Explained: Lithium-ion Solar Batteries for Home Storage

Lithium-ion solar batteries are the most popular option for home energy storage because they last long, require little maintenance, and don’t take up as much space as other battery types. Lithium solar batteries typically cost between $12,000 and $20,000 to install.

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When paired with solar panels, excess solar energy can be stored in the battery and used later, like at night or during a power outage. Depending on the area, lithium ion batteries can even help save extra money on electricity bills.

Let’s take a closer look at what you need to know about lithium-ion batteries before getting one installed. 

How do lithium-ion batteries work as home storage?

Lithium batteries are rechargeable energy storage solutions that can be installed alone or paired with a solar energy system to store excess power. 

Standalone lithium-ion batteries can be charged directly from the grid to provide homeowners with backup power in case of a power outage. They can also be used to avoid paying for peak electricity rates, by charging with grid power when electricity is cheap and discharging when it’s expensive. 

Pairing a battery with solar will give you the most bang for your buck, especially if you don’t have access to net metering. The lithium battery can recharge with excess solar energy that is generated by your panels, so you can run your home entirely with solar even when the sun isn’t shining. 

How much do lithium-ion solar batteries cost?

Lithium-ion solar batteries don’t come cheap, with installations ranging from $10,000 for a simple single-battery solution, to well over $30,000 for whole-home backup. This is significantly higher than that of installing lead-acid batteries, which typically run between $5,000 and $15,000. 

Despite the price difference, people still tend to choose lithium-ion batteries over lead-acid because of increased performance and fewer maintenance concerns. The total cost of a solar battery installation depends on the battery brand you choose, the features it has, how many batteries you need, and labor costs. 

Battery incentives can help lower costs. There are a number of solar battery incentives that help lower installation costs. The biggest is the federal tax credit, which is equal to 30% of the total costs of qualifying battery installations. There are a number of local battery incentives and rebates, pilot programs like Green Mountain Power's battery lease, and things like virtual power plant programs are becoming more popular, as well.

How much can you save annually with solar-plus-battery-storage?

What are the pros and cons of lithium-ion solar batteries?

Pros

• High depth of discharge

• Long lifespan

• High energy density

• High efficiency

• Little maintenance

Cons

• High cost

• Thermal runaway

Advantages of lithium-ion solar batteries

Lithium-ion batteries are the most popular option for homeowners looking for battery storage for good reason. Here are some of the benefits of lithium-ion home batteries:

Higher depth of discharge (DoD) 

The DoD of a battery is the amount of the stored energy in the battery that has been used compared to the total capacity of the battery. Most batteries come with a recommended DoD to maintain their health. 

Lithium-ion solar batteries are deep cycle batteries, so they have DoDs around 95%. Compare this to lithium ion batteries, which have DoDs closer to 50%. Basically, this means you can use more of the energy that’s stored in a lithium-ion battery and you don’t have to charge it as often. 

Long lifespan 

Because lithium ion batteries have a high DoD and don’t need to be charged and recharged as often, they have a long lifespan. 

Most lithium-ion solar batteries have a minimum warrantied lifespan of around 10 years, or a cycle life of 10,000 cycles - whichever comes first. Lead acid batteries, on the other hand, only have warrantied lifespans of around 5 years. 

Higher energy density 

The energy density of a battery is how much power the battery can hold relative to the physical size of the battery. 

Lithium-ion batteries can store more power without taking up as much space as lead-acid batteries, which is great for homes where space is limited. 

High efficiency 

Lithium-ion batteries have a higher round-trip efficiency rating than other types of solar batteries on the market. 

Efficiency refers to the amount of usable energy you get out of your battery compared to how much energy it took to store it. Lithium-ion batteries have efficiencies between 90 and 95%. 

Less maintenance 

Not having to worry about regular maintenance is one of those advantages that you just can’t put a price on. Lithium-ion batteries require little to no regular maintenance - just make sure they’re clear of debris and. Some lead-acid batteries, on the other hand, require frequent off-gassing.

Disadvantages of lithium-ion solar batteries

Although lithium-ion batteries have numerous benefits, there are still some draw backs.

High cost 

Lithium-ion batteries tend to be the most expensive battery storage option, especially when compared to lead-acid batteries. 

The good news is that solar battery systems qualify for incentives like the federal tax credit, which helps make lithium-ion batteries more affordable. 

It’s also important to remember that while lead-acid batteries may be cheaper upfront - they have to be replaced more often, increasing your overall storage costs. 

Thermal runaway 

Lithium-ion batteries run a higher risk of thermal runaway, AKA overheating and catching on fire. While the risk is technically there, the chances of this happening with a properly installed lithium-ion battery is slim to none.

