Boat Batteries: Staying Charged And Maintained

Boaters need to keep their boat batteries charged to avoid getting stranded in the middle of a lake with a dead battery. Boat batteries are responsible for starting the engine and powering the electronics on board, such as lights, GPS, and radios. There are two main ways to charge a boat battery: using an onboard charger or a portable charger. Onboard chargers are permanently installed and connected to the boat's electrical system, while portable chargers can be used anytime, anywhere. When charging a boat battery, it's important to select the right charger for the specific type of battery and to ensure that the battery terminals are clean. Additionally, it's crucial to not overcharge the battery, as this can cause irreparable damage. Proper maintenance of boat batteries includes regular cleaning, checking for corrosion, and storing them in a cool, dry place when not in use.

Onboard vs. portable chargers

Onboard and portable chargers are the two primary methods of keeping boat batteries charged. The choice between the two depends on factors such as boating habits, frequency of use, and budget. Here is a detailed comparison between onboard and portable chargers:

Onboard Chargers

Onboard marine chargers are permanently installed on the boat and connected directly to its electrical system. They offer the convenience of automatic charging, as they continuously monitor the battery's condition and adjust the charging rate accordingly. Onboard chargers are ideal for boaters who frequently stay near shore power sources or marinas, eliminating the need to carry a portable charger. Onboard chargers can be further categorised into two types:

• Waterproof Onboard Chargers: These chargers are designed to survive wet conditions and are commonly found on bass boats and other open boats. They charge each battery individually, making them suitable for multi-voltage applications. However, their sealed design limits heat dissipation, making them unsuitable for larger boats with higher charging requirements.
• Vented Onboard Chargers: Vented chargers are suitable for cruisers, yachts, and larger boats with shore power connections. They can handle heavier-capacity batteries and are mounted in dry areas to avoid contact with water. Their vented design, along with cooling fans in some models, aids in heat dissipation during the charging process.

Portable Chargers

Portable marine chargers are compact and versatile, allowing them to be carried on board or used on land when docked. They offer flexibility and are preferred by boaters who frequently venture far from shore power sources. They come in various models, including manual, automatic, and smart chargers, catering to different battery types. Portable chargers are a cost-effective option compared to installing onboard systems. Additionally, they are easy to use and can be simply plugged into an extension cord for charging.

The decision to choose between onboard and portable chargers depends on individual boating needs and preferences. Onboard chargers provide the convenience of automatic charging and permanent installation, while portable chargers offer flexibility and are suitable for various boating scenarios. Budget and boating habits are also important considerations when making this decision.

Choosing the right charger

Battery Type and Compatibility

Firstly, determine the type of battery you have. Common types include AGM (Absorbed Glass Mat), gel, flooded, and lithium batteries. The chosen charger should be compatible with your battery type. For instance, gel cell batteries require a charger designed or adjustable for gel cell batteries.

Voltage

The charger's voltage must match the output voltage of your battery. If you have a 12V battery, you'll need a 12V charger. If you have multiple 12V batteries in a series setup, the output voltage doubles, and you'll require a charger with the corresponding voltage.

Amp Rating

The amp rating, or amperage, of the charger determines how quickly your battery will recharge. Higher amp ratings result in faster recharging. To calculate the amp rating you need, multiply the amp-hour rating of your battery by 10%. For example, a Group 24 battery with an 85-amp hour rating would require a charger with at least an 8.5-amp output.

Number of Batteries

Consider whether you have more than one battery to recharge. Many boats utilise multiple batteries to power different components. If you need to charge several batteries, look for a multi-bank charger that can simultaneously charge multiple batteries.

Charging Time

The charging time is influenced by the amp rating of the charger. Higher amp ratings lead to faster charging. However, it's important not to exceed the maximum recommended charging time to avoid damaging your battery.

User Interface

Choose a charger with a clear and user-friendly interface. This will allow you to easily monitor the charging status and select different charging modes.

Safety

Prioritise safety by selecting a charger that prevents overcharging and overheating. Smart chargers are a good option as they automatically adjust the charging process to avoid overcharging.

Permanent vs. Portable

Decide between a fixed onboard charger or a portable charger. Onboard chargers are convenient for boats used near shore power sources, while portable chargers offer versatility and are useful for boats that venture further from shore.

Environmental Conditions

Consider the ambient temperature of the environment you'll be operating your boat in. If you plan to use your boat in extremely high or low temperatures, you may need to adjust the charging voltage accordingly.

Battery Banks

The term "bank" refers to a single connection from the battery to the charger. If you have multiple batteries, a multi-bank charger will allow you to charge them simultaneously.

Dimensions

Don't forget to consider the physical size of the charger and whether it will fit in the available space on your boat. Also, check the cable lengths to ensure they are sufficient for your setup.

Charging times

The charging time for a boat battery depends on several factors, including the type of battery, the charger used, and the battery's charge level.

Onboard Chargers

Onboard chargers are permanently installed on the boat and connected directly to the boat's electrical system. They offer automatic charging by continuously monitoring the battery's condition and adjusting the charging rate. Onboard chargers are typically connected to a standard 120-volt outlet and charge relatively quickly. They are also equipped with protection against overcharging, switching to a float or maintenance mode once the battery reaches its ideal charge state.

Portable Chargers

Portable chargers are less expensive and can be used anytime, anywhere. They are ideal for charging a boat's battery while it is afloat. However, they may take longer to charge a battery fully compared to onboard chargers.

Charging Time Calculation

The charging time for a marine battery can be determined by dividing the battery's amp-hour rating by the amperage of the battery charger. For example, a 75Ah battery charged with a 7.5-amp charger will take approximately 10 hours to fully charge.

It is worth noting that higher-amp chargers can damage batteries due to the generation of higher temperatures. Therefore, it is recommended to avoid chargers with amperage above 20 amps.

Battery Types

The type of battery also influences charging time. Deep-cycle batteries, for instance, have thicker plates and can be drained and recharged multiple times. AGM (absorbed glass mat) batteries have excellent life cycle expectancy if they are not discharged more than 60% between recharges, while some deep-cycle batteries offer 80%+ deep cycle abilities.

Additional Factors

Other factors that can impact charging time include the battery's charge level before charging and the charging temperature. It is recommended to maintain a full charge on boat batteries, as lead-acid batteries are prone to sulfation if kept in a partially charged state for extended periods. Additionally, the optimal charging temperature for ionic lithium batteries is above freezing, although they can be charged at temperatures as low as -4°F without causing damage.

Battery maintenance

Boat batteries are the heart of your vessel, so it's crucial to keep them well maintained. Here are some detailed tips to ensure your boat batteries stay charged and in good condition:

• Battery Type Awareness: Familiarize yourself with the type of battery in your boat, such as cranking (starting), dual-purpose, or deep-cycle batteries. Each type has different functions and requirements.
• Charging Practices: Always keep your battery fully charged. Lead-acid batteries are prone to sulfation if they remain partially charged for extended periods. Lithium batteries are less susceptible, but it's still best to keep them charged.
• Avoid Overcharging: Overcharging can damage batteries and reduce their lifespan. Use smart chargers that prevent overcharging, or manually monitor the charging process.
• Regular Maintenance: Periodically check the battery's state of charge, electrolyte levels (for flooded batteries), and the condition of the terminal connections. Clean terminals if they're corroded and ensure they're tight.
• Proper Storage: When not using your boat for extended periods, disconnect the batteries and store them in a cool, dry place. Consider using a battery maintainer or trickle charger to keep the battery in good condition during storage.
• Manufacturer's Instructions: Always refer to the manufacturer's guidelines for charging and maintaining your specific battery type. This includes recommendations for voltage, amperage, and charging procedures.
• Battery Compatibility: If using multiple batteries, avoid mixing battery types or old and new batteries. This can lead to underperformance and shorten the lifespan of your battery bank.
• Cleanliness and Safety: Keep your batteries clean and free from dust or debris. Always wear gloves when working with batteries to protect your hands from acid. Be cautious of flammable materials and sparks when working around batteries.
• Battery Replacement: Batteries typically last for about three to five years, depending on maintenance and usage. When a battery reads 11.8 volts, it's considered dead and needs replacement. Consult your boat dealer for recommendations and proper disposal of old batteries.
• Charger Selection: Choose a charger that matches the voltage and capacity of your battery. Lower-amp chargers are generally better for your battery but take longer to charge. Avoid chargers over 20 amps as they can cause damage.
• Battery Voltage: Know the voltage at which your battery is fully charged. For example, a flooded battery is fully charged at 12.6 volts, while an AGM battery is fully charged at 12.8 volts.
• Battery Tender or Smart Charger: Using a battery tender or smart charger can help maintain your battery's charge without overcharging. These devices can extend the life of your battery and improve its performance.

Battery storage

Storing your boat batteries correctly is essential to ensure they remain in good condition and prolong their lifespan. If your boat is not in use for an extended period, it is recommended to use a battery maintainer or trickle charger to keep the battery in good condition. This is especially important for deep-cycle batteries, which have thicker plates. A trickle charger helps to even out the charge in the battery.

When storing boat batteries, always keep them in a cool, dry place. Batteries should be fully charged before storage and maintained at a full charge level. Lead-acid batteries, in particular, are prone to sulfation if they remain in a partially charged state for extended periods. Lithium batteries are less susceptible to this issue and can withstand being partially charged without significant harm.

It is also crucial to keep the batteries clean and check for corrosion regularly. Corrosion can be cleaned off using a solution of baking soda and water. Ensure that the battery terminals are tight and free from grime, as dirty terminals can disrupt the charging process and make it less efficient.

Additionally, when storing your boat batteries, make sure to follow the manufacturer's instructions and guidelines for charging and maintenance specific to your battery type. By properly storing and maintaining your boat batteries, you can maximize their lifespan and ensure reliable performance when you need them.

Frequently asked questions