Boat Batteries: 12-Volt Standard For Reliable Marine Power

Marine batteries are used for two types of power needs: starting load and running load. Starting load requires a large, short-term burst of electricity to turn over the engine, while running load powers accessories like lights, trolling motors, and depth finders. A 12-volt battery is typically sufficient for most boat engines, but larger boats may require multiple batteries. For example, trolling motors often require 24 or 36 volts of power, which can be achieved by connecting two or three 12-volt batteries in series.

Boat battery types: starting, running, deep cycle, dual purpose

Marine batteries are designed to power everything from a boat's engine to electronics and accessories. They are built to withstand the unique challenges of the marine environment, such as constant motion, vibration, and exposure to moisture.

There are three main types of marine batteries, each serving a different purpose: starting, deep cycle, and dual-purpose.

Starting Batteries

Also known as cranking or engine start batteries, these batteries deliver quick bursts of energy to start the boat's engine. They are not designed for extended, continuous use. Starting batteries are specifically designed to provide high-cranking amps (CA) and cold-cranking amps (CCA) for quick engine ignition. CA and CCA refer to the battery's ability to deliver a burst of power at mild temperatures and in cold weather conditions, respectively.

Deep Cycle Batteries

Deep-cycle batteries are built to provide consistent power over a long period, making them ideal for running electronics, trolling motors, and appliances. These batteries are commonly used to power lights, trolling motors, fish finders, radios, and refrigerators. They are designed for steady, sustained energy output and can withstand repetitive deep discharging and recharging without damage. Deep-cycle batteries are crucial for boating activities that require a reliable and long-lasting power source.

Dual-Purpose Batteries

Dual-purpose batteries, as the name suggests, combine the cranking power of a starting battery with the deep-cycle capability. They deliver the high burst of power needed to start an engine and provide moderate sustained power for running electronics. While dual-purpose batteries are less efficient than specialized batteries, they are a good option for smaller boats with less demanding engines.

12-Volt Marine Batteries

12-volt marine batteries are commonly available and used for various marine applications. They are suitable for both deep cycle and starting battery types. The voltage of a marine battery is important as it determines the battery's power output and the rate at which it can charge or discharge.

Voltage requirements for trolling motors

The voltage requirements for trolling motors depend on the size and type of the motor. Trolling motors typically operate at 12 volts, 24 volts, or 36 volts. The motor's thrust level is a key factor in determining the necessary voltage configuration. For instance, a 55-pound thrust motor usually requires a single 12-volt battery, while a motor with 80 pounds of thrust or more will need two 12-volt batteries connected in series, totalling 24 volts.

The number of batteries needed is directly related to the trolling motor's thrust. If your motor produces 55 pounds of thrust or less, a single 12-volt battery is sufficient. Motors with a thrust greater than 55 pounds and up to 80 pounds require two 12-volt batteries connected in series, resulting in a total of 24 volts. For motors with a thrust exceeding 80 pounds, three 12-volt batteries connected in series are necessary to achieve a total of 36 volts. E-Drive motors are an exception, as they require four 12-volt batteries connected in series to produce a total of 48 volts.

It is important to note that the battery's group size, which refers to its physical dimensions, can influence your choice. Larger group size batteries tend to have higher amp-hour ratings, which determine how long the motor can run without recharging.

When selecting a battery for your trolling motor, you can choose from various types, including Flooded Lead Acid (FLA), Absorbent Glass Mat (AGM), Gel, and Lithium batteries. Each type has distinct features that may impact your decision. For example, FLA batteries are generally cheaper but require more maintenance, while AGM batteries are sealed and more expensive but demand less care. Gel batteries are maintenance-free and spill-proof but are temperature-sensitive. Lithium batteries, on the other hand, offer consistent power output and do not require the same level of maintenance as FLA batteries, but they are the most expensive option.

To ensure safety and compliance, it is crucial to adhere to marine regulations and standards for battery choices in your region. For instance, in the United States, only batteries that meet U.S. Coast Guard regulations and American Boat and Yacht Council (ABYC) standards should be used.

In summary, the voltage requirements for your trolling motor will depend on the motor's size and type, with 12-volt, 24-volt, and 36-volt configurations being the most common. The number of batteries and their group size will also depend on the motor's thrust level. Additionally, you have a choice between several battery types, each with its own advantages and disadvantages, so consider your specific needs and budget when making a selection.

How to connect two marine batteries in series

Marine batteries are available in 12-volt options, and connecting two of them in series is a good idea if you want to add a powerful stereo subwoofer system, cabin lighting, electric windlass, or any other electrical accessories to your boat.

Connecting two marine batteries in series involves increasing the voltage of the battery pack while keeping the amp-hour (AH) rating the same. Here is a step-by-step guide on how to do it:

• Select Appropriate Batteries: Choose two 12-volt marine batteries with the same voltage, capacity rating, and batch. This ensures you don't encounter charging problems or shorten the battery life.
• Connect the Batteries in Series: Using a jumper wire, connect the negative terminal of the first battery to the positive terminal of the second battery. This setup leaves you with a positive terminal on the first battery and a negative terminal on the second battery, which you can use for your boat's electrical system.
• Avoid Short-Circuiting: Never cross the remaining open positive and negative terminals with each other, as this will short-circuit the batteries and cause damage or injury.
• Consider a Crossover Cable: While not mandatory, you can add a crossover cable between the negative terminals of the two batteries for a proper dual-battery system.
• Use Appropriate Tools: Ensure that you have the right tools, such as a power drill, heavy-duty crimper or soldering gun, cable clamps, and tie-wraps, to make secure and safe connections.
• Follow Safety Guidelines: Always wear safety glasses when working with batteries, and have a water hose or another method to flush battery acid in case of accidental contact with eyes or skin.

By following these steps, you can successfully connect two marine batteries in series, providing your boat with the extra power it needs to run various electrical accessories.

Battery voltage maintenance

Testing Voltage Levels

To assess the health of your 12-volt marine battery, regularly test its voltage levels using a multimeter. A fully charged marine battery should read around 12.6 to 12.8 volts when not in use. Consistent testing can help you identify issues before they escalate. When you begin to consistently observe readings below 12.4 volts, it's an indication that your battery might not be holding a charge effectively, and you should consider replacing it.

Slow Cranking When Starting

One of the initial signs that your marine battery might be in trouble is slow cranking during the engine start-up. If you notice a sluggish or delayed response when turning the key, it could indicate a weakened battery due to internal corrosion or sulfation. Sulfation occurs when lead sulfate crystals form on the battery plates over time, hindering the chemical reactions necessary for efficient energy transfer.

Dimming Lights and Electronics

If you observe a gradual dimming of lights or a decrease in the performance of electronic gadgets, it's a red flag. Dimming indicates that the battery is struggling to maintain a consistent power output, potentially signaling the need for a replacement.

Frequent Jump Starts

If you find yourself needing to jump-start your boat more than three times within a short period, it's a clear sign that your battery is losing its ability to hold a charge and could leave you stranded. Frequent jump-starts can also harm the alternator and other electrical components over time.

Visible Damage or Corrosion

Perform regular visual inspections of your marine battery. Cracks, leaks, or excessive corrosion around the terminals are signs of trouble. Corrosion typically accumulates on the battery terminals, where metal components are exposed to the elements and electrolyte. Clean the terminals regularly, and replace the battery if you observe significant damage.

Maintenance Tips

• Keep the battery compartment well-ventilated, as gases escaping from the battery, especially from overcharged lead-acid batteries, can be explosive.
• Top up lead-acid batteries with distilled water as they need to be topped up from time to time. Tap water contains too many impurities and should not be used.
• When working around batteries, wear gloves to protect your hands from acid, and avoid getting acid on your clothing.
• Ensure that connections to the battery terminals are clean, bright, and well-made. Poor connections will increase electrical resistance, causing a voltage drop that can affect the performance of your electrical equipment.
• Keep the battery properly charged. All batteries will self-discharge if left idle. The discharge rate varies depending on the type, size, and age of the battery. Periodically charge a battery not in use to bring it up to full capacity.
• Use a marine smart battery charger, which is designed for permanent installation, can be safely left connected to the batteries, and will automatically reduce the charge to avoid overcharging.

Battery chargers

Marine batteries are indeed 12-volt batteries. If you're looking for a 12-volt marine battery, there are many options available from various vendors.

When it comes to battery chargers, there are a variety of options to choose from, depending on your specific needs and requirements. Here are some factors to consider when choosing a battery charger:

Voltage Compatibility: Ensure that the charger is compatible with your marine battery's voltage. In this case, you would need a charger that supports 12-volt batteries.

Charging Capacity: Consider the charging capacity of the charger, typically measured in amps. Different batteries may require different charging capacities, so it's important to match the charger to your battery's needs.

Number of Batteries: If you have multiple batteries, you may want to consider a multi-bank charger that can charge multiple batteries simultaneously. These chargers usually specify the number of banks and the amps per bank.

Charging Speed: Some chargers offer faster charging speeds than others. If you need to charge your batteries quickly, look for chargers with higher amp ratings or those specifically designed for fast charging.

Water Resistance: For marine applications, consider a waterproof or water-resistant charger to protect it from moisture and corrosