Table Of Contents

Solar Batteries Explained

A solar battery is a type of solar device that stores electricity for usage. It allows you to keep appliances running during a power outage. Solar batteries store much of the solar energy you generate at home and, in many situations, even help you save money on electricity. They're known as "deep cycle batteries" because of their ability to charge and discharge a large amount of electricity compared to an automobile battery.

Battery Specifications Important For Home Needs

When analysing the best energy storage alternatives for your home, there are different selection criteria and comparative points to consider. Here are some of the typical decision factors to consider:

  • Look for solar batteries with a high-power rating if you want to power more appliances in your home at once.
  • Look for a solar battery with a high instantaneous energy rating if you wish to power more energy-intensive items.
  • If you want to use your solar battery to power your home for a more extended period of time, choose one with a higher usable capacity.
  • Look for solar batteries with higher round-trip efficiency to get the most out of every kilowatt-hour of electricity you put into your battery.  
  • Look for lithium-ion nickel manganese cobalt (NMC) solar batteries if you're short on space and want to get the uttermost storage out of the least space.
  • Look for lithium iron phosphate (LFP) batteries if you want a battery that will last the longest and be cycled the most.
  • Look for LFP solar batteries if you want a battery with the best possible safety rating.

Six Factors Before Buying A Home Solar Battery

Battery storage systems offer a variety of advantages, ranging from emergency backup power to cost savings. Plus, they also carry a new level of smartness and technology with them. Here are some key features to look for if you plan to purchase solar home batteries:

Battery power rate

The battery's power rating is the kilowatts (kW) of power that a battery can provide at any given time. In other words, a battery's power rating indicates both how many and which appliances the battery can power simultaneously.  Varying appliances require different quantities of electricity, measured in kilowatts (thousands of Watts) or Amps.

For example, a standard compact fluorescent lamp consumes 12 Watts (or 0.012 kW) of power, whereas a 3-ton AC unit consumes 20 Amps or 4.8 kW. The vast majority of today's batteries have a constant power output of roughly 5 kW.  Solar batteries frequently feature two power ratings.

One of them is continuous, and the other is five-minute or instantaneous, implying that they can offer greater power in short bursts. This is crucial if you have a sump pump or other device that requires a lot of energy to start on but then runs at a low power level.

Size or capacity of the battery

A solar battery's capacity (or size) is the quantity of electricity it can store and supply to your home. While power is measured in kW, battery capacity is measured in kWh, power multiplied by time. As a result, the storage capacity of a battery indicates how long it can power various components in your home.

Look for a battery's useable capacity, which signifies the quantity of stored electricity that you can access in the battery. As the use of electricity is power multiplied by time, you will deplete your stored electricity more quickly if you use more energy.

On the other hand, if you're only utilising your battery to back up a few low-power appliances, you can keep them running for a longer period. Because the length of time a battery's charge lasts is directly influenced by how much power it outputs, the size of a battery can be deceiving.

Round-trip efficiency

The round-trip efficiency of your energy storage system (battery + inverter) is a system-level metric that assesses how successfully it converts and stores electricity. Any electrical operation involves losses, which means you'll lose some kWh of electricity as you convert it from direct current (DC) to alternating current (AC) or when you put electricity into a battery and then remove it.

The round-trip efficiency of a solar battery shows how many units of power you'll get out of it for every unit you put into it.

Lifespan of the battery

Three metrics are used to calculate battery lifetimes: estimated years of service, expected capacity, and expected cycles. The estimated capacity and cycles of a battery are similar to the mileage warranty on a car. The capacity allows you to compare how much electricity your battery will be able to move over its lifespan.

Cycles are actually the number of times you can charge and discharge your battery. To convert a battery's expected or warranted throughput into an expected lifespan, multiply the throughput (kWh) by the battery's usable capacity to estimate how many complete cycles you'll receive.

Next, multiply this amount by the total number of days in the year. For instance, on a 10-kWh battery, a 20,000-kWh throughput warranty can translate to 2,000 anticipated cycles or one cycle per day for five years.

