Solair World

Solar Batteries: Everything You Need To Know


If you don’t have a way to store the power your solar panels make, they wouldn’t be very useful. Your devices would only work during the day when it’s sunny.

Any electricity that you don’t use right away would just go to waste, and you wouldn’t have any for nighttime. That’s where solar batteries come in.

They save the electricity that your panels create so you can use it whenever you need to.

Instead of sending extra power back to the power grid, you can keep it.

Solar batteries can make your home or building less affected by blackouts and can even allow you to disconnect from the power grid completely.

Table of Contents

Solar Battery Basic

What Is a Solar Battery?

A solar battery is a device that stores energy from the sun that is captured by solar panels.

It allows you to keep the electricity generated by your solar panels for later use.

For example, when the sun isn’t shining at night or on cloudy days, you can still have power.

This means you can have electricity whenever you need it, not just when the solar panels are producing it in real time.

Solar batteries are key for a solar power system to provide a consistent power supply, especially in areas where there is no access to the main electricity grid or where power outages are common.

What Is DoD (Depth of Discharge)?

Depth of Discharge is a term that refers to the percentage of the battery’s capacity that has been used.

Most solar batteries need to retain some charge at all times due to their chemical composition. Therefore, a battery’s usable capacity may be less than its total capacity.

What Is an AC Coupled Solar Battery?

An AC-coupled solar battery is a system that stores the energy produced by solar panels for later use. Here’s how it works in simpler terms:

  1. Your solar panels generate power as DC (direct current) when the sun shines on them.
  2. This DC electricity is then converted to AC (alternating current) by your usual solar inverter, the same way it does for immediate use in your home.
  3. Instead of using this AC electricity right away, it goes into the solar battery system, like the Tesla Powerwall, where it’s stored.
  4. Even though the battery stores electricity as DC, the Tesla Powerwall is special because it can take in AC electricity. It has a built-in device that changes some of the AC electricity back into DC to charge its battery.
  5. Later, when you need this power, the stored DC electricity is changed back into AC and sent through your home’s electrical panel so you can use it in your house.

Both homes with single-phase and those with 3-phase electrical systems can use a system like the Tesla Powerwall. This versatility makes AC-coupled batteries a flexible choice for different types of properties.

What Is a DC Coupled Solar Battery?

A DC-coupled solar battery is a type of system that stores the energy from your solar panels directly as DC (direct current) electricity.

Here’s the straightforward process of how it functions:

  1. The solar panels on your roof collect sunlight and convert it into DC electricity.
  2. This DC electricity is sent to a special device called a ‘hybrid inverter.’ A hybrid inverter combines the jobs of a traditional solar inverter and a battery charger. It takes care of both converting solar power for immediate use and charging the battery.
  3. The battery stores this DC electricity until you need it.
  4. When you want to use the stored energy, the DC power from the battery goes back through the hybrid inverter.
  5. The inverter changes the DC electricity into AC (alternating current) electricity, which is what your home uses.
  6. This AC electricity is then delivered to your home through your electrical panel, allowing you to power your appliances and lights.

An example of a DC-coupled battery is the LG Chem Resu, which requires a hybrid inverter to work correctly.

It’s important to note that systems like these are generally designed for single-phase properties.

If you have a 3-phase property, you would need additional equipment to make such a battery setup work.

How Do Solar Batteries Work?

The process of storing and using solar energy involves a few steps, and it varies depending on whether you have a DC-coupled system or an AC-coupled system.

For a DC-coupled system:

  1. Sunlight hits your rooftop solar panels, which turns them into DC (direct current) electricity.
  2. This DC electricity is sent straight to the solar battery where it’s kept until you need it.
  3. When you need to use it, this stored DC electricity is moved to an inverter, which changes it into AC (alternating current) electricity that your home appliances can use.

The steps are a bit different for an AC-coupled system:

  1. Sunlight is converted to DC electricity by the solar panels.
  2. This DC electricity is immediately converted to AC electricity by a solar inverter so you can use it in your home.
  3. If there’s extra electricity that you don’t need right away, it goes through another inverter that changes it back into DC so it can be stored in the battery.
  4. Later, when you need the power stored in the battery, it has to go through the inverter once more to change back into AC electricity for your home to use.

