How to Choose the Best Solar Battery for Your Home?

A battery system will keep the power generated by your solar panels in reserve and allow you to use it even when there’s no sunlight, such as at night or on cloudy days.

But choosing the right solar battery system can be confusing, especially when you’re unfamiliar with how they function and how they compare to the different types of batteries currently on the market.

To help you choose the best solar battery for your home, we’ve put together this simple guide that will take you through all the main considerations that go into making an informed decision and selecting the ideal type of solar battery system for your home and your lifestyle needs!

What is a Solar Battery?

A Solar Battery is an energy storage system that can be charged by energy from the sun or the grid. Solar batteries provide your home with clean, fairly green, renewable energy that would otherwise need to come from an outside source. Energy storage systems are perfect for homeowners who want to maximize energy offset, aka the consumption of self-produced energy.

Solar batteries are often referred to as “deep cycle batteries”, due to their ability to charge and discharge a significant amount of electricity compared to something like a car battery.

There are different types of solar batteries, such as lead acid, lithium-ion, flow and nickel cadmium batteries.

Types of Solar Batteries for residential use

Solar battery technologies vary depending on their chemical composition. We’ve broken down the most popular energy storage technologies to help you find the right battery backup for your solar system.

Lead Acid battery

Lead acid batteries are the most popular type used in homes for decades. Although these come with frequent maintenance requirements compared to some other battery types, they are still one of the cheapest options available.

They have a low energy density (meaning they can’t hold much energy per kg of weight). Lead acid batteries come in both flooded and sealed varieties. But do pay attention that flooded lead acid batteries require ventilation and regular maintenance to operate correctly, which increases the chances of the battery leaking. Discharging the battery beyond 50% may irreversibly damage the battery and its lifespan.

Lithium-ion battery

New home energy storage technologies often include lithium-ion batteries due to their lightweight, compact size and increased capacity.

Lithium-ion batteries quickly became one of the most widely used solar batteries and are commonly used in EV’s.

Lithium-ion batteries last relatively long, require little maintenance and are more compact and lightweight than lead acid batteries.

Most modern lithium-ion batteries have Depth-of-Discharge ratio (DoD) ranging anywhere from 80% to 95%, showing how much battery you use in between charges.

These benefits come at the cost of being more costly than its counterpart battery type.

Flow battery

Flow batteries are relatively new technology. Unlike other battery systems, it does not rely on heavy metal in its composition and instead uses a water-based electrolyte liquid. When charged, chemical reactions occur which allow the energy to be stored and subsequently discharged.

Flow batteries offer high efficiency, with a depth of discharge of 100% and have a lifespan of 30 years, but they are larger in size, more expensive and still in the development stage.

Nickel cadmium (Ni-Cd) batteries

A favorite amongst the aircraft industry. Nickel cadmium batteries are durable and have the ability to operate at extreme temperatures. It is noteworthy that they don’t require complex battery management systems and are essentially maintenance-free.

That being said, Ni-Cd batteries are rarely used in residential settings. Cadmium is a highly toxic element that can have a significant negative impact on our environment and for that reason they are banned in some countries.

What You Need to Know Before Buying a Solar Battery

The type of battery you choose will depend on how much power you need, how often you need it, and how many days you will use it per year.

Energy storage systems have various benefits, from emergency backup power to financial savings.

And although they may seem complex at first glance, here are the important factors you should look out for when shopping around for deep cycle solar batteries.

Battery size and usable capacity

The capacity of a battery indicates how much electricity it can store, measured in kilowatt-hours (kWh). Say you’re consuming 1kWh of energy and you have a 12kWh battery, then that battery would last for 12 hours.

Some batteries may show two capacities: the total capacity and the usable capacity. You want to look at the latter, which is just what portion of that stored power you can use.

Consider batteries with usable capacity ratings of at least 10 kWh because these are good for most homeowners’ basic energy needs and offer enough backup power in the event of a blackout. You could add more than one battery to your system for greater benefit.

Power Rating

A battery’s power rating measures how much electricity it can produce, typically expressed in kilowatts (kW). The continuous power rating is the maximum amount of electricity a battery can provide for appliances that need constant power, such as refrigerators. Or in other words, it tells you both how many appliances your battery can power at once and which appliances those are.

Most solar batteries have a continuous power rating between 3-5kW and a peak power rating between 5-7kW. The peak power rating lets you know what type of appliance would require a large burst of power to turn on, but then runs at lower power.

Lifespan

Battery lifetimes are measured with three different metrics: expected years of operation, expected throughput and expected cycles.

• Expected cycles measure how many times the battery can be fully recharged and discharged.

• Throughput lets you compare how much electricity you’ll be able to move through your battery over its lifetime.

In general, Lithium-ion batteries last five to 15 years and lead-acid batteries typically five to seven years depending on how they’re used.

Battery type

A battery’s type is determined by the chemicals within it that are used to store energy. The battery type, or battery chemistry, determines almost every aspect of how the system will work. Once lead acid batteries were the most popular choice for solar-plus-storage systems; however, lithium-ion batteries have taken center stage over recent years. Today there are two main types of lithium-ion batteries on the market: nickel manganese cobalt (NMC) and lithium iron phosphate (LFP).

Round-trip Efficiency

There are losses associated with any electrical process. The round-trip efficiency of a solar battery represents the amount of usable power available after charging it and then using power from it.

Say your solar panels sent 10 kilowatt hours (kWh) to your battery, but only 7 kWh were stored for later use.

This means the battery’s operating system uses 3 kWh to store and release energy, so there is an overall 70% round trip efficiency rating. The higher the rating, the less energy is lost in the storage process.

What is the Best Solar Battery?

It’s hard to say. The best battery for you will depend on several factors, from the size of your home to the characteristics of your solar installation and what you even want to get from an energy storage system.

Typically the best battery for a home solar installation is a lithium ion battery. However, if you are on a budget, lead acid batteries could be the best option for you.

If you are still in the process of going solar or planning to change your roof, make sure to get an offer from Solarstone for a premium-looking, yet affordable in-roof solar system.