Depth of Discharge

Utilizing solar power isn’t something new. In fact, solar energy became readily available to many in the 1980s and has been increasingly recognized as a popular alternative energy source ever since. And with new technologies and features, we now see solar generators revolutionizing how homes in the United States harness and store energy from the sun.

Crucial to the efficiency and lifespan of solar systems, are the batteries that serve as storage (especically for cloudy days or when the grid goes down) for the surplus energy that is generated by the solar panels. One important factor affecting solar batteries' performance is the depth of discharge. In this article, we’ll further look into depth of discharge, and its importance for battery life, and we’ll also share some strategies on how to prolong battery life and optimize the performance of your solar-powered generator.

What is Depth of Discharge?

For a quick explanation, a depth of discharge, or DoD in short, refers to the percentage of the battery’s overall capacity that has been used before it is recharged.

For example, a solar battery with a 100Ah total capacity has already discharged 50Ah before it is recharged, which means the DoD is 50%. So, primarily, depth of discharge indicates how much energy has been used relative to the battery’s total capacity.

What is the significance of Depth of Discharge in solar batteries?

Suppose you’re looking to buy batteries for your home’s solar-powered backup system. In that case, one thing that you should consider is the depth of discharge, as it has a significant effect on battery life, performance and efficiency.  

Battery Lifespan

The depth to which a battery has been discharged directly impacts its lifespan. It’s important to remember that the chemistries of batteries, such as lead-acid or lithium-ion batteries, degrade as they are charged and discharged, thus gradually reducing their efficiency in storing energy.

There are two important factors in the degradation of solar batteries: the number of discharge and recharge cycles and the maximum depth to which the batteries are discharged. If a solar battery, for example, is discharged to 80% DoD each time it is used, it can accelerate the battery’s chemical degradation compared to when the battery is only discharged to a maximum of 50%. In short, the lifespan of the battery would be longer if the depth of discharge is kept low as this results in lesser wear and tear.

A word of caution: Keeping the depth of discharge too low could lead to a negative impact on the battery called the “memory effect” when it is only partially discharged. The key here is to keep the DoD at a recommended range to maximize the battery’s lifespan – but we’ll get into that later.

Cycling Efficiency

As mentioned, batteries go through cycles of charge and discharge in their lifetime. Deeper discharges can reduce the overall cycling efficiency, while a lower DoD means the battery will have more useful cycles. To put it simply, the fewer times the batteries are charged and discharged, the longer their lifespan is.

Performance

Batteries that are often subjected to high DoD can experience voltage drops and reduced efficiency. Note that consistent, reliable power output is essential in solar generator systems and keeping DoDs at recommended levels will help preserve the battery’s consistent performance.

What is the recommended Depth of Discharge for solar batteries?

The ideal depth of discharge varies depending on the battery you are using. Most manufacturers provide specifications of the maximum recommended depth of discharge for optimum battery performance. But to give you an idea, sealed lead acid batteries should only be run to a maximum of 50% DoD and nothing higher than that. Lithium-ion batteries are deep-cycle batteries, so their depth of discharge is around 95%, while Flow batteries have a DoD of 100%, meaning you can use the entire energy stored in the battery.  

Related Read: Types of Solar Batteries

Strategies to Maximize a Solar Battery’s Lifespan

Before we get into the tips, let us remind you that a solar battery’s lifespan depends on a couple of factors, and these include the type of battery, usage, depth of discharge, exposure to weather and temperatures, as well as how you maintain it. 

Typically, solar batteries will have a lifespan of around 10 to 15 years, and it is possible for batteries to last longer than this with proper usage and maintenance.

Charge solar batteries to 100%

A way to ensure that your solar batteries have a long lifespan is by charging them fully each cycle. If you are not planning to use your solar batteries anytime soon, make sure that they are 100% charged before you put them away. Also, remember to charge them at least once every 3 to 6 months to prevent the batteries from completely draining.

Avoid fully discharging batteries

Routinely check your solar batteries to ensure that you prevent them from fully discharging. It’s important to note that you should only allow your batteries to be discharged to their maximum DoD capacity if you want your batteries to reach their maximum lifespan.

Be mindful of where your batteries are stored

The temperature where your batteries are kept is also an important factor affecting their longevity. Batteries stored in hot and humid areas can possibly overheat and have a shorter lifespan. Similarly, keeping batteries in low temperatures also has a negative effect as batteries need to work double time and on a higher voltage in order to charge.

Choosing the Right Solar Battery

Although depth of discharge is an important parameter that affects battery life, it isn’t the only factor to consider when choosing which one is the right one for your needs. Luckily, you won’t have to scour various manufacturers since at Nature’s Generator, we have developed solar batteries that work well with our solar generators.

Nature’s Generator Elite is a customizable, and upgradable home backup where you can add Power Pods to meet your power needs. We also have Nature’s Generator Powerhouse, a whole home solar and wind system that can utilize both Powerhouse SLA and LiFePO4 Power Pod for added capacity.

To learn more about these solar batteries and your options, you can always reach out to our friendly customer service representatives at support@naturesgenerator.com or fill out this form.

* We want to give credit where credit is due. Professional writer, Ishna Sablaya, contributed research and content to this blog titled: Depth of Discharge Thank you, Ishna, for your contributions!