Marine Deep Cycle vs Starting Battery

Different Types of Marine Batteries

Flooded Lead Acid

Flooded Lead Acid batteries are the traditional choice for marine applications. They are cost-effective and widely available but require regular maintenance, such as topping up with distilled water, and may not be as durable as other types.

Absorbed Glass Mat (AGM)

Absorbed Glass Mat (AGM) batteries use a glass fiber separator to hold the electrolyte in place. This makes them more resistant to vibrations and allows for mounting in various positions, and they are also maintenance-free with a longer lifespan than Flooded Lead Acid batteries. However, AGM batteries can be more expensive.

Gel

Gel batteries use a thickened electrolyte, which makes them highly resistant to vibrations and leakage. They are also maintenance-free and offer a long service life, but they can be sensitive to charging rates and damaged by improper charging.

Lithium-ion

Lithium-ion batteries have become increasingly popular due to their lightweight and high performance. They offer a longer lifespan, faster charging, and better energy density than other battery types. However, they can be more expensive and may require specific charging systems.

Starting Batteries

These batteries are designed specifically for starting boat engines. Their primary function is to deliver a powerful burst of energy for a short period to crank the engine. Once the engine runs, the boat’s alternator takes over, providing power to the electrical system and recharging the battery.

High Cranking Amperage (CCA) Rating

Cranking batteries are characterized by their high Cold Cranking Amperage (CCA) rating. The CCA rating measures the battery’s ability to deliver a high current for a short time at low temperatures. A higher CCA rating means the battery can provide more power to start the engine, especially in cold conditions.

Limitations

While they excel at providing a powerful initial boost, they have limitations. They are not designed for deep discharge or providing continuous power to onboard equipment. Using them for such purposes can significantly shorten their lifespan and cause damage.

• Pros: Powerful engine starting, high CCA rating
• Cons: Not suitable for deep discharge or continuous power supply

Deep Cycle Batteries

These are designed to provide a steady and continuous power flow to your boat’s onboard equipment over an extended period. They are ideal for powering accessories such as lights, radios, trolling motors, and other devices requiring constant energy.

Lower Cranking Amperage (CCA) and Higher Reserve Capacity (RC) Rating

Unlike cranking batteries, these batteries have a lower Cold Cranking Amperage (CCA) rating and a higher Reserve Capacity (RC) rating. The RC rating indicates the battery’s ability to provide power continuously over a specified period. This makes them more suitable for long-term use and powering onboard equipment.

Examples of Equipment Powered by These Batteries

• Lights
• Radios
• Trolling motors
• GPS systems
• Fish finders

Advantages and Disadvantages

They offer several benefits, such as handling deep discharges and providing continuous power. However, they may not be suitable for starting large engines due to their lower CCA rating.

• Pros: Long-term use, continuous power delivery, handling deep discharges
• Cons: Lower CCA rating, may not be suitable for starting large engines

Key Differences 

CCA vs. RC Rating

One of the main differences between deep cycle and starting is their Cold Cranking Amperage (CCA) and Reserve Capacity (RC) ratings. Cranking batteries have a higher CCA rating, enabling them to deliver a powerful burst of energy to start engines. On the other hand, deep-cycle batteries have a higher RC rating, making them suitable for providing continuous power over a more extended period.

Discharge Depth and Recharging Requirements

Deep cycles are designed to handle deep discharges, meaning they can be drained significantly before recharging. This makes them ideal for continuous power delivery to onboard equipment. Starting batteries, however, should not be deeply discharged, as doing so can damage the battery and shorten its lifespan.

Use Cases and Limitations

Starting batteries are specifically designed for engine starting and should not be used for long-term power supply to onboard equipment. On the other hand, deep-cycle batteries are designed for continuous power delivery and can handle deep discharges. However, their lower CCA rating might make them unsuitable for starting large engines.

Lifespan and Durability

Deep-cycle generally have a longer lifespan and are more durable than starting when used for their intended purpose. This is because they are designed to withstand repeated cycles of discharging and recharging. They can have a decent lifespan if used only for engine starting, but using them for deep discharge applications can significantly shorten their life.

