A solar battery’s chemistry impacts everything from its charging rate and weight to its lifespan.
Not only that, your choice of battery type has environmental and ethical implications too.
Deciding on the right solar battery chemistry is an essential step in choosing the right solar power system for you.
Learn about the different types of solar battery chemistry and how to select the right one for your needs.
What Is a Solar Battery?
A solar battery is an essential component of any off-grid solar power system. A rechargeable solar battery stores the power captured by photovoltaic (PV) panels as DC electricity. A portable power station or other balance of system converts the DC power into AC (household) electricity.
Solar power is the fastest-growing source of electricity generation worldwide — but it’s not without challenges. Solar panels still capture the sun’s rays on cloudy days, but they won’t generate as much electricity as they would in peak sunlight. And they don’t generate electricity at night.
A solar battery stores the electricity your panels generate during the day to ensure you have a reliable source of power, rain or shine, day or night. Off-grid solar power systems require a solar battery to function. In grid-tied solar systems, many homeowners add a solar battery to protect against power outages and gain additional independence from aging utility infrastructure.
As long as they have sufficient storage capacity and AC output, solar batteries can power just about anything — even an electric vehicle (EV)! You can also get small enough batteries to take backpacking and keep all your devices running off-grid.
No matter your use case, there’s a solar battery or portable power station that’s right for you.
How Do Solar Batteries Work?
Solar batteries store the energy captured by photovoltaic (PV) panels, and a balance of the system converts solar power into AC (household) electricity.
The solar battery plays an essential part in any portable power station or other balance of system (BOS). Other required components in an off-grid solar BOS include:
EcoFlow’s portable power stations — like the DELTA 2 Max — are all-in-one solar energy solutions. Each has all the BOS components — including the solar battery — to recharge using solar panels. They can also recharge quickly using other inputs, such as AC wall outlets, car adaptors, and USB-C.
One of the most crucial factors to consider when shopping for a solar battery is its chemistry. There are numerous types of solar battery chemistry. Let’s take a closer look at them here.
What Are the Different Types of Solar Batteries?
The most common types of solar batteries currently available to consumers are:
- Lead acid
- Nickel-cadmium (NiCad)
- Lithium-Ion (Li-ion)
- Lithium Iron Phosphate (LFP/LiFePO4)
Each type has its advantages and disadvantages, depending on the application.
Here’s a brief overview of the different kinds of solar battery chemistry to help you determine which one’s right for you.
Lead acid battery cells were the first ever invented for commercial use — way back in 1859!
Lead acid batteries are still in common use for small electronics — like Duracell and Eveready — and traditional gas-powered vehicles.
One selling point of lead acid batteries for solar power storage is that they’re cheap. If price is your only concern, lead acid is hard to beat.
However, lead acid solar batteries have numerous drawbacks compared to the newer chemistries listed below and are rarely used in modern residential or commercial solar power installations.
Here are a few of the factors that make it hard for lead acid to compete with more modern battery chemistries on anything other than price:
- Short Cycle Life (Life Span): Depending on the specific type, a lead acid battery’s cycle life (number of full discharges/recharges) can be anywhere from 500 – 2,000 cycles. The most common deep-cycle lead acid solar battery types, AGM and Gel, last about 1,500 cycles on average — about half the lifespan of EcoFlow’s LiFePO4 batteries.
- Shallow Depth of Discharge: Lead acid batteries commonly have a depth of discharge (DoD) of around 50%, which means you can only use 50% of the electricity stored in the battery before performance decreases. Operating the battery below the recommended DoD will reduce the battery’s lifespan and efficiency and potentially cause lasting damage. LiFePO4 batteries, on the other hand, often have a depth of discharge of 80%.
- Heavy and Bulky: Due to lead acid’s low energy density, lead acid solar batteries are bigger and heavier than lithium-ion (Li-ion) or LiFEPO4 batteries with similar storage capacity. They’re rarely compact, making them ill-suited for applications where portability is a concern. There are also restrictions on where you can install certain lead acid batteries in your house.
- Regular Maintenance and Replacement: Again, depending on the type of lead acid solar battery, it may require routine maintenance. The cheapest lead acid batteries also tend to have the shortest lifespan and require regular replacement.
