Charging Boat Batteries: Keep Your Boat Afloat

Keeping your boat battery charged is crucial to ensuring a seamless and worry-free boating experience. There are two main types of boat battery chargers: onboard and portable. Onboard chargers are permanently installed on the boat and connected directly to the electrical system, offering automatic charging. Portable chargers, on the other hand, are compact and versatile, designed to be carried on board or used on land. They come in various models, including manual, automatic, and smart chargers. The choice between the two depends on factors such as boating habits, frequency of use, and budget. To maintain battery health, it is important to avoid overcharging, conduct regular maintenance, and store the battery correctly.

Onboard vs. portable chargers

Onboard and portable chargers are the two types of boat battery chargers available. The choice between the two depends on factors such as boating habits, frequency of use, and budget. Here is a detailed comparison between the two:

Onboard Marine Battery 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. Onboard chargers are ideal if you frequently use your boat near shore power sources or marinas, eliminating the need for a portable charger.

Onboard chargers can have up to four separate battery chargers (called "banks") housed in a single casing, allowing you to charge multiple batteries simultaneously. They usually come with protection against overcharging, switching to a float or maintenance mode once the battery is fully charged.

Portable Marine Battery Chargers:

Portable marine chargers are compact and versatile, designed to be carried on board or used on land when docked. They offer flexibility and are crucial if you frequently find yourself far from shore power or marinas. With a portable charger, you can recharge your batteries wherever you anchor. They are also cost-effective compared to installing onboard systems.

Portable chargers come in various models, including manual, automatic, and smart chargers, catering to different battery types. Smart chargers, in particular, are excellent for marine use due to their advanced technology, employing a multistage charging approach to speed up the process and safeguard battery longevity.

The decision to choose between onboard and portable chargers depends on your specific needs. Onboard chargers provide the convenience of automatic charging and simultaneous charging of multiple batteries, while portable chargers offer versatility and are essential for remote boating adventures.

How to choose the right charger

Choosing a battery charger for your boat can be more complicated than choosing other marine electronics because there are additional factors to consider when charging batteries in a marine environment. Here are some key considerations to help you select the right charger:

Battery Type

Firstly, determine the type of battery you have. This could be an AGM (absorbed glass mat), flooded, or gel battery. Knowing your battery type will help you choose a compatible charger.

Input Voltage

The input voltage for marine batteries is typically either 120 or 230 VAC. The voltage of the charger must match the output voltage of your boat's battery. For example, if you have a 12V battery, you'll need a 12V charger.

Battery Capacity

Check the battery's capacity, which should be listed on the battery as "Ah" (amp-hour capacity). This information is crucial for determining the correct charging rate and choosing a suitable charger.

Charging Rate and Overcharging

A safe charging rate is generally accepted as about 20% of the Ah capacity of your battery. For example, a 100 Ah battery should be charged at a 20 Adc rate. Overcharging can damage your battery, so choose a charger that won't overcharge.

Battery Bank Configuration

If you use a battery bank with multiple batteries, ensure the charger is compatible with this setup. Some chargers have separate banks for different battery types, allowing you to charge multiple batteries simultaneously.

Environmental Conditions

Consider the environmental conditions in which you'll be operating your boat. The ambient temperature can affect the type of charger you should buy. Higher temperatures require lower charging voltages, and vice versa.

Waterproof and Vented Chargers

If your boat is frequently exposed to wet conditions, consider a waterproof charger. However, keep in mind that waterproof chargers may have limited heat dissipation capabilities, making them less suitable for larger boats or continuous loads. In such cases, a vented charger might be a better option.

Smart Chargers

Modern "smart" chargers offer advanced features such as automatic charging, multi-stage charging, temperature compensation, maintenance mode, and diagnostic functions. These features help prolong battery life, enhance safety, and provide more efficient charging.

Portable vs. Onboard Chargers

Depending on your boat's size and setup, you may opt for a portable charger or an onboard mounted charger. Portable chargers are suitable for smaller boats like dinghies, kayaks, and fishing boats, while onboard chargers are ideal for larger vessels.

By carefully considering these factors, you can choose the right charger for your boat's battery, ensuring reliable and long-lasting battery power during your time on the water.

Overcharging

Lithium batteries, in particular, favour the inclusion of a battery management system (BMS) in most applications on boats. The BMS ensures that the battery is not over or undercharged, and that it doesn't overheat, freeze, or have to deal with oversized currents. While the BMS will protect the batteries, it does little to protect your charging sources, such as your alternator, solar or wind chargers, wiring, or electronics.

Charging sources can be permanently damaged when they are run at full blast for too long to charge your less-than-fully-charged lithium batteries. Lithium-ion or LiFePO4 batteries seek charging at full speed ahead until they are 100% charged. Therefore, careful consideration must be given to the charging source's future health during an upgrade to lithium batteries. While those same chargers will push power out as hard as requested, the chargers are not designed to run at 100% output for an extended period. At worst, a charger will be ruined quickly; at best, it will prematurely wear out over time running continuously at full output.

