Solar batteries can be a brilliant addition to your residential solar system. These devices work by storing the excess energy your solar panels generate to be used at night when the sun isn’t shining, or during a power outage. Solar batteries come in four major types, each with its unique strengths and weaknesses. These types include: lead-acid, lithium-ion, nickel-cadmium and flow. Understanding the differences between these battery types will help you get prepared to make the right choice for your home.
Benefits of Solar Batteries
A solar battery is an energy storage device that works directly with your solar system. As your solar panels generate energy from the sun during the day to power your home, any surplus energy can be sent to charge your battery for later use. Solar batteries have a range of benefits to make them a valuable addition to your solar system:
- Saving on energy bills – By storing the excess solar energy captured by your solar panels within your batteries for later use, you can reduce your reliance on electricity purchased from the grid.
- Backup energy – By installing a battery can allow you to continue powering your home through a blackout, using its stored energy.
- Provides electricity after the sun goes down – Solar panels need sunlight to provide electricity. Therefore, during the night or cloudy days, your solar panels won’t be as effective. Using energy from your solar batteries when the sun isn’t shining is a great solution.
- Noiseless power solution – Solar batteries are typically quiet and non-disruptive. Unlike popular gas or diesel-powered generators, which tend to be especially loud, solar batteries are a great alternative.
- Helping the environment – Adding a solar battery to your home reduces your reliance on electricity, generated from burning fossil fuels. This promotes the use of renewable energy, which is cleaner for the environment.
Types of Solar Batteries
Lead-acid batteries
The oldest type of solar battery. These devices have been a staple of energy storage since their invention in the 19th century. They have continued to endure, primarily because of their affordability. Lead-acids are relatively cheap, particularly when compared to other battery types. This makes them great for a variety of quick applications, providing short bursts of energy for a smaller cost. They are also dependable and have been around for over a century, with a proven longevity in handling energy storage.
Although it’s been around for decades, as other battery types utilise advanced technology, the lead-acid has become old-fashioned. They are typically big and bulky and require high levels of maintenance to continue operating. While they are affordable, their lifespan is relatively poor, at around 5 years when used consistently. This means they have a high cost per kWh of stored energy, making them unsuitable for use as an on-grid solar battery for modern households.
Lithium-ion batteries
Considered the most common choice for modern households, lithium-ion batteries have grown in popularity due to their high efficiency and longevity. Using a similar technology to batteries in smartphones, they incorporate the flow of ions away from a lithium compound to store energy.
They are great because of their lightweight, compact design, while still being able to provide a high number of cycles with a strong energy capacity. Maintenance of lithium-ion batteries is also relatively easy, with an impressive longevity of between 10 and 15 years, depending on your environment and usage.
Their major drawback is their price. Upfront costs are expensive and can reach as high as $15,000.
Furthermore, if your lithium-ion batteries are not installed correctly, they pose a risk of catching fire due to a process called thermal runaway, when the internal temperature of the battery cell rapidly rises. Choosing a qualified installer, such as Tasmanian Safer Solar, can ensure your battery is safely installed.
Flow batteries
These batteries are unique for using a liquid electrolyte that flows between the two chambers in the battery. They are still a relatively new technology that has yet to fully enter the residential storage market.
These batteries are an exciting technology with a variety of benefits. Firstly, they have a 100% Depth of Discharge (DoD). DoD refers to the usable portion of a battery’s capacity. Exceeding this measurement will reduce your battery’s lifespan. A flow battery having a 100% DoD means you can use all of the available energy within the battery, without damaging any of its mechanisms. This gives these batteries an impressive lifespan, often lasting around 30 years.
The biggest disadvantage of flow batteries is that they are still relatively new and are not readily available for residential use. Furthermore, they are very expensive, with costs exceeding lithium-ion batteries. Flow batteries are also very large and bulky, requiring considerable space for installation.
Nickel-cadmium batteries
Although less common than lead-acid or lithium-ion, Nickel-cadmium batteries are renowned for their durability in extreme conditions.
Their biggest advantage is their long lifespan and their ability to thrive in extreme temperatures due to their robust construction. Even when temperatures reach as high as 50°C, these batteries can continue operating without any significant performance loss.
However, they have been largely phased out due to the toxicity of cadmium. They are also highly vulnerable to the memory effect, which is a phenomenon where they gradually lose capacity.
What is the Best Battery Type For You?
In the majority of cases, a lithium-ion battery will be the right choice for you. They can hold a large amount of energy, with high efficiency, while only requiring a small amount of space. They have a high depth of discharge (DoD) of 80%, and due to their popularity, solar companies are experienced in installing them, ensuring both safety and precision.
Although, if cost is a primary concern, choosing a lead-acid battery may be a smart alternative. They are the cheapest of the four major battery types, and can be at least half the price. They have also been used successfully for decades, with a proven track record of storing energy. However, you should also consider their major drawbacks, namely their shorter lifespan and higher maintenance requirements.
Ultimately, unless cost is a major issue, lithium-ion batteries are likely to be the most practical choice. To find out more about which solar battery type is right for you, you should contact our friendly team at Tasmanian Safer Solar (TSS).
AC vs DC-coupled batteries
Another way to categorise solar batteries is by how they are connected to your solar power system, as either AC-coupled or DC-coupled. Solar panels generate electricity in the form of direct current (DC), and batteries also store energy as DC. However, the electricity used in your home is alternating current (AC), so a conversion from DC to AC is necessary. The difference between AC- and DC-coupled batteries is in where and how this conversion takes place. Understanding the key characteristics of each type can help you choose the best option.
AC-coupled battery
In an AC-coupled system, your battery takes in AC electricity, inverts it to DC, stores it, and then inverts it back to AC electricity when your home needs power. This means there are multiple inversions taking place, with a small amount of electricity lost in the process. Due to the inversion, AC-coupled battery systems typically have a round-trip efficiency of approximately 85-90%, which means 10-15% of the electricity is lost during the process.
DC-coupled battery
DC-coupled battery systems don’t require multiple inversions, with your battery getting charged straight from your solar panels. These systems employ a hybrid inverter, which can work to juggle both solar and battery inversion in one. A DC-coupled battery is highly efficient, with only one inversion, meaning just 2.5% of electricity is lost.
Are AC or DC-coupled batteries better?
Although DC-coupled systems are more efficient, they are more difficult to install into an existing solar system with already established inverters. An AC-coupled system is more flexible for established systems, because they don’t require major changes to the existing inverter or wiring. Therefore, If you are planning on installing a battery with your solar system, at TSS we recommend choosing an AC-coupled battery. These devices provide the lowest cost per kWh over their warranty period, and are compatible with any photovoltaic (PV) inverter making them an ideal retro-fit battery solution. Manufactured by APstorage, they are the perfect choice for Tasmanians.
Other Factors to Consider When Choosing a Solar Battery
- Solar battery capacity – Measured in kilowatt-hours (kWh), your battery’s capacity is the amount of energy it can store. Choosing the right capacity allows you to maximise your entire solar system, with enough backup energy for use when the sun isn’t shining. Battery capacity is determined by estimating your daily usage and how much you want to rely on backup power.
- Solar battery size and installation requirements – The size of your solar battery type will determine how seamlessly it can fit in your household space during installation. Lithium-ion batteries are the smallest of the four battery types, making them a compact, versatile choice for households with limited space. Flow batteries are generally the largest and are better suited for large-scale storage, due to the bulky tanks required to hold the liquid electrolyte.
- Solar battery efficiency – Solar battery efficiency refers to the percentage of energy that can be stored and then used. Higher efficiency means less energy is lost during the charging and discharging process, resulting in more electricity for your household. Lithium-ion batteries are typically considered the most efficient type, due to their high energy density, longer lifespan, and ability to maintain performance over multiple charge cycles.
- Warranty and expected lifespan – When purchasing any device, it’s important to consider its lifespan. While lifespan is often measured in years, for batteries, it’s more accurately assessed by the number of charge cycles. The exact lifespan and warranty will vary depending on the battery type. For example, lithium-ion batteries typically last up to 10-15 years and often come with a 10-year warranty.
Understanding the right type of battery can help maximise your residential solar system. Our guide has unpacked the four major battery types: lead-acid, lithium-ion, nickel-cadmium and flow. Understanding how AC and DC-coupled systems factor into your decision and the additional factors for purchase. Our specialist team at Tasmanian Safer Solar (TSS) are always here to help. If you have any further questions, please contact our team here.
1300 655 808