Dual Purpose Batteries

Dual purpose marine batteries, also known as hybrid or combination batteries, are designed to serve the functions of both starting and deep-cycle batteries. They provide the necessary power to start your boat’s engine while also being capable of handling deep discharges for powering onboard equipment.

Characteristics of Dual Purpose Batteries

Dual purpose batteries typically have a higher Cold Cranking Amperage (CCA) rating than deep-cycle batteries, allowing them to be used for engine ignition effectively. They also have a higher Reserve Capacity (RC) rating than starter batteries, enabling them to provide continuous power for longer periods.

Advantages and Disadvantages

Dual-purpose batteries offer several benefits, including:

• Versatility: They can handle both engine starting and continuous power supply, making them suitable for many boating applications.
• Space and cost savings: By serving dual functions, these batteries can save space on your boat and reduce the need for multiple batteries, potentially saving money.

However, dual-purpose batteries also have some drawbacks:

• Compromise on performance: Although they can handle both starting and deep-cycling, they may not perform as well as dedicated starting or deep-cycle batteries in their respective roles.
• Potentially shorter lifespan: When subjected to both starting and deep cycling demands, dual-purpose batteries may have a shorter lifespan than dedicated batteries.

Choosing a Dual Purpose Battery

When selecting a dual purpose battery, consider the following factors:

1. CCA and RC ratings: Ensure the battery has sufficient CCA and RC ratings to meet your boat’s engine starting and onboard equipment requirements.
2. Battery type: Dual purpose batteries are available in Flooded Lead Acid, AGM, Gel, and Lithium-ion types. Consider each type’s maintenance requirements, durability, and cost before deciding.
3. Manufacturer’s recommendations: Consult your boat and engine manufacturer’s battery requirements and compatibility guidelines.

How to Choose the Right Battery for Your Boat

Factors to Consider

When selecting the correct battery for your boat, consider the following factors:

1. Boat Size: Larger boats may require more powerful batteries, while smaller boats might need less power. Consider the size of your boat and its electrical requirements when selecting a battery.
2. Engine Type: The type of engine your boat has can influence the battery you need. Some engines may require a starting battery with a higher CCA rating, while others might be fine with a deep cycle battery.
3. Onboard Equipment: Consider the equipment on your boat, such as lights, radios, trolling motors, and other electronic devices. Deep cycle batteries are generally better suited for powering this equipment.
4. Usage Patterns: Consider how you use your boat. A starting battery might be sufficient if you primarily use it for short trips and engine starting. However, a deep cycle battery may be more appropriate if you use your boat for longer outings or require continuous power for onboard equipment.

Consult the Manufacturer’s Recommendations

Always consult the manufacturer’s recommendations for your boat and engine when selecting a battery. Manufacturers often provide specific guidelines for battery type, CCA rating, and other requirements.

Maintenance Requirements and Ease of Use

Consider the maintenance requirements and ease of use when choosing a battery. Flooded Lead Acid batteries may require more maintenance, while AGM, Gel, and Lithium-ion batteries are typically maintenance-free. Choose a battery that fits your preferences and lifestyle.

Environmental Considerations

Select a battery resistant to spills, leaks, and vibrations if you use your boat in rough waters or demanding conditions. AGM, Gel, and Lithium-ion batteries offer better resistance to these factors than Flooded Lead Acid batteries.

Conclusion

Choosing the correct marine battery is crucial to ensuring optimal performance and safety for your boat. In this guide, we’ve explored the key differences between deep cycle and starting marine batteries and the various types of batteries available, including Flooded Lead Acid, Absorbed Glass Mat (AGM), Gel, and Lithium-ion.

Consider your boat’s size, engine type, onboard equipment, and usage patterns when selecting the appropriate battery. Always consult the manufacturer’s recommendations and consider maintenance requirements, ease of use, and environmental factors.

By understanding the distinctions between deep cycle and starting marine batteries and considering the factors we’ve discussed, you can make an informed decision that best suits your boat’s needs. This ensures optimal performance, safety, and a more enjoyable boating experience.