Lithium-Ion Solar Battery: Definition and How it Works

A lithium-ion solar battery (Li+), Li-ion battery, “rocking-chair battery” or "swing battery" is the most popular rechargeable battery type used today. The term "rocking-chair battery" or "swing battery" is a nickname for lithium-ion batteries that reflects the back-and-forth movement of lithium ions between the electrodes during charging and discharging, similar to the motion of a rocking chair or swing.

Lithium-ion battery represents a type of rechargeable battery used in solar power systems to store the electrical energy generated by photovoltaic (PV) panels. There are parts of a lithium-ion battery include the cathode, anode, separator, and electrolyte. Both the cathode and anode store lithium. The cathode is typically the positive side, while the anode is the negative side. The electrolyte transports the positively charged lithium ions from the anode to the cathode through the separator, causing the battery to charge and discharge. The separator allows lithium ions to flow through the battery.

Lithium-ion batteries usually employ one of two popular chemistries for solar storage, lithium iron phosphate (LFP) or nickel manganese cobalt (NMC). Lithium Iron Phosphate (LFP) batteries use lithium iron phosphate and a graphite carbon electrode as the anode material. Nickel Manganese Cobalt (NMC) batteries use a combination of nickel, manganese, and cobalt in the cathode.

Lithium-ion batteries work with solar panels, storing the energy generated by the solar panel through a chemical reaction before it is converted into electricity in the form of direct current (DC). The DC electricity from the solar panels flows through an inverter, which converts it into alternating current (AC) electricity. The AC electricity is used to power your home appliances.

One of the key advantages of lithium-ion batteries is that they have a high energy density. This makes lithium batteries capable of storing a large amount of energy in a relatively small space, especially in solar power systems where space for equipment is usually limited. Another key advantage of lithium-ion batteries is their long lifespan, usually 5-15 years. Lithium-ion batteries are able to go through about 300-500 charge and discharge cycles without significant degradation.

While lithium-ion solar batteries have many benefits, they have some downsides. One key disadvantage of lithium-ion batteries is the high upfront cost. Lithium-ion batteries are typically more expensive, costing around $9,000 to $37,000, which is more than other types of batteries, such as lead acid batteries, which cost around $5000-$10,000. Another key disadvantage is the risk of thermal runaway, especially if it is not adequately installed or managed. Thermal runaway usually causes the battery to overheat or potentially catch fire.

What is a Lithium-Ion Solar Battery?

A lithium-ion solar battery is a type of rechargeable battery used in solar power systems to store the electrical energy generated by photovoltaic (PV) panels. Lithium-ion is the most popular rechargeable battery chemistry used today. Lithium-ion batteries work as a renewable energy storage system, storing energy generated by your solar system rather than sending it back to the grid.

As sunlight is converted into electricity by solar panels, any extra energy generated during sunny periods is captured and stored within your lithium-ion batteries for future use. This ensures a continuous power supply all year round. Inside the solar battery, chemical reactions take place to store the surplus electricity as potential energy. When electricity is needed during nighttime or overcast days when the sun isn’t shining, the stored energy is converted from the battery back into usable electricity and readily supplied to your home.

A lithium-ion battery has four main components, which include the cathode, anode, separator, and electrolyte. The cathode (the positive side) is typically a combination of nickel, manganese, and cobalt oxides. The anode (the negative side) is commonly made out of graphite. Both the cathode and the anode store the lithium. The electrolyte transports the positively charged lithium ions from the anode to the cathode through the separator, causing the battery to charge and discharge. The separator allows lithium ions to flow through the battery while preventing the movement of electrons, creating an electric current that powers various devices such as cell phones and computers.

