What is a Deep Cycle Battery?

What is a deep cycle battery? The answer to this question isn’t strange to those who own boats and recreational vehicles (RVs). These types of batteries are also popular in large solar power systems (where a battery stores up power from the sun during the day for use at night), golf carts and also can be used for kayaks as trolling motor batteries.

Deep cycle batteries are also common in emergency power systems. You can utilize them instead of gasoline-powered generators. Buying an inverter and powering it from one or more deep cycle batteries can save you during outages.

So, what is a deep cycle battery? It is the type that’s designed to discharge small amounts of current over a long period of time. The name of the battery suggests the cycle of its constant use, draining, and recharging for the main power source. This is opposed to those batteries that are secondary sources of current such as the ones often used for back up purposes.

What are the Different Types of Batteries?

Lead acid batteries come in two types: starter and deep cycle. With its greater plate count, the starting or SLI (starting lights ignition) battery can deliver quick bursts of current. Its plates are thinner and of a different material composition from that of deep cycle batteries.

The deep cycle battery provides less instant current but delivers it over a longer period of time. These types of batteries can survive many discharge cycles, thanks to their thicker plates. For this purpose, you should never use a starter battery for deep cycle applications since the thinner plates are susceptible to pitting and warping on their discharge.

Lead acid batteries come in various versions. They include:

Wet Cell or Flooded Batteries

 These are the most popular and affordable option. Their name refers to the flooding of the batteries’ cells and plates in electrolyte fluid (usually a mixture of water and sulfuric acid). If you overcharge the battery frequently, its electrolyte level falls. Topping off with distilled water on a regular basis avoids exposure of cells and plates, which may lead to damage to the product and shortening of its lifespan. Although they are the cheapest of all lead acid battery versions, wet cells have more disadvantages such as high susceptibility to vibrations and spillage.

Absorbed Glass Mat (AGM) Batteries

 The construction of AGM batteries allows the suspension of the electrolyte in close proximity with the active material of the plates. This enhances the efficiency of discharging and recharging. These batteries offer the best and most versatile options when it comes to applications like marine, RV, power sports, audio, solar, standby power, among others. An AGM battery holds its charge better as compared to other types if you’re not using or operating your equipment on a daily basis. These batteries are also sealed, making them maintenance-free. Moreover, they’re spillproof, less susceptible to vibration, and lighter.

Gel Cells

 These are quite similar in style to AGM batteries in that there’s a suspension of the electrolyte. However, the gel cell’s electrolyte has silica additive instead of a fluid. The recharge voltage on gel cells is lower than that of the other versions of lead acid batteries. Unfortunately, this type of battery is probably the most sensitive when it comes to over-voltage charging. That’s why you need to use the right charger. Otherwise, you’ll experience poor performance and short lifespan. It’s best to use gel batteries in very deep cycle application. Their advantage is that they can last longer in hot weather conditions.

AGM batteries and gel cells are specialty products that usually cost twice as much as premium wet cells. However, they have the advantage of storing well and lack the tendency of sulfating or degrading as easily as their cheaper counterparts.

Gel cells and AGM batteries are the safest versions of lead acid batteries on the market since they do not corrode or cause hydrogen gas explosion easily. The only requirement is that you’ll have to use special charging rates to keep them functioning optimally for many years to come.

What Makes a Deep Cycle Battery Different to a Starter Battery?

Although large and heavy car batteries are more popular with consumers, in a real sense, there are two battery types that fit this description. They include deep cycle and starter options. Even though they have similarities in their appearance and weight, they’re different in their way of discharging current.


The design of a deep cycle battery ensures the provision of a steady amount of current for an extended period of time. It can also provide surge as required but not as much as that of starter batteries. With its thicker plates, you can deeply discharge a deep cycle battery over and over again without causing damage. This isn’t possible with starter batteries.

A starter battery is designed to provide large amounts of current but for a short period of time. For instance, car batteries release a big surge of power to start the engine. After starting, the alternator provides all the power that the vehicle needs. To provide large amounts of current, starter batteries use thin plates to increase their surface area.

Draining Capacity

It’s possible for a starter battery to last all its life without the load ever discharging 20% of the battery’s total capacity. If you use it the right way, it can last longer. Contrarily, the proper utilization of a deep cycle battery involves constantly draining it below 50% of its total capacity. For it to last long, you’ll also need to recharge it after every use.

Reserve Capacity

Typically, a car battery has two ratings:

Cold Cranking Amps (CCA), which is the number of amps the battery can deliver at 0 degrees Celsius (32 degrees Fahrenheit) for 30 seconds and not fall below 7.2V. This measurement is especially important for starter batteries as well as in cold weather.

Reserve Capacity, which is the number of minutes a fully charged battery can produce 25 amps at 80 degrees Fahrenheit while maintaining its voltage above 10.5V

Typically, deep cycle batteries have two or three times the car batteries’ RCs but deliver a half or three-quarters the CCAs. Moreover, they can withstand hundreds of discharge/recharge cycles. Car batteries, on the other hand, aren’t designed for total discharge.


I hope that my article helped you understand the purpose and workings of the deep cycle battery. See you on the water!