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 solar battery is capable of surviving prolonged, repeated and deep discharges which are typical in renewable energy systems that are "off grid" (disconnected from the electric utilty company).  If you are new to solar  energy system, please be sure to read our free & informative Solar Education provided to you courtesy of Solar Power Mart.

See below for several types of batteries appropriate for solar energy systems plus useful accessories for optimizing your solar battery bank's performance and safety.

Solar Batteries (Deep Cycle Batteries) are a key component in a stand-alone renewable energy system.  If you are installing a solar panel 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 to about 20%. (That means the deep cycle batteries will be at 80% capacity or better.)  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 solar batteries (deep cycle), you'll have the option to use flooded lead acid (FLA) batteries or sealed batteries (AGM or Gel cell).  Keep in mind that FLA batteries require a bit of maintenance, however, they generally last longer than their sealed counterparts. Water Miser Vent cap - Reduces Battery Watering can reduce the frequency that the deep cycle batteries need watering.  You'll need one vent cap for each 2 V cell.  Desulfater are another good low cost investment that can help prevent sulfation and boost the performance of the batteries.  Flooded Lead Acid batteries can build up sulfate crystals on their lead plates over time. 

Sealed deep cycle batteries may be a bit heavier and therefore cost a bit more to ship.  Deep cycle batteries come in many sizes: from sealed batteries that are less than 10 pounds to flooded lead acid batteries 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 of storage.  So if you need a lot of electrical storage, be sure that you have the appropriate space to house the batteries.

Whether you have one battery or a bank of 36, proper storage is essential.  Enclosures 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 Ventilation fans that can vent the hydrogen gas that is naturally exhausting by the lead acid batteries. The vent also helps maintain a comfortable operating temperature for the batteries in cold climates.

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 battery can be 2, 4, 6, or 12 volts.  The choice of individual solar battery voltage will depend upon your total system voltage (12, 24 or 48 vdc) and your desired amp hours of storage.  Often the 2 V 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.  Connect your solar batteries (i.e. deep cycle batteries), using Battery Interconnects, 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 battery bank sizing.  While 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.