Popular lithium-ion solar battery brands

There are many lithium-ion solar batteries on the market. Some of the best solar battery brands include Enphase, Panasonic, and Tesla. 

The following table outlines some other popular lithium-ion solar batteries on the market:

Types of lithium-ion batteries

There are two main types of lithium-ion batteries used for home storage: nickel manganese cobalt (NMC) and lithium iron phosphate (LFP). 

An NMC battery is a type of lithium-ion battery that has a cathod made of a combination of nickel manganese and cobalt. When people say “lithium-ion batteries” they’re often referring to NMC batteries. These batteries are what shot lithium-ion to the mainstream, with better performance than that of their lead-acid competitors. The Generac PWRcell, LG RESU Prime, and Tesla Powerwall 2 are NMC batteries. 

LFP battery cathodes are made of lithium irone phosphate (LiFePO4) and are still considered lithium-ion batteries. The iron and phosphate used to make the cathode are more abundant and less expensive than some of the materials used in NMC batteries - mainly cobalt. The Enphase IQ, Panasonic EverVolt, and Powerwall 3 use LFP technology. 

More battery manufacturers have been switching to LFP batteries because they dont contain expensive, toxic cobalt. LFP batteries are easier to recycle, a little bit cheaper, longer lasting, and ,most notably, safer. Aside from having fewer toxic metals, LFP batteries are better at handling temperature fluctuations and are even less likely to experience thermal runaway than their NMC competitors. 

How are lithium-ion batteries recycled?

Batteries are recycled by being shredded and mixing all of their components. Once all of the metals are mixed into a powder, they need to be separated by either being liquified or dissolved in acid so that the desired metal can be retrieved.

Since the process of recycling batteries is still in the early stages, the United States has suggested an enhancement to the Defense Production Act. The goal is to put money towards securing the metals we need for a clean energy transition while also researching and investing in recycling lithium-ion batteries.

Alternatively, instead of shredding old batteries, sometimes batteries within an EV can be reused. Lithium-ion batteries have a very long lifespan, and while they will lose their ability to power a car, they can still be used for less intense energy storage needs, like backup power.

Currently, when you replace technology such as your EV or storage battery, recycling the old one is a chore. You can find certified electronics recyclers through the EPA website. Alternatively, some manufacturers like Tesla will take back their lithium-ion batteries at the end of their life to be recycled.

What makes recycling lithium-ion batteries a challenge?

At this stage, current recycling methods are not sophisticated enough to extract most of the key metals that can be reused in a way that is more cost-effective than mining.

It is cheaper to mine most metals found within a lithium-ion battery than recycle them. Perhaps ironically, cheap lithium mining is one of the many reasons we can invest heavily in batteries. Unfortunately, if we build cheap lithium batteries that are not recycled, we will end up with landfills full of electronic waste.

While recycling batteries may require some extra work and additional cost, the metals within the batteries are durable and usable. Recycling needs to become economical to reduce our dependency on freshly-mined lithium.

Since lithium mining emits a high amount of CO2, using lithium and other metals from recycled batteries is a more environmental and sustainable alternative.

Suggested reading:
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Want more information on what is c&i energy? Feel free to contact us.

Additionally, a potential shortage of metals that are used in batteries is looming. Discovering a way to reuse all the metals within old batteries will help meet supply needs.

Do you need a lithium-ion solar battery?

Lithium-ion solar batteries are the best solar energy system for everyday residential use because they take up little space while storing a substantial amount of energy. They last longer and provide more usable energy than lead-acid batteries, plus they require little maintenance. 

However, sometimes a lead-acid battery might be the better choice. If you’re only using a solar battery for backup storage and not daily use, or if you’re looking for storage for an off-grid solar project, lead-acid batteries will get the job done and won’t break the bank. 

However, if we’re being totally honest, most homeowners probably don’t need a battery at all. Solar batteries do provide numerous benefits, but their substantial upfront costs means they don’t quite make sense as a financial investment in most cases. It depends largely on local policy, utility rates, battery incentive programs. and how frequently you expertience power outages.

The best way to figure out if a solar battery is worth if for you is by speaking with multiple solar installers. Solar companies can give you an idea of how much a lithium-ion battery can save you (if anything) and if it’s something you should consider for your home.  

Get lithium-ion battery quotes from local trusted solar companies

Solar energy is a fantastic way to get power anywhere the sun shines. It works great but only when the sun is out, so it’s critical to have the best battery possible for storing solar energy. LiFePO4 battery chemistry is one of the best options for solar storage for a number of reasons.

Join us as we take a closer look at the best option for storing the sun’s energy.

What Is Solar Battery Storage? 

