Incorporating energy storage into a solar array is not as easy as just picking a battery off the shelf. Certain chemistries work better in certain environments and storage capabilities are influenced by the solar application.

Lead-acid batteries have been popular within off-grid solar installations for decades. However lithium-ion batteries are preferred choice for solar, EV and residential applications since they have a longer life cycle, lighter weight, and decreased maintenance. In addition, a recent study in the US found that lithium-ion batteries represented more than 80% of the installed power and energy capacity of large-scale energy storage applications.

Lithium-ion batteries are not the only choice for batteries used in solar+storage installations. Here’s a brief rundown of the common storage technologies used in the renewable industry.

Lithium-ion Batteries

Lithium-based energy storage systems are overwhelmingly the most common storage technology used within the solar market. These batteries are characterized by the transfer of lithium ions between electrodes during charge and discharge reactions. Additional materials, such as cobalt, nickel, and manganese, are inserted into the battery cells and can affect the battery’s performance, voltage, and safety. Lithium-ion batteries are more expensive than other chemistries, mostly because of their need for battery management systems to monitor voltage and temperature. The benefits of lithium-ion include long life cycle, high charge, and discharge efficiency, lighter weight, no maintenance, solid and they don’t require refills.

Types Lithium-ion Batteries

There are many different types of Lithium-ion batteries. To name a few: Lithium Cobalt Oxide, Lithium Manganese Oxide, Lithium Nickel Manganese Cobalt Oxide, Lithium Nickel Cobalt Aluminum Oxide, and Lithium Iron Phosphate.

Lithium Cobalt Oxide batteries are very stable and small, making them a popular choice for cell phones and laptops. They have a higher risk of thermal runaway and fire danger, which is why often hear news of some cell phones catching fire.

Lithium Manganese Oxide batteries have fast-charging properties and increased thermal stability making them a popular choice for medical devices and power tools.

Lithium Nickel Manganese Cobalt Oxide batteries have high specific energy and stability. But their use of cobalt increases the risk of thermal runaway.

Lithium Iron Phosphate batteries have increased safety, thermal abilities, and a long lifecycle. Since they generate little heat, they can be installed in more unique, indoor applications.

Lead-acid Batteries

Lead-acid chemistry is one of the oldest forms of energy storage and is widely used. Lead-acid batteries are known for being dependable and inexpensive. Lead-acid batteries are heavy because of the materials involved. They have a limited cycle life and are inefficient when it comes to charge and discharge compared to Lithium chemistries. But they’re cheap to manufacture and reliable if it’s operated and maintained properly.

Types of Lead-acid Batteries

Flooded lead-acid batteries must be flooded with a liquid. They require significant care and maintenance. Flooded batteries need to be refilled regularly as the electrolytes evaporate during charging. These batteries must also be housed in an enclosure with enough ventilation to keep off-gassing levels from reaching a dangerous point.

Valve Regulated Lead-Acid batteries are “sealed” and use valves to regulate off-gassing. They require little to no maintenance when compared to flooded lead-acid batteries. There are two categories of Valve-Regulated Lead-Acid batteries – AGM and gel. AGM batteries perform better in colder temperatures, while gel batteries work better in warmer temperatures.

Flow Batteries

Flow batteries use two chemical components dissolved in liquids separated by a membrane to provide a charge. Flow batteries can be recharged instantly by replacing the electrolyte liquids and store additional electrolytes externally in tanks that are pumped into the system as required. Flow batteries excel in long-duration storage applications and require little maintenance.