Safety

All solar batteries must meet specific safety requirements to be licensed for installation in homes and businesses. Some battery chemistries have also been examined for safety to varying degrees. This goes above the government-mandated safety regulations for batteries. It simplifies that some battery chemistries are comparatively safer than others.

Chemistry

The primary chemical utilised to store power inside a battery is referred to as the battery's chemistry. Because chemistry eventually impacts many of the features of batteries, it may be the most significant characteristic to compare. Different lithium-ion chemistries, for example, may be more power-dense.

It means they can store more electricity in less space or cycle more efficiently, allowing them to perform at a higher level for a more extended period. And that's just within lithium-ion chemistries; there's also the difference between lithium-ion and lead-acid batteries, vanadium flow batteries, and other experimental battery chemistries. Different solar battery chemistries often come at different pricing points, as with most things.

How To Spot The Best Solar Battery

The ideal battery for you will be determined by various factors, including the size of your home, the characteristics of your solar system, and even what you want to get out of an energy storage system. If you have a big house with copious gadgets, you'll want a high-capacity battery that can keep pumping out power for hours.

If you're on a relatively strict budget and want to maximise the efficiency of your solar energy system, a smaller battery with excellent battery integration can be the best option.

The Differences Between Solar Batteries

When selecting a solar battery, there are numerous factors to consider. Understanding the many chemistries and configurations available for solar batteries can be challenging, so you need to consider some critical variables before selecting the best battery for your needs. Before comparing the top brands and products, let's go through some of the most important considerations.

Chemistry

Lithium-ion batteries are available in a variety of chemistries, but the top two are generally:

  • Lithium Nickel, Manganese Cobalt Oxide (NMC)
  • Lithium Iron Phosphate (LFP)

Although NMC batteries are the most prevalent solar batteries, LFP batteries are gaining popularity due to their outstanding power ratings and longer lifespans.

Integrated inverter

Batteries can have an integrated inverter or not. Without an internal inverter, storage solutions must be connected with an external, third-party inverter. Storage systems with built-in storage inverters can convert your home's usable alternating current (AC) energy to storable direct current (DC) energy and vice versa.

Suppose your storage system has a hybrid inverter built-in. In that case, it can provide efficient integration for solar-plus-storage systems by covering both the production from your solar panels and the demand of your storage system.

Battery coupling

Batteries can be AC or DC. They are easy to install and connect to solar panels. If you are retrofitting your storage system, AC-coupled storage systems have traditionally been the most popular residential solar systems.

On the other hand, installing a DC-coupled storage system may be a better alternative if you're going to create a new solar-plus-storage system because it will deliver higher overall efficiency.

Configuration flexibility

Many battery manufacturers provide a variety of storage system configurations, allowing you to tailor your system to your specific needs. Some companies sell a series of batteries with varying capacities, and many of them can be "stacked," which means you can stack many batteries to have the storage capacity you need.

Now, before deciding on a battery storage system that matches your needs, you'll want to examine the power and performance of the various options. The next factors are some of the essential aspects that affect the capacity and performance of your battery.

Capacity

The usable capacity is the maximum amount of electricity stored in your battery systems on a full charge, measured in kilowatt-hours (kWh).

Continuous power rating

A battery's continuous power rating, measured in kilowatts (kW), specifies the most significant amount of electricity that can be released continually.

Depth of discharge (DoD)

The depth of discharge (DoD) refers to the percentage of the battery that has been discharged compared to its overall capacity. For optimal battery performance, many battery manufacturers specify a maximum DOD level. And batteries with higher percentages are generally regarded as higher-grade products.

Round-trip efficiency

The round-trip efficiency measures the electrical losses that occur when a battery is charged and discharged. The higher the percentage, the better the battery converts incoming electricity into stored electricity and then back into usable electricity.

Now, another area of consideration is warranty. It might be difficult and time-consuming to sift through warranties for your required information. The next factors we will look at are some of the essential features of a battery warranty and a comparison of the best manufacturers and products.

Warranty time

The most popular energy storage systems come with a ten-year guarantee covering the system's integrity and output.

