There are many factors to take into consideration when shopping for solar batteries for your home solar power system. Two things to keep in mind are the type of battery you’re looking for, and what exactly you’re wanting to get out of your battery.
We’ve broken down the most popular energy storage technologies to help you find the right battery backup for your solar panel system.
Lead acid batteries
Lead acid batteries are the tried and true technology of the solar battery world.
These deep-cycle batteries have been used to store energy for a long time - since the 1800's, in fact. And they’ve been able to stick around because of their reliability.
There are two main types of lead acid batteries: flooded lead acid batteries and sealed lead acid batteries.
Lead acid batteries are the cheapest energy storage option, making them the most cost effective. They are also reliable. Plus, because the technology has been around for years, they can be easily disposed of and recycled.
Flooded lead acid batteries require ventilation and regular maintenance to operate correctly, which increases the chances of the battery leaking.
This also limits how flooded lead acid batteries can be installed, because they can’t be placed on their side. They also have a low depth of discharge (DoD), so they need to be charged more often.
Having a low depth of discharge also means they have a shorter lifespan - between 5 and 10 years.
The reliability of lead-acid batteries is great for off-grid solar systems, or for emergency backup storage in case of a power outage.
Lithium ion batteries
Lithium ion batteries are the new kids on the energy storage block.
As the popularity of electric vehicles began to rise, EV manufacturers realized lithium ion’s potential as an energy storage solution. They quickly became one of the most widely used solar battery banks.
Lithium ion batteries require almost no regular maintenance.
They also have a higher battery energy density, meaning they can hold more energy in a smaller space than a lead acid battery.
Lithium ion batteries have a longer lyfe cycle, or lifespan, as well - most have a guaranteed warranty of at least 10 years. This longer lifespan has to do with lithium ion batteries having a higher depth of discharge, so you can use more of the energy stored within the battery before it has to be recharged.
One of the biggest disadvantages of lithium ion batteries is that they are more expensive than other energy storage technologies.
Also, because of their chemistry, lithium ion storage systems have a higher chance of catching fire due to something called thermal runaway. However, if installed properly, the chance of your battery catching fire is close to zero.
Lithium ion batteries are best for residential solar installations because they can hold more power in a limited space, and allow you to use more of the energy stored within the battery, which is great for powering a home.
Nickel cadmium batteries
Nickel cadmium (Ni-Cd) batteries aren’t as widely used as lead acid or lithium ion batteries.
Ni-Cd batteries first sprung on the scene in the late 1800's, but they got a makeover in the 1980s that greatly increased how much energy they could store. They are a favorite amongst the aircraft industry.
Enersys and Saft are some of the top manufacturers of Ni-Cd batteries.
The main benefit of Ni-Cd batteries is that they are durable. They also have the ability to operate at extreme temperatures. Additionally, they don’t require complex battery management systems and are basically maintenance-free.
The biggest downfall of Ni-Cd batteries is that cadmium is extremely toxic.
In fact, the use of cadmium is banned in some countries. This makes them hard to dispose of. They also are prone to the memory effect, which limits their ability to hold a charge.
Ni-Cd batteries are popular for large scale applications, like utility solar energy storage, because of their durability.
Flow batteries are an emerging technology in the energy storage sector.
They contain a water-based electrolyte liquid that flows between two separate chambers, or tanks, within the battery. When charged, chemical reactions occur which allow the energy to be stored and subsequently discharged. These batteries are now beginning to rise in popularity.
Their larger size makes them more expensive than the other battery types. The high price, combined with the large size, makes it hard to adapt them to residential use. However, redflow manufacturers a residential flow battery, which they call ZCell.
One of the best things about flow batteries is that they have a 100% depth of discharge. This means you can use all of the energy stored in the battery without damaging the battery’s health.
The liquid within the battery is also fire retardant, so you don’t have the risk of thermal runaway. Flow batteries have the longest lifespan on this list - 30 years! And as an added bonus, they’re low-maintenance.
Flow batteries are unfortunately much more expensive than other types of solar batteries. They also have a relatively low storage capacity compared to other battery systems, so in order to hold a substantial amount of energy they need to be large.
They have very low charge and discharge rates, which also means that in order to be effective, they must be large in size.
Flow batteries are best for large-scale installations.
Because of how they work, they need to be very large to hold any substantial amount of energy, which increases their price. This has prevented flow batteries from becoming a popular residential option.
How to find the right solar battery type for you
In most cases, the best battery for you to get for a home solar installation is a lithium ion battery.
They are able to hold more energy in a small amount of space, discharge most of their stored energy, and they have high efficiencies. Also, because these are the most common, many solar companies will be able to install a lithium ion solar battery both accurately and safely.
If you are on a budget, lead acid batteries could be the best option for you. They have been used for decades, plus they come at a low cost.
Although you could get a Ni-Cd battery or a flow battery to pair with your solar system, lithium ion and lead acid are the go-to solar batteries for a reason.