In Parts 1 and 2 of this series, pv magazine reviewed the productive lifespan of residential solar panels, and inverters. Here, we examine home batteries, how well they perform over time, and how long they last.
Residential energy storage has become an increasingly popular feature of home solar. A recent SunPower survey of more than 1,500 households found that about 40% of Americans worry about power outages on a regular basis. Of the survey respondents actively considering solar for their homes, 70% said they planned to include a battery energy storage system.
Besides providing backup power during outages, many batteries are integrated with technology that allows for intelligent scheduling of the import and export of energy. The idea here is to maximize the value of the home’s solar system. And, some batteries are optimized to integrate an electric vehicle charger.
Although deployment of energy storage is on a steady climb, attachment rates of batteries remain low: in 2020 8.1% of residential solar systems attached batteries, according to Lawrence Berkeley National Laboratory (LBL).
Many options exist with multiple battery chemistries available for home energy storage. Bottom line, however, is that in the United States two brands dominate the space. More than 90% of the market is served by LG Chem and Tesla Powerwall, which are lithium-ion batteries, according to LBL. Tesla has more than 60% of the entire market share.
Warranties
The Tesla PowerWall has a limited warranty that says the device will be free from defects for 10 years following installation. It also warrants that the PowerWall will start its life with a capacity of 13.5 kWh, and will retain energy capacity based on a degradation schedule.
LG warrants that its system will retain at least 60% of its nominal energy capacity (9.8 kWh) for 10 years. The battery must operate between -10 degrees Celsius and 45 degrees Celsius to remain warranted. Total throughput of energy within the warranty is limited to 27.4 MWh.
Solar installer Sunrun said batteries can last anywhere between 5-15 years. That means a replacement likely will be needed during the 20-30 year life of a solar system.
Battery life expectancy is mostly driven by usage cycles. As demonstrated by the LG and Tesla product warranties, thresholds of 60% or 70% capacity are warranted through a certain number of charge cycles.
Two use-scenarios drive this degradation: over charge and trickle charge, said the Faraday Institute. Overcharge is the act of pushing current into a battery that is fully charged. Doing this can cause it to overheat, or even potentially catch fire.
Trickle charge involves a process in which the battery is continually charged up to 100%, and inevitably losses take place. The bounce between 100% and just under 100% can elevate internal temperatures, diminishing capacity and lifetime.
Another cause of degradation over time is the loss of mobile lithium-ions in the battery, said Faraday. Side reactions in the battery can trap free usable lithium, thereby lowering capacity gradually.
While cold temperatures can halt a lithium-ion battery from performing, they do not actually degrade the battery or shorten its effective life. Overall battery lifetime is, however, diminished at high temperatures, said Faraday. This is because the electrolyte that sits between the electrodes breaks down at elevated temperatures, causing the battery to lose its capacity for Li-ion shuttling. This can reduce the number of Li-ions the electrode can accept into its structure, depleting the lithium-ion battery capacity.
It is recommended by the National Renewable Energy Laboratory (NREL) to install a battery in a cool, dry place, preferably a garage, where the impact of a fire (a small, but non-zero threat) may be minimized. Batteries and components around them should have proper spacing to allow cooling, and regular maintenance check-ups can be helpful in ensuring optimal operation.
NREL said that whenever possible, avoid repeated deep discharging of batteries, as the more it is discharged, the shorter the lifetime. If the home battery is discharged deeply every day, it may be time to increase the battery bank’s size.
Batteries in series should be kept at the same charge, said NREL. Though the entire battery bank may display an overall charge of 24 volts, there can be varied voltage among the batteries, which is less beneficial to protecting the entire system over the long run. Additionally, NREL recommended that the correct voltage set points are set for chargers and charge controllers, as determined by the manufacturer.
Inspections should occur frequently, too, said NREL. Some things to look for include leakage (buildup on the outside of the battery), appropriate fluid levels, and equal voltage. NREL said each battery manufacturer may have additional recommendations, so checking maintenance and data sheets on a battery is a best practice.
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The life span of a solar battery determines how long you can store and use excess solar energy before purchasing a replacement. A solar battery’s type, depth of discharge, usage and temperature exposure significantly impact how long it can effectively operate in one cycle and how many cycles it can work total.
Understanding how long a solar battery lasts can help you choose the best battery for your home or business property’s needs.
Supplementing your solar panel system with a battery backs your system up when you need additional power. A solar battery stores excess energy from a solar panel system so a home or business property can use it when the sun is not shining. This setup is also beneficial for the environment because it prevents you from using electricity from the power grid.
Installing a solar battery can help you save money on your electric bill because it provides energy on days solar panels absorb less sunlight and at night when sunlight is unavailable. It can also provide your home or business with energy during a power outage.
The amount of time a solar battery can provide power before needing to recharge depends on its power output, energy storage capacity and the appliances it powers. While most solar batteries do not supply the electricity to power an entire property, a solar battery can effectively power your most important appliances, such as your lights, refrigerator and internet router.
A battery’s kilowatt hours (kWh) determine how many kilowatts it can deliver to appliances before recharging. The amount of time it can last depends on each appliance’s wattage. Powering appliances with lower wattages allows a battery to operate longer than it would if it were powering appliances with higher wattages. Additionally, powering fewer appliances allows it to operate longer before needing to recharge.
The life span of a solar battery is around 10 to 15 years. Most solar battery warranties are for 10 years, but a battery may remain in good condition and last longer than its 10-year warranty. A solar battery’s exact life span depends on the following factors:
The battery type a homeowner chooses also affects its life span. Solar battery types consist of the following:
Lithium-ion batteries have a higher upfront cost than lead-acid batteries, but they provide a greater value. You can expect to replace lithium-ion batteries much less frequently than lead-acid batteries, saving you money long-term.
The number of times you use a battery significantly impacts how long it lasts. Similar to a phone battery, a solar battery’s life span lowers slightly with each usage cycle. A battery’s storage capacity decreases each time the battery drains, and each cycle slightly increases the frequency you need to recharge a battery.
The ability to withstand more discharge cycles is one reason why lithium-ion batteries last longer than lead-acid batteries. A lithium-ion battery can continue to operate effectively after more discharge cycles than a lead-acid battery.
Limiting battery usage allows it to maintain storage capacity and extend its life span. Using half of a battery’s capacity each day allows a battery to last longer than draining its full capacity daily.
A solar battery’s depth of discharge (DoD) determines how much of its capacity it can discharge without taking on damage or shortening its life span. For example, a lithium-ion battery’s DoD is typically around 90%, allowing it to discharge 90% of its capacity without degradation. Some solar batteries contain built-in protection to prevent them from discharging 100% of their capacities.
Extreme weather and temperatures can shorten a solar battery’s life span. Environmental conditions affect lithium-ion batteries less than lead-acid batteries, but protective storage can benefit both battery types.
While a lithium-ion battery can handle temperatures between zero degrees Fahrenheit and 90 degrees Fahrenheit, a lead-acid battery performs better and lasts longer when property owners store it between 40 and 80 degrees Fahrenheit. Installing energy storage in a temperature-controlled space such as a garage can help extend a battery’s life span.
Solar batteries require minimal maintenance, but monitoring your battery can help it last as long as possible. Checking your battery’s performance helps prevent damage so it can work properly over its entire life span.
Solar panels last longer than solar batteries do. Panels typically last about 25 to 30 years, and lead-acid batteries last between four and 15 years. Whether you use lithium-ion batteries or lead-acid batteries, you will need to replace your battery at least once to store energy throughout your solar panel system’s entire life span.
You can help your solar battery last as long as possible with the following tips:
The length of time you can depend on a solar battery largely depends on the type of battery you choose and its quality. 8MSolar offers high-quality solar batteries from brands such as LG and Tesla. The LG Chem features a 9.8 kWh storage capacity, and the Tesla Powerwall features a 13.5 kWh capacity.
These long-lasting batteries can power your home or business at night and during inclement weather to help you save money and reduce your carbon footprint. Contact 8MSolar to learn more about solar batteries and choose the best option to supplement your solar energy system.
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