Deep-Cycle Battery 101: What is a Deep-Cycle Battery?

When looking for batteries for solar and renewable energy applications, or just batteries for recreational and practical uses that can power recreational vehicles, wheelchairs, CPAP machines, boats, and more, chances are, you need a deep-cycle battery. What sets the deep-cycle battery apart from the other types is its ability to be cycled repeatedly while providing a consistent rate of power over extended periods.

A deep-cycle battery is a kind of lead-acid battery that is designed for continuous power, and it can be deeply discharged. The lead-acid battery was invented in the 19th century when the need for high surge currents arose. Most traditional batteries have fluctuation issues, and lead acid batteries are able to provide a steady current. These batteries are also more durable and are considered to be the best option for long-term use because of the active materials and the fact that the lead plates are much thicker.

A Comparison of a Deep-Cycle Battery versus Marine Battery

Starting batteries are mainly used for starting and running engines. These batteries call for a huge starting current that comes in a short burst. Made with many thin plates for maximum surface area, the batteries are made from a lead material that is similar to a fine foam sponge. This material does not make the starting battery a good choice for deep-cycling because this sponge-like lead material will be consumed quickly and fall to the bottom of the cells. Some automotive batteries are starting batteries and these will usually fail after 30-150 deep cycles.

Deep-cycle batteries are made with much thicker plates than Starting batteries, and these can handle being repeatedly discharged down to as much as 80%. What greatly differs in the deep-cycle battery is the fact that its plates are made from solid lead, which gives it a smaller surface area. Because of this surface area, it does not give the same strong surge of power that starting batteries are capable of. Although the deep-cycle battery can be discharged down to 20%, it is best to keep the average cycle at around 50% for the best lifespan to cost ratio.

Marine batteries are a combination of starting and Deep-cycle batteries, although a few marine batteries are considered to be true deep-cycle. In this hybrid battery, the material of the plate may be composed of a coarser and heavier lead sponge.

The Benefits of Using Deep-Cycle Batteries

Choosing a deep-cycle battery over a traditional battery is a good decision, especially if you are in need of the type of power deep-cycle batteries provide. Deep-cycle batteries have longer running times and can be used for long periods even if they are only charged once. They are ideal for extensive use because they have a high-energy storage capacity and a slow discharge rate, saving you from having to charge them often. The deep-cycle battery is more durable because of its thick plates, giving it a longer shelf life than traditional batteries. Best of all, this type of battery gives a steady and stable flow of power compared to traditional batteries, which often fluctuate.

Which deep-cycle battery is best suited to my needs?

Not all deep-cycle batteries are the same, and no single design of battery is suitable for all applications. When determining which type of battery you need, it is good to know which application the battery is going to be used for.

There are two primary categories of batteries available: Flooded and Valve-Regulated Lead-Acid (VRLA) which is subdivided into two types, Absorbed Glass Mat (AGM) Batteries and Gel Batteries.

VRLA vs. Flooded

In installations with difficult accessibility and limited space, VRLA batteries are preferred. They have good flexibility in positioning because of their sealed and leak-proof design. The VRLA battery is subdivided further into AGM and Gel categories. Gel batteries have the upper hand in terms of recovery from deep-discharge because they have more electrolytes and are less prone to stratification than AGM and flooded types. The Gel batteries have a lower high-rate charge and discharge capacity because they have a higher resistivity than the fluid electrolyte.

Flooded batteries are well-known for their reliability, long lifespan, and affordability. Usually made from thick antimony alloy grids, they are suited for a long cycle life compared to the calcium alloy grids used in VRLA batteries. Because they have more electrolyte than VRLA batteries, they have a good deep discharge recovery which acts as a heat sink to help keep them cool. Flooded types need regular maintenance with water, and automatic watering systems exist to increase reliability and reduce labor cost.

VRLA batteries are not optimized for recurrent deep discharging because they were mainly developed for standby power applications that require little cycling.  When choosing between Gel and AGM batteries, the temperature is also a factor to consider because the capacity of gel batteries is reduced at lower temperatures.

The Lifespan of Deep-Cycle Batteries

The lifespan of a deep-cycle battery is largely determined by its usage, maintenance, charging, temperature, and other factors. In extreme cases, batteries like the AGM battery can have a very short lifespan due to severe overcharging. In one day, a Gel battery can be killed when overcharged with an incompatible charger. Some golf cart batteries are destroyed from lack of usage when stored in hot conditions without being charged.

