Without somewhere to send energy produced by your solar panels, solar would be inefficient—your appliances would only work when the sun is shining and your panels are working. If you don’t use the energy, it’d be wasted—and you wouldn’t be able to use it at night. Enter solar batteries, which store energy generated by your panels for use when you need it. Solar batteries are an alternative (or addition to) feeding energy back to the grid and can help you make your house or facility somewhat immune from power outages and even help take it off-grid entirely.
Solar Battery Types
The four main types of batteries used in the world of solar power are lead-acid, lithium ion, nickel cadmium and flow batteries.
Lead-Acid
Lead-acid batteries have been in use for decades and are one of the most common types of battery used in automotive and industrial applications. They have a low energy density (meaning they cannot hold much energy per kg of weight), but remain both cost-effective and reliable and thus have become a common choice for use in a home solar setup.
Lead-acid batteries come in both flooded and sealed varieties and can be classified as either shallow cycle or deep cycle depending on the intended function and safe depth of discharge (DOD). Recent technological advancements have improved the lifespan of these batteries and lead-acid continues to be a viable option for many homeowners.
Lithium-Ion
The technology behind lithium-ion batteries is much newer than that of other battery types. Lithium-ion batteries have a high energy density and offer a smaller, lighter and more efficient option. They allow the user to access more of the energy stored within the battery before needing to be recharged, making them great for use in laptops and phones-and in your home.
The major drawback of lithium-ion batteries is the significantly higher cost to the consumer. If improperly installed lithium-ion batteries also have the potential to catch fire due to an effect called thermal runaway.
Nickel-Cadmium
Nickel-cadmium batteries are rarely used in residential settings and are most popular in airline and industrial applications due to their high durability and unique ability to function at extreme temperatures. Nickel-cadmium batteries also require relatively low amounts of maintenance when compared to other battery types.
Unfortunately, cadmium is a highly toxic element that, if not disposed of properly, can have a significant negative impact on our environment.
Flow
Flow batteries depend on chemical reactions. Energy is reproduced by liquid-containing electrolytes flowing between two chambers within the battery. Though flow batteries offer high efficiency, with a depth of discharge of 100%, they have a low energy density, meaning the tanks containing the electrolyte liquid must be quite large in order to store a significant amount of energy. This size makes them a costly and impractical option for most household use. Flow batteries are much better suited to larger spaces and applications.
Things to Look for When You’re Picking a Solar Battery
Several factors contribute to the performance of your solar battery. Before choosing your battery system, consider the following:
Type or Material
Among the types of batteries to choose from, each type offers a different major advantage. Weighing these pros and cons can help you decide which style is right for you. If you’re looking for something compact and longer-lasting, lithium-ion may be right for you. Lead-acid might be better for those conscious of more immediate budget constraints.
Battery Life
The “lifespan” of any battery is multifaceted; the age, type, quality and depth of discharge of the battery all contribute to its longevity. Referring to the manufacturer’s specifications for a battery can help you determine how long it’s likely to last.
In general, lead-acid batteries can last anywhere from one to 10 years depending on how they’re used. Lithium-ion batteries typically last seven to 15 years.
Depth of Discharge
Depth of discharge refers to how much of a battery’s stored energy is used before the battery is recharged. Typically, the deeper the battery is discharged, the shorter its lifespan will be.
Batteries often come with both a cycle life estimate (indicating how many cycles it will last given a particular depth of discharge) and a recommended maximum depth of discharge.
Efficiency
Solar systems and batteries are not 100% efficient when transferring and storing the collected solar energy from panels to batteries, as some amount of energy is lost in the process. Depending on the amount of energy you’re able to generate from your panels and how your system is configured, it may be worth investing in a more expensive, more efficient battery. This can help save money long-term.
