The Best Deep Cycle Batteries to Use with Your Solar Power System
- by Joe Weber - updated on 7/10/2023
Having solar panels for your home is only half of the ideal solar power setup. You need a way to store excess energy that you are collecting to use when the power goes out so you aren't stuck using a noisy, gas-powered generator. Keep reading to learn more about the best battery options for your solar system.
What Is A Solar Battery For?
Before we dive into the best batteries to use for your system, let's take a step back and review what a battery for a home solar system is and why you should have one.
A battery for a solar system is often referred to as a home battery backup and stores excess energy that is collected from the solar panels for future use. Without a battery backup, any excess energy that is collected by the solar panels would be sent back through the utility grid for others to use.
That's why having one as part of your solar power system is so important, the energy you collect is yours and yours alone. No one else can use it. They are also great for providing backup power to keep your home powered during a power outage during a storm or natural disaster.
Important Note
Home backup batteries are a huge convenience and are a great thing to have for your home. However, it is important to understand that you can't just buy a battery and plug it into the wall. For batteries to work with an existing solar system that doesn't currently have a battery you need to have a charge controller, an inverter, and other equipment. All of this needs to be installed by a licensed professional electrician.
What Kind of Batteries Are Used with Solar Systems?
Deep-cycle batteries are the best and clear option for use in energy storage applications. They may look like car batteries but they are quite different. Deep-cycle batteries are made for cyclical use, meaning that you charge them up, use most of the battery's capacity daily, and then recharge them, over and over vs. the starting energy and low cyclic use that a car battery offers.
The two main types of deep-cycle batteries used in solar applications are lead-acid and lithium.
Lithium
The current, most popular type of lithium deep-cycle battery used for solar is the Lithium Iron Phosphate (LiFePO4) battery. Lithium Iron Phosphate is the lithium chemistry of choice for deep-cycle batteries for several reasons:
- They charge up to 4 times faster than lead acid batteries.
- You can use the full power of your battery down to a 1% charge. The available power will not drop as the battery depletes.
- 50% lighter than the equivalent lead-acid battery.
- Stays charged longer in storage.
- The onboard battery management system keeps the battery operating within pre-set safety limits.
Lead-Acid
The lead-acid battery options are the old reliable. They've been around for more than 150 years and have had plenty of improvements during that time. Some benefits of lead-acid deep-cycle batteries are:
- They are cheaper than lithium batteries.
- They have been around for a long time and have had many years of research and development.
- Available in different designs to fit your needs. (Flooded, AGM)
- Works better in cold climates.
What Do I Need to Consider When Shopping for Solar Batteries?
Shopping for your new deep-cycle battery doesn't have to be difficult. Be sure to pay attention to these factors to ensure you get the best battery for your needs.
Price
Like any project, you need to stay within your budget. Deep-cycle batteries can range anywhere from around $100 for a flooded battery up to over $1000 for the latest lithium batteries.
Maintenance
Some types of batteries, like some flooded deep-cycle batteries, need routine maintenance to keep the battery at an optimal state. This could be things like filling the batteries with distilled water or regularly removing corrosion.
Capacity
The capacity of the battery is hugely important. The higher the capacity of the battery, the more energy you can store. Capacity in deep-cycle batteries is measured by Amp Hours (AH).
Voltage
It's important for you to verify what voltage your system will accept before purchasing batteries. Solar panels come in a variety of voltages from 12V - 48V depending on the size of the system.
Cycle Life
Different batteries have different life cycles. Lead-acid batteries average about 300 - 500 cycles whereas lithium batteries can last 2000 or more.
Each time the battery is charged, used (discharged), and recharged to a full charge, is considered a cycle. Every time you charge the battery to 100%, use the battery to 50% state of charge (20% for lithium), then recharge back to 100% is considered a complete charge cycle.
Warranty
Having the peace of mind of warranty protection is a great feeling. Deep-cycle batteries come with warranties that range anywhere from 1 year all the way to up to 10 years.
Which Type of Deep-Cycle Battery Is Right for Me?
Now that you know what to look for in the battery, which one is best for your system? The answer is, it depends.
Flooded - Lower Cost, More Maintenance
Flooded batteries are the most cost-effective option with batteries starting as low as $100. They can get your system up and running with the least amount out of your pocket. However, these do have some drawbacks. Flooded lead-acid batteries use an electrolyte that is completely free-flowing. If you pick one up and move it around you may hear it sloshing around inside. These also need to be housed in a ventilated room or outdoors since they will emit gasses.
Due to their design, flooded batteries are a little less durable than other deep-cycle batteries. They also require regular maintenance to potentially remove any corrosion from the terminals and they also require distilled water to be added to the electrolyte solution to keep the plates submerged.
AGM - Low Maintenance, Higher Cost
Instead of a liquid electrolyte, AGM or Absorbed Glass Mat batteries use a fiberglass mat that absorbs the electrolyte liquid, keeping it in place within the plates of the battery. AGM deep-cycle batteries for solar applications start at around $250 but are much more durable than flooded batteries.
Because there is no free-flowing liquid in the battery, AGM batteries have lower internal resistance which lets them supply more power. They have a longer runtime and are much more durable than flooded batteries. AGM batteries also perform better in extreme climates, making them ideal if you live in an area that gets really cold or really hot.
Lithium - Highest Upfront Cost, Highest Performance, Zero Maintenance
Lithium iron phosphate (LiFePO4) batteries may have the highest initial cost but they last 4 times longer than lead batteries, 2,000 cycles vs. 500, which means you can spend less money over time by not replacing them as often. They discharge deeper, charge faster and are so safe that you can even use them indoors. This is great if you live in cold or hot environments, you can install them in your insulated garage.
Some newer LiFePO4 batteries, like some of our own 2nd generation X2Power lithium batteries, even have Bluetooth connectivity so you can monitor them from your phone.
The Bottom Line
As you can see, each battery has its own unique qualities that could make it the right choice for you and your system. But the bottom line is that you should get a battery that works and provides you with what you need for your system, and for your budget.
However, there is a clear winner here if you are looking for a battery that is the best of the best, with relentless power, the deepest discharge, the fastest recharge and the longest life of all the other batteries, it's the X2Power LiFePO4 deep-cycle battery! With X2Power LiFePO4, you get more bang for your buck in every way.
Stop into our local Batteries Plus or shop online to learn more about our premium X2Power LiFePO4 batteries and see why they are the best batteries for your solar power system.