It is hard to give a fixed number for the usual lifespan expectations of batteries that are used in deep-cycle service because of the many factors that affect its lifespan. Starting batteries can last a minimum of 3 months to 1 year. Marine batteries can last for 1 to 6 years, AGM deep-cycle batteries last for 4 to 10 years, and Gel deep-cycle batteries have a lifespan of 2 to 7 years.

Charging Deep-Cycle Batteries

Correctly charging your deep-cycle batteries is important to maintain optimum performance and long life spans. Battery life and performance are commonly decreased because of faulty procedures and incompatible charging equipment. Choosing the suitable methods and charging circuit is as important as choosing the correct battery. To ensure maximum service life and performance, a constant voltage to current limited charging is recommended.

While charging, lead dioxide is converted from the lead sulfate of the positive plate. As the battery becomes fully charged, dioxide is generated from the positive plate, and this causes a rise in voltage because of the low internal resistance. The detection of this type of voltage increase and control of the current charge amount is enabled by a constant voltage charge.

If the battery is overcharged, it will heat up, thus accepting more current and causing it to heat up even more. This is referred to as thermal runaway, and it can destroy a battery in a matter of hours. When a low charge voltage is used, current flow will stop before the battery is even fully charged. Because of this, lead sulfate will be retained on the electrodes, thus reducing the capacity of the battery.

Sulfation can happen when the battery accepts far less current than what is normal. This usually happens when the battery is stored in a discharged state, or stored for a long period. If this happens, a good solution is to leave the battery connected to the charger. It is not a sure solution, but if it is successful, the battery will start accepting increasing amounts of current until the normal level is achieved.

Deep-Cycle Battery Technology: Cycles vs. Life

One full discharge and recharge is considered to be a battery cycle. The usual consideration for a cycle is to discharge from 100% to 20% then recharge back to 100%. The ratings for the depth of discharge cycles often differ, but the most common levels are 10%, 20%, and 50%. The depth of cycling the battery is directly related to the life of the battery. A battery that is discharged daily to 50% will last twice as long if it is cycled to 80% depth of discharge. If a battery is cycled at 10% depth of discharge, its life will be five times as long as a battery cycled to 50%. The best option for the depth of discharge is to discharge it to 50% regularly. This usually ensures a good and stable performance and long battery life.

Deep-Cycle Battery Maintenance Tips

  • Deep-cycle batteries should not be stored at high temperatures in a discharged state.
  • Repeated overcharging or undercharging is the greatest destroyer of lead-acid batteries. Chargers should be disconnected after cycle charging, and the float voltage should be at the correct setting at all times.
  • Batteries should be stored at 10 degrees Celsius or lower to prolong its shelf life without charging.
  • Ensure proper ventilation when charging or discharging a battery. Because of the mixture of gasses that are produced by batteries, a reaction can cause a spark that may result in an explosion.
  • It is not recommended to mix batteries that have different capacities, makes, or ages. The differences can cause some batteries to be overcharged, while some can remain undercharged.

Installation and Handling Guidelines

Here are some tips to ensure trouble-free usage of deep-cycle batteries:

  • Make sure to fasten the battery tightly and make allowances for shock absorption.
  • It is best to securely attach it at the lowest practicable point.
  • Do not attach the battery to any equipment during testing.
  • Avoid applying force to the unit terminals so as not to bend them.
  • If soldering the terminals is a necessity, it should be done within three seconds with a soldering iron that does not exceed 100 watts.
  • Avoid placing the battery near highly flammable objects and heat-emitting components.
  • Mixing one battery with another battery with a different capacity, age, or make is not recommended and can cause damage to the unit.
  • The ideal temperature range to optimize the battery’s performance and lifespan is to keep it within -40 degrees Celsius to 60 degrees Celsius
  • Disassembled batteries are hazardous, and contact with sulfuric acid is harmful. It is important to wear gloves when handling the battery.

Top Choices for a Deep-Cycle Battery

Unfortunately, to know whether the battery you are purchasing is a true deep-cycle battery or not, you would have to resort to cutting it in half to see the interior, and that is not a viable option. It is best to purchase a battery from well-known, trusted manufacturers. Here are some of the good choices and top-rated options for deep-cycle batteries:





   Vmaxtanks Vmaxslr125 AGM Deep Cycle Rechargeable Battery  $$$  4.6/5
   YellowTop Optima battery  $$  4.5/5
   Optima BlueTop high-performance AGM battery  $$  4.4/5
   Chrome Battery’s 35AH Deep Cycle SLA battery  $  4.0/5
   Mighty Max ML35-12  $  4.6/5
   ExpertPower 12v 33ah Rechargeable Deep Cycle Battery  $  4.3/5
 WindyNation 12V 100 Amp-Hour AGM SLA Deep Cycle VRLA Battery  $$  4.3/5
 Renogy Deep Cycle Pure Gel Battery 12V 100Ah  $$$ 4.8/5
 12V 35AH GEL Replacement Battery for Deep Cycle Solar  $ 5.0/5
 12V 55Ah AGM Deep Cycle Battery  $  5.0/5