Types of Solar Batteries

Solar batteries come in various types, each with its own set of characteristics and uses. Here are the primary types you’ll encounter:

  1. Lead-Acid Batteries: These are one of the oldest types of rechargeable batteries. They are more affordable but have a lower energy density and a shorter lifespan. They come in two main types: flooded lead-acid (which requires maintenance) and sealed lead-acid (maintenance-free).
  2. Lithium-Ion Batteries: Lithium-ion batteries are considered deep-cycle batteries. They have a higher energy density, which means they can store more electricity in a smaller space, and generally have a longer lifespan with less maintenance required than lead-acid batteries. LiFePO4 batteries are a subtype of lithium-ion batteries that utilize unique chemistry to provide advantages over related lithium technologies.
  3. Nickel-Cadmium (NiCd) Batteries: NiCd batteries are durable and can operate well in a wide range of temperatures and conditions. They are less common in residential solar applications due to cost and environmental concerns, as cadmium is a toxic heavy metal.
  4. Flow Batteries: They excel in scalability and have long lifespans, but they are generally used for larger, industrial applications rather than residential.

Advantages and Disadvantages of Solar Battery

Solar batteries stand as a beacon of modern energy innovation, allowing homeowners and businesses alike to store and manage the power generated by solar panels.

Although the huge upfront cost of solar batteries, they can be worth it if they align with your goals and circumstances. They offer the potential for reduced utility bills, increased energy independence, and backup power.

However, the story isn’t one-sided.

The upfront cost of solar batteries can be considerable, and the technology isn’t entirely without environmental impact, considering the resources needed for their production and eventual disposal.

Despite this, the benefits of solar batteries often outweigh the drawbacks, especially as advancements in technology continue to improve their efficiency, lifespan, and recyclability, making them a compelling choice for those looking to invest in a sustainable energy future.

Solar Batteries Charging

How to Charge a Solar Battery With Solar Panels?

Charging a battery with solar panels is a process that harnesses sunlight to generate electrical power.

It involves using photovoltaic panels to capture energy from the sun and convert it into a form that can be stored in a battery for later use.

This is accomplished through a series of steps that ensure the energy is transferred in a safe and efficient manner, taking into account factors such as the battery type, the solar panel’s output, and the energy requirements of the system.

Essential components like a charge controller play a pivotal role in managing the flow of electricity into the battery, protecting it from being overcharged, and maximizing its lifespan.

How To Know If the Solar Panel Is Charging the Battery?

To determine if your solar panel is charging the battery, you would typically monitor the charge controller, as it often provides a clear indication of the charging status through LED lights or a digital display.

Another reliable method is using a multimeter or a voltmeter to check the voltage at the battery terminals; if the solar panel is charging, the voltage will typically be higher than the battery’s resting voltage.

Regular monitoring helps ensure that your system is functioning correctly and that your battery is receiving the charge it needs.

How to Know if Solar Battery is Fully Charged?

Knowing if a solar battery is fully charged typically involves monitoring indicators on a charge controller or measuring the battery’s voltage with a multimeter.

Charge controllers usually have LED indicators or screens that display the battery’s charge status.

A fully charged battery will have a stable voltage that aligns with its specific fully charged baseline, which for many 12V batteries, is around 12.6 to 12.8 volts when not connected to a load or charging source.

Can a Solar Battery Charge and Discharge at the Same Time?

A solar battery cannot charge and discharge simultaneously in the literal sense because charging and discharging are opposite actions — charging involves storing energy in the battery while discharging means releasing that energy.

However, in a practical application within a solar power system, it may appear that a battery is doing both at the same time, due to the way the system manages power flows.

How Long Do Solar Batteries Hold Charge?

Similar to other types of batteries, solar batteries require periodic recharging.

The length of time your solar battery will hold a charge depends on the battery and the amount of energy being stored, generally, a fully charged solar battery will store energy for one to five days.

In the case of Tesla batteries, they can maintain their charge for up to seven days.

Solar batteries also have impressive longevity, with an average lifespan approaching nearly two decades.

This makes them a durable and reliable option for long-term renewable energy storage.

Solar Batteries Lifespan: How Long Do Solar Batteries Last?

The lifespan of solar batteries can range significantly, with most lasting between five to 15 years, although some top-quality models may even last up to 20 years.

However, these figures are approximations.

The actual service life of a solar battery will depend heavily on the battery’s make and model, as well as how well you adhere to the manufacturer’s guidelines for using and taking care of the battery.

Regular maintenance and proper usage according to the manufacturer’s instructions are key to maximizing a solar battery’s lifespan.

It’s also worth noting that the capacity of all batteries will degrade over time, meaning they will store less energy as they age. However, higher-quality batteries generally degrade more slowly than cheaper options.

