Solar panel systems use four main types of solar batteries: lead-acid, lithium-ion, nickel-cadmium, and flow. Each battery type has different benefits and works for different scenarios.
Lead-acid batteries have the longest history in the solar industry. These batteries are most common because they’re reliable and affordable. Manufacturers classify them as deep-cycle batteries, meaning they can handle regular draining and recharging. However, lead-acid batteries can only safely discharge 50% of their capacity without affecting their life span.
Lead-acid batteries come in two varieties: flooded and sealed. Flooded lead-acid batteries are water-based and require regular maintenance, such as adding distilled water. Sealed lead-acid batteries don’t require any maintenance. Both battery types work with solar power systems, but homeowners prefer sealed options for convenience and safety.
Lead-acid batteries have a low energy density, meaning they don’t hold much energy within their form. This makes them larger and heavier than other battery options. They also take longer to recharge and have shorter life spans, lasting between three and five years. They contain environmentally harmful chemicals that must be disposed of properly.
- More affordable than other battery types
- Reliable technology with decades of history
- Universal compatibility with most solar systems
- Heavier and bulkier than other batteries
- Limited discharging capabilities
- Shorter life span of three to five years, requiring more frequent replacement
An off-grid system or backup power during power outages.
Lithium-ion batteries use newer technology than other options and are becoming more popular for residential solar panel systems. This technology is employed in some of the most popular solar batteries, including the Tesla Powerwall and LG Chem RESU.
Lithium-ion batteries have a higher discharge capacity than lead-acid options. They can discharge up to 80% of their total storage capacity without affecting their life span. Some models can expel 100% of their capacity without sustaining damage, allowing for better energy use and storage. Lithium-ion batteries also take less time to charge.
Lithium batteries come in two options: lithium nickel manganese cobalt oxide (NMC) and lithium iron phosphate (LFP). NMC batteries are more common and use older but reliable technology. These batteries offer midlevel power ratings and have a lower price point. LFP varieties use a new technology that improves their stored energy retention, making them more efficient. They have a higher power rating but cost more than NMC options.
Lithium batteries have a high energy density, giving them a lighter and more compact build. They work well in tight spaces and are ideal for smaller homes. Lithium-ion batteries have a life span of up to 10 years and require little to no maintenance. Due to their more advanced technology, lithium-ion batteries are more expensive than lead-acid batteries.
High temperatures, overcharging, or improper installation can cause lithium-ion batteries to overheat, leading to a condition known as thermal runaway. This results in them catching fire. You can minimize the risk of thermal runaway by ensuring proper installation.
- Have discharging capabilities of 80%–100%
- Use newer technology with better battery capacity and efficiency
- Are smaller, lighter, and longer-lasting than lead-acid batteries
- Are more expensive than other battery options
- Require special equipment for installation, limiting their system compatibility
- Are subject to thermal runaway when overcharged or overheated
Residential solar installations.
Residential solar systems rarely use nickel-cadmium (Ni-Cd) batteries, as they’re primarily designed for commercial-scale solar installations. However, some manufacturers are testing Ni-Cd models for home solar systems, with the potential for more.
These batteries can discharge 80%–100% of their capacity. They can handle many charge and discharge cycles, or deep cycling, without affecting their life span. Unfortunately, these batteries have higher self-discharge than other options, meaning they lose charge over time when unused.
These rechargeable batteries have a lower energy density, making them heavy and bulky. Nickel-cadmium batteries have longer life spans than lead-acid and lithium-ion varieties, lasting up to 20 years or more. They’re low maintenance and work well in extreme temperatures.
Ni-Cd batteries use very old technology containing toxic materials that can harm the environment when not disposed of properly. Due to their toxicity, several countries, including Canada, Japan, and many American states, have banned their use. These batteries also cost more than lead-acid batteries but less than lithium-ion options.
- Excellent performance in extreme conditions
- Higher discharge capabilities of 80%–100%
- Life span up to 20 years or longer
- Its toxic components make it harmful to the environment
- Lower stored power retention than other battery types
- Not available for residential solar systems
Large-scale solar installations and commercial projects.
Flow batteries are another emerging technology. They use water-based electrolytes that flow between two internal chambers, or tanks. The batteries charge and discharge through chemical reactions inside. Adding more tanks can increase their total solar energy storage capacity. Flow batteries are becoming more popular in large facilities but have limited availability to homeowners.
These batteries have 100% discharge capabilities and excellent efficiency, with little energy lost when charging and discharging. Due to the internal tank size and electrolyte liquid, these batteries have a low energy capacity. They’re quite heavy and require significant space since additional tanks are needed to increase their storage capacity. Flow batteries are also high-maintenance and require frequent refilling and flushing of the electrolyte tanks. They can last 20 years or longer when used properly.
Flow batteries use nontoxic chemistry and nonflammable electrolyte liquid. However, they’re costly and impractical for residential solar systems, though some manufacturers have begun creating household-friendly flow batteries.
- Ability to add tanks makes storage capacity customizable
- Excellent efficiency and life span of 20 years or longer
- Nontoxic and nonflammable components for improved safety
- Too expensive for residential use
- Low power density due to internal tanks’ size and weight
Large-scale installations. There is currently no residential version available at an affordable price.