Lithium-ion batteries are popular for solar storage due to their high energy density, long lifespan, and decreasing cost. There are several types of lithium-ion batteries, but two types are the most commonly used for solar storage: lithium iron phosphate (LFP) and nickel manganese cobalt (NMC). Lithium Iron Phosphate (LFP) batteries use lithium iron phosphate as the cathode material and a graphite carbon electrode with a metallic backing as the anode. The energy density in LFP batteries is lower than that of nickel manganese cobalt (NMC) batteries, which means they require more space for the same amount of energy. However, LFP batteries have a longer lifespan and are generally considered safer because they are more stable at high temperatures. Nickel Manganese Cobalt (NMC) batteries use a combination of nickel, manganese, and cobalt in the cathode. NMC batteries offer a higher energy density than LFP batteries, which means they are able to store more energy in the same amount of space. However, the lifespan of NMC batteries is typically shorter than that of LFP batteries, and they require more sophisticated management systems to ensure safety and longevity.

How does Lithium-Ion Solar Battery work with Solar Panels?

Lithium-ion batteries work with solar panels by storing the excess energy generated by the solar panel in the form of direct current (DC) electricity. The DC electricity from the solar panels flows through an inverter, which converts it into alternating current (AC) electricity. The AC electricity is used to power your home appliances. Lithium-ion batteries store the excess energy that is not used for later use. When the sun goes down, and the solar panels stop producing electricity, your appliances are powered by the stored energy in your battery. The two main ways lithium-ion batteries work with solar panels are charging the battery and releasing energy.

First, when the battery is charging, lithium ions move from the positive electrode (cathode) to the negative electrode (anode) through the electrolyte. Then, as the lithium ions leave the cathode, they leave behind their associated electrons. This creates free electrons at the cathode, which creates a charge. This charge difference between the anode and cathode causes the electrons to flow as an electrical current from the cathode through the external circuit (the device being powered, such as mobile phones or laptops) and then to the anode.

Next, when you discharge the electricity stored in the battery (i.e., use the stored energy), the flow of lithium ions is reversed. The lithium ions move from the anode to the cathode, and the electrons flow from the anode through the external circuit to the cathode. Finally, this flow of electrons provides the electrical current that powers your devices.

What are the benefits of a Lithium-Ion Solar Battery?

Lithium-ion batteries offer several unique benefits that significantly contribute to the overall efficiency and effectiveness of the solar energy system. One of the main benefits of lithium ion batteries for solar is that they have a high energy density. Lithium-ion batteries have the capacity to store a large amount of energy in a small space, making them an efficient choice for energy storage. Other key benefits of lithium-ion solar batteries include long lifespan, high efficiency, low maintenance, deep depth of discharge, and low environmental impact

More information on the 6 main benefits of lithium-ion batteries is below.

• Higher Energy Density: Lithium-ion batteries are widely known for their high energy density. This means that lithium batteries are capable of storing a large amount of energy in a relatively small space, especially in solar power systems where space for equipment is usually limited. The high energy density of lithium-ion batteries allows you to store more energy from your solar panels without needing a large amount of space for your battery storage.
• Long Lifespan: Another significant benefit of lithium-ion batteries is their long lifespan, which is about 5-15 years. They are able to go through about 300-500 charge and discharge cycles without significant degradation, meaning they are likely to be used for several years before needing replacement. This long lifespan reduces the overall cost of your solar power system and makes it more convenient as you don’t need to replace the batteries frequently.
• High Efficiency: Lithium-ion batteries are highly efficient at both charging and discharging. They charge faster than many other types of batteries, which means they quickly store energy produced by your solar panels. Lithium-ion batteries have a low self-discharge rate, which means that they retain their charge well over time.
• Low Maintenance: Unlike some other types of batteries, lithium-ion batteries require little or no maintenance. This is likely to save you time and effort in the long run, as you don’t need to regularly check or adjust the batteries. Low maintenance makes lithium-ion batteries a convenient choice for many solar power systems.
• Deep Depth of Discharge: Lithium-ion batteries allow for a deeper depth of discharge of 80%, which is more than many other types of batteries. Depth of discharge (DoD) refers to the percentage of a battery's capacity that has been discharged relative to its total capacity. It is calculated as the amount of energy discharged from a fully charged battery divided by the battery's nominal capacity. In essence, this means that a more significant portion of the battery’s capacity is able to be used before it needs to be recharged. Depth of discharge in lithium-ion batteries provides more usable power from each battery, increasing the effectiveness of your solar power system.
• Low Environmental Impact: Lithium-ion batteries have a lower environmental impact than other battery types. They are recyclable, reducing waste and helping to protect the environment. The long lifespan of lithium ion batteries means that fewer batteries need to be produced and disposed of, further reducing their environmental impact.

