Solar batteries are really deep cycle batteries that provide energy storage for solar, wind and other renewable energy systems. Different from a car battery, a deep cycle battery is designed to handle prolonged, repeated and deep discharges which are typical in renewable energy systems that are off grid (disconnected from the electric utility company).
If you are new to solar and renewable energy systems, feel free to hop over to our blog and read our articles on batteries for solar and renewable energy systems. Have questions about deep cycle solar batteries? Give an altE energy storage expert a call today at 877-878-4060.
How many deep cycle batteries do I need? Check out our instructional video on deep cycle battery sizing for solar and wind power systems. The video teaches you how to do the load calculations and battery bank sizing.
Deep Cycle Batteries for Solar Power Systems
Solar Batteries (Deep Cycle Solar Batteries) are a key component in a stand-alone renewable energy system—whether the solar system is off-grid or the battery bank is used for backup in case of electrical grid failure. If you are installing a wind, solar panel or hydroelectric system that will be tied to your utility grid, you will still need deep cycle batteries if you are trying to use power in the event of an outage. Without deep cycle batteries, you can only use power at the time you produce it (i.e. you will not have power when the sun isn't out if you don't have batteries in your solar electric system).
In renewable energy systems, deep cycle batteries provide the energy storage for your system. Unlike your car battery, deep cycle batteries that are used in renewable energy applications are meant to be discharged and recharged (cycled) repeatedly. To maintain healthy batteries and prolong battery life, most manufacturers suggest limiting the depth of discharge (DoD) to about 20%. (That means that deep cycle batteries should always have a State of Charge (SoC) of 80% or greater.) At the very least, do not allow the batteries to be discharged below 50% Depth of Discharge (DOD). Often an inverter will have a Low Voltage Disconnect feature that will disconnect loads at a given "set point." Low voltage alarms can provide audible warnings as well. Ammeters, Voltmeters, Battery Monitors can help better maintain deep cycle battery health, and provide statistics about the overall health of the system.
Types of Solar Batteries
When selecting deep cycle batteries for storage from your solar array or wind turbine, you'll have the option to use flooded lead acid (FLA) batteries, sealed batteries (AGM or Gel cell), or lithium batteries. Keep in mind that FLA batteries require a bit of maintenance, however, they generally last longer than their sealed counterparts. Water miser vent caps, which reduce battery watering, can also reduce the frequency at which deep cycle batteries need watering. You'll need one vent cap for each 2 V cell.
Learn About Lithium Deep Cycle Batteries
Watch our video on the KiloVault lithium iron phosphate (LFP or LiFePO4) line of deep cycle batteries. These batteries are lightweight, have a long cycle life (over 5000 cycles at 80% DoD), and can be deeply discharged repeatedly without harming the lifespan of the battery.
Deep Cycle Batteries Storage Capacity: Battery Bank Sizing
Deep cycle battery banks consist of one or more batteries, and are measured in amp hours of storage capacity. Each deep cycle battery can be 2, 4, 6, or 12 volts DC (Vdc). The choice of individual solar battery voltage will depend upon your total system voltage (12, 24 or 48 Vdc) and your desired amp hours (Ah) of storage. Often the 2V deep cycle batteries offer the largest amount of storage; however, you may need up to 24 of these huge deep cycle batteries if your system is 48 volts. Also, see our video above on Battery Bank Sizing for Off Grid Home Solar Systems, that will cover the calculations for load analysis, battery bank capacity, array wattage, charge controller and inverter sizing. You can also use our load calculators to begin sizing your system.
Wiring Up your Deep Cycle Batteries
Connect your solar batteries (i.e. deep cycle batteries), using solar battery interconnect cables, in series, parallel, or a combination of both depending upon your system voltage and the storage capacity you need. Read more about this in the how to section about deep cycle battery bank sizing. While deep cycle batteries may be a large expense for a sizeable off grid system, with proper care and maintenance, they should last 5-10 years. Let us know how many watt hours per day you need to provide, and the number of days of storage you need, and we'll be happy to offer specific sizing recommendations for your deep cycle batteries.
Deep Cycle Batteries Range Widely in Weights
Deep cycle batteries come in many sizes: From batteries that are less than 10 pounds to ones that weigh over 200 pounds each! They can be small (and fit in a backpack) or large (2' x 2' x 1') and anywhere in between. Generally, the size and weight correspond with amp hours (Ah) of storage. If you need a lot of energy storage, be sure that you have the appropriate space to house the batteries, and brawny people to help you put them in place.
Whether you have one battery or a bank of 36, proper storage is essential. Battery boxes can provide a neat and safe way to contain the batteries, or you can build your own battery box. Often people add an optional battery ventilators or battery fans. Battery fans can vent the hydrogen gas that is naturally exhausted when deep cycle batteries are charging.
Desulfators are a Great Way to Extend Deep Cycle Batteries' Life
Desulfators are another good, low-cost investment that can help prevent sulfation and boost the performance of the batteries. Flooded Lead Acid deep cycle batteries can build up sulfate crystals on their lead plates over time. Our desulfators "shake" these sulfate crystals off the surface electronically, and can prolong the life of a battery that would otherwise need to be thrown out.
Can I Add Battery Backup to a Grid-tied Solar System?
Yes you can! Adding a battery bank to a grid-tied (or grid tie) solar system is a possible and increasingly-popular option, given the increased frequency of extreme weather. Watch our video where we explain the two main ways to add battery back to an existing grid-tied solar system. If you are already creating energy with the sun, there's no reason you can’t store your own energy for when the power grid is down.