Nickel-cadmium solar batteries are durable and function well at extreme temperatures. They’re especially useful in utility and commercial air travel applications and are low-maintenance compared to lead acid batteries.
Like lead acid, NiCad batteries have been around since the 1800s. NiCad is superior to lead acid chemistry for solar battery applications and was often used in older residential systems before lithium-ion became commonplace.
One major drawback of NiCad batteries is that cadmium, one of its essential materials, is highly toxic. If NiCad batteries are recycled or disposed of improperly, they cause serious harm to the environment.
Lithium-ion batteries made their commercial debut in 1991 and power most modern rechargeable electronic devices — From smartphones and laptops to solar generators and EVs.
Many of the portable devices we take for granted today wouldn’t exist without Li-ion battery chemistry.
The first commercially available cell phone, Motorola’s Dynatac 8000X (far left), used a NiCad battery that provided 30 minutes of talk time after charging for 10 hours. The Dynatac 8000 weighed 2.5 lbs (1kg), and its list price in 1983 was $3,995 USD — equivalent to over $11,000 in 2023.
Lithium-ion battery chemistry significantly improved on NiCad. Its high energy density allowed for more portability and increased electricity storage capacity.
As Li-ion chemistry improved, so did the quality of mobile devices and smartphones. You can see the evolution in the image above.
Today, lithium-ion is the most common chemistry found in solar batteries for both residential and commercial use. Many of the attributes of Li-ion chemistry that helped revolutionize modern electronics, from smartphones to EVs, also apply to solar power systems, including:
- High Energy Density: Lithium-ion batteries can store significantly more energy using less size and weight than lead acid or NiCad batteries. Li-ion’s high energy density makes it an excellent choice for devices where portability is a concern, which is obviously true for smartphones, tablets, and laptops — and it’s true for solar batteries too. If you want to go backpacking off-grid, EcoFlow’s RIVER 2 solar generator weighs only 7.7 lbs (3.5 kg), can fit in your knapsack, and powers up to 99% of consumer electronics.
- Fast Charging: Whether you’re recharging with AC power or solar panels, Li-ion batteries charge much faster than lead acid or NiCad alternatives. For example, EcoFlow’s RIVER 2 series portable power stations charge from 0-100% in 60-70 minutes using AC (household) electricity and in as little as 3 hours using solar power.
- High Performance, Deeper DoD, Longer Lifespan: Li-on batteries deliver more current than lead acid or NiCad chemistry — often 3-5 times as much. They also offer a significantly deeper depth of discharge. Typically, you can operate them until they reach 20% of their storage capacity before you see diminished performance, and it won’t harm the battery. Cycle life is also much longer — typically between 2,000-3,000 full discharges/recharges before the storage capacity begins to diminish. That’s equivalent to 5 years or more of regular use and over a decade of occasional use.
Lithium Iron Phosphate (LFP/LiFePO4)
If you’re looking for a solar battery with a deeper depth of discharge (DoD), faster charging, and a wider range of operating temperatures, consider lithium iron phosphate (or LiFePO4) batteries. A newer, more advanced subset of Li-ion battery chemistry, LiFePO4 even offers additional safety features by being more stable and less prone to thermal runaway.
LiFeP04 batteries can be more expensive up-front, but that’s changing fast with wider adoption and improved technology. In the long run, benefits like longer cycle life, faster charging times, and better durability outweigh any difference in the sticker price.
Lightweight and Compact
LFP batteries are typically lightweight and compact, making them easy to transport and use in various settings. You can take them with you on off-grid adventures or install them in tight spaces — like a van — that may not be suitable for larger solar batteries.
For example, consider the RIVER 2, Ecoflow’s lightest portable power station (solar battery) option. At just 7.7 pounds (3.49 kg) and dimensions of 9.6 x 8.5 x 5.7 in (24.4 x 21.6 x 14.5 cm), it’s incredibly compact. It’s light enough to take backpacking or camping, delivering sufficient electricity to run up to 99% of consumer electronics without ever weighing you down.
Long Life Span
Do you want to enjoy the benefits of your investment in your solar power systems for years to come? LFP solar batteries can last ten or more years under regular use. The built-in Smart Battery Management System in EcoFlow portable power stations prevents overcharging or over-discharging the battery — protecting its LiFePO4 chemistry and increasing its cycle life.