One charging source that is at high risk is your alternator. With lead-acid batteries, the last 10% to 20% of the battery capacity in amps will only be charged very slowly, and the alternator relaxes its output. Lithium batteries, on the other hand, request 100% full-blast current, and if the alternator is willing to pump it out, the batteries will take it full blast until almost 100% charged. This will cause premature or instant failure of the alternator, as it will work hard at full output for too long.

To prevent such damage, you can install an external regulator like the Balmar MaxCharge 614 Alternator regulator, which has alternator temperature regulation and built-in belt manager software. The belt manager software allows the boat owner to easily limit the percentage of maximum output the alternator is allowed to produce.

Battery maintenance

To keep your boat batteries in good condition, it is important to follow some basic maintenance practices. Here are some detailed instructions to help you maintain your boat batteries effectively:

Charging and Storing Batteries:

Before storing your boat for an extended period, such as during the winter, charge your batteries one last time to prevent them from freezing in cold weather. It is recommended to disconnect the terminals from any electrical loads, as even a small load can damage the battery when not in use.

When storing your batteries, choose a cool, dry place, like a garage, to prevent freezing temperatures from damaging the battery. Ensure that the storage area has easy access to an outlet for convenient charging.

It is important to use a charger that is specifically designed for your battery type. While some chargers are compatible with multiple battery types (flooded, AGM, and lithium), not all chargers are universal. Select a charger that matches the voltage of your battery (e.g., a 12V battery requires a 12V charger).

Charging Options:

You can choose between onboard and portable marine battery chargers. Onboard chargers are permanently installed, automatically charging the batteries, while portable chargers are versatile and can be carried on board or used on land.

Onboard chargers are ideal if you frequently use your boat near shore power sources or marinas, eliminating the need to connect a portable charger each time. On the other hand, portable chargers offer flexibility and are crucial if you often find yourself far from shore power.

Charging Techniques:

There are different methods of charging your boat batteries:

• Shore Power Charging: This is the most common method when docked at a marina or connected to an external power source. It involves using a battery charger designed for marine use.
• Offshore Charging: This method uses onboard generators or alternative power sources, such as solar power systems, to charge the batteries while away from the mainland.
• Alternator Charging: The boat's engine alternator can charge the batteries while on the water. However, it primarily maintains the starting battery's charge and may not fully recharge a deep cycle battery.
• Regularly check the battery's state of charge, electrolyte levels (for flooded batteries), and the condition of terminal connections.
• Clean the terminals if they show signs of corrosion and ensure they are tight.
• Avoid overcharging: Overcharging can reduce the battery's lifespan. Smart chargers can help prevent this by monitoring battery conditions and adjusting the charging process accordingly.
• Maintain a full charge: Lead-acid batteries should be stored at nearly full charge to prevent sulfation. Lithium batteries, while less susceptible, should be stored at around 50% charge and monitored to prevent dropping below 30%.
• Follow manufacturer guidelines: Always refer to the manufacturer's instructions for charging and maintaining your specific battery type.

Winter storage

When the temperatures drop, many boat owners put their boats into storage for the winter. Before doing so, it's important to understand how to store your boat battery correctly to ensure it remains in good working condition. The best approach depends on the climate, the type of battery, and the facilities available.

One option is to remove the batteries from the boat and store them in a cool, dry place, such as a garage, where they won't freeze. This method is recommended if you have a lead-acid battery and your boat is stored in an area that experiences sub-zero temperatures. Before removing the battery, be sure to charge it to reduce the risk of freezing during the cold weather. Disconnect the terminals from any electrical loads, as even a small load can damage the battery over time.

If you choose to remove your battery, store it in a place with easy access to an outlet so you can charge it monthly or keep it connected to a trickle charger. This prevents self-discharge and extends the battery's lifespan. When charging, always use a charger that is designed for your specific battery type.

If you have a lithium-ion battery, such as a Battle Born LiFePO4 battery, it is less impacted by cold weather and will not freeze under most conditions. In this case, you can usually leave the battery in the boat during winter storage, as long as temperatures remain above -15°F. Fully charge the battery and use the battery disconnect switch when you're away from the boat.

Another approach is to use an onboard charging system, which allows you to keep the batteries on your boat. However, this method can be controversial as it may damage the batteries and even pose a fire hazard. If you choose this option, be sure to follow the manufacturer's instructions carefully to avoid any potential risks.

In summary, the key to successful winter storage of your boat battery is to ensure it is properly charged, protected from extreme temperatures, and maintained according to the manufacturer's recommendations. By taking these steps, your battery will be ready for the boating season when spring arrives.

Frequently asked questions