Regardless of the solar power system type, solar batteries are a worthwhile investment. They’ll provide the peace of mind you need if your grid-tied system suffers an outage or your off-grid system suddenly stops generating electricity.
Either way, quality solar battery storage can become the key element in keeping your system operational. However, solar batteries and storage don’t come cheap.
How do you choose the right type of battery that’s tailored to your energy needs?
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What Is a Solar Battery and How Do They Work?
A solar battery is a device used to store excess electricity generated from your solar panels. Homeowners can then tap into the excess energy to use when their solar panels aren’t producing enough or during power outages.
Simply put, a solar battery helps homeowners enjoy using their solar power system to its fullest potential.
Solar battery storage systems are either DC- or AC-coupled, whether it’s a DIY solar battery bank or one purchased directly from a vendor. In DC-coupled storage, the electricity generated flows from the solar panels through a controller and gets stored directly into the battery.
DC-couple storage is much more efficient than AC because it only needs to convert the electricity into AC one time. With AC-coupled storage, the DC energy generated by the solar panels must run through solar inverters to convert into usable AC electricity.
It’s less efficient because AC-coupled storage systems run electricity through an inverter on three separate occasions. The first is from the panels to the house, the second is from the house to battery storage and the third is when you pull energy from the battery to the house.
Although AC-coupled solar battery systems are slightly less efficient than DC, they have the benefit of being able to pull from solar panels and directly from the grid.
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Types of Solar Batteries
When searching for solar batteries online, you’ll come across two major players — lithium and lead-based batteries. Although there are a few other types available, these two are by far the most popular. It’s important to understand the difference between each battery type before placing your purchase.
Lithium-Ion
Lithium batteries are the newest and the go-to power source for cellphones and laptops. They come with a higher price tag than lead-based alternatives, but the benefits make them a popular choice for many renewable systems globally.
These batteries require zero to minimal maintenance and generally have a longer lifetime use than lead-based alternatives. The longer life is attributed to these batteries losing less capacity when idling.
This is essential for renewable energy systems when it’s used more for storage and only occasionally tapped. They also provide more efficient power use and come with more usable storage.
Lead-Acid
Unlike lithium batteries, there are two types of lead-acid batteries used in solar power systems. The first is a flooded lead-acid (FLA) battery. This type of battery is one of the oldest and is used more for off-grid systems. They’re very inexpensive to purchase and almost entirely recyclable at 99 percent. Additionally, FLA batteries are easy to dispose of when they finally require replacement.
FLA batteries are the go-to option if you want an inexpensive option. However, they are much more hands-on. Flooded lead-acid batteries emit gas because they’re designed for daily charge cycling, so they must be properly ventilated. Additionally, FLA batteries require routine maintenance at least once a month.
This is because the plates of the cells within the battery must be constantly submerged for optimal functionality. Homeowners who use these batteries will typically have to add water every three months to keep the plates submerged in water.
If routine maintenance presents an issue and you require a lead-acid battery, you’ll want one of the two sealed lead-acid types. Both types of sealed batteries — absorbent glass mat and gel — are spill-proof and self-contained systems. They don’t require refilling every one to three months with water. These are excellent batteries for those who have an off-grid home that they spend minimal time in.
Solar Battery Considerations
When considering which type of solar battery fits your needs, you’ll want to consider the following factors:
- Overall capacity
- Round trip efficiency
- Depth of discharge
- Battery lifetime use and any warranties
The capacity of a battery is essential and should be one of the first factors to look into. Capacity is the amount of electricity that an individual battery can store and is measured in kilowatt-hours.
It’s important to determine how much capacity is required to ensure you have access to power as needed. For example, if you’re looking to store electricity for your off-grid system for full-time use, you’ll want to consider a lithium-ion battery to keep up with your daily energy usage.
With any self-sustaining solar power system, being economical is typically at the forefront of every decision. For solar batteries, having a higher round trip efficiency of around 80 percent is generally the most economical.
Additionally, you’ll want to consider the expected lifetime use for each battery type and if they come with a warranty. The truth is, battery performance will 100 percent decline over time. Purchasing a solar battery with a warranty guarantees optimal performance and capacity for a set number of years.
Choosing the Best Battery Type
There’s no blanket answer to the best solar battery for each person. The best battery will depend on numerous factors, from the type of system you have to your daily energy usage.
These are just a few criteria to consider when shopping for a solar battery. Ultimately, the battery type you require — lithium or lead — will depend on your individual needs and having the right system design.