End-of-warranty capacity

Many manufacturers guarantee a particular level of performance when your warranty period expires. Multiply the end-of-warranty capacity by the battery's usable capacity to get the warrantied capacity at the end of the warranty period.

Cycle

We can define cycles as the process of draining and charging your battery because each cycle diminishes your battery's ability to retain a full charge. Some manufacturers include a cycle clause, which stipulates that if you reach your warranty's maximum number of cycles before the end of the warranty period, you may void your guarantee.

Throughput

The total energy a manufacturer anticipates the battery to deliver over its lifespan is included in the throughput clause. These provisions, expressed in megawatt-hours, state that you may void your guarantee if you reach your battery's throughput prior to the end of its warranty period.

Price

Comparing battery prices isn't always simple. Your battery's price will vary depending on the parameters we've discussed so far, and it could include the cost of the entire installation or just the Manufacturer's Suggested Retail Price (MSRP).

It's vital to analyse the price of batteries relative to the valuable capacity, as this will have the most significant impact on what you pay. It would be best to think about the various configurations available, as it is sometimes less expensive to stack two small battery systems than to install a larger one.

Top Brands Of Solar Batteries

Enphase

Enphase is well-known for its inverter technology, but it also entered the battery industry in 2019 with the Enphase Encharge, recently relaunched as the IQ Battery. It's no wonder, then, that the IQ Battery's completely integrated Enphase IQ Series micro inverter technology is one of its main selling points.

The IQ Battery also employs cutting-edge LFP chemistry, which gives your battery a longer lifespan and enables it to achieve its outstanding DOD of 100%.

Tesla Powerwall

After introducing the Tesla Powerwall in 2015, Tesla swiftly became one of the most well-known names in the residential energy storage sector. The Powerwall has a sleek appearance and is stackable. So, you can use multiple Powerwall's in your storage arrangement to expand your storage capacity.

Tesla's Powerwall has a 100% DOD, and the company backs it up with a ten-year warranty. This includes a throughput clause of about 37.7 MWh for commercial applications and no throughput clause for most residential applications. It also comes with the guarantee of 70% capacity at the end of the warranty term. The Powerwall is also at the lower end of the solar battery price range.

Sonnen Eco

One of the most well-known energy storage businesses, Sonnen, launched the Sonnen eco in 2016. The eco uses modern LFP battery chemistry, which has excellent power ratings and long lifespans.

The eco does not disappoint: the largest battery in the series has the highest maximum power of any battery on this list, at eight kW, as well as one of the most incredible usable capacities, at 20 kWh. It also has a high DOD of 100% and a reasonable ten-year or 10,000-cycle warranty guaranteeing 70% capacity after the warranty period.

Panasonic

Panasonic is one of the world's top battery cell producers, and with the debut of the EverVolt in 2019, they officially joined the solar battery market. The EverVolt is exceptionally adjustable, allowing you to create a storage solution that is tailored to your specific requirements.

It is available in two different capacities, 11.4 kWh and 17.1 kWh, and can be AC or DC linked. This implies that if you already have a solar system, you can easily retrofit the EverVolt with the AC-coupled variant, or if you're building solar-plus-storage, you may want to go with the DC-coupled model, which is more efficient. To maximise your battery storage, you can stack up to six EverVolt batteries with the DC-coupled version.

Enjoy Electricity Even When The Sun Is Not Up!

As you know, solar energy is only available at specific hours of the day, when the sun is up. However, you'll have electricity even when the sun is down when you add a solar battery storage system to your home. Most solar batteries are designed to last for a longer time period.

However, they eventually lose efficiency and stop working, usually before the solar panel's lifespan, which is typically 25-40 years. Charging the batteries during peak photovoltaic periods and then using the stored electricity when the sun goes down is one of the most acceptable ways to put a solar PV system with battery backup to good use.

Therefore, there is less reliance on local utility electricity and the monthly expenses that come with it. This makes solar energy a great power source and a clean alternative to generating electricity. Plus, having a solar battery will serve as a backup even in cases of power blackouts.

If you're looking to get a reliable solar battery, it's best to work with a professional solar installer to help you select the best battery suitable for your needs.