What are the Downsides of a Lithium-Ion Solar Battery?

While Lithium-Ion Solar Batteries have many benefits, they have some downsides to consider as well. One key disadvantage of lithium-ion batteries is the high upfront cost. Lithium-ion batteries are considered more expensive than other types of batteries. Other key disadvantages of lithium-ion batteries include the risk of thermal runaway, installation and space challenges, capacity limitations, and reduced efficiency in extreme temperatures.

More information on the five main downsides of lithium-ion batteries is below.

• High Cost: Lithium-ion batteries are typically more expensive, costing anywhere from $9,000 to $37,000, which is more than other types of batteries such as lead acid batteries (which cost around $5000-$10,000). This higher cost is likely to be a barrier for some people when considering a switch to battery storage. However, the long lifespan and high efficiency of lithium-ion batteries often offset this initial cost over time.
• Risk of Thermal Runaway: Lithium-ion batteries are likely to pose a risk of thermal runaway if not properly installed or managed. Thermal runaway represents a chain reaction that usually leads to the battery overheating and potentially catching fire. The risk of thermal runaway is high if the battery is overcharged or if there is a short circuit. To mitigate the risk of thermal runaway in lithium-ion batteries, you need a battery management system to monitor the battery’s temperature and charge levels.
• Installation and Space Challenges: Lithium-ion batteries are large and heavy, weighing around 50 grams each, which sometimes poses challenges in terms of installation and space requirements. The size and weight of the battery make it difficult to install, especially in residential settings where space is limited. The size and weight of lithium-ion batteries are likely to pose challenges in transportation and handling.
• Capacity Limitations: In specific applications, there is a trade-off between a lithium-ion battery's size and capacity. This means the battery needs to be larger to have a higher capacity, which is not feasible in all situations. For example, in some residential settings, there is insufficient space to install a larger battery, limiting the amount of solar energy that is likely to be stored.
• Reduced Efficiency in Extreme Temperatures: The efficiency of lithium-ion batteries decreases in extreme temperatures, especially in NMC (Nickel Manganese Cobalt), which decreases by up to 0% after 120 days. This means that in very hot or very cold environments, a lithium-ion battery is likely not to perform well. In a hot environment, NMC batteries are at risk of overheating, which usually leads to reduced performance and a shorter lifespan. In a cold environment, the capacity of an NMC battery is expected to be reduced, limiting the amount of energy that is able to be stored.

What are the Most Popular Lithium-Ion Solar Batteries?

The three most popular lithium-ion solar batteries are the Tesla Powerwall series, the LG Chem RESU series and the Sonnen EcoLinx.

More information about the three most popular lithium-ion solar batteries is below.

• Tesla Powerwall: The Tesla Powerwall is a 13.5-kilowatt-hour (kWh) lithium-ion battery widely used for residential energy storage. The Powerwall is considered one of the best solar batteries, with well-rounded performance and a 10-year cycle warranty. Tesla Powerwall comes in three main models: Powerwall Plus (+), Powerwall 2, and the new Powerwall 3. The Powerwall 2 and Plus have a Nickel Manganese Cobalt (NMC) chemistry and are compatible with new and existing solar panel systems. The newer Powerwall 3 has an LFP (Lithium Iron Phosphate) chemistry and is not compatible with other battery types. Reading Tesla Powerwall reviews is often the best way to understand which type is most suitable for your needs. The latest 3 version is one of the best lithium-ion batteries on the market today.
• LG Chem RESU: LG’s Chem RESU lithium-ion battery is another popular option for solar energy storage, with an impressive energy capacity of 9.6-16 kWh. LG Chem RESU batteries are known for their reliability and efficiency. They are configured for easy installation in either on- or off-grid photovoltaic systems, and they are one of the leading alternatives to Tesla Powerwall batteries. The current models available are the RESU 10H and the newer 16H Prime. They are designed to pair with a home solar system and connect directly to a storage-ready solar inverter for charging and discharging.
• Sonnen EcoLinx: The Sonnen EcoLinx is a high-quality lithium-ion solar battery best suited for Virtual Power Plants (VPPs). It’s recognized for its advanced smart energy management features. The ecoLinx synchronizes the energy usage of your property to efficiently and intelligently manage how you use energy in your home, all without disrupting your lifestyle. With an energy capacity of 12 kWh-20 kWh and a 15-year warranty, Sonnen ecoLinx is a powerful and smart home energy management system.

