Deep Cycle Battery

Before we dive into what is a deep cycle battery, we need to understand a few basic knowledge of battery for what a cycle is, what depth of discharge means, and what is real meaning to the deep discharge of batteries.

One full cycle is considered to be a complete discharge and recharge of a battery. What is a complete discharge? Discharge is measured by the capacity consumed from the battery, the depth of the discharge (DOD) is used to indicate how much of the battery capacity has been used during a single discharge. A complete discharge is 100% DOD.

DOD is the depth of discharge, it is inversely related to the state of charge (SOC), which is the amount of charge that remains in the battery so 100% DOD = 0% SOC.

With this understanding of DOD and battery cycles, you might be wondering what a truly deep discharge is. Deep discharge is classified as 80% - 100% of the capacity discharged from lithium batteries.

What is a Deep Cycle Battery?

Deep cycle batteries probably look like car batteries to those people who are not familiar with them, but in reality, they are quite different. Deep cycle batteries are designed to provide sustained power over a long period and run reliably until it is 80% - 100% discharged, at which point they need to be recharged. However, it is important to note that when batteries are discharged at 100% (DOD), batteries' cycles will be around 2000 times, and at 80% DOD the cycles of batteries will be about 5000 times.

Types of Deep Cycle Battery

In SLA (sealed lead acid) batteries, electricity is created in the plates. In high-rate batteries, there are many thin plates to allow a larger surface area to generate power energy quickly. In deep-cycle batteries, the plates are thicker than those inside high-rate batteries because the energy-induced chemical reactions go into the plates and therefore they need to be thick enough to be able to handle the reaction. if the electrode plates were thin, as in high-rate and starter batteries, the lead electrode plates would degrade very quickly and would not withstand multiple deep discharges over time.

Deep cycle SLA batteries are divided into two subcategories, which are gel deep cycle and AGM (absorbent glass mat)deep cycle. The gel battery uses a substance that converts the electrolyte acid inside the battery into a thick gel, therefore, making it non-spillable. The gel is better than the AGM in heat distribution and off-gassing, and therefore the gel has a better performance throughout its lifespan. in an AGM battery, the glass pad is placed between the negative and the positive plates to keep the electrolyte in place. The mat keeps the battery from spilling and optimizes the surface area of the plates to distribute the electrolyte better than conventional batteries.

In lithium deep cycle batteries, energy cells are used. Energy cells are designed to provide continuous current over long periods of time, making them ideal for use in cycling and deep cycle applications. in addition to the cell pack makeup inside a lithium battery, the circuitry is also important because the protections may set limits to how much current can be drawn from the battery. Different lithium batteries probably have different levels of protection, so make sure to check the technical documentation and specifications for further information before you use batteries.

Besides different types of chemistries, deep cycle batteries can come in a variety of voltages and capacities, for example, the most popular voltages are 12-volt lithium deep cycle batteries and 24-volt lithium deep cycle batteries.

Deep Cycle Battery Applications

Before selecting a battery, you will need to have a clear idea of what devices the battery needs to power, for how long, how often, and how much power it needs. Generally, the deep cycle battery is a cyclic application where the user can use the battery when needed.

For example, a medical cart used in a hospital will be kept away from an electrical outlet and need battery power for the entire time it is unplugged. In this case, the nurse or doctor will start to use batteries when they will be used by turning on the medical cart. And they will be used every single day for many hours each day. Batteries need to provide continuous and steady power for long periods of time, which means this is a deep discharge use and therefore needs a deep cycle battery.

Another example of a deep cycle battery is the battery inside the cell phone. This battery is depending on the age, let's get an assuming to this battery can last all day on a single charge and be used every day. You tell when the battery is time to be used by turning on the phone or unplugging it from the charger. If you are like most users, you can wait until your phone is completely dead before plugging it in - the DOD is 100 %/SOC is 0%. You are expecting this battery to provide continuous power all day long, so a deep-cycle battery must be used.

There are many other applications that utilize deep cycle battery technology, such as include marine boats, RVs, leisure mobility scooters, all types of electric vehicles, and solar applications.

To differentiate, high-rate batteries are typically used in backup or emergency-use type applications. This would be an application where a battery sits in the elevator, and waits to provide backup power in the event of a power outage. Such batteries will need to deliver large amounts of energy very quickly in an emergency. Those batteries may even need to be replaced before use. Think of high-rate batteries as your power insurance policy, delivering a lot of power all at once in an emergency, whereas deep cycle batteries are going to be your workhorse, delivering steady power very frequently as often as full discharge cycles daily.

How Long Will Deep Cycle Batteries Last?

One of the main differences between lead acid batteries and lithium deep cycle batteries is the cyclic performance. With lithium deep cycle batteries the capacity is independent of the discharge rate, this means in deep cycling applications where the discharge rate is often greater than 0.1C, a 100Ah capacity-rated lithium battery will often outperform the equivalent 100Ah lead acid battery.

When it comes to measuring how long deep cycle batteries will last the correct way is in cycles rather than time. Lead acid batteries can give 200 cycles (based on 100% capacity to 50% DOD ) whereas deep cycle lithium batteries can achieve over 10 - 20 times the amount at 2000 - 5000 cycles ( lithium batteries: >2000 cycles at 100%DOD, UP TO 5000 cycles at 80% DOD).

How to Charge Deep Cycle Batteries

If you want to maximize the life and performance of your deep-cycle batteries, it is essential to charge them in the correct way. Charging your battery in the correct way with the right type of charger depends on batteries chemistry, voltage, and capacity. You can also use other types of chargers, which have a lithium option.

Additionally, the wrong operation for lithium batteries will also lead to damage or shortening their life. So you need to understand them before use.

Conclusion

The deep cycle battery is this battery that is designed to produce continuous and steady power output over an extended period of time, discharging the battery significantly, at which point it must be recharged to complete the cycle. By contrast, a regular car battery is designed to provide a momentary burst of energy (starting battery), typically enough to get your car started, before handing off power production to the alternator. In this case, the starting battery is not designed to be deep cycle because it should be kept fully charged at all times.