Deep Cycle Batteries 101: Types, Uses & Maintenance Tips

By Steve George

December 16, 2020Blog Electronics

Batteries are the most important invention powering our modern lives. Just think about it. The concept of capturing lightning in a bottle and then using it to for your electrical needs has been developed to the point where now you have over dozens of types and sizes of batteries. From your everyday AA battery to your phone and car batteries, all the way to the deep cycle battery, the designs vary and serve their own unique purposes and applications. And as Metallica said in the opening track of their legendary Master of Puppets album, “Battery is here to stay”.

How Do Batteries Work?

picture of batteries and black background
source: Image by StockSnap from Pixabay

A battery consists of two types of metals suspended in an electrolytic environment which can be a liquid, gel or solid compound material. Such configuration of matter produces a galvanic effect where electrons from one metal, travel to the other metal via the electrolytic catalyzer that’s most often than not a strong acidic material. Due to the chemical energy of the acid, and the physical properties of the anode and cathode, an electric current is produced that can later be used for various application.

Some of the most powerful batteries available today are deep cycle batteries. And now that we know what the basic principles of battery power are, let’s get to the nitty-gritty of today’s topic, the deep cycle battery: what it is, what it can do and tips on what you can do to prolong its lifespan.

What Is a Deep Cycle Battery?

picture of Deep Cycle Battery and it usage

A deep cycle battery is a battery designed to produce a long continuous stream of current for an extended period of time before having to be recharged. Basically, it’s a portable power source designed for off the grid applications such as solar power systems. Unlike car batteries that provide a short powerful burst of current but cannot maintain that output for a long period of time, deep cycle batteries can hold that output for hours on end.

Normal batteries usually can discharge up to 5-10% of their charge before needing to be changed or recharged. Deep cycle batteries on the other hand can discharge up to 80% of their full capacity before needing to be recharged, though most manufacturers wouldn’t recommend going past 50%. Just to illustrate what this means for those of us who don’t want to think about percentages:

Say you have a 240Ah battery. This translates to 24 hours worth of 2 amp current that’s usually needed for most appliances, but with the manufacturer recommendations in mind, you get a continuous 2A current for 12 whole hours on a single charge. Not bad at all. Now let’s take a look at the different types of deep cycle batteries.

Types of Deep Cycle Batteries & Their Application

picture with type of deep cycle batteries

Depending on the type of electrolyte suspension, deep cycle batteries can be AGM, flooded, gelled or AGM batteries. Let’s examine their main features and applications.

AGM (Absorbent Glass Mat)

An AGM deep cycle battery contains a special glass mat separator that binds the electrolyte solution between the battery plates which enables the fiberglass to be saturated with electrolyte. As the battery works, the electrolyte is transferred from the glass mat to the battery plates and the current flows continuously.

Due to the fact that liquid is not supposed to be added or watered down, the AGM deep cycle battery is relatively maintenance-free. As long as the battery is continuously charged and not discharged past 50%, its lifespan can range from 4 to 8 years. It also has a very low discharge rate of 1-3%. However, this depends on the weather conditions. But as long as the battery is kept at temperatures no higher than 20oC, you’re golden. Because of this, there are many reasons one would want to purchase an AGM deep cycle battery.

This type of battery is usually used for off-grid solar power systems. A set-up of AGM batteries can store a significant amount of solar power produced by the panels, allowing you to use it after the sun has gone down. So whether you have a shack in the outback, or want to travel the country in a solar-powered RV , the AGM solar battery has got you covered.

Other uses include powering small electric vehicles such as golf carts, forklifts and ATVs that require a steady and continuous flow of power for extended periods of time.

They can cost more than the other types of deep cycle batteries, but their maintenance-free status and durability make them well worth the price.


A flooded deep cycle battery is probably the more “traditional” type of battery, where its insides contain a combination of liquid electrolyte between the plates. Unlike the AGM battery, the flooded kind needs to be inspected and maintained regularly. Similarly to its AGM counterpart, the flooded deep cycle battery requires regular charging and its limit should also not be exceeded for a longer lifespan.

Due to the liquid being in free flow, it’s recommended not to expose the liquid battery to turbulence and movement, for it can damage the material or cause it to leak its electrolytes. This makes it suitable for power storage in electric and utility grids, where they are mostly stationary and aren’t moved often.


The gelled deep cycle battery is sort of a hybrid between the two, where instead of a free-flowing liquid, a high viscous electrolyte gel is placed between the electric plates. Though this makes them virtually spill-proof, due to gel physics, it has to be charged at a lower voltage and for a lot longer in order to prevent bubbles manifestation that severely reduces the battery’s capacity. These batteries are rarely used or sold anymore due to the AGM having a lot more advantages and none of the gel battery’s disadvantages.

Tips for Prolonging the Lifespan of Deep Cycle Batteries

picture of a battery charger for prolongating the lifespan

Now, let’s get down to maintenance. Similar to how you would take care of an AA battery , the deep cycle batteries require some love too. We’ll narrow it down to the following tips:

  • Charge your battery regularly to keep the battery alive for longer;
  • Use smart chargers to prevent wasting power and overcharging the battery;
  • Use temperature-compensated charging to charge your battery optimally according to the temperature around;
  • Use the right type of voltage to prevent damage to the electrolyte solution;
  • Avoid charging the battery in voltage dipping sockets;
  • Keep your battery in a cool and dry environment for optimal life.