What Is the Life Expectancy of a Solar Battery?

What Is the Life Expectancy of a Solar Battery?

By Renogy UK
Renogy UK
renogys blog Dec 9th 2021

Anyone hoping to set up a useful home solar system will start investigating solar batteries sooner than later. Solar batteries are perfect for home energy storage and creating emergency backup systems for your solar panels in the event of a blackout. With a solar battery or a battery bank, you can produce power efficiently, store the excess, and use it when you need it most.

Like with any purchase, homeowners will want to determine which solar battery provides the most value for their needs. One of the first questions homeowners ask is, “how long do solar batteries last?” In this article, we’ll discuss solar battery lifespan and everything that affects it so you can get the most value out of your purchase.

Factors That Determine the Lifespan of Your Battery

The lifespan of solar batteries typically falls between 5 and 15 years. For many, this may seem like a relatively large range, and it is. The truth is that there are quite a few variables that determine solar battery lifespan, including the type of solar battery, how often you use the battery, the temperature of the battery, and how well you maintain it.

Solar Battery Type

The first and one of the most important decisions you can make when selecting a solar battery is choosing a solar battery type. The type of solar battery will impact the lifespan of your solar batteries. However, your decision won’t be as simple as selecting the solar battery type with a longer lifespan. Instead, you need to be aware of the functions, capabilities, and limitations of each.

Each type of solar battery is designed to serve a specific purpose. Before choosing a solar battery type, consider your needs and the type of solar system you’re building.

Lead-Acid Batteries

Lead-acid batteries offer one of the least expensive options available. However, with savings come limitations. Lead-acid batteries have a lower depth of discharge (DoD) and a shorter lifespan than lithium-ion batteries.

While lithium-ion batteries boast superior specs in almost every category, that doesn’t mean you should skip over lead-acid batteries entirely. One particular use case that makes efficient use of lead-acid batteries is in off-grid solar installations.

If you have an off-grid solar installation that doesn’t see frequent use, you can get around some of the drawbacks tied to lead-acid batteries. Ultimately, lead-acid batteries tend to last between three to five years but can live as long as 12+ years. This is primarily due to the lower usage rate of lead-acid batteries and can save you a significant amount of money when putting together a power backup system for an RV or boat.

Lithium-Ion Batteries

Lithium-ion batteries are generally the go-to batteries for most solar system applications. They are compact, light, have a higher depth of discharge, and last longer compared to other options. Even better, lithium-ion batteries tend to enjoy superior capacity and efficiency.

Lithium-ion batteries tend to last two to three years, or 300 to 500 cycles (whichever comes first). While, at a glance, it may seem like lithium-ion batteries have a shorter lifespan, in terms of years, keep in mind that lithium-ion batteries are best for active use.

Also significant is the value of each cycle in a lithium-ion battery compared to a lead-acid battery. Because lithium-ion batteries have higher capacities, higher depth of discharge, and higher efficiency, a single cycle on a lithium-ion battery means a lot more than it does for a lead-acid battery.

How Often You Use the Batteries

It’s less useful to measure battery lifespan in terms of years and better to measure lifespan in terms of “cycles.” Each cycle is an opportunity to drain and recharge a battery. Because of this, solar batteries will most likely have a lifespan measured in maximum cycles. The more you drain and recharge your battery, the closer it is to degrading. Degradation happens slowly over time but accelerates at the end of a battery’s life.

What Is Battery Degradation?

To explain degradation, consider a smartphone or device. Most such devices tend to stay powered on a single charge for a long period of time. At least, to start. As the battery is fully drained and recharged, each subsequent charge discharges faster and faster. Eventually, the battery discharges so quickly that it isn’t worth using.

One of the best ways to extend your solar battery’s lifespan is to follow your manufacturer’s recommended depth of discharge. Generally speaking, a depth of discharge is the remaining charge in a battery, measured as a percentage. If your battery’s manufacturer recommends a depth of discharge of around 40%, you should avoid draining the battery to below 40% of its full charge. Ignoring the recommended depth of discharge can significantly reduce the lifespan of your solar battery.

Partial-Discharge Cycles

As a tip, try using partial-discharge cycles as often as possible. Using only 20% or 30% of your battery’s total capacity can extend cycle life significantly. Likewise, you should avoid charging your battery to 100%.

Battery Maintenance

When asking yourself, “how long do solar batteries last,” you’re also asking yourself how committed you are to battery maintenance. More than any other factor, battery maintenance is the most important. Without proper care, you might even find your new solar battery more or less useless in just a matter of weeks.

Lithium-Iron Batteries

For lithium-ion batteries, maintenance is very straightforward. Once in a while, take a State of Charge reading to ensure your battery is properly holding a charge. Typically, lithium-ion batteries come with a tool as recommended by the installer or manufacturer of your battery. Then, examine any cables and terminals, and tighten as necessary. Always dust your battery as much as possible.

Lead-Acid Batteries

For lead-acid batteries, things are a little more involved. There are two types of lead-acid batteries. These are flooded lead-acid batteries and sealed lead-acid batteries.