What is the Most Expensive Lithium-Ion Solar Battery?

The most expensive lithium-ion solar battery among the popular brands is the Sonnen EcoLinx. The cost of the Sonnen EcoLinx battery is currently around $30,000-$36,000, excluding the installation cost. This price is significantly higher compared to the other popular brands, such as Tesla Powerwall 2, which costs around $9,000-$15,000, and LG Chem RESU, which costs around $9,500-$13,000. The cost of lithium-ion solar batteries varies based on factors such as installation costs and location. The installation cost includes labor, equipment, permitting, and inspection. The location cost includes local regulations, shipping costs, and climate.

The cost of labor for lithium-ion solar batteries varies depending on the complexity of the installation. For example, it often takes additional time and expertise to integrate lithium-ion batteries with an existing solar panel system, ultimately increasing the cost. In some cases, additional equipment, such as mounting hardware or wiring, is required for the installation. The cost of these materials adds to the overall installation cost. Depending on local regulations, permits, and inspections are likely needed, which increase the overall installation cost.

In terms of location cost, some locations have specific regulations or requirements for installing battery systems, which affect the price. The shipping cost adds to the overall cost if the battery needs to be shipped to your location, especially true for remote locations. The climate in your area is likely to affect the price. You are likely to need additional equipment to protect the battery from extreme temperatures if you live in a very hot or cold climate.

What is the Cheapest Lithium-Ion Solar Battery?

The cheapest lithium-ion solar battery among the popular brands is the Tesla Powerwall 2. Tesla Powerwall 2 is a 13.5 kilowatt-hour (kWh) battery that costs around $10,000-$12,000, including installation when purchased with Tesla solar panels. Tesla Powerwall 2 is considered cheap compared to other popular brands like LG Chem RESU, which costs around $9,5000-$13,000, and Sonnen EcoLinx batteries, which cost around $30,000-$36,000. The Tesla Powerwall is a popular choice for residential energy storage due to its affordability.

Lithium-ion solar panel battery prices vary based on location, installation costs, and whether the battery is being installed as part of a new solar panel system or added to an existing one. In terms of location, the cost of a Tesla Powerwall 2 varies significantly depending on where you live. This is due to differences in shipping costs and local regulations. Labor fees and the complexity of the installation affect the cost of installing the Tesla Powerwall 2. Installing Tesla Powerwall 2 is likely to be more cost-effective if the Powerwall 2 is being installed as part of a new solar panel system. This is because the installation is done simultaneously with the solar panel system, reducing labor costs. Purchasing Tesla Powerwall 2 makes you eligible for cost-saving rebates like the 30% federal solar tax credit, which is likely to help lower your electricity bills.

Which Solar Battery, Lead-acid or Lithium-ion, is preferable for a home solar panel?

Lithium-ion batteries are generally preferable for home solar panel systems over lead-acid batteries. The preference for lithium-ion solar batteries compared to lead-acid solar batteries is due to four key reasons. One of the key reasons lithium-ion solar batteries are preferable is their high efficiency. Lithium-ion batteries have a round-trip efficiency of about 85-95%, compared to 50-85% for lead-acid batteries. This means that lithium-ion batteries are able to store and deliver energy more efficiently. Other key reasons lithium-ion batteries are preferable to lead-acid batteries include high storage capacity, low maintenance, and low cost.

