Installing a new solar-powered system can appear confusing. There are so many types of solar panels, batteries, and other components — the amount of research needed to understand solar power can be daunting.
Luckily, solar batteries are one of the more straightforward decisions you will have to make when installing a DIY solar system.
Here, we look at the four main solar battery types: lithium-ion, lead acid, nickel cadmium, and flow. Then, we’ll explore how to choose the right type of solar battery for you.
4 Main Types of Solar Batteries
The residential solar battery market is dominated by lithium-ion and lead-acid batteries. Manufacturers heavily used lead-acid for the first few decades of residential solar adoption. However, lithium-ion has quickly become the new standard for modern solar systems.
Lithium-ion technology has evolved fast — the price point, longevity, efficiency, and other factors make them the best choice for most homeowners. Most new solar installs and all-in-one units — like EcoFlow’s solar generators — utilize lithium-ion technology.
Additional battery types, including nickel-cadmium and flow batteries, are primarily used in commercial applications. You’ll rarely see them in home solar setups, but the technology may improve and decrease in price in the coming years to make them more suitable for use in smaller systems.
Lithium Ion Phosphate (LFP/LiFePO4)
Lithium-ion is currently the gold standard for solar power. It’s lightweight and has a much greater depth of discharge than lead-acid options.
Lithium iron phosphate is the newest generation of lithium batteries used in portable power stations and hubs like the EcoFlow Power Kits. LFP achieves more cycles and boasts higher efficiency. Plus, the power kits use 48V systems, rather than 12V, to minimize the amount of wiring and copper in the system. The result is reduced power loss to heat and resistance.
Any worthwhile solar generator or power station will include lithium ion or LFP. If a solar kit still includes lead acid, it’s probably not a wise investment.
Lithium-ion has a high energy density, requiring less volume to store the same amount of energy as a lead-acid battery. Lithium-ion batteries are virtually maintenance-free and can operate for years or decades without any loss in efficiency.
Manufacturers are so confident in the technology that they often offer a warranty of 5 -10 years or more. The guarantee makes your battery a “set it and forget it” component — your lithium-ion battery will outlive most other parts of your solar system.
Lithium-ion has a depth of discharge between 80 and 95% — meaning you can use more of the electricity you generate and store. This is far superior to lead acid’s 50% depth of discharge.
Lithium-ion has a higher purchase price than lead-acid. However, given their longer lifespan, lithium-ion usually costs less over time than its lead-acid counterparts.
When improperly installed, lithium-ion may pose safety hazards. They may catch fire due to a phenomenon called thermal runaway. If you are not confident in your installation abilities, hire a professional to avoid any issues or go with a plug-and-play system.
Lithium-ion is perfect for residential and mobile solar systems. The batteries are small and lightweight, making them excellent for off-grid camping and RV solar energy storage.
Some manufacturers are coming out with solar energy systems specifically for RVs, campers, and off-grid builds. The EcoFlow Power Kits are one example, offering a plug-and-play solar solution that includes 48V batteries and all the other components you need for more efficiency and safety.
Lead-acid is best known as the traditional standard for cars and the disposable batteries you buy for flashlights and other small devices. But lead-acid batteries are also available in residential and mobile solar systems.
Lead-acid is a tried-and-true technology, but they are quickly going out of fashion for solar applications. They are heavier than lithium-ion, have a lower depth of discharge, and require much more frequent replacement. As the price decreases for lithium ion and other batteries, lead-acid technology is having a hard time staying relevant.
Lead-acid costs less than most other battery systems. However, lithium-ion prices have dropped dramatically in recent years as demand has increased, and the pricing may soon eclipse that of lead-acid.
Lead acid has been used for decades, so consumers know what to expect. The technology offers reliability and consistency over the battery’s short lifespan.
Lead-acid will need replacing several times over the lifespan of a solar system. Lead-acid solar batteries may only last 3 to 5 years, depending on the specific type of lead-acid technology and the usage case.
The cost of frequent replacement negates the lower initial purchase price. The cost over 15 to 20 years will be significantly higher than that of lithium-ion.
More frequent replacements mean more hazardous waste. You can recycle lead-acid batteries by returning them to a retailer or finding a waste management program for hazardous waste. These are the best options for disposal.
Lead-acid is best in situations when weight and size are not a concern. They also work well in short-term applications. Lithium-ion is always the better choice if a homeowner is committed to investing in a permanent solar system.
Nickel Cadmium (Ni-Cd) Batteries
Nickel-cadmium (Ni-Cd) is an older technology invented in the late 19th century. Improvements to Ni-Cd in the 1980s made them a viable energy storage solution for modern applications.
They are widely used for large commercial operations, including utility companies and the aircraft industry.
Ni-Cd is durable and long-lasting, making them useful for heavy industries like commercial air travel and utilities. A Ni-Cd battery may have a lifespan of over 20 years.
Nickel-cadmium can also withstand extreme temperatures and is safe to store in temperatures ranging from -85°F (-65°C) to 140°F (60°C).
These batteries have a higher power density than lead-acid, meaning they can store more energy in a lighter package.
The cadmium in Ni-Cd is highly toxic. The batteries are difficult and dangerous to dispose of properly. Some countries have even banned the use of cadmium in batteries because of this!
A Ni-Cd battery is also susceptible to the “memory effect” — over time, this reduces its ability to hold a charge. The effect is not an issue for other types of batteries like lithium-ion.
Large commercial industries that use solar power. Utility companies often use nickel-cadmium technology to store large amounts of energy. Most commercial aircraft use nickel-cadmium batteries, but they may switch to other technologies in the near future.
Many new types of solar batteries are on the horizon. Flow batteries are one of the most promising new solar battery technologies. Large-scale solar systems are currently testing the viability of flow batteries, such as with the Viejas community in California.
Flow batteries have a 100% depth of discharge, meaning the solar power system can fully deplete the energy in the battery without any long-term damage or loss of functionality.
This depth of discharge is in stark contrast to other battery types — lithium batteries typically have a DOD rate of around 80-95%, while lead-acid can only discharge approximately 50%.
Flow batteries are a new, emerging technology. The prices are steep, and few options are available for residential applications.
Due to their high cost and large size, flow batteries are best for commercial solar projects. Unfortunately, flow batteries are not currently accessible to the average homeowner. In 10 to 20 years, the technology may improve to the point where flow batteries are available for residential and portable applications.
Why Do You Need Good Solar Batteries?
To maximize the efficiency and longevity of your off-grid solar system, you must purchase high-quality solar batteries. Batteries are the heart of your solar system. They store the energy that the solar panels work so hard to gather.
Purchasing cheap batteries may seem like a good idea at first, but you will only cause yourself frustration down the line. When batteries fail, your entire solar system goes out of commission until you can find a replacement. Lead acid batteries will fail 3 to 4 times sooner than lithium-ion, costing you more headaches and money as your system ages.
How to Choose the Right Type of Solar Battery for You
Lithium-ion and lead-acid batteries are the most popular options for residential and mobile solar systems. Here are the most important considerations when choosing a solar battery.
Size and Weight
Lead acid batteries weigh much more than lithium-ion ones. Plus, they require much more volume to store the same amount of energy. If you are building an RV or tiny home solar system, you will undoubtedly want to consider your space and weight limits.
Even if you plan on cramming the interior components of a residential solar system into a closet, you’ll want a compact setup. The smaller size of a lithium-ion battery system can benefit the homeowner in these cases.
Initial and Ongoing Costs
Lead-acid batteries have a lower purchase price but require replacement more often than lithium-ion and deliver far less efficiency. The replacement costs lead to a higher expense over the lifespan of a solar system. Lithium-ion is the better choice when considering costs unless you can’t afford the initial price.
Battery capacity can determine the type of battery to choose. If you’re only powering something small, you don’t require a large-capacity battery. In this case, a lead acid battery’s extra size and weight won’t be as much of a consideration.
In the case of a full-fledged solar system, you will need thousands of amp-hours worth of battery storage. Lithium-ion technology reduces the size and weight of a large-capacity battery system.
The ambient temperature has a significant effect on battery operation. Lithium-ion batteries can receive a charge between 32°F (0°C) and 113°F (45°C). However, they can discharge at temperatures as low as -4°F (-20°C) and as high as 140°F (60°C).
Lead acid batteries can charge and discharge between -4°F (-20°C) and 122°F (50°C).
You may need lead-acid batteries if you plan on charging in extremely cold temperatures. Alternatively, those using batteries in extreme heat should consider lithium-ion.
Every time you use a battery, it cycles through the capacity. The more cycles the battery can go through, the longer it will last.
For example, EcoFlow Portable Power Stations can last up to 6500 cycles before storage capacity diminishes to fifty percent of the original capacity.
Warranty and Brand
Not all batteries are made the same. Every brand will have slight variations in its batteries. Different warranty lengths are also an important consideration.
Stick with reputable companies when purchasing a crucial (and costly) component like your solar batteries. Generic, brandless batteries are often made with inferior parts and are far more likely to fail and perform less efficiently.
Steer clear of batteries and other solar components that do not include a warranty.
There is nothing inherently different between a solar and a regular battery. Solar systems often use batteries designed for boats or golf carts, as the usage case is much the same.
Solar systems require deep-cycle batteries instead of the standard lead-acid batteries used in cars. Deep cycle batteries provide steady streams of power over long durations. In addition, solar batteries discharge to lower energy levels more often than standard batteries.
Regular car batteries provide big bursts of energy to start the car but rarely discharge more than 20%.
Lithium-ion batteries are considered the best for solar. Lithium technology has rapidly advanced in recent years. They are affordable, lightweight, and usually last for over ten years.
Solar lithium ion and LFP batteries last longer than lead-acid. Most lithium-ion batteries are rated for ten or more years, while lead-acid batteries often don’t function well past five years.
There are several different types of solar batteries, but only two stand out for residential usage: lithium-ion and lead-acid. Homeowners are increasingly turning to lithium-ion batteries for their reduced size and weight, increased efficiency and longevity, and general ease of use.
With EcoFlow, you can gain peace of mind that your solar battery will last. All of our solar generators and power stations boast lithium-ion or LFP batteries, giving you higher efficiency and a longer-lasting battery.