Flooded Lead-Acid Batteries

For flooded lead-acid batteries, inspect your battery every two to four weeks. As water levels drop, refill using distilled water only and up to the max level line. Then, using a refractometer, check your battery’s state of charge to see if it is holding a charge after a full charge cycle. To make sure your cells are charging equally, perform a controlled overcharge every one to three months.

Sealed Lead-Acid Batteries

For sealed lead-acid batteries, simply check the state of charge with a multimeter every so often, specifically when the battery is under no load. Inspect cables and terminals, and tighten as necessary. Dust thoroughly.

Solar Battery Warranty

While a warranty by itself won’t extend the life of a single battery, it can extend the value of your purchase. If something goes wrong with your solar battery and its lifetime was cut short prematurely, you can rely on your battery’s warranty to get a replacement. Generally, most lead-acid batteries have warranties of 5 years or fewer. Lithium-ion batteries tend to have warranties of 10 years or more.

Solar Battery Temperature

Temperature is critical, both to your cycle life as well as the lifespan of your battery. Neither extreme heat nor cold will do your battery any good. Instead, you need to find a temperature-controlled space where your battery won’t be exposed to the elements.

High heat will accelerate chemical reactions in batteries, decreasing lifespan and increasing the rate of wear and tear. Cold slows chemical reactions, causing electrons to slow and chemical reactions to end more rapidly. This drains the battery more quickly than under normal circumstances.

Lead-acid batteries are more vulnerable to extreme temperatures than lithium-ion batteries, but you should always keep aware of ambient temperature, just in case. For lead-acid batteries, try to keep ambient temperatures between 40°F and 80°F. Lithium-ion batteries can withstand temperatures as low as 0°F or as high as 140°F, but do your best never to expose them to such extremes.

How Do I Know If My Solar Battery Is Bad?

As you use your solar battery, your chances of finding something wrong increase. If you’re worried your solar battery is dead, start with a visual inspection. Check for broken terminals, discoloration, leaking, cracks or ruptures in the plastic, and bulges or bumps in the casing.

Broken terminals are very serious and can lead to short-circuiting. Replace any batteries with broken terminals as quickly as possible. Bulging tends to signify overcharging, which indicates a problem with the charge controller. Cracks and ruptures are signs of heavy degradation.

Of course, knowing your battery is bad isn’t always as easy as looking at it. The next thing you want to do is check the battery’s state of charge or perform a voltage reading. Always use the right tool depending on the type of battery you’re testing.

In many cases, a digital multimeter will do. Find your battery’s spec sheet to find your battery’s normal voltage. Otherwise, this is usually listed on the side of the battery. With that number in mind, check your battery’s voltage. If it reads 0 volts, your battery may have suffered a short circuit.

If it cannot go beyond 10.5 volts while charging with your solar battery chargers, there’s a dead cell. If voltage reads normal, but your battery won’t hold a charge, there’s a high chance the battery has sulfated and needs replacing.

The Best Batteries for Solar Power Storage

The best batteries for solar power storage will depend on your needs. However, to get started, several batteries are available that will provide you with reliable performance. Make sure to consider the following solar batteries:

The 12V 100Ah Smart Lithium Iron Phosphate Battery is perfect for caravan, cabin, and marine use, thanks to its auto-balanced, long life cycle battery with incredible discharge performance. The 12V 170Ah Lithium-Iron Phosphate Battery boasts a higher capacity, making it an excellent choice for cabins, solar/wind energy systems, UPS battery backups, telecom systems, and medical equipment. The 12V 50Ah Lithium Iron Phosphate Battery is an incredible, smaller capacity alternative, with BMS protection, low self-discharge, and Triplex Sealed construction.

12V 100Ah Smart Lithium Iron Phosphate Battery w/ Self-Heating Function is another beast entirely. This battery is auto-balancing among parallel connections, is equipped with BMS protection, and offers ultra-safe long cycle life while staying lightweight. The most notable feature is its smart self-heating function, making it suitable for lower-temperature applications.

The 12V 100Ah Smart Lithium Iron Phosphate Battery w/ Self-Heating Function boasts an incredible lifespan of 4000+ cycles with an 80% depth of discharge. Because of the self-heating feature, it can recharge successfully, even in low-temp conditions. For your peace of mind, it includes a five-year prorated warranty.

Of course, just because a battery is promising doesn’t mean it is appropriate for your application. Always keep in mind the conditions of the install site, how you will be using it, how often you plan to use it, and the temperature of the area. Also, keep in mind that not all batteries are designed to be connected in series and may only be compatible when connected in parallel. Even then, always make sure you use the same manufacturer when using multiple batteries.

Start Storing Solar Energy Today!

Solar batteries are one of the best ways to detach yourself from the grid, even if temporarily, and equip your home with an emergency backup power system. These devices can enable you to be more mobile if you ever want to take powered equipment on the road. Explore the countryside with camping solar panels and a few deep cycle batteries. You can even bring power to an isolated fishing cabin while you get away from the world.

Before asking “how long do solar batteries last,” make sure to ask yourself why you need solar batteries in the first place. Depending on the application and the level of care you can provide, the lifespan of solar batteries can swing widely. But with proper care, you can squeeze out thousands of cycles before needing a replacement.