How Long Will a Solar Battery Power Your House?

How long a solar battery keeps your house running is determined by the size of the battery and how much electricity your home uses.

Typically, a 10 kWh solar battery could last from half a day to a full day.

If you want it to last longer, you could use energy-saving appliances, be smart about when and how you use electricity, take good care of your solar equipment, and make sure you choose the right number of batteries for your needs.

Applications of Solar Battery

Solar batteries are not just about energy efficiency; they represent a step towards energy sovereignty, providing stability and independence in a world of fluctuating energy prices and grid uncertainties.

In residential settings, they offer the peace of mind that comes with reliable backup power and the financial benefits of reduced utility costs.

For businesses, they serve as a critical backup, support grid stability, and open opportunities for smart energy management.

In remote or specialized applications, they are used in portable solar generators, enabling power in the most isolated of locations.

This article will illuminate the myriad of applications for solar batteries, showcasing how they are integral to not just individual energy strategies, but also the broader goal of creating a sustainable and energy-secure future.

Solar Battery Costs

The cost of a solar battery or battery system varies based on the type and capacity of the battery selected.

Lead-acid batteries generally have a lower initial cost compared to lithium-ion batteries.

However, long-term savings could make lithium-ion batteries a more economical choice, depending on usage patterns.

For lead-acid batteries, individual units can range in cost from $200 to $800 or even higher, depending on their size and power capabilities.

Multiple lead-acid batteries may be required to fully power a household.

In contrast, the average price for a residential lithium-ion solar battery system, including installation, tends to fall between $7,000 and $14,000.

As for nickel-cadmium and flow batteries, their costs can fluctuate greatly and are largely influenced by the scale of the installation.

However, nickel-cadmium batteries are rarely seen in residential settings, being more suited for commercial or industrial applications.

As part of a residential solar energy system, solar batteries qualify for the solar investment tax credit, which allows you to deduct a certain percentage of the cost of installing the solar battery from your federal taxes.

This can result in significant savings on the upfront cost of your solar energy system.

How Many Solar Batteries Do You Need?

Suppose you have a residential solar system connected to the power grid.

In that case, you might need between one to three lithium-ion batteries, each with a capacity of at least 10 kilowatt-hours (kWh), to save on electricity costs, keep essential appliances running when the power goes out, or power your entire home.

Research from the Lawrence Berkeley National Laboratory in 2022 found that for a solar system designed to completely offset your energy use, just one 10 kWh battery can keep crucial household systems running for three days for almost all areas in the United States throughout the year.

If you want to make sure your heating and air conditioning are also covered during a power outage, you’ll likely need a bigger solar setup with around 30 kWh of storage, which means about two to three lithium-ion batteries. This should cover almost all your electricity needs.

The total number of solar batteries you’ll need will mainly depend on what you want to achieve with your solar system.

Choosing a Solar Battery

When choosing a solar battery, it’s essential to consider several factors that will ensure you get a reliable and cost-effective solution for your energy storage needs.

The battery’s capacity tells you how much electricity it can store, which determines how much power you can use before needing a recharge.

It’s also critical to look at the power rating, as this indicates the amount of electricity the battery can deliver at one time, dictating how many appliances you can run simultaneously.

It would help if you also thought about the battery’s lifespan, which is described in terms of cycles and years.

Furthermore, the depth of discharge (DoD) is an important aspect because it reflects how much of the battery’s capacity can be used without negatively impacting its lifespan. Higher DoD usually means you can utilize more of the battery’s capacity.

The type of battery technology, whether it’s lead-acid or lithium-ion, will affect performance, maintenance, and initial costs.

The efficiency of the battery will determine how much of the stored energy can actually be used, as some energy is lost in the charge and discharge process.

Safety is paramount, so ensure that the solar battery you choose has a solid safety record and is made by a reputable manufacturer.

The battery should be suitable for the climate conditions it will be operating in since temperature can significantly impact battery performance and lifespan.

Lastly, warranties and manufacturer support are crucial as they give you an indication of the battery’s reliability and the company’s confidence in their product.

Solar Batteries Recommendation

When looking for the best solar batteries to complement your solar generator system, the most recommended types are usually Lithium-Ion (Li-ion) and Lithium Iron Phosphate (LiFePO4) due to their efficiency, longevity, and safety profile. 

Dive into our solar batteries buying guide, spotlighting the market’s premier solar batteries. We assess their performance, longevity, and value, simplifying your search for the solar solution that meets your energy demands.