Vmaxtanks Vmaxslr125 AGM Deep Cycle Battery


  • Voltage: 12 Volt
  • Amp Hours: 125Ah Group
  • Dimensions: : 12.9 inches (L) x 6.8 inches (W) x 8.7 inches (H)
  • Float service lifespan: 8 to 10 years
  • Designed for 99% recombination capabilities
  • Does not emit dangerous fumes or gasses.
  • Weight: 75 Lbs.
  • Reserved capacity: 260 minutes
  • Maximum Charging Voltage: 14.7V
  • Warranty: 12 Months
  • Plates are made from military-grade and custom alloys
  • Torqued terminal bolts for easy wiring and better conductivity

When looking for a high-performance deep cycle battery that is suitable for heavy duty applications, VMAX USA is a company that can meet your needs because they specialize in creating deep cycle batteries that stand out in the field. VMAXTANKS Vmaxslr125 AGM Deep Cycle provides unfailing power with the best value and minimum maintenance requirements.

Made with high quality and military-grade custom alloys and glass mats, this durable and reliable for heavy duty use. It is the best choice for use in renewable energy systems because of its short recharge time and slow discharge. It has a lifespan of 8-10 years, providing top-notch performance the whole time.

Optima Batteries 8171-767 YellowTop Prius Battery


  • Premium Starting And Deep Cycle Power
  • Resistant to Vibration
  • 100% Spill-proof and Maintenance-Free
  • Dimensions: 9.9 inches (L) x 5.1 inches (W) x 8.9 inches (H)
  • Weight: 26 pounds
  • Voltage 12 volts
  • Amperage: 38 A
  • Plate design: would cell configuration with Spiral Cell Technology
  • Post type: JIIS: 46B24R
  • 20-hour capacity: 38 Ah
  • Reserve capacity: 66 minutes
  • Open circuit voltage: 13.1 V
  • Case color: Light gray
  • Cover color: Optima Yellow
  • Case material: Polypropylene

Optima is a trusted battery manufacturer that ensures quality and consistency in their batteries. They also ensure that their manufacturing process upholds high and demanding standards. The company’s goal is to provide the ultimate power for the ultimate professionals, for the ultimate enthusiasts, and for the ultimate experience.

The Optima battery has a core of a series of individual spiral-wound cells that are made of 99.9% pure lead plates, precisely coated with lead oxide. The Spiral Cell Technology is a high-precision process that ensures that Optima’s superior batteries will be able to outperform other traditional batteries.

Optima YellowTop battery is a great choice for higher than average electrical loads. The Spiral Cell Technology ensures that it is power-packed and energy dense. The pure lead used in making this battery minimizes the contaminants in the material, guaranteeing a long life expectancy. The spiral winding also gives this battery a more efficient output.

Because of its AGM technology, it is 100% spill-proof and maintenance-free. Because of its rigid and sealed construction, the battery is able to withstand heavy vibrations and rough weather conditions. Optima’s Yellowtop battery can retain charges for long periods of time and can easily handle heavy loads of power.

Optima Batteries 8016-103 D34M BlueTop


  • 12 Volts of Power
  • 750 Cold Cranking Amps
  • 870 A cranking Amps
  • Size: 10 inches (L) x 6 7/8 inches (W) x 7 13/16 inches (H)
  • Weight: 43.5 pounds,
  • Stud Posts: Dual SAE, 5/16 inches tall, made from stainless steel
  • 55 Ah C20 capacity
  • Dual purpose: good for starting and powering
  • Suitable for multiple accessory loads
  • Optimal starting power even in bad weather conditions
  • Resistant to heavy vibrations
  • Maintenance-free operation
  • 100% spill proof
  • Highly flexible mounting options
  • Reserve capacity: 120 minutes
  • Full recharge time: 6 to 12 hours
  • Up to 3x more recharges than other marine batteries
  • The case is made from Polypropylene material, which is lightweight and weatherproof

The Optima BlueTop high-performance AGM battery is an extremely powerful dual-purpose marine battery. Using this battery in recreational vehicles or boats will ensure that you will have an exceptional running time. Created by Optima, which manufactures batteries to high and demanding standards, the battery guarantees that ultimate enthusiasts and professionals are given the ultimate power for the ultimate experience. This company aims to discover different possibilities for their batteries by studying technological advances.

