deep cycle battery

Deep cycle batteries overview: what you need to know

You are probably already familiar with a range of batteries–from the AAAs in your TV remote to the larger battery under the hood of your car that you hopefully rarely think about. Just as different types of batteries are most useful for different types of applications in your home, there is one type of battery that is ideal for being paired with solar energy systems: deep cycle batteries.

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Energy storage terminology

At their core, batteries charge and discharge electricity. A great analogy for batteries is a water pitcher. When the pitcher is being filled with water, it is charging. When the pitcher is pouring out the water, it is discharging. In energy storage parlance, this process of a single charge (i.e., filling the pitcher) followed by a single discharge (i.e., emptying the pitcher) is called a “cycle”.

Two other key terms to understand before diving into deep cycle batteries are depth-of-discharge and the state-of-charge. Depth-of-discharge is a metric for how much of the battery’s electricity you’ve used, while the state-of-charge is a metric for the amount of electricity remains stored in the battery. Using the same water pitcher analogy, if you were to pour out only three-quarters of the water pitcher, the depth-of-discharge would be 75 percent while the state-of-charge would be 25 percent.

There are a lot of terms and jargon associated with batteries. To learn more about relevant terminology, check out our energy storage glossary.

Deep cycle batteries vs. starting batteries

There are two main distinctions between types of batteries, each appropriately named for the situations when they are most useful: starting batteries and deep cycle batteries. Starting batteries are used for turning on appliances, such as lighting or a car’s ignition. These types of batteries provide a very large amount of power over a very short period of time to get an appliance (or car) up and running.

Deep cycle batteries, on the other hand, produce a smaller amount of energy but are able to do so for a very long period of time. The nomenclature of deep cycle batteries comes from the fact that they are designed to be discharged as fully as possible each time they are used, a “deep-cycle” of the battery. Whereas discharging a starting battery fully can decrease the lifetime of the battery, discharging a deep-cycle battery fully is exactly the battery’s intended purpose.

Best applications for deep cycle batteries

The nature of deep cycle batteries is to provide a consistent source of energy over a prolonged period and to be frequently fully charged and discharged. As a result, that makes deep cycle batteries ideal for pairing with renewable energy resources and home energy storage applications. In particular, deep cycle batteries are a perfect complement for solar energy. While the sun is shining during the day, deep cycle batteries can store generation from your solar panels. When the sun goes down, you can use the electricity stored in the battery to power devices in your home. And then, when the sun comes up the next morning, your partially- or fully-emptied battery will be ready be charged anew by the electricity generated by your solar panels.

As opposed to starting batteries, which are meant to never be discharged fully and are only intended to provide an initial kick-start of power for other systems, deep cycle batteries are ideal for home energy storage purposes. For the most part, home energy storage systems must be capable of providing a steady amount of electricity over a period of several hours – exactly the service provided by deep cycle batteries.

Choosing the right deep cycle solar battery

If you are considering a solar plus storage system or already have solar and are looking to add energy storage, a deep cycle solar battery is the way to go. In fact, all of the major brands offering solar batteries on the market are currently offering deep cycle solar batteries. Depending upon your electricity consumption habits, there are a number of different batteries that can meet your needs. To get started, you can register for the EnergySage Marketplace to receive free solar (and storage!) quotes from local solar companies.

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About Spencer Fields

Spencer is the Manager of Market Strategy & Intelligence at EnergySage, where he's able to showcase his expertise around all things energy. Prior to joining EnergySage, he spent five years at Synapse Energy Economics, providing environmental, economic and policy analysis for public interest groups. Spencer has degrees in Environmental Studies and Hispanic Studies from Brown University, meaning when he's not in the office you can find him outside or traveling somewhere to work on his Spanish.

3 thoughts on “Deep cycle batteries overview: what you need to know

  1. Gener Alcoreza

    We have a solar feasibility in an island I the Philippines that require at least 1megawatg of electricity. what would be the ideal battery package required to run a solar plant that size.

  2. Thomas Isensee

    Please send me a sales brochure on these magic deep cycle batterys that can take a full discharge, and I’l buy some.

  3. Jon Eisenberg

    Is this quite correct? We use deep cycle batteries in our RV. They start fully charged at 12.8V. We are advised not to discharge them below 12.0V to avoid damaging the batteries. We could certainly run them down to 11.5 or 11.0, but we are advised this will greatly shorten the battery life. If have a chart that is commonly used if you would care to see it. And jus to confirm, these are deep cycle batteries not starting batteries. They run lights, fans, refrigerator, furnace, etc. Thank you.


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