, thereby creating a variation in the system operation.

Advantages:

Easy to install on existing solar panels.
Flexible to install more than one inverter and battery in different locations.
Batteries can be charged from the solar panels and grid. This only happens if the panels aren’t producing sufficient electricity and the battery still gets charged from the grid.

Disadvantages:

Higher cost due to usage of multiple inverters.
The AC Coupled Battery Energy Storage System (AC BESS) can be used off-grid, and they are not transformer-based and cannot handle the peak loads from various appliances.
Lower efficiency since the stored energy is converted 3 times from DC to AC and results in small energy loss during the conversion process.

DC Coupled Systems:

To charge the battery from solar panels, DC-coupled systems utilize solar charge controllers or regulators and a battery inverter to transform the current flow to AC. The same grid interconnection is shared between the solar panels and battery components that use the same inverter to minimize equipment cost and power loss by turning on the current and operating individual interconnection lines to the grid.

Advantages:

Affordable price than AC coupled system.
DC Coupled Battery Energy Storage System (DC BESS) reduces energy losses and increases efficiency.

Disadvantages:

Less Flexibility than AC coupled system.
Inverter failure can cause a loss in solar energy and battery capacity due to a single inverter in a DC-coupled system.

Things to Look for When Picking a Solar Battery

These are the important factors to consider while selecting a solar battery:

1. Type / Material: The solar battery types can be either lead-acid batteries (used in car batteries) or lithium-ion batteries that are highly efficient and have a higher capacity lifespan.

2. Battery Life: Usually the lifespan of solar batteries is measured in cycles, which is one full discharge from 100% to 0% and recharged to 100%.

3. Depth of discharge: The Depth of Discharge (DoD) is the estimation from the manufacturer for how much power you can draw from the battery related to its overall capacity.

4. Round Trip Efficiency: The round trip efficiency is a measure of original power that can be invested into a system that you can use for future use. For example, if you provide an input of 90 units of power into the system and recover 70 units later, the round-trip efficiency will be 70%.

5. Capacity: The usable capacity is a value to represents the power you can consume from the battery at a time.

6. Safety Considerations: Few batteries such as lithium-ion require advanced safety procedures to prevent overheating and malfunctions.

7. Cost: The cost of installing solar batteries starts with the basic brand of 6,000 USD to the premium quality of 24,000 USD or more, depending upon the storage capacity, market price, installation fees, and several other factors. Also, the U.S. government offers a 30% solar incentive for installing solar power systems in your home. Since the batteries degrade over a certain time, the warranties assure the performance for a specified time.

Are Solar Batteries Worth It?

Yes, Solar batteries are a worthy upfront investment due to many benefits such as providing backup power, reducing dependence on the utility grid, and saving more money on electricity bills. If you’re planning for long-term savings on solar batteries, you need to look for these investment strategies:

If you install one battery system for a single home, it can cost you a minimum of $12,000, and sometimes more than $20,000, to lower your electricity costs. For example, a lead acid battery starts at a price range of $200, whereas the high-quality Lithium-Ion batteries cost upto $30,000 or more.
Batteries are beneficial for homeowners if your utility company doesn’t pay the complete price for solar power generated, to back up electricity during outages, or to use possible renewable energy. Then the battery is the best choice for you. But, if your utility company pays you the full price for extra solar power and your energy supplier has a complete net metering system, then the battery might not be suitable for your requirements.
Solar Batteries provide backup power during outages to reduce dependence on the utility grid.

How Much Energy can be reserved in a Solar Battery?

The capacity of a solar battery is measured in kilowatt-hours (kWh), which determines the amount of energy it can store. When considering residential solar battery systems, can store electricity starting from 1 kWh to several tens of kWh.

Linking multiple solar batteries helps to increase the overall efficiency of a solar system, thereby providing greater adaptability and increasing storage capacity as well as grid independence.

How many batteries are required for my solar system?

Based on your energy usage and requirements, you need to select the number of batteries required for the solar system. Every homeowner can easily calculate their energy usage by following these simple steps:

1. Estimate your energy usage: You can calculate your system’s energy consumption by using an off-grid solar load calculator.

2. Battery Type Selection: You need to select the battery type which includes the two main categories such as LiFePO4 (lithium iron phosphate) batteries and lead acid batteries. Lead Acid batteries come in different types such as sealed (SLA), flooded, gel, and AGM (Absorbent Glass Mat). Each has its unique characteristics and benefits, but the main component commonly used is lead acid for storing electrical energy.

3. Select a Battery Storage: The most common preferred voltages for solar batteries are 12V, 24V, and 48V.

4. Pick a Depth of Discharge (DoD): Based on the battery type, you need to consider the standard depth of discharge (DoD). The lead acid batteries have required DoD of 50% whereas LiFePO4 batteries have a capacity of 100%. Most importantly, the average depth of discharge for a battery influences the lifespan, and the estimated number of cycles from various DoDs is printed out in the battery’s specifications.

5. Select the number of Backup Days: This is the number of days required for the system to operate when the panels don’t produce any power.

6. Estimate Your Solar Battery Size: To calculate the size of your battery, you need to have the following numerical values:

Daily energy consumption (Wh/day)
Battery type
Voltage of the Battery Bank
Depth of discharge
Number of days required for Battery backup

Can I include additional solar batteries in my existing system?

Adding a solar battery to an existing grid-tied system can be performed in many ways and the method chosen depends upon your requirements and existing setup of solar system:

1. DC Coupled System: Replacing your present inverter with an existing hybrid inverter (integrated with a battery and solar system) is possible through the DC Coupled system.

The battery is charged with the help of DC power produced by your solar panels. Furthermore, the power is passed through the hybrid inverter that converts the DC into AC electricity, which can be used to power the appliances in your home or businesses to the grid.

2. AC Coupled System: Using a standard inverter in combination with a storage inverter charges the battery in the AC Coupled System. The energy can be stored efficiently without damaging the grid-tie inverter and the AC power is converted back into AC to charge the battery.

3. Storage Prepared Solar System: If your system was already designed for adding extra batteries, then your inverter is ready for the installation of a battery with a budget-friendly option that requires less labor and materials.

Can I install my own solar battery?

Yes, There are certain technical methods to install your own solar battery. However, you need to know that solar batteries are one such complex electronic device that requires to be installed safely under the guidance of experts.

Let’s compare the risks and benefits of professional vs DIY solar battery installation:

Professional Solar Battery Installation:

Benefits:

Professionals guarantee a safe installation and provide 24/7 services when there are any issues with the power or production. Also, they ensure that the installation satisfies the electrical code requirements and is free from any errors.
The solar installers have years of experience, and you can expect the workmanship and installation to be superior in quality.
Professional installers offer ongoing maintenance programs, and warranties as well as perform scheduled inspections.

Risks:

Hiring the services of a professional installer can be costlier when compared to a DIY installation.
It becomes mandatory to complete all the paperwork if you plan to employ an installer. Also, you should be aware of the rules and regulations for installing in your area, and appointing an installer with proper knowledge can be challenging.

DIY Solar Battery Installation: