Deep cycle batteries are a crucial component for a variety of applications, from powering marine vessels and RVs to supporting solar energy systems and backup power solutions. Unlike regular car batteries, which deliver short bursts of high energy, deep cycle batteries are designed to provide a steady amount of power over a long period, making them ideal for sustained use. Understanding the differences between deep cycle and starter batteries, the various types of deep cycle batteries, their maintenance requirements, and how to choose the right one for your needs can significantly enhance the performance and longevity of your equipment. In this comprehensive guide, we’ll cover everything you need to know about deep cycle batteries, ensuring you're well-equipped to make informed decisions and get the most out of your investment.
Deep Cycle Batteries vs Starter Batteries
Starter batteries are the sprinters of the battery world. They are designed to discharge a lot of power during a short burst of time. They are designed to supply the power needed to start something up, like a motor, which then runs on gasoline. A deep discharge can damage a starter battery's lifespan and performance. This is the type of battery you'll find in a car. Once the motor starts, the alternator begins charging the battery back up to full charge.
However, sometimes you need batteries that can continuously supply power for long periods of time, such as to power electronics on a fishing or sailboat, or in an RV. For these applications, deep cycle batteries are the optimal choice. They are the marathon runners of the battery world. Rather than a short burst of lots of power, they supply a lesser amount of power but for a much longer period of time. You may also be wondering if both capabilities - short bursts of power as well as continuous power - exist in a single unit. In short, yes, they do. This is what is known as a dual-purpose battery.
What Are Dual Purpose Batteries?
Dual-purpose batteries handle both starting and cycling, making them an excellent choice when you are working with a small footprint. They deliver powerful cranking amperage for easy starting, and low amp draw service for reliable auxiliary power. A perfect example of this would be RELiON’s HP series of lithium batteries that are designed to handle getting you started and keeping you running.
Deep Cycle Battery Discharge Capability
As mentioned above, deeply discharging a starter battery will hurt its performance. However, deep cycle batteries not only are designed to provide continuous power for a long period of time, but also can discharge much more of their stored energy. The amount you can safely discharge varies from battery to battery. Some batteries can only handle discharging 45% of their energy reserves, whereas others can safely discharge up to 100%. Certain types of lithium batteries, for example, are known for their ability to be deeply discharged - up to 100% - without sustaining any damage. Many lead-acid batteries, on the other hand, can only be discharged up to 50% before the battery is harmed. Just be sure to check the manufacturer's recommendation for your specific battery.
Uses of Deep Cycle Batteries
We've already touched on the fact that familiar car batteries are starter batteries. So what are deep cycle batteries used for? In general, for anything that needs continuous power for longer periods of time. Listed below are some examples of good applications for deep cycle batteries:
- Electric golf carts
- Electric floor cleaning machines
- Electric scissor lifts
- Electric wheelchairs
- Electric scooters
- Electric forklifts
- Recreational Vehicles
- Trolling motors on boats
- Navigational devices on a boat (when the main motor is inactive)
- Renewable Energy systems
Types of Deep Cycle Batteries
There are also a few types of deep cycle batteries. While they perform the same function, the materials used to build the battery vary. Thus, the different types of deep cycle batteries each have their own pros and cons. Here are some of the main ones:
- Flooded Lead-Acid (FLA)
- Gel and Absorbent Glass Matt (AGM) or Valve Regulated Lead-Acid (VRLA)
- Lithium-Ion
Flooded Lead-Acid Batteries
This is the oldest type of battery that is still in use today. Also called a wet cell, the name comes from the battery having a liquid electrolyte inside, consisting of water and sulfuric acid. If you've ever worked on an older car, you may be familiar with having to open the tabs at the top to add water to the battery on occasion. With deep cycle, flooded lead-acid batteries, adding water is needed more frequently.
Due to the liquid, these batteries must stay upright at all times. They also require proper ventilation since these batteries produce hydrogen gas and it must have a way to escape. It is not uncommon for electrolytes to spit out of the vents during the charge cycle, leaving acid residue on the battery cover and often even on the battery tray and vehicle chassis.
Overall, flooded batteries require the most maintenance, including: adding water, and cleaning acid residue from battery covers, terminals, and surroundings. These types of batteries are also quite heavy when considering the ratio of battery weight to the amount of energy they provide. For these reasons and more, their popularity has significantly waned in recent years.
Valve Regulated Lead-Acid (VRLA) – Gel and AGM Batteries
Gel and AGM batteries are other types of lead-acid deep cycle batteries but with a key improvement. They don't have free-flowing liquid electrolytes in them and therefore don’t require any addition of water. They are more expensive though and often don’t last as long as flooded batteries in more demanding applications. VRLA batteries also will not last as long as lithium batteries and will require more frequent replacements over time.
Instead, gel batteries use a gelled electrolyte and AGM batteries use an electrolyte absorbed in glass mat. If they are used and charged properly, they won’t release any gasses. However, in the event they overpressure, the safety valve will open and release the buildup. As such, they don't have to remain upright and they virtually eliminate any spillage, cutting down on the corrosion problems common with the flooded variety. They have been used in boats, recreational vehicles, and other applications.
Lithium-Ion Batteries
Lithium-ion batteries are quite possibly the wave of the future when it comes to deep cycle batteries. They require no maintenance, can be discharged more deeply without affecting their lifespan, and charge much faster than other types of batteries.
Because of the higher upfront cost, their popularity has not soared as quickly as you might expect. The fact that they last much longer than lead-acid batteries, can actually make them similar in price or even less expensive over the long run.
And they have many other benefits over their lead-acid predecessors. They are lightweight, they provide their rated capacity at any rate of discharge, they do not get damaged from being left or operated in a partial state of charge, they provide more power throughout the discharge cycle, and more.
What Deep Cycle Battery Has More Capacity?
Capacity differs greatly between lead-acid and lithium batteries due to their inherently different chemistry. The major difference is their capacity in relation to their rate of discharge. Lithium batteries can provide up to 100% of their rated capacity regardless of their rate of discharge. Lead-acid batteries provide significantly less usable energy with higher rates of discharge. Although both battery types may lose capacity in colder weather, the changes in performance are far less drastic with lithium. At 0°C, for example, a lead-acid battery's capacity is reduced by up to 50%, while a lithium iron phosphate battery suffers only a 10% loss at the same temperature.
How Long Do Deep Cycle Batteries Last?
The lifespan of a deep cycle battery is affected by a few factors. More factors impact the life of a lead-acid battery than lithium. In other words, lead-acid batteries are more likely to be damaged than lithium batteries. Proper maintenance, as well as properly charging and discharging can extend the battery’s lifespan. Improper watering, over-discharging, over-charging, and under-charging a lead-acid battery regularly can greatly reduce its lifespan.
Lithium batteries don’t require watering, so the issue of improper watering is eliminated. They are also not damaged by a partial state of charge, or under-charging, so those issues are also eliminated. RELiON lithium batteries also come with a built-in smart BMS that helps protect the batteries, which further extends the batteries’ lifespans.
Heat affects the battery as well. Higher temperatures degrade the battery much quicker. Because of these factors, plus the fact that different types of batteries have different lifespans, it's hard to state a specific time frame. On average, batteries like RELiON’s lithium iron phosphate batteries have a lifespan that is 10 times longer than a lead-acid battery. Make sure to check the manufacturer's specifications to get an idea of the capabilities of your battery.
Which Deep Cycle Battery Should You Choose?
Now that you know more about deep cycle batteries, you understand why they are important for a wide range of applications. If you still have questions about which battery to choose for your needs, don't hesitate to contact us! We'll be happy to answer your questions and help you decide on the right battery.