All the power stations in the EcoFlow RIVER 2 series — and many of the current DELTA Series —- use LiFePO4 batteries. After 3,000 cycles, the batteries will still be at 80% (or more) capacity. The extended cycle life offers reliable power for years of use.
LFP solar batteries also have a short charging time compared to other types of solar batteries.
If fast charging is essential, consider the EcoFlow RIVER Series. RIVER 2 and RIVER 2 Max boast a 0-100% recharge time of only 60 minutes when connected to AC electricity. RIVER 2 Pro takes just 10 minutes longer to reach full charge. All the RIVER 2 Series can reach a full charge using solar panels in 3-4 hours, depending on environmental conditions.
From an ethical and humanitarian standpoint, one of the most significant downsides of traditional Li-ion batteries is that they rely on cobalt to function. Cobalt is a highly problematic metal to extract and process.
Even though LiFePO4 batteries are technically a subset of Li-ion, they don’t require cobalt to function, nor do they lead to increased demand for a material sourced in such an unethical manner.
LiFePO4 Batteries Can Supply Off-Grid Power for a Whole Home
LFP battery-powered off-grid power solutions can provide sufficient electricity to operate an entire home. As long as you have enough electricity generation capacity (solar panels/smart generator dual fuel), storage capacity (portable power stations/smart extra batteries), and AC output, you can live off-grid and achieve personal energy independence.
EcoFlow’s DELTA Pro, DELTA Pro Smart Extra Battery, and the Whole Home Generator all use LFP batteries. Many different configurations are available — one of which should allow you to power your home off-grid, depending on your electricity consumption needs.
Can You Power an RV Off-Grid
First marketed as Recreational Vehicles, for many, RVs are now a way of life. With so many models and features available, you can easily live in your RV on the road year-round if you want to. Many RVs come standard with 12V appliances that rely on electricity generated when operating your vehicle — or a stationary shore power hookup to run reliably for extended periods.
Being tied to campgrounds/locations with electrical hookups or the power stored when driving can severely limit your RV freedom — and doesn’t that kind of defeat the purpose?
EcoFlow’s modular Power Kits are modular electricity generation and storage designed to fit comfortably in even the tiniest RVs. With multiple options, ranging from 2 kWh — 15 kWh of LiFeP04 battery storage and all the balance of system components you need to generate, convert and store solar power, Power Kits are the ultimate choice for extended off-grid RV living.
And with up to 4,800W of solar input/charging capacity, you can connect up to 12 x 400W Rigid Solar Panels simultaneously — or mix and match with portable and flexible to maximize your available surface area.
Check out the online Power Kit calculator to see if a solution meets your needs.
The Benefits of Solar Battery Storage
Solar batteries are NOT optional for off-grid solar power systems. You need somewhere to store the electricity you generate during daylight hours for use during the night or on highly overcast days when electricity production may be diminished.
Grid-tied solar power systems do not require solar batteries, but many homeowners use them for energy security in case of a blackout.
Energy Security During Power Outages
A home battery backup system or solar generator provides electricity (and peace of mind) during power outages. As blackouts from extreme weather and aging grid infrastructure become more common, having reliable electricity backup is vital, at least for your essential appliances.
Reduces Your Carbon Footprint
Solar batteries store the sun’s energy that your solar panels capture, and your balance of system (BOS) converts. The production of solar panels and BOS components like inverters, charge controllers, and solar batteries have some impact on the environment:
- Extraction and processing of materials used in construction
- Power used in manufacturing
- Fuel used in transportation
But no manufacturing and supply chain process production is entirely without adverse environmental consequences.
The point is, once your solar power system is installed and generating electricity, there are no greenhouse emissions and no fossil fuels consumed. Solar power is about as net-zero as can be.
Solar panels, solar batteries, and other required balance of system components can reduce or eliminate your electricity bills completely. With the right solar power system, you’ll have access to the reliable electricity you need without paying for expensive grid-based power.
Once you achieve the solar payback period, any money you save on electricity bills stays in your wallet! The upfront costs can be steep, even with all the government incentives and financing options available. But the long-term return on investment can be significant.