First, let’s simply define solar battery storage. Solar panels convert sunlight into energy, but you can’t always count on having enough sunlight to provide consistent power on demand. If it’s overcast or nighttime, you’d be out of luck without a good battery. 

When the solar panels absorb the power, it is transferred to the battery until it reaches capacity. You can use the power stored within when it’s overcast or night and rely on fresh solar power when it’s sunny. The battery can also provide a larger amount of energy for a short period of time. It is possible to run a 1200 watt microwave on a 300-watt solar panel, but only if you have a batter to store and provide the larger amount of energy for a shorter period.

The battery is the heart of the solar system because none of the other components are much help without it.

Solar Battery Storage Options

As you might have gathered from the title, LiFePO4 is our top choice and what we specialize in at dragonfly energy. It stands head and shoulders above traditional lead-acid batteries of all types, and we consider it the best lithium battery option for solar.

Here are a few of the most common types of solar battery storage options

Lead-Acid Batteries

Lead-acid batteries are likely the most familiar type that can be used for storage. The vast majority of gas-powered passenger vehicles operate with a lead-acid battery to power the starter and other electrical components.

The battery chemistry is tried and true, having been around for generations. It’s easy to find, and they tend to be less expensive than lithium options. There are many different types of lead-acid such as flooded, Gel, AGM, or crystal but they all perform similarly for storage.

These are industrial lead-acid cells that have been used in solar systems of the past. Due to their major drawbacks, they are becoming obsolete.

While lead-acid is less expensive upfront, there are many drawbacks to solar storage. Chief among these is their usable capacity; you can only discharge them to 50% before they suffer damage. They also last for many fewer life cycles than lithium batteries. Charge rates are also slower and they suffer damage when not fully recharged properly a common occurrence with solar energy systems.

Lithium-Ion Batteries

As mentioned, lithium batteries, like LiFePO4, have a more advanced chemical makeup. Though they’re generally more expensive upfront, lithium batteries have proven their worth over the years in both small applications like cameras and cell phones as well as in large appliances and vehicles.

Lithium batteries store more energy, put out more power and deliver a more consistent supply, and last longer, particularly compared to lead-acid batteries. Charging can start and stop anywhere in the charge cycle and they last thousands of more cycles than lead-acid.

The initial cost is the biggest drawback of lithium batteries. They can be much more expensive initially, but it pays off in the long run. We guarantee our LiFePO4 battery to last 5 years, but they normally last much longer.

LiFePO4 Batteries

Lithium-ion batteries can boast different kinds of chemistry based on the application. Regarding solar battery storage, LiFePO4 (lithium iron phosphate) has a battery chemistry that stands out above both lead-acid and other lithium batteries.

LiFePO4 batteries are widely considered the safest type of lithium battery, and they last for a decade or longer. They also offer flexible charging and deeper discharge cycles without damage. 

This solar system available in Montana Fifth Wheels includes two dragonfly LiFePo4 Batteries at the heart.

There aren’t many drawbacks to LiFePO4 batteries other than the initial upfront cost. Although, many would say it’s not truly a disadvantage since you’ll likely save money buying just one lithium-ion battery in 10-15 years rather than several lead-acid batteries. 

Why LiFePO4 Batteries Are the Best Batteries for Storage Power Storage

As you can see, the positives of LiFePO4 batteries greatly outweigh the negatives. Their efficiency and consistent energy output make it a clear winner. Let’s go over the specifics. 

Long Battery Life

Battery life is where LiFePO4 batteries make up for the higher initial cost. A high-quality LiFePO4 like Dragonfly Energy is designed to last 3000-5000 cycles of deep discharging and still retain 80% of its original capacity. This is critical for a solar system because the batteries are used every single night and recharged every day.

In reality, the battery life cycles are even higher as most discharges are not full. 10,000-15,000 cycles are common for LiFePO4 in a solar application making them good for many years.

Little to No Maintenance

Because our LiFePO4 batteries come with a built-in battery management system, they’re highly efficient. This also means that they require little to no maintenance. Even if you’re using your battery for RVing or marine capacities with constant movement and jostling, LiFePO4 batteries still hold up well.

Lightweight

LiFePO4 batteries also come with considerable weight savings. They generally weigh about one-third to one-half of what a lead-acid battery weighs. This means you can ramp up your battery bank since it takes two or three LiFePO4 batteries to equal the weight of one lead-acid battery. They also have more usable capacity, which maximizes their weight to power ratio.

Fast Charging Time

LiFePO4 batteries offer lower resistance, and they don’t require a float charging cycle. So they charge much faster than lead-acid batteries. When you’re relying on solar power, a battery that recharges faster is significant. If there are only a few hours of pure sunlight per day where you are, a shorter charge time is gold. 

