Solar batteries are a smart investment for energy storage. Without a battery bank, you won’t be able to store energy generated by your system for later use. If you’re tied to the grid, no battery means no backup power when the utility grid suffers an outage. If you live off-grid, your system simply won’t work at all.
Batteries are crucial to keeping your system running. Choosing the best battery for your solar panels involves many factors in your decision, including the battery’s capacity, power, efficiency, and costs depending on your needs. To help you make the right choice, let’s review how solar batteries work, the different types of batteries available, and how to compare solar batteries.
How Do Solar Batteries Work?
When installing a solar battery as part of your solar panel system, you can store excess solar energy instead of sending it back to the power grid. If your panels are producing more electricity than you need, this energy can go back into charging your battery.
When your solar panels aren’t producing electricity, you can draw from the stored energy when you need it. The electricity is sent back to the grid only when your battery is full or draws from the grid only when the battery is low.
What Are the Different Types of Batteries?
Batteries for energy storage are typically made of lead acid or lithium-ion. When selecting the best battery for your solar system, it’s important to understand the difference between what a deep cycle battery vs. flooded lead acid, sealed lead acid, and lithium batteries is before making your selection. Here are some of the differences between lead-acid vs. lithium-ion batteries:
Flooded Lead-Acid Batteries
Flooded lead-acid (FLA) batteries have been used for the last 150 years and are among the most common batteries used for off-grid solar setups. These batteries are inexpensive, 99% recyclable, and easy to get rid of at the end of their lifespan.
These are the best batteries for solar if you’re looking for an affordable option but with the following hands-on monitoring:
Flooded lead-acid batteries are designed to handle daily charge cycling. They do emit gas as a byproduct, so they must be ventilated correctly.
Flooded lead-acid batteries are ideal for people who prefer to be hands-on with their system. They’re the most affordable option but require occasional upkeep to work properly.
These batteries need regular maintenance. The plates of every cell in the battery must be submerged in water to function properly (which is why they are called “flooded” batteries). You’ll need to add water every 1 to 3 months to keep the plates submerged. It’s smart to check on them once a month.
Sealed Lead-Acid Batteries
If you are unable to perform regular check-ups, the best battery for your solar panels is the sealed lead-acid battery with these advantages:
These batteries are spill-proof and non-hazardous. There are two types of sealed lead-acid batteries with fairly similar characteristics: AGM (absorbent glass mat) and GEL.
Sealed batteries are a self-contained system. They don’t need to be refilled with water, like flooded batteries. For that reason, they work well at properties that aren’t occupied full-time, like an off-grid vacation cabin you visit once or twice a year.
Sealed batteries are better at handling temperatures. They won’t self-discharge as fast if they sit idle for extended periods while you’re away.
Lithium batteries are a newer technology that hit the market in the 1970s. They are common in laptops and cellphones, but lately they have become more popular in the renewable energy space. Lithium batteries are more expensive, but there are several benefits to justify the higher price tag:
- Longer lifespan
- No maintenance
- More efficient power usage
- More usable storage capacity (deeper discharges)
- No off gassing/ventilation
How Do I Compare Solar Batteries?
As you consider your solar battery options, you’ll want to compare each type of battery based on the capacity, depth of discharge (DoD), round trip efficiency, and battery life to find the best batteries for solar depending on your system’s requirements. Make sure to check the following:
Capacity is the total amount of electricity that a solar battery can store. This power is measured in kilowatt-hours (kWh).
Depth of discharge (DoD):
The depth of discharge (DoD) indicates the amount of battery capacity that’s used. The higher the DoD, the more usage you’ll get from the battery’s capacity. Your depth of discharge should generally be at least 40% or higher.
Round-trip efficiency is the difference between the amount of energy used to charge it and the available amount of energy. A higher round-trip efficiency is generally more economical. You should look for a round-trip efficiency of around 80%.
Battery life & warranty:
Since battery performance declines over time, a warranty guarantees good performance for years or cycles as well as ensures the battery maintains a certain capacity.