The Optima BlueTop high-performance AGM battery is made with a SpiralCell technology which provides you with a strong, clean, reliable power source that is safe for people and the environment. The battery’s outstanding vibration resistance gives the BlueTop an efficient, faster recharge time. Ideal for those requiring a sure-starting, strong cranking, and maintenance free power source, Optima BlueTop provides better performance than most batteries in the same class.

Chrome Battery Deep Cycle SLA Battery


  • Dimensions: 7.68 inches (L) x 5.16 inches (W) x 7.13 inches (H)
  • Amperage: 25 AH
  • Max Discharge Current: 525A (5s)
  • Nominal Voltage: 12V
  • Internal Resistance- 0.0028 ohms
  • Weight: 23.50 Lbs.
  • Battery Life Stand By Time: 3 – 5 Years
  • Color: Black
  • Repeated recharging
  • Perfect for use in electric scooters, wheelchairs, emergency lighting, snowmobiles, watercraft, alarm systems, UPS systems, etc.
  • Thick plates and robust design
  • Consistent power for long durations
  • Deep discharging
  • Leak-proof and sealed construction
  • Maintenance-free
  • 60-Day No Questions Asked Money-Back Guarantee’
  • 18-month warranty

Chrome Battery’s 35AH Deep Cycle SLA battery is a great choice for those looking to power their ATVs, snowmobiles, electric scooters, emergency lighting, alarm systems, and even wheelchairs. This battery can go for long periods of time on a single charge because of the solar powered systems durability. It has the highest powerful amp hour capacity and also the longest life-cycle.

The 35AH Deep Cycle SLA battery is maintenance-free, spill-proof, and leak-proof because of its lead calcium alloy construction and glass mat technology. This type of construction and material also helps extend the durability of the battery by making it resistant to heavy vibrations and the roughest conditions. Chrome Battery’s 35AH Deep Cycle SLA battery is sure to satisfy your needs for a reliable and top-quality power source because it is manufactured with high-quality materials and meticulously tested for safety, OEM compatibility, and optimal performance.

Mighty Max ML35-12 Deep Cycle AGM Solar Battery


  • Voltage: 12 Volts
  • Amperage: 35 AH
  • Battery Dimensions: 7.68 inches (L) x 5.16 inches (W) x 7.13 inches (H)
  • Chemistry: SLA, AGM
  • Weight: 23.15 Lbs.
  • Rechargeable
  • Long-lasting high performance in extreme situations
  • Maintenance-free
  • Spill-proof design
  • Thicker plates for a deeper discharge than other batteries
  • Better resistance to corrosion, compared to non-deep-cycle batteries
  • 1 Year Warranty

Because of its state-of-the-art heavy-duty calcium-alloy grid, Mighty Max ML35-12 has exceptional power, performance, and service life in both float and cyclic applications. Considered to have Absorbent Glass Mat technology, the fiberglass mat separators make sure that electrolyte distribution is equally spread on the charged plate surfaces. Because of its valve-regulated design, the Mighty Max ML35-12 is leak-proof and maintenance free. Since it is leak-proof, it enables a wide range of flexibility when mounting.

The high-quality make of Mighty Max ML35-12 gives it a long service life, high discharge rate, wide operating temperatures, and deep discharge recover, making it suitable for a wide range of applications in consumer electronics, electric vehicles, medical mobility, emergency lighting, solar power, and more.

The heavy-duty calcium-alloy grid ensures that the Mighty Max ML35-12 battery is provided with extraordinary power, performance and service life. The thicker plates allow a deeper discharge than other batteries, which means you don’t have to constantly worry about charging it often.

For its affordable price, the battery is one of the best AGM batteries found in the market. Even if it is under the hundred dollar price range, it is able to provide solar power storage while remaining very portable. Because of its portability, a whole range of possibilities opens up because it can be used to power various applications requiring maximum power.


One has to consider a lot of factors when choosing a deep-cycle battery. You have to really know why you are going to get one, and figure out what purpose the battery will serve. Deep-cycle batteries are a great deal because they have long running times so they can be used for extended periods on a single charge.

Because they have a large storage capacity and a slow discharge rate, they are ideal for extensive use. They are also extremely durable because of their sturdy construction and technology. The deep cycle battery’s best feature is that it is able to give a steady and stable source of energy.

Choosing the right kind of battery for your application can save you a lot of time and also keep unnecessary hassles at bay. It is important to know your needs and be aware of the many factors that were discussed in this article, and soon you will be able to purchase the best deep-cycle battery to suit your needs.