Flooded vs. Sealed Deep Cycle Battery: What’s the Difference?

Terminals plus of the old battery. Charging car battery with electric current.

Do you own a boat, golf cart, motorcycle, or recreational vehicle?

If you do, you’ve probably bought some batteries, had them installed and never looked at them again. This is a common mistake many vehicle owners make because some batteries require more than just scraping corrosion off of the battery terminals. 

Most people who own a deep cycle battery buy either flooded batteries or sealed deep cycle. 

The problem?

Most people don’t know the difference between the two. If you’ve ever pondered the differences between the two, then this article is for you. Below, we will show you the main differences between flooded batteries and sealed deep cycle batteries.

What Is a Deep Cycle Battery?

A deep cycle battery is a lead-acid battery that is used to provide power for different applications such as boats, solar energy, and RV’s to name a few. They are designed to sustain power over long periods of time and can reliably run even when discharged between 60 and 80 percent. 

It is important to note that most manufacturers recommend not discharging deep-cycle batteries more than 50 percent. This will extend the life of your deep cycle battery.

The difference between your car battery, also known as a starter battery, and a deep cycle battery is that a starter battery provides short bursts of energy to start an engine compared to a deep cycle battery where its primary use is to provide continuous power over long periods.

Using a starter battery would not be ideal to power the vehicle’s electrical systems for very long if the car is not running. If there’s a significant load running and the engine is turned off, the battery can be discharged within minutes.

What Is a Flooded Battery?

A flooded deep cycle battery is a battery that has thick plates, large separators, and high-density paste material. This design resists the occurrence of corrosion from multiple charges and discharge cycles.

This battery type uses electrolyte fluid that completely submerges the plates. This fluid allows the battery to charge more efficiently and discharge at a steady rate. 

Does a Flooded Deep Cycle Battery Require Maintenance?

Yes. Like any other battery, you want to check for any corrosion at the contact terminals and any other signs of deformity to the battery. Such signs are bubbling from the top of the cell or any signs of burning. 

If you see any of these symptoms, discontinue use and take it to a shop that works explicitly on batteries or replace the unit.

Specifically for flooded batteries, you want to make sure that the electrolyte level is where it should be. On every flooded battery, you will find one to three covers where the electrolyte fluid goes. 

Some fluid will evaporate over time during the charge/discharge process. To check this, take the cover off of the cells and check the water level. If the water level is low, pour distilled water into the cell reservoirs until the water reaches the fill level.

An important tip is to only refill water levels when charging is complete. If you add water before or during an incomplete charge, this can cause the gases to expand and potentially damage the charging process. Although the maintenance process may seem like a lot, flooded batteries tend to last longer than sealed batteries.

Advantages of flooded deep cycle batteries include:

  • Inexpensive
  • Easy to troubleshoot
  • Lasts longer than sealed batteries

What Is a Sealed Deep Cycle Battery?

A sealed deep cycle battery is also known as a VRLA maintenance-free battery. It is nearly identical to a flooded battery—the only difference is the electrolyte fluid is sealed into the battery. This is why they call it maintenance-free because you don’t have to maintain the electrolyte level manually.

One of the main benefits of sealed deep cycle batteries is that they don’t need to be upright and can be placed in different orientations. This would be ideal for boats or recreational vehicles that shake or move quite a bit.

Advantages of sealed deep cycle batteries include:

  • Lighter
  • Charges faster
  • No regular maintenance is required
  • Can be positioned in any orientation
  • Does not require a “dangerous goods” label when shipped
  • Smaller than a flooded lead-acid deep cycle battery
  • Better for extreme temperatures

Types of Sealed Deep Cycle Batteries

AGM – Absorbed glass mat (AGM) are sealed batteries that use woven glass fiber separators. The electrolyte in the battery is suspended within a close distance to the active plates. This provides excellent charge and discharges efficiency.

GEL Batteries – This type is similar to AGM but is still considered to be a wet cell battery. Gel cell batteries are best used in high deep cycle applications such as off-grid living and solar.

Which Deep Cycle Battery Is Right For Me?

In the end, deep cycle batteries may be right for one person’s needs, but not the other. Ask yourself these questions—what am I using these batteries for? What is my budget? Do I have time to maintain them regularly? Use the advice below to choose the battery that is right for you.

Choose a flooded deep cycle battery when:

  • Use in extreme temperatures are not an issue
  • You have time to maintain the batteries regularly
  • You are looking for a cost-effective battery
  • You have a well-ventilated area to store the batteries
  • You want longer-lasting battery performance
  • You want to be able to troubleshoot your battery manually

Choose a sealed deep cycle battery when:

  • You prefer to go maintenance-free
  • You need a battery that can be positioned in different orientations
  • Budget is not an issue
  • You are using the battery in extreme temperatures, hot or cold
  • You want a fast-charging battery

Here at RB Battery, we have the knowledge to answer all of your battery related questions. If you need help deciding which battery is right for your application, feel free to contact us, and we would be happy to help you out. 

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