First, lithium-ion batteries have high efficiency. Lithium-ion batteries are known for their high efficiency, which measures the energy that is usually used as a percentage of the energy stored. Lithium-ion batteries have a round-trip efficiency of about 85-95%, compared to 50-85% for lead-acid batteries. This means that for every 100 units of energy stored in a lithium-ion battery, about 85-95 units are used. This high efficiency means you get more usable power from a lithium-ion battery than a lead-acid solar battery of the same capacity.

Secondly, lithium-ion batteries are able to store a larger amount of energy in a smaller space than lead-acid batteries, making them a good choice for home solar storage. This is particularly important in residential settings where there is limited space. Lithium-ion batteries are capable of handling high charge and discharge rates, which makes them suitable for applications that require a lot of power in a short amount of time.

Thirdly, lithium-ion batteries have low or no maintenance compared to lead-acid batteries. Lead-acid batteries need to be topped up with distilled water regularly and require regular equalization charges to prevent stratification. Stratification occurs when the water rises to the top, and the acid sinks to the bottom due to the separation of the electrolyte, which happens when the battery sits idle for long periods. Lithium-ion batteries do not require water top-ups or equalization charges, making them easier and cheaper to maintain. This saves you time and effort over the life of the battery.

Finally, low cost is another factor that makes lithium-ion batteries preferable to lead-acid batteries. While the upfront cost of lithium-ion batteries is higher than that of lead-acid batteries, the total cost of ownership is likely to be lower. This is because lithium-ion batteries have a longer lifespan and higher efficiency than lead-acid batteries. Lithium-ion batteries require less maintenance, which saves costs over time. When you factor in these benefits, the cost per kilowatt-hour (kWh) of a lithium-ion battery is likely to be lower than that of a lead-acid battery. This makes lithium-ion batteries a cost-effective choice for solar storage in the long run.

Do you need a special Solar Panel to charge Lithium-Ion Solar Batteries?

No, you do not need a special solar panel to charge lithium-ion solar batteries. Charging a lithium-ion battery is possible with any solar panel. However, there are essential considerations to ensure safe and efficient charging of your lithium-ion batteries with your solar panels. These four key considerations help ensure that your lithium-ion batteries are charged optimally without potentially overcharging, which damages your battery. One of the key considerations when charging your lithium-ion batteries with a solar panel is compatibility with output requirements. This means that your solar panel must have the accurate output requirement to charge your lithium-ion batteries. Other key considerations when charging your lithium-ion batteries with solar panels include the use of a solar charge controller, voltage and currents, the size of your solar panel, and the temperature of your lithium-ion batteries.

The first consideration when charging your lithium-ion battery with your solar panel is compatibility with power output. This ensures that your lithium battery is compatible with solar power. Some lithium batteries require a special charger specifically designed for lithium-ion cells to charge them safely.

Secondly, the use of solar charge controllers is another key consideration when charging your lithium-ion batteries with solar panels. While solar panels are able to charge lithium batteries, solar charge controllers are required. An MPPT (Maximum Power Point Tracking) solar charge controller is an example of a solar charge controller that allows more current into the battery, leading to faster battery charging. PWM (Pulse Width Modulation) is another example of a solar charge controller allowing more current into the battery. However, PWM solar charge controllers are less efficient and are likely not to fully utilize the power from the solar panels.

Thirdly, voltage and current are key considerations when charging your lithium-ion batteries with your solar panels. The voltage of your solar panel is a significant factor in how much energy you get, as this determines what type of regulator you need to use with your lithium battery. Next, the size of your solar panel is another limiting factor, as larger panels give more amps, which means faster charging.

Finally, the temperature of your lithium-ion batteries is another key consideration. You are likely to experience a reduction in the amount of energy that goes into or out of the battery cell if the temperature gets too hot.

What is the lifespan of a Lithium-Ion Solar Battery?

The lifespan of a lithium-ion solar battery is typically between 5 and 15 years. However, the lifespan of lithium-ion batteries is influenced by several factors. One of the key factors that affects the lifespan of lithium-ion batteries is extreme temperatures. Lithium-ion batteries are known to perform at their best within a specific temperature range, which reduces the degradation of the components. Other key factors that affect the lifespan of lithium-ion batteries include protective coatings, charging cycles, time in use, usage, maintenance, and battery type.