How to Choose a Solar Battery System
Not sure how to make the right choice on which solar battery system is best for you?
Here’s what you should keep in mind.
Consider the Size (Storage Capacity)
Solar batteries come in various sizes. “Size” can refer to dimensions and weight. But when people talk about battery size, they typically refer to how much electricity the battery stores when fully charged. For solar batteries, storage capacity is usually measured in watt-hours (Wh) and kilowatt-hours (kWh). How much electricity storage you require depends on your total electricity consumption between charges — and the rate at which solar panels recharge the solar batteries during use.
Here’s the most accurate way to estimate how much electricity storage you’ll require:
Identify the wattage requirements of your appliances. Survey the starting and running wattage requirements of the appliances and devices you plan to plug into the generator. You can usually find the wattage requirements labeled on the appliance, but we’ve also compiled the starting and running watts of typical household appliances in the table below.
- Convert volts/amps to watts. If your appliance’s power requirements are in volts or amps, you can calculate an appliance’s running watts with this equation:
Volts (V) x Amps (A) = Watts (W)
- Count the running watts of your appliances. Add up the running watts of the appliances you plan to use — does the total exceed the running watts listed on your generator? If so, consider buying a generator with more output capacity.
- Factor in starting watt requirements. Identify the appliance with the highest starting wattage. Add that appliance’s starting wattage to the running wattage total.
- Calculate the sum. That final number is the total starting watts you need from your generator. As discussed above, to avoid overloading your generator, do not exceed its starting watts rating.
Starting and Running Watts of Typical Household Appliances
|Appliance||Rated (Running) Watts||Starting Watts|
|20” Box Fan||200||350|
Solar Battery Cost
The price of solar batteries varies significantly based on various factors, including:
- Solar battery chemistry
- Storage capacity (size)
- Charging Methods
- Solar Input/Charge Capacity
Finally, consider safety factors when choosing a solar battery system. Lithium batteries are safer than lead acid alternatives since they don’t utilize corrosive or hazardous chemicals. Additionally, Li-ion and LiFePO4 batteries require almost no maintenance. LiFePO4 batteries are even more stable and safe to use as they’re less likely to experience thermal runaway.
Options for Storing Solar Energy
There are three primary options to choose from for storing your solar energy.
DC-Coupled Energy Systems
DC storage systems have been around for decades in off-grid solar applications.
- A well-established option for small mobile systems used in RVs or small residential off-grid systems
- High efficiency
- Modular, allowing you to add additional panels if needed
- More complex to set up
- More expensive for solar systems over 6kW
- Lower efficiency if you need to power large AC loads in the daytime
AC-Coupled Energy Systems
Often used for larger-scale off-grid systems, AC-coupled systems are simple to set up and powerful but less efficient.
- More efficient when powering AC loads during the daytime
- Powerful, better for large systems over 6kW
- Allow solar energy to go directly from the photovoltaic panel to the load
- Lower efficiency when charging batteries
- Limited solar inverter capacity
- Lower efficiency to power direct DC loads in the daytime
BiDirectional AC-Coupled Energy System With Islanding
The most efficient and powerful of the three options is a BiDirectional AC-Coupled Energy System With Islanding. They’re an excellent choice for larger solar systems, with a simple design that is easy to modify.
- Ensures that if the grid goes down, you can still generate power through your solar power system until regular power returns
- Photovoltaic systems and battery systems can work independently without interference
- You can separate the solar and battery systems from a large grid to form a microgrid
- More expensive than DC coupling
- Not well-suited for smaller systems
- Lower efficiency due to conversion
Frequently Asked Questions
What Is the Best Battery Chemistry for Off-Grid Solar?
A lithium iron phosphate (LFP) battery is best for off-grid solar applications. While LFP batteries are more expensive than lithium-ion or lead acid alternatives, they offer the longest cycle life, energy density, safety, efficiency, and fastest charging times, making them a wise long-term investment.
Before deciding on a battery, consider your daily electricity consumption needs and budget. While each type of solar battery offers different chemistry, the most reliable and best long-term investment is the LiFePO4 battery.
By opting for LiFePO4, you’re investing in the best consumer solar battery chemistry on the market.