Solar panels allow backup power and create an off-grid system but rely on batteries to store the power. The batteries are necessary to prevent the wastage of excess power, and they can also be used in a net metering setup. So choosing good batteries that last is an important consideration.
Solar panel batteries are usually made to help you last one day with backup power, but an off-grid system should have batteries to last a few extra days to allow for cloudy weather and reduced sunlight days.
Regarding lifespan, lead-acid solar batteries are designed to last between 3 and 5 years and can undergo about 500-800 charge-discharge cycles. Lithium-ion batteries have a lifespan of up to 10 years and can undergo between 300 and 15,000 charging cycles, and flow batteries can last up to 25 years. Batteries are considered useful only until they charge at least 60% of their capacity.
I will also cover solar panel battery types and factors that affect battery lifespan below.
| Battery Type | Capacity | Lifespan | Charge Cycles | Efficiency | Cost | Warranty |
|---|---|---|---|---|---|---|
| Lead-Acid | Low | 3-5 years | 500-800 cycles | Low | Affordable | 2-3 years |
| Lithium-Ion | High | 5-10 years | 300-15,000 cycles | High | Expensive | 5-10 years |
| Flow | High | 15-25 years | Unlimited | High | Expensive | 10 years |
| Sodium-Ion | High | TBD | TBD | High | Affordable | TBD |
How Long Solar Batteries Should Last
For Backup Power
Solar-Powered systems are usually designed with enough battery capacity to provide backup power overnight when the solar panels are not producing energy to provide continuous power all day.
So the batteries must last long enough to enable this constant power. You need to make a few calculations to know what capacity batteries you need, as it depends on your power consumption and other factors.
For example, suppose your usage is 30 kWh per day, you’ve installed a system capable of delivering 10 kWh, and you’re relying on solar power for your entire home. Also, suppose you get 6 hours of peak sunshine per day (which will be less in winter) and consider that most batteries operate up to 90% of the stated capacity. You would probably need at least three batteries in this situation.
This is only to help you last one day. In an off-grid setup, you would need the batteries to last a few extra days to account for cloudy weather and reduced sunlight days.
For Longevity (Long Term Years Lasting)
When considering how long the solar batteries should last before they need replacing, try to get batteries that would last at least five years.
You don’t want to be replacing the batteries every few years. A minimum 5-year interval is better, but the longer they last, the fewer times you will have to worry about buying new replacement batteries. Investing in a long-lasting battery is worthwhile.
Let’s consider the lifespan of solar panel batteries.
The Lifespan of Solar Panels Batteries
Batteries used for solar panels have a limited lifespan.
They only last for a certain period, usually mentioned in years, after which they become too weak and must be replaced. The degradation is natural and unavoidable.
The useful life of a battery ends when it provides less than 60% of its capacity. You can still use such a battery, but it might not provide enough charge for your needs. Otherwise, it will give you more time but in a weaker condition, which will not be useful.
Battery vs. Panel Lifespan
Solar panel batteries have a much shorter lifespan relative to the lifespan of solar panels.
Solar panels typically last 2 or 3 decades, whereas (lead-acid and lithium-ion) solar batteries only last between 3 and 15 years. It means you may need to replace the solar batteries several times during the lifetime of the solar panels or at least once if you buy long-lasting ones.
Why Battery Life Matters
Battery life matters because the cost of batteries in a solar-powered system is a significant factor, and their capacity diminishes or exhausts after a certain limited period.
So, the batteries are an important component. They store the sun’s energy the PV (photovoltaic) solar panels capture.
Choosing a Battery for Your Solar Panels
When choosing a battery for your solar panels, consider its capacity, longevity, efficiency, and cost.
In this article, we’re helping you choose the right longevity, although they are all related—for example, more efficient batteries usually last longer than less efficient ones. Also, longer-lasting batteries will cost you more, so your budget is a major constraint.
Additionally, consider the warranty. A reputable company should give a long enough warranty to allow you to get a free replacement if the battery is defective or expires much sooner than its expected lifetime.
Battery Types for Solar-Powered Systems
The type of battery is a very important factor that affects battery lifespan.
Two popular types of batteries are used in solar-powered systems: lead-acid and lithium-ion. Additionally, I cover flow batteries and mention the emerging technology of sodium-ion batteries.
Depending on other factors and how well they are maintained, different battery types can last only within a certain range of years.
Lead-Acid Batteries
Lead-acid batteries are the most popular and affordable option.
Small-scale and budget solar-powered systems typically use lead-acid batteries. However, their lifespan, compared to lithium-ion batteries, is much shorter.
Lead-acid batteries typically last between 3 and 5 years. They can last longer, up to more than double this lifespan, if used infrequently and well-maintained.
Lithium-Ion Batteries
Lithium-ion batteries are most commonly seen in more expensive and extensive (higher performance) solar-powered systems.
They are either LiFePO4 or LFP-type batteries. Compared to lead-acid batteries, they last longer and are more powerful and lighter. This is because they are capable of storing more electrical energy. However, they are flammable, so they must be kept secure.
