If you’ve been boating for any length of time, you’re probably familiar with the terms “marine battery” and “deep cycle battery.” But what do these two terms mean, exactly?
What are marine and deep cycle batteries, and are they just two different terms that mean the same thing?
How can you tell if your marine battery is also a deep cycle battery, or if your deep cycle battery can be used for marine applications?
Let’s find out, shall we?
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Deep Cycle Battery Vs. Marine Battery
Deep cycle and marine batteries are two specific types of battery. A battery may be one or the other, or it may be both. Confusing, right?
To better understand the differences between marine and deep cycle batteries, we should look at each type of battery in turn.
Deep Cycle Battery
A deep cycle battery is any battery that can be more deeply discharged than other batteries. It is set apart from other battery types, specifically starting batteries, because deep cycle batteries can supply sustained amounts of power for longer periods of time.
Most batteries can’t be discharged more than 20 to 50 percent of their capacity; if you try to run them any lower, they will begin suffering in performance and could potentially sustain irreparable damage. Some will even stop producing power once they have been discharged this far.
On the other hand, deep cycle batteries can regularly be discharged from 50 to 80 percent of their total capacity without running into any problems; some lithium deep cycle batteries can be discharged up to 95 percent.
What does this mean for you?
Using a deep cycle battery results in much longer run times for whatever it is you’re powering. Since you can use up so much more of a battery’s total capacity, you won’t have to worry about recharging that battery until it reaches that deeper discharge.
In other words, deep cycle batteries may power your devices for hours, whereas other types of batteries may be exhausted after only an hour or so.
A marine battery is any battery made for marine use. These types of batteries can be used for some other purposes as well, but they are specifically designed for conditions faced on boats and, as a result, can be more expensive than other batteries.
Marine batteries are fully waterproof, made to withstand the high humidity levels found near bodies of water. They can even handle getting sprayed and splashed from choppy waters. Many marine batteries are also corrosion-resistant so they can be used around saltwater.
Marine batteries are usually sealed so they can be mounted in any position, which makes it easier to fit them into tight spots on boats.
The internal lead plates of marine batteries are thicker and more durable than those found in most other batteries, so they can withstand shocks and vibrations of being on a boat. There are also fewer of these plates which allows power to flow more efficiently through the battery.
Simply put, you wouldn’t want any other kind of battery on your boat. Even a high-quality deep cycle battery that isn’t made for use around water will not hold up when exposed to marine conditions.
Is a Marine Battery a Deep Cycle Battery?
As noted above, a battery may be either deep cycle or marine, or both. Many marine batteries are also deep cycle batteries, and some deep cycle batteries are also rated for marine use, but this is not true in every case.
Remember, marine and deep cycle batteries are two distinct types of batteries. Sometimes they overlap; in other words, some batteries are both marine and deep cycle, while other batteries are only one or the other. It all depends on how they’re made and what their intended uses are.
Marine batteries are often deep cycle batteries and used for things like powering trolling motors for hours on end. A marine battery that was not deep cycle would need to be recharged much more frequently and wouldn’t give you as much time out on the water.
That said, you don’t want to use a deep cycle battery that isn’t rated for marine use. Many deep cycle batteries are made for other specific conditions, such as running solar-powered systems at night or generating electricity at night. These batteries will not last long when used on a boat.
How Do I Know if My Marine Battery is a Deep Cycle Battery?
Not sure how to tell whether your battery is a marine battery, deep cycle, or both? You will probably find some answers by looking at the battery label.
It should say on the label whether or not the battery is a deep cycle battery. Look for the “deep cycle” distinction or any information on the label about how deeply the battery can discharge. If it can be discharged to 50 percent or more of its total capacity, it is likely a deep cycle battery.
If you can’t find any useful information on the label, look for the battery’s model number or serial number and research it online; Googling this number will likely turn up a wealth of information on that specific battery.
If you still can’t find the information you’re looking for, contact the battery’s manufacturer with the model or serial number. The manufacturer should be able to tell you whether or not the battery is deep cycle or not.
To make sure the battery is a marine battery, search the label or somewhere on the battery for its group number followed by an “M;” for example, 24M, 27M, 31M are all common marine battery distinctions.
Marine batteries are made for use on boats; they are waterproof and made to handle the shocks and vibrations experienced on boats. Deep cycle batteries are any batteries that can be regularly discharged more than 50 percent; these batteries provide exceptional run times.
Sometimes deep cycle batteries are rated for marine use, and marine batteries are also made to be deep cycle batteries. But they are two distinct battery types that do not always overlap.