Extreme temperature influences the lifespan of lithium-ion batteries. Lithium-ion batteries perform best within a specific temperature range, usually 15°C~35°C. Exposure to extreme heat or cold significantly impacts their lifespan. High temperatures accelerate the degradation of almost every battery component, leading to significant safety risks, including fire or explosion. Very low temperatures reduce the energy and power capabilities of lithium-ion batteries.

Protective coatings are another essential factor that influences the lifespan of lithium-ion batteries. Protective Polymer Coatings (PPCs) protect lithium metal anodes in rechargeable batteries to stabilize the Li/electrolyte interface. These protective coatings reduce parasitic reactions and improve the lithium deposition morphology by extending the cycle life. The metal covering on a lithium-ion battery’s cathode reacts with the battery’s electrolyte at higher temperatures and voltages, which results in added degradation over time.

Charging cycles affect the lifespan of lithium-ion batteries. Every time a lithium battery is charged and discharged, it undergoes a certain amount of wear and tear, which usually has a direct impact on its overall longevity. The number of charge cycles gives an estimated lifespan, which is altered by temperature, overcharging, storage conditions, fast charging, and discharge rates.

Time in use influences the lifespan of lithium-ion batteries. Lithium-ion batteries inevitably degrade with time and use. Almost every component is affected, including the anode, cathode, electrolyte, separator, and current collectors. Chemical reactions causing self-discharge and deterioration occur naturally over time, leading to decreased performance and lifespan. Then, usage is another key factor that reduces the lifespan of lithium-ion batteries. This represents the way a battery is used. Frequently discharging a battery to a very low level before recharging it shortens its lifespan. Maintenance is another key factor that reduces the lifespan of lithium-ion solar batteries. Proper maintenance helps extend the life of lithium-ion solar batteries. This includes practices like avoiding overcharging, storing the battery at optimal temperatures, and using the appropriate charger. Finally, the battery type is a significant factor that influences the lifespan of lithium-ion batteries. Different types of lithium-ion batteries have different lifespans due to variations in their design and materials. Lithium-ion batteries with a higher energy density are likely to have a shorter lifespan than those with a lower energy density.

Is it worth it to use a Lithium-Ion Solar Battery for your Solar Panel?

Yes, it is generally worth it to use a Lithium-Ion Solar Battery for your Solar Panel. It is worth it to use lithium-ion solar batteries for your solar panels because they usually have a higher charge rate, which makes them highly efficient. Other factors that make lithium-ion batteries a worthwhile investment include longevity and low maintenance, limited space, and energy storage. In addition to these factors, you need to consider the cost and temperature sensitivity.

Lithium-ion batteries have a higher charge rate, which means they are able to be refilled much faster than other battery types. Higher efficiency means your lithium batteries charge faster, and you probably need fewer solar panels installed.

Lithium-ion solar batteries have a long lifespan and are low maintenance. Lithium-ion batteries last about 5-15 years, and are able to go through about 300-500 charge and discharge cycles without significant degradation. Using up to 90% of a charge per cycle is possible with lithium-ion solar batteries without inflicting much damage.

Lithium-ion solar batteries do not take up as much space as other battery types, which is a significant advantage in residential settings. Energy storage makes lithium-ion batteries a worthwhile investment. When paired with solar panels, excess solar energy produced during the day is stored in the battery and used by a home at night when the solar panels are not generating electricity.

Another key consideration to determine whether using lithium-ion batteries is a worthwhile investment is the cost. The cost of installing lithium-ion batteries is much higher than the cost of installing lead-acid batteries. The total cost to install a lithium battery storage system is currently around $9,000 to over $37,000.

Temperature sensitivity is another key consideration in determining whether using lithium-ion batteries for your solar panels is worth it. Lithium-ion solar batteries are significantly more sensitive to temperature, and in extreme climates, additional measures must be taken to protect the battery.