What Are Deep Cycle Batteries?

If you are like most people, you probably do not give much thought to the batteries that provide power to the equipment and devices you use on a daily basis. For instance, you have probably not considered how the batteries for your key fob differ from one that is used to give energy to an all-terrain vehicle. You also not may not know the answer to the question, "What is a deep cycle battery?"

A simple fact is that all batteries store energy that can then be transferred into the power needed by the devices we use. However, the different types of batteries available to you can differ greatly in the ways they work, so it is important to understand why some batteries are more important for certain applications than others.

What Is a Deep Cycle Battery?

Deep cycle batteries will oftentimes look like a car battery to people who are unfamiliar with them. However, the two battery types are pretty different. Deep cycle batteries are lead batteries specifically designed to provide long-term energy to the objects powered by the battery. These types of batteries are rechargeable and will usually operate effectively until 80% of the energy they have stored is depleted. The deep cycle battery gets its name from the extra-thick plates it possesses that allow it to endure more discharge cycles than other types of batteries.

Deep Cycle Battery Uses

The sustained energy provided by deep cycle batteries is perfect for applications that favor a long-term energy supply over a battery that provides a quick start. If you are a boat owner, it is likely you use a deep cycle battery to power your craft. Many consider it to be the best boat battery. Other deep cycle battery uses include:

  • Golf carts
  • Forklifts (and other vehicles used in material handling)
  • Recreational vehicles
  • Marine applications
  • Renewable energy (made available off-grid)

Hybrid batteries are sometimes used and are most popular for marine applications. Hybrid batteries provide sustained power that is the norm for deep cycle batteries but also deliver the added benefit of a starter burst. However, hybrid batteries will not last as long as a deep life battery specifically designed for longevity in most cases. Let’s look at the most commonly used deep cycle batteries: the flooded and deep valve battery types.

Flooded Deep Cycle Batteries

The first type of deep cycle battery is a flooded deep cycle battery. These are not very different from the standard lead-acid car batteries. This battery is currently referred to as a “wet-cell” battery and is the oldest and most commonly used deep cycle battery type.

Flooded batteries will require more maintenance than other battery types due to the liquid contained within the batteries. Flooded deep cycle battery owners will need to refill the battery’s liquid container with distilled water when the electrolyte levels inside the battery are low.

  • Advantages: Flooded deep cycle batteries are cheap to purchase and are designed in a way that makes their use and repair relatively simple. The flooded battery type also provides a huge energy surge that can be applied to a wide variety of uses.
  • Disadvantages: The unsealed battery case will allow electrolytes to leak out if care is not taken. The propensity for leakage also means that extra precaution is needed whenever a flooded deep cycle battery is transported in a vehicle. The trade-off for the high energy surge possessed by the battery is low energy density. Remember to position your battery in a well-ventilated place when charging to compensate for the hydrogen that will be released.

Valve Regulated Deep Cycle Batteries

The next answer to the question “what is a deep cycle battery?” is the valve regulated deep cycle battery. This is also commonly referred to as a sealed lead-acid battery and does not possess the need to be watered. Sealed batteries do not require the maintenance that is necessary with other types of batteries but should still be routinely monitored.

The “recombinant” feature of the battery signifies that both oxygen and hydrogen are present within the battery. The valve possessed by this deep cycle battery type is activated when the high voltage is used to recharge the battery. When the valve is activated, materials inside the battery make an exit and the battery capacity is decreased. The two types of valve regulated deep cycle batteries available are the AGM and gel varieties.

How to Charge a Deep Cycle Battery Properly

Individuals searching for information on how to charge a boat battery should first understand the need to ensure the battery is dust- and corrosion-free. You should also make sure the battery charger you buy is capable of providing the amperage your deep cycle battery needs in a time frame that is acceptable. A charger that is not well-suited for your battery will not provide you with an adequate charge for your boat battery and may do damage to it.

Ratings for Deep Cycle Batteries

One common rating that will help consumers decide the best boat battery for them is “amp hours.” This rating informs battery users of how much amperage is available to them during one complete hour of battery usage. Amp hours for deep cycle batteries measure the capacity for the chemical energy that exists within the battery to be converted to electrical energy. An amp hour rating will also provide users with a measure of how much battery usage they can enjoy before a recharge is necessary.

Life Span of Deep Cycle Batteries

It is important to understand that many manufacturers choose to measure the life span of their batteries by cycles and not solely in calendar years. A cycle represents a single and complete discharge of a battery. The manner in which your battery is used, charged, and maintained will affect the amount of use you enjoy per cycle.

When performing your calculations, you should remember that it is never a good idea to allow a 100% discharge of your deep cycle battery as you will have an even greater need to know how to charge a boat battery. The specific life span you can expect will be ultimately determined by your usage habits and other factors particular to your unique situation. However, you can ensure you enjoy maximum possible battery life by properly maintaining your battery. You should provide water as needed and adhere to the recommendation that your battery is never discharged by more than 50%.

You should also use a charging system that is appropriate for your battery. A deep cycle battery is designed to provide a steady supply of energy over an extended period of time. If you need help selecting the correct deep cycle battery for your best boat battery, you can end your search at your local AutoZone.

Advice, how-to guides, and car care information featured on and AutoZone Advice & How-To’s are presented as helpful resources for general maintenance and automotive repairs from a general perspective only and should be used at your own risk. Information is accurate and true to the best of AutoZone’s knowledge, however, there may be omissions, errors or mistakes.

Be sure to consult your owner’s manual, a repair guide, an AutoZoner at a store near you, or a licensed, professional mechanic for vehicle-specific repair information. Refer to the service manual for specific diagnostic, repair and tool information for your particular vehicle. Always chock your wheels prior to lifting a vehicle. Always disconnect the negative battery cable before servicing an electrical application on the vehicle to protect its electrical circuits in the event that a wire is accidentally pierced or grounded. Use caution when working with automotive batteries. Sulfuric acid is caustic and can burn clothing and skin or cause blindness. Always wear gloves and safety glasses and other personal protection equipment, and work in a well-ventilated area. Should electrolyte get on your body or clothing, neutralize it immediately with a solution of baking soda and water. Do not wear ties or loose clothing when working on your vehicle.

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