This is an example of solar system power in watts charging a LiFePO4 battery. As the solar climbs for the first part of the day the battery rapidly takes the charge of almost 2000 watts. Notice that once it’s charged it immediately goes to a float charge. Other battery types taper off and can waste solar energy or not get fully charged if there is not enough sun.

Environmentally Friendly 

LiFePO4 batteries are non-toxic and recyclable. Many of us want to use solar energy for its environmental benefits, so it only makes sense to utilize solar battery storage that’s not detrimental to the environment. There are fewer gas emissions from them and no risk of acid spills.

How Much Do LiFePO4 Batteries Cost? 

A 100 amp-hour LiFePO4 battery typically costs between $800 and $1,000. That certainly sounds like a lot when compared to lead-acid batteries that run around $300. But remember that because you won’t damage them by deeply discharging them, LiFePO4 batteries can easily last 10-15 years with between 3,000 and 5,000 cycles.

What to Look for in Solar Battery Storage

While we’ve already talked about why LiFePO4 batteries are good for solar power storage, we want to make sure you understand all that goes into choosing a great battery.

• Flexible and fast charging cycle
• Has 100 percent usable capacity (otherwise you need to stop using the battereis under certian conditions to prevent damage)
• Long battery life under solar charging and discharging conditions
• Safe and non toxic
• Good energy denisty to pack more power into a smaller space

We’ll explore each here to help you make a more informed battery purchase. 

Flexible Charge Cycles

Choose a battery that has flexible charging cycles. Basically, that means you can deeply discharge a battery without damaging its lifespan. Also, batteries should efficiently recharge, no matter how low the power level gets.

Here is an example of a battery charge-discharge in a solar system. The yellow line is current and every time it crosses the dashed line it changes from charging to discharging. A solar storage battery needs to handle this regular change without damaging the battery.

You can only discharge some batteries (lead-acid) to about 50% capacity before they start suffering irreparable damage. But you can discharge LiFePO4 batteries almost entirely without causing harm. Charging can also start and stop at any point with LiFePO4 batteries.

Usable Capacity

Usable capacity considers how much you can discharge a battery before it sustains damage. If you have batteries that cannot be fully discharged, you must program the solar system to cut out early or risk battery damage.

Let’s look at an example: Battery A is a lithium-ion LifePO4 battery rated for 200 amp-hours, and Battery B is a 200-amp-hour lead-acid battery. You might think the lithium and lead-acid batteries have the same usable capacity because they have the same power rating. However, you can completely discharge Battery A without causing damage. But if you let Battery B dip below 50%, it will sustain damage that shortens its lifespan and power capacity. 

Because of the potential damage issues, Battery A gives you a full 200 amp-hours of energy. Meanwhile, Battery B only gives 100 amp-hours. The practical, usable capacity of Battery A is thus twice that of Battery B.

Battery Life

Always factor in your battery’s lifespan, especially when you’re considering the cost. A lead-acid battery can cost a couple of hundred dollars, while a lithium-ion battery might run several hundred or upwards of a thousand dollars. But when you think about how long your battery lasts, you’ll recognize the colossal bang for your buck.

This is a test we ran comparing one of our LiFeP04 packs to a traditional lead-acid running deep discharges. The test was stopped for the lead-acid when 80% of its original capacity was left. It only made 100 cycles which would be less than a year in a solar system. The Dragonfly Energy battery was on its way to 5000 even with deep discharges.

Lithium batteries also last longest under solar charge and discharge conditions that change rapidly. As the sun comes and goes, charge and discharge cycling can happen tens to hundreds of times per day.

Safety

While it’s not very common anymore, you can purchase non-sealed lead-acid batteries. They require significantly more maintenance than other battery types, and if they’re jostled too much (like in an RV or boat), they could leak battery acid. This is a safety hazard, and it’s toxic to the environment. 

Additionally, most batteries can let off flammable or toxic gases if they overheat or are not well-ventilated. But some present more of a hazardous gas problem than others. Lead-acid batteries are more likely to produce a gas called hydrogen sulfide. It smells like rotten eggs and is colorless, flammable, and very poisonous. 

Your battery might also emit flammable gases if it’s overcharged, so finding a battery that will automatically stop charging when it’s full is highly valuable. 

Dragonfly Energy lithium-ion batteries have many built-in safety parameters and a perfect safety record that should assuage your concerns here.

What is the Best Battery for Solar Power Storage? 

When weighing the options for solar battery storage, there’s really no argument: LiFePO4 batteries are the best option. The advanced technology and battery chemistry can stand the test of time and be worth every cent. 

We’ve covered the many benefits here, but if you have any other questions about our LiFePO4 batteries for your solar system or another application, feel free to reach out.

If you are looking for more details, kindly visit lifepo4 battery energy storage system supplier.