Lithium-ion batteries typically last between 5 and 10 years.
Flow Batteries
Flow batteries are relatively newer than those mentioned above (lead-acid and lithium-ion).
They work by pumping liquid electrolytes through electrochemical cells. They have the edge over lead-acid and lithium-ion batteries by allowing 100% discharge depth.
Flow batteries typically last between 15 and 25 years.
Sodium-Ion Batteries
Sodium-ion batteries are an emerging technology that could have a useful future role in solar-powered systems.
They are expected to last longer than lead-acid batteries, much cheaper and safer than lithium-ion ones. As such, they could be a good alternative to using lithium-ion batteries.
Other Factors that Affect Battery Lifespan
Besides the type of battery, four other key factors affect the lifespan of a battery used with a solar panel.
They are depth of discharge, charge cycles, the environment, and maintenance.
Depth of Discharge (DoD)
The depth of discharge is the percentage of the battery’s capacity that can be discharged without degradation of the battery’s health quality.
| Battery Type | Maximum Depth of Discharge | Lifespan |
|---|---|---|
| Lead-Acid | 50% | 3-5 years |
| Lithium-Ion | 80-95% | 5-10 years |
| Flow | 100% | 15-25 years |
| Sodium-Ion | TBD | TBD |
The greater the depth of discharge, the greater the battery’s capacity to discharge completely without degrading its condition. Lithium-ion batteries have a discharge depth of around 80-95%. Usually, a battery has a built-in protective mechanism that prevents using more than this limit.
Assuming one such battery has a capacity of 12 kWh and a discharge depth of 90%, you can safely use 10.8 kWh without degradation.
Flow batteries have the greatest discharge depth, enabling them to last longer.
Charge Cycles
Batteries used in solar-powered systems have various charge cycles.
The number of charge cycles possible is the number of times the battery can undergo a full charge and discharge. This counts as one cycle. It is usually mentioned as an indication of the battery’s lifespan rather than the number of years.
| Battery Type | Charge Cycles | Lifespan |
|---|---|---|
| Lead-Acid | 500-800 cycles | 3-5 years |
| Lithium-Ion | 300-15,000 cycles | 5-10 years |
| Flow | Unlimited | 15-25 years |
| Sodium-Ion | TBD | TBD |
A lead-acid battery is typically good for about 500 to 800 charge-discharge cycles, and a lithium-ion battery typically has a lifespan of 300 to 15,000 full charging cycles.
So, rather than life in years, charge cycles are the actual thing to consider because the lifespan depends more on how much you use the batteries than on how regularly you use them.
Temperature
The temperature has a significant impact on battery life.
It would be best to protect your batteries from extreme temperatures, i.e., cold and very high temperatures. Both conditions would reduce the battery’s useful life.
| Battery Type | Optimal Temperature Range | Lifespan |
|---|---|---|
| Lead-Acid | 20-30°C | 3-5 years |
| Lithium-Ion | 15-25°C | 5-10 years |
| Flow | 5-40°C | 15-25 years |
| Sodium-Ion | TBD | TBD |
When the temperature falls below 30°F (-1°C), it will require more voltage to reach maximum charge, and when the temperature exceeds 90°F (32°C), it may overheat and require a charge reduction. [Ghezelayagh, 2021]
I recommend using an earth-sheltered enclosure to protect your solar batteries from extreme temperatures. If temperature variation and extremity are a big factor in your location, consider buying a lithium-ion battery with a built-in temperature moderation feature, such as a Tesla battery.
Maintenance
All the batteries used in solar-powered systems require maintenance to maximize their lifespan.
| Battery Type | Recommended Maintenance | Lifespan without Maintenance |
|---|---|---|
| Lead-Acid | Check water and acid levels regularly | 1-2 years |
| Lithium-Ion | No maintenance required | 5-10 years |
| Flow | Minimal maintenance required | 15-25 years |
| Sodium-Ion | TBD | TBD |
Regenerate Response
Ideally, you should regularly check the battery to see if it is operating optimally. For example, you must maintain lead-acid batteries’ water and acid levels. If the water is depleted completely, or you accidentally short-circuit the two terminals, the battery’s lifespan will significantly decrease.
The recommended and maximum water levels are usually marked on the outside of the batteries. Some smart batteries also allow you to monitor their condition via a mobile phone app.
References
High voltage long last solar battery. https://www.amazon.com/Renogy-12V-200AH-Rechargeable-Maintenance/dp/B084C3VZRY/ref=sr_1_3
Lead-acid solar battery. https://www.batterymax.pk/osaka-ta-1800-deep-cycle-lead-acid-unsealed-tubular-ups-solar-battery.html.
Lithium-ion solar battery. https://solarshop.pk/product/buy-12v-100ah-lithium-ion-battery-in-lahore-pakistan/.
Maty Ghezelayagh. Protection & Control Systems of Solar Power Plants: (Small, Medium & Large). Dr. Maty Ghezelayagh. 2021
Video Reference
Southern Energy Management