Lead Acid vs. Lithium-Ion Batteries: Which is better for storing solar?

by Anna Gretz
June 17, 2016
Home Battery

Lead acid, or lithium-ion home batteries?

New solar home battery models have gotten a lot of press lately, but energy storage has been around for decades. Homes venturing off the grid 20 years ago turned to lead acid or sometimes nickel based home batteries to store their solar energy. With growing interest in solar home batteries, solar battery technology has skyrocketed. Solar battery models being released today are more exciting than ever, with innovative improvements in nearly every aspect. But which is better for storing rooftop solar? Lead acid, or lithium-ion home batteries? We’ve done the research, but we’ll let you decide.

New Home Battery Technology

Though lithium-ion battery technology was introduced in the 1970’s, it took twenty years for it to really gain popularity. Lithium, the lightest of all metals, has the greatest electrochemical potential. This means that lithium provides the highest energy density per weight--far lighter and more efficient than the popular lead acid battery. Lead acid batteries can weigh up to 350 pounds, making them far more difficult to transport. Lead acid battery weight also makes usability much less convenient for residential solar customers.

The growth of lithium ion technology has brought along with it many advantages. In comparison to solar home batteries that have been popularly used in the past, lithium-ion batteries are cleaner, live longer, recycle better, and require much less maintenance. But the advantages don’t stop there. Keep reading to find out how lithium-ion batteries make our homes not only cleaner, but smarter, too.

Not Just a Fair-Weather Battery

One major downfall of the lead acid solar battery is that its power capacity drops significantly in colder temperatures. In 0 degree Fahrenheit temperatures, a lead acid battery’s capacity is only 40-60% of its overall potential. This means that cold weather greatly decreases the amount of solar energy a lead acid battery can store, and with it, limits the amount of power your household has available on a cold day. Unfortunately, cold days are often when households need the energy generated from their solar panels the most to keep electric heaters running.

The same low temperature of 0 degrees Fahrenheit will only take a lithium-ion battery down ten percent or so. This means that even when your solar home battery gets cold, it can still store and provide your household with almost as much solar energy as it would on a normal day. If your home depends on your solar home battery for energy, reliability is key. Lithium-ion battery capacity is there for you, whatever the weather.

Cleaner Clean Energy

As far as environmental impact goes, lead acid doesn’t impress. Lead acid batteries require many times more raw materials than a lithium-ion battery to achieve the same level of solar energy storage. More raw materials means more mining, and a bigger environmental impact. The lead acid battery industry is also very energy intensive, requiring a lot of energy to even produce the battery itself. This leads to large quantities of pollution being dumped into the air, and into the environment.

Though the lithium in the lithium-ion battery does require mining, each solar home battery requires less material, minimizing the impact on the earth. Lithium-ion solar battery manufacturing plants are also looking to use renewable energy sources for power, which may result in an impressively small carbon footprint. Imagine manufacturing a solar home battery used to store renewable energy in a factory that runs on renewables and solar energy storage itself. It just makes sense, doesn’t it?

Longer Life

Lithium-ion solar batteries have a significantly higher cycle life than lead acid batteries do in deep discharge applications. This means that lithium-ion batteries can support a higher number of complete charge/discharge cycles before their capacity falls under 80%. Recent data shows that a lead acid battery would have to be 2.5 times larger in capacity than a lithium-ion battery to get comparable cycle life. When you’re considering bringing a solar battery into your home, size matters.

The difference in cycle life is even greater in extreme climates. In warm climates where the temperature hovers around 90 degrees Fahrenheit, the difference in cycle life between lithium-ion solar batteries and lead acid batteries is huge. In these extreme temperatures, it takes less than 1000 charge/discharge cycles for lead acid batteries to drop below 80% in retention, while lithium-ion batteries wouldn’t see that much of a drop until at least 2000 cycles. This huge jump in battery lifetime is an exciting development for consumers who don’t want to worry about their solar home battery capacity dropping when they need power the most (like when your air conditioner is pretty much keeping you alive.)

This also means that lithium-ion solar home batteries won’t require replacement nearly as quickly as lead acid home batteries. After charging and discharging a lithium-ion solar battery thousands of times, it remains highly functional. Lead acid batteries decline much more quickly, leaving solar home battery owners with thoughts of replacement looming in the near future. More frequent replacement means less return on the initial investment made in each solar home battery system.

Low Maintenance

Another inconvenience of lead acid batteries comes in the amount of maintenance each unit requires to prolong its battery life. Lead acid solar home battery users need to keep track of battery voltage, water levels, overcharge functions, and routine electrolyte maintenance. All this information is necessary to make sure lead acid solar home batteries are being maintained and serviced on a regular basis. Failure to track this data could result in even more costly repairs, or even earlier replacement of the solar home battery itself.

Lithium-ion solar batteries, on the other hand, are virtually maintenance-free, allowing owners to enjoy using their solar home battery without worrying about permanent damage due deep discharge. There are many other things in life that demand and captivate our attention. Your solar home battery no longer has to be one of them. Your solar home battery system can now be here to support you and your household, instead of the other way around.

Recycling

Currently, lead acid solar batteries are recycled much more frequently than lithium-ion batteries, boosting their case for environmental friendliness. Lithium-ion solar batteries, however, have a very high ability for recovery and recyclability, even though their recycling rate is lower than lead acid batteries. The reason for the lower recycling rate of lithium-ion home batteries is simply because the technology is still emerging, and the machinery needed to recycle them is still costly, and in a more developmental stage. As the industry grows, lithium-ion solar battery recycling is expected to quickly rival lead acid batteries, and perhaps even surpass it due to the lower cost of using recycled lithium instead of mining more. Watch for some major advancements in lithium-ion solar battery recycling in the years to come.

Easy Installation

The cost of transporting and installing lead acid batteries has been historically discouraging to consumers. The sheer weight of lead acid solar home batteries makes them difficult to transport, and harder to install. Because of the weight of lead acid solar battery materials, there is no easy way to cut this cost. Instead, many are turning to lithium-ion solar batteries to offer a lighter alternative.

Lithium-ion solar home batteries weigh much less, lowering shipping costs by 80%. The installation cost of lithium-ion solar batteries are similarly cut by over $16 per kilowatt hour. This makes the price of lithium-ion solar home batteries considerably lower to ship and to install, making them much more appealing to consumers. With the rising demand for solar home batteries across the country (and world), lower transportation and installation costs will become more and more important.

Smarter Than Your Average Battery

New solar home battery models have revolutionized residential energy storage by being connected and controlled by the cloud. “Smart” technology is infiltrating all devices (think phones and televisions) and solar home batteries are no exception.

Smart home batteries will give renewable energy users, like those with solar panels, huge advantages. Smart solar home batteries have the ability to learn weather and energy trends, so they can focus on storing energy during the sun’s hours of peak performance to make sure it’s available when the sun’s rays are not as strong. This practice can help maximize power usage, and also minimize the waste of energy when its abundant. Smart solar home batteries also facilitate communication with solar home battery owners, and are able to accept wireless commands, giving owners even more control over their energy.

There’s our take on the lead acid vs. lithium-ion battery battle.

We’re pretty big fans of lithium-ion solar battery technology, so forgive our bias. Ultimately, it’s up to you to decide which solar home battery technology is a better fit for your household. Have more questions? We would love to keep this conversation going. Don’t hesitate to hit us up here, or in the chat window below.