Difference in marine deep cycle and starting battery

June 27 2023, by Sally Zhuang, 10 min reading time

Marine vessels rely heavily on batteries to power their various accessories and components. Without a reliable battery, the ship cannot anchor or sail through the water with ease. When choosing a battery for your marine vehicle, it is important to understand the different types available and how they differ. Two common types of marine batteries are the marine deep cycle and marine starting batteries. This article aims to highlight the differences between these two types of batteries.

Part 1: All about the Marine Deep Cycle Battery

A marine deep cycle battery is a type of battery specifically designed to provide consistent current output over a long period of time. It is designed to withstand deep and repeated discharges without rapid failure. The battery can be continuously discharged and then slowly recharged over a period of time, called a discharge/charge cycle. This type of battery is typically used in deep cycle applications that require constant and uninterrupted power. Examples of such applications include fishing boats, sailboats and electric propulsion systems.

Types of Marine Deep Cycle Batteries

The marine deep cycle battery comes in various types including liquid acid batteries, sealed lead acid batteries and lithium ion batteries. Each type has its advantages and disadvantages depending on the intended use and budget.

Liquid acid batteries are a cost-effective option. Still, there are some disadvantages associated with this type of battery. First, they have the lowest C rating compared to the other types discussed, meaning they cannot handle rapid charging or discharging without damage.

In addition, they require a more sophisticated charger that can provide equalization charging to ensure they last as long as possible. Inadequate maintenance can lead to sulfation. These batteries should not be left in a partially discharged state and should not be discharged below 50% of their rated capacity, meaning their usable energy is far less than their capacity.

Their orientation is also important as immersion in water can result in the release of dangerous hydrogen chloride gas. They require continuous floating charge even when not in use and regular refilling of water is important.

Finally, proper ventilation in the battery compartment is important to avoid explosions caused by hydrogen gas released during charging.

Sealed lead-acid batteries, also known as valve-regulated lead-acid batteries, are maintenance-free and last longer than liquid acid batteries.

However, there are also some disadvantages to consider.

The main disadvantage of sealed lead-acid batteries is their limited deep discharge capacity compared to liquid acid batteries. They are not designed for deep cycle applications and can be damaged if discharged below a certain point. This means they may not be optimal for long sailing trips or the use of trolling motors that require constant power for extended periods.

Another point is that sealed lead-acid batteries are more expensive than liquid acid batteries and may not be within the budget of some users. Lithium-ion batteries are more expensive than both sealed and liquid acid batteries, but offer the added benefit of higher energy density.

Finally, sealed lead-acid batteries can suffer from thermal runaway, which is caused by excessive heat generation when charging or discharging the battery. To prevent this, proper ventilation is required to remove heat from the battery case.

Lithium-ion batteries are becoming increasingly popular in the deep cycle battery market due to their many advantages over conventional lead-acid batteries. Li-ion batteries typically offer higher energy density, longer lifespan and lower weight compared to lead-acid batteries. This makes them ideal for marine applications. However, it is important to note that currently only the Lithium Iron Phosphate (LiFePO4) battery is approved for maritime use.

Part 2: All about marine starting batteries

Unlike the deep cycle battery, the marine starting battery is designed to deliver a quick pulse of power to quickly start the marine vehicle's engine. The battery can deliver a high current in a short period of time. As soon as the engine is running, the marine generator recharges the battery. Marine starting batteries come in different types, each suitable for different types of engines.

Types of Marine Starting Batteries

There are two main variants of marine starting batteries:

Liquid batteries: The most common type of marine starting batteries are liquid batteries, also known as wet batteries. They use lead-acid chemistry and require regular maintenance, which involves adding distilled water intermittently to replenish water used from the cells during charging. Liquid batteries are generally less expensive than other types of marine batteries.

Absorbent Glass Mat (AGM) Batteries: AGM batteries require no maintenance and have a longer lifespan than liquid batteries. They are equipped with a fiberglass fleece that absorbs and holds the battery's acidic electrolyte. This eliminates the need to add water or monitor electrolyte levels. Additionally, AGM batteries are vibration resistant and can have a higher discharge rate than liquid batteries, making them an optimal option for high performance boats. However, AGM batteries are a more expensive alternative compared to liquid batteries.

Part 3: Differences between Marine Deep Cycle and Starting Batteries

Marine deep cycle batteries are designed to provide constant power to electrical components over an extended period of time. They are designed with thicker, robust plates that can withstand repeated deep discharge cycles without damaging the battery. Deep cycle batteries are commonly used for electric motors, onboard electronics, and other applications that require a constant power source.

Marine starting batteries are designed to deliver high power for a short period of time to start an engine. They use thinner plates that can deliver high currents for a short period of time before rapidly discharging.

Overall, the main difference between marine deep cycle and starting batteries is their design and intended use. Deep cycle batteries are designed to deliver consistent power over an extended period of time, while starting batteries are designed to deliver a high power pulse to start an engine or other heavy-duty applications.

Part 4: Common Misconceptions About Marine Batteries

There are several misconceptions about marine batteries that can lead to selecting the wrong battery type. A common misconception is to assume that any type of battery can be used for the marine vehicle. While some batteries may work for a period of time, they may not be long-lasting and may fail sooner than expected. Another misconception is to assume that marine starting batteries can be used interchangeably with deep cycle batteries. As mentioned, the intended use varies, and therefore the battery type varies. Finally, choosing the most expensive battery with the highest performance specifications does not always guarantee good quality. Other factors such as durability, performance requirements and maintenance must be taken into account.

FAQs on Marine Deep Cycle and Starting Batteries

1. Can I use a marine starting battery as a deep cycle battery?
It is not recommended to use a marine starting battery as a deep cycle battery. Starting batteries are designed to discharge quickly and recharge quickly, while deep cycle batteries discharge more slowly and recharge more slowly.

2. How long does a marine deep cycle battery last?
A traditional lead acid deep cycle battery can last about 3-5 years, while a LiFePO4 battery can be used for over 10 years.

3. Can I charge a marine battery while on the water?
Yes, you can charge a marine battery while on the water. Many boats have built-in chargers that can charge the battery while the boat is in use. Alternatively, you can use a portable charger or generator to recharge the battery.

Final Thoughts

After a thorough investigation of both battery types, we strongly recommend using Lithium Iron Phosphate (LiFePO4) batteries if you need a deep cycle battery for your marine vehicle. LiFePO4 batteries are an excellent choice due to their unmatched efficiency, extended life, and ability to handle deep cycle applications.

At Power Queen we specialize in high-quality LiFePO4 batteries for maritime use. Our batteries are designed to withstand and excel in the demanding maritime environment. They feature a lightweight design, maintenance-free operation and premium performance. Let us help you meet your marine power needs by contacting us today to learn more about our high-quality marine batteries.

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