If you’ve been investigating batteries for your golf cart, marine vessel, or RV, you’ve probably run across the term “deep cycle” batteries. This term was traditionally used to designate the difference between a starter battery and a lead-acid battery.

But what is a deep cycle battery, and how is it different from the more advanced lithium batteries that have quickly become all the rage for these types of vehicles? Let’s take a look.

What is a Deep Cycle Battery?

A deep cycle battery is designed to offer steady, continuous power over a long period of time. It’s intended to be charged and deeply discharged repeatedly without damaging or shortening the battery’s lifespan.

As previously mentioned, this is different from a starter battery, which delivers a short burst of large amounts of power to start your vehicle and is recharged by the alternator.

Deep cycle batteries are also structurally different from starter batteries. The thicker plates offer resistance to corrosion during extended charging cycles.

What is a Lithium Battery?

A lithium battery is also designed to be fully charged and discharged. It also provides a steady current of power over time. So, technically, a lithium battery is a “deep cycle” battery. However, they are not usually referred to as deep cycle batteries.

While the deep cycle function is used by both lead-acid and lithium technologies, there are significant differences between traditional deep cycle batteries and lithium batteries, which we’ll go over in detail next when we discuss the different types of deep cycle batteries and the advantages and disadvantages of each.

Types of Deep Cycle Batteries

If you include lithium batteries, there are four different types of deep cycle batteries. Let’s examine each a little closer.

Flooded Lead Acid Batteries

The flooded lead-acid battery is the oldest vehicle battery technology. This type of battery has lead plates submerged in a liquid electrolyte mix consisting of water and sulfuric acid.

There’s really only one advantage to using FLA batteries: they’re the most affordable option. However, there are quite a few disadvantages as compared to lithium batteries.

Lead-acids are very heavy, especially when you consider the amount of energy they actually provide. These batteries only have a usable capacity of 50% since they can be damaged if discharged below this level.

FLA batteries charge slowly, taking between 8-16 hours, and they lose voltage and power as the battery’s level of charge decreases. They also require a fair bit of maintenance, as you’ll need to add water, check acid levels, clean corrosion, and more.

These batteries also have the shortest lifespan of deep cycle batteries, with only 200-500 life cycles or about 3-5 years.

AGM (Absorbent Glass Mat) Batteries

AGM batteries are very similar to FLAs. However, they don’t have a free-flowing liquid electrolyte mix. Sometimes called sealed lead-acid batteries (SLA) or valve-regulated lead-acid batteries (VRLA), AGMs have thin fiberglass mats between the lead plates that absorb the electrolyte mix.

This has many benefits, such as keeping the liquid from moving and acting as a damper between the plates. Because of the glass mats, the battery is shock and vibration resistant, and it can withstand colder temperatures.

AGM batteries charge much faster than lead-acid batteries, in about five hours, and can be discharged down to 20% without causing any damage to the battery. They’re also maintenance-free since they’re sealed, so there’s no need to add water and no risk of leaks.

These batteries are more expensive than the FLAs but less than lithium batteries. They need a regulated charger to prevent overcharging, and they still lose power as the battery’s charge decreases.

A typical lifespan for AGM batteries is around seven years, so they last longer than FLA batteries.

Gel Cell

Like the AGM battery, this is another VRLA or SLA battery. Gel cells use a gelled electrolyte instead of using glass mats to absorb the electrolyte.

You’ll get a 75% depth of discharge with a gel cell lead-acid battery, which is a significant improvement over flooded lead-acids. They’re also spill-proof and don’t require any type of maintenance. These batteries have a higher tolerance to heat than both FLAs and AGMS.

However, they don’t charge very fast, taking 5-10 hours. They are more expensive than any of the previous types of batteries, and are sensitive to overcharging, so they require a special charge and regulator.

Gel deep cycle batteries also have a shorter lifespan, lasting only 2-5 years.

Lithium Batteries

Lithium batteries offer the latest technology in batteries. These advances provide several benefits over the traditional deep cycle batteries listed above.

These batteries weigh about half as much as a flooded lead-acid battery. They are also maintenance-free.

The biggest advantage to these batteries is that they have a higher usable capacity, meaning you can discharge your battery completely before you need to recharge it. They also provide constant voltage and power, no matter the battery’s charge level.

Lithium batteries charge quickly, in just 2-3 hours, and they last much longer. They have 2,000-5,000 charge cycles, which means you could potentially get up to 20 years of use out of these batteries, depending on a variety of factors.

As compared to the other types of batteries, most lithium batteries use LiFePO4 technology, which is inherently safer. They also have a built-in BMS (battery monitor system) that ensures the battery runs optimally and prevents overheating and other safety issues.

There’s really only one disadvantage to lithium batteries: they’re the most expensive. However, based on their lifespan, lack of maintenance, and higher usable capacity (meaning you might not need as many total), these batteries prove to be more cost-effective over the long run.

Conclusion

While all four types of deep cycle batteries have their advantages and disadvantages, it’s evident that the pros far outweigh the cons when it comes to lithium batteries, whether you’re trying to power your golf cart, boat, or RV.

No matter the application, if you’re thinking about making the switch to lithium batteries, Patriot Power Source can help. We’re happy to answer any questions or concerns you may have and guide you through the conversion.