Deep-Cycle Batteries: Can They Power And Start Boats?

Marine batteries are essential for boating and marine adventures, providing the electrical energy needed for various applications, from starting engines to powering onboard electronics. There are two main types of marine batteries: cranking batteries and deep-cycle batteries. Cranking batteries, also known as starter batteries, are designed to provide a burst of power to start the engine, while deep-cycle batteries deliver a steady and sustained power output over an extended period, making them ideal for applications that require continuous power delivery. Deep-cycle batteries are commonly used to power electrical systems and appliances such as lights, music, and navigation equipment. While cranking batteries have more thin plates to increase surface area and facilitate higher amp flow, deep-cycle batteries have fewer, thicker plates, enabling them to withstand repetitive deep discharging and recharging.

Cranking batteries vs deep-cycle marine batteries

Cranking batteries and deep-cycle marine batteries are two of the most common types of marine batteries. They are designed for different purposes, and it is important to understand the differences between them to ensure you are choosing the right battery for your boat.

Cranking Batteries

Cranking batteries, also known as starter batteries, are used to start a boat's engine. They provide short and intense bursts of energy to the engine when the ignition switch is activated. The design of cranking batteries includes many thin plates to increase the surface area and make it easier to provide the necessary power. This allows for a smooth and reliable engine start.

Deep-Cycle Marine Batteries

Deep-cycle marine batteries, on the other hand, are used to provide continuous and reliable power to a boat once the engine has started. They are designed to deliver power over long periods, running electronics such as sonar, GPS, and radios. Deep-cycle marine batteries have fewer, thicker plates that allow them to withstand repetitive deep discharging and recharging without damage. They can be entirely drained and recharged frequently, which is not possible with cranking batteries.

Key Differences

The main difference between cranking and deep-cycle marine batteries lies in the amount of power they deliver and the duration of power output. Cranking batteries provide large amounts of energy in short bursts, while deep-cycle batteries operate at lower amperage and are designed for extended periods of use. Additionally, deep-cycle batteries can handle higher load capacities and can be discharged and recharged more frequently than cranking batteries.

Dual-Purpose Marine Batteries

It is worth noting that there is a third option available: dual-purpose marine batteries. These batteries aim to provide a balance between the characteristics of cranking and deep-cycle batteries. They can deliver the high burst of power needed to start an engine and provide sustained power for running electronics. While dual-purpose batteries can work for both cranking and trolling, they may not always allow a vessel to perform optimally.

Marine battery maintenance

Marine batteries are essential for providing power for various applications on boats, yachts, and other watercraft. To ensure optimal performance and longevity, regular maintenance is crucial. Here are some detailed instructions for maintaining your marine battery:

Regular Inspection and Cleaning:

Monthly visual inspections are recommended, especially during heavy usage periods. Check for any signs of corrosion, loose connections, or physical damage. A clean battery is a happy battery, so make sure the terminals are nice and shiny. Use a wire brush and a mixture of baking soda and water to gently clean the terminals, neutralising any corrosion build-up. Reinstall and tighten the terminals after cleaning.

Secure the Battery:

Boats move through the water with a jerky motion, which can cause the battery to slide or bounce around. Ensure the battery is properly seated and secured in the battery compartment to prevent any movement.

Charging Best Practices:

Proper charging is critical to extending the life of your marine battery. Avoid deep discharges and invest in a quality marine battery charger with an automatic shut-off feature to prevent overcharging. Always follow the manufacturer's recommendations for charging cycles. Before extended storage, make sure to fully charge the battery.

Disconnect to Prevent Parasitic Drains:

Disconnect the battery from any devices or systems that may cause parasitic drains during storage. Even when not in use, some electrical components draw small amounts of power, which can lead to a discharged battery over time.

Ideal Storage Conditions:

Store your marine battery in a cool, dry place, away from direct sunlight and extreme temperatures. Heat and cold can affect the chemical reactions within the battery, impacting its overall health.

Consider a Battery Maintainer:

For added protection during long-term storage, consider using a battery maintainer or trickle charger. These devices provide a low, steady charge, preventing excessive discharge and ensuring the battery stays in optimal condition.

Monitor Discharge Levels:

Regularly check the depth of discharge (DoD) of your marine battery to avoid irreversible damage. Avoid discharging below the recommended levels.

Equalization Charging:

Perform periodic equalization charging to prevent the accumulation of sulfation, which occurs when lead sulfate crystals build up on the battery plates. Equalization charging helps break down these crystals, maintaining the battery's capacity and performance.

Grease the Terminals:

Use dielectric grease, a type of silicone lubricant, to insulate, seal, and lubricate the terminals while providing some waterproofing. This will help prevent corrosion and maintain clean battery terminal posts.

Check Electrolyte Levels:

If you have a flooded battery, maintain its water level using only distilled water. Regularly check the water level, especially during hot days and after heavy usage, and add enough water to cover the plates if they are exposed.

Choose the Right Battery Type:

Understand the different types of marine batteries, such as starting batteries, deep-cycle batteries, and dual-purpose batteries, and choose the one that suits your boat's requirements. For larger boats with more powerful engines and extensive electronics, consider using separate starting and deep-cycle batteries.

Correct Charging Practices:

Utilise smart chargers that deliver the right charging voltage and current based on the battery's capacity and state of charge. Overcharging or undercharging can harm marine batteries and reduce their lifespan.

By following these maintenance steps, you can maximise the performance and longevity of your marine battery, ensuring reliable power for all your boating adventures.

Dual-purpose batteries

Marine batteries are designed to provide power for boats, yachts, and other watercraft. There are three main types of marine batteries: starting batteries, deep cycle batteries, and dual-purpose batteries. Dual-purpose batteries are designed to serve both starting and deep cycle purposes. They provide the high burst of power needed to start an engine and supply a moderate amount of sustained power for electronics and accessories.

Dual-purpose marine batteries are ideal for smaller boats with less demanding engines. They can be used to start the engine and keep a trolling motor running consistently. For instance, the RELiON HP line, which includes the RB100-HP and RB300-HP, are dual-purpose models that can provide up to 800 amps for two seconds to start a boat's motor. The RB100-HP is a Group 31 marine battery, while the RB300-HP is a Group 8D battery.

However, dual-purpose batteries may not be suitable for larger boats with more powerful engines and extensive electronics. In these cases, it is generally recommended to use separate cranking and deep cycle batteries. Dual-purpose batteries may also be more prone to overheating in harsh conditions and may not stand up well to total discharges. Therefore, it is important to consider the specific needs of your boat when choosing a battery type.

Marine battery storage

Marine batteries are essential for any boat, providing power for everything from starting the engine to running electronics. There are three main types: starting batteries, deep-cycle batteries, and dual-purpose batteries. Deep-cycle batteries are particularly important for boaters, as they provide continuous, reliable power for activities like trolling and running electronics.

To ensure your marine battery lasts through the off-season and performs well when you need it, proper storage is key. Here are some detailed instructions for storing your marine battery:

• Perform end-of-season maintenance: Before storing your marine battery for the off-season, it's important to perform some basic maintenance. Inspect the cables, connections, and battery case for any signs of damage. Remove any dirt or corrosion from the battery terminals. If you have a conventional lead-acid battery, make sure to water it properly, following the manufacturer's guidelines for the correct water level.
• Give the battery a final charge: Before storing your battery, give it one last full charge. This helps maintain the battery's life and capacity, and also helps prevent it from freezing during cold winter temperatures.
• Check the state of charge (SOC): Use a hydrometer to check the specific gravity of each cell. For a conventional flooded lead-acid battery, you're looking for a specific gravity of 1.265–1.285. Alternatively, you can use a voltmeter to check the voltage. A fully charged flooded lead-acid battery should read 12.6V, while an Absorbed Glass Mat (AGM) battery should read 12.9V or higher.
• Disconnect the battery cables: Disconnect the negative cable first and then the positive cable. This will prevent parasitic draw from any electronics that may still be connected, which could drain your battery over time.
• Remove and store the battery: Remove the battery from your vessel and store it in a cool, dry location. Ensure the storage area is well-ventilated and that the battery won't be exposed to freezing temperatures, as this can damage the battery. If you have a conventional lead-acid battery, store it in a plastic bin or on a surface that won't react with acid in case of leaks.
• Maintenance charging: To prevent self-discharge and extend the lifespan of your battery, consider using a trickle charger or a smart charger to charge it monthly during storage. Just be sure to select the right type of charger and settings for your specific battery.

Marine battery charging

Onboard Marine Battery Chargers

Onboard chargers are permanently installed on the boat and connected directly to the electrical system. They offer automatic charging by continuously monitoring the battery's condition and adjusting the charging rate. This is a convenient option if you frequently use your boat near shore power sources or marinas, eliminating the need for a portable charger. Onboard charging methods include shore power charging, offshore charging, and alternator charging.

Shore Power Charging

Shore power charging is the most common method when docked at a marina or connected to an external power source. It involves using a battery charger designed specifically for marine use to charge your batteries.

Offshore Charging

Offshore marine charging uses onboard generators or alternative power generation methods, such as solar power systems, to charge the boat's batteries. This method is crucial for long-distance voyages, ensuring self-sufficiency away from the mainland.

Alternator Charging

The boat's engine alternator can also charge the batteries while on the water. The alternator generates electrical power when the engine is running and can charge the starting battery and, if connected, the deep cycle battery. However, alternators are typically designed to maintain the starting battery's charge rather than provide a complete deep cycle battery recharge.

Portable Marine Battery Chargers

Portable marine chargers are compact and versatile, designed to be carried on board or used on land when docked. They come in various models, including manual, automatic, and smart chargers, catering to different battery types. Portable chargers offer flexibility and are ideal when far from shore power or marinas, with rental boats, or when managing multiple boats with diverse charging needs. They are also a more cost-effective option compared to installing onboard systems.

Charger Compatibility

Regardless of the charger type, ensuring charger compatibility with your battery is crucial. When determining charger compatibility, consider the voltage and amperage requirements. The charger's voltage should match the battery's voltage, typically 12 volts for most marine batteries. The charger's amperage output should be around 10-20% of the battery's capacity, measured in ampere-hours (Ah).

When dealing with multiple batteries, the charging approach becomes more complex. The charger requirements depend on how the batteries are connected in the electrical system, either in series or parallel. In a series configuration, the voltages of the batteries add up, and a charger compatible with the higher voltage is needed. In contrast, when batteries are connected in parallel, the voltage remains the same, but the capacity increases, and the charger should handle the combined amperage needs.

Best Practices for Marine Charging

To maintain battery health and safety, it is essential to follow some best practices for marine charging:

• Avoid overcharging, as it can damage batteries and reduce their lifespan. Smart chargers can help prevent this by monitoring battery conditions and adjusting the charging process.
• Maintain a full charge, especially for lead-acid batteries, to prevent sulfation, which occurs when the battery remains partially charged for extended periods.
• Regularly check and maintain the battery, including the state of charge, electrolyte levels, and terminal connections.
• Store the battery properly when not in use for extended periods, using a battery maintainer or trickle charger, and keep it in a cool, dry place.
• Always follow the manufacturer's instructions for charging and maintaining your specific battery type.

By following these guidelines and choosing the right charger for your needs, you can ensure a reliable power source for your boating adventures.

Frequently asked questions