“What’s the difference between deep cycle and marine battery?”. This is quite a common question asked by boat owners. In reality, both the terms “deep cycle” and “marine” are used as marketing information and not specifically for describing batteries.
For instance, if you’re going to visit a boat shop and ask for a new battery for your vessel, you can expect the dealer to offer you a marine battery to buy. He’ll tell you that it’s what you need for starting your boat’s motor, as well as supplying the power for your boat’s equipment.
A deep cycle battery, on the other hand, is typically used for industrial purposes. Apparently, the two terms were joined by some battery manufacturers. To them, both terms apply to a battery with a longer lifespan.
Battery Design Basics
Batteries are categorized depending on their design, specifically by the thickness of their lead plates. Those with thin plates provide higher cranking power and are designed for starting the motor. These batteries are also less expensive. Another type are batteries with thick plates, which, while not having high cranking power, are designed to last longer and used to power boat accessories.
Basically, starting batteries have thinner plates, while deep cycle batteries have thicker ones. Marine batteries, on the other hand, are considered by some as hybrid and may have plates a bit thicker than those of starting batteries, but not as thick as those of deep-cycle batteries. At the same time, marine batteries can also either be a deep cycle battery (with thicker plates) or a starting battery (with thinner plates).
Deep Cycle Battery Basics
Deep cycle batteries are so called because they have been designed to be repeatedly discharged down to 80 percent (this is called deep cycling) without being damaged. They have the thickest plates of all battery types and can last longer, which is why they are often found being used in many industrial applications, such as energy storage units, where prolonged discharged times are very critical.
There are several types of deep cycle batteries, each one having its pros and cons. There’s the AGM or Absorbed Glass Mat type, the gel type, flooded batteries, and then the more recently designed lithium-ion batteries.
Among these four, the flooded type are no question the most popular. These batteries are very similar to the lead-acid battery of your car. Along with AGM and gel batteries, flooded batteries are the most frequently used battery types right now, but it will only be a matter of time until lithium-ion types will also just as recognized and used.
Now, if you’re wondering whether deep cycle batteries can be used to cranking or starting a motor, the answer is YES, as long as the battery has an ampere-hour rating that’s above 20 percent of what’s recommended for cranking a particular motor.
Investing In A Deep Cycle Battery
Should you use a deep cycle battery for your boat? Definitely. In fact, you’ll need a deep cycle battery, plus, a starting battery. As the term implies, the starting battery is for cranking up the motor of your vessel. This battery would remain fresh with the help of your boat’s alternator that will keep it charged all the time.
Many boat owners actually invest in separate banks of batteries. The first bank is for starting the boat, and the other one is for house loads (your boat’s accessories). If you intend for your boat to stay running overnight, for instance, you will do best by having a separate bank of deep cycle batteries to draw power from for your house loads.
Rating Deep Cycle Batteries
There are two ways batteries are rated. The first is by Ah or Amp hours. This refers to the battery’s capacity to store chemical energy. In short, it tells you how much energy the battery can store. It can also be considered as the battery’s discharge rate, which measures how long it takes for the battery to discharge before recharging.
And then there’s the C rate, which measures the rate at which a certain battery is discharged in relation to its max capacity. A C1 or 1C rate, for instance, would mean that the discharge current will discharge the cells in one hour. Larger power systems will have batteries with a higher C rate, for example, C100. These batteries typically last up to 4 days before discharging and have a lifespan of up to 15 years.
Just recently, batteries for home use are now referred to by their kWh or kilowatt-hour capacity. This, as a result of the advent of home energy storage.
Understanding Discharge Cycles
Knowing how many times a battery can be discharged and recharged is crucial for boaters. Manufacturers will all claim that their products are best suited for energy storage use, but not all deep cycle batteries are equal.
One way you can determine the longevity of a battery is through its cycle rating or the number of times a battery can be discharged and charged again. The higher the cycle rating of a battery, the more reliable it is for extended use.
Now, when i say discharge cycle, i don’t only mean the process it takes to consumer all the power stored up in the battery. I also mean the battery’s lifespan or the length of time it can be used before it ultimately loses its ability to hold a charge.
There are two types of discharging: deep discharge and shallow discharge. The former pertains to fully discharging a battery before recharging it. The latter, on the other hand, refers to partially discharging a battery and then charging it once more either to a full status or a higher level. Apparently, you’ll need something that will last you the distance.
Selecting The Right Battery For Your Boat
You probably know already that unlike with cars, your boat cannot run on a single battery alone; it will need both a starter battery and a deep cycle battery.
Starter Battery Considerations
In selecting a starter battery, you’ll need to consider three factors. The first one is Cold Cranking Amps (CCA) or Marine Cranking Amps (MCA). The CCA pertains to the number of amps the battery can generate for half a minute at 0° F while retaining a voltage of 7.2 and up. MCA, on the other hand, is gauged at 32° F.
The second factor to consider are the reserve minutes, or the length of period a battery can sustain 25 amps of load before dropping to 10.5 volts. However, since starter batteries are not utilized to carry loads for extended periods, this factor is not that crucial.
The third and final factor is the battery size. In selecting the correct battery size, you’ll need to consider the size and type of the engine, plus the ambient temperature. For colder temperatures, larger batteries with high cranking power are essential.
You’ll also need the same for diesel engine boats, and boats with high compression gas engines. Consequently, you’ll need to choose a battery that meets your boat’s minimum CCA.
Deep Cycle Battery Considerations
Reserve minutes are more critical for deep cycle batteries since these batteries are required to sustain house loads. Amp-hours are also important considerations when choosing a deep cycle battery. It measures the total amount of power a battery can produce for 20 hours at a constant discharge rate down to 10.5 volts.
If you have a 200Ah battery, that means you can power a 10A load for twenty hours. It’s important to know that house loads generally range between 5A and 25 Am, sometimes more.
Considering these things, i can say that for a starter battery, you’ll need one with a high cranking power. And, for a deep cycle battery, consider one with higher Amp-hours and reserve minutes.
Best Performance Tips
It’s not enough to know that you need a starter battery and a deep cycle battery for your boat. There are important things to consider to make sure your batteries perform at their best. For instance, you would want to stick to one battery chemistry, whether it’s an AGM, a gel, or a flooded type. This way, you won’t risk under-charging or over-charging your banks, because when this happens, you’ll need to replace all the batteries at the same time.
In the same manner, you wouldn’t want to mix old batteries with new ones. Just like rotten tomatoes, old batteries will cause new batteries to deteriorate fast. (Read this page, if you need to refurbish your batteries).
You’d also want to ensure that your charging system is able to deliver the right amount of amperage when charging your batteries. Not doing so will result in your batteries failing prematurely.
Finally, make sure that you keep your batteries clean and dry all the time. Check the terminals regularly to make sure there aren’t lose connections. Don’t forget to add distilled water to flooded lead-acid batteries, too, when needed. And never, ever forget to keep your batteries charge, because laving them in a discharged state will lower their capacity.
Now that you understand the difference between deep cycle and marine battery, you will know next time what type of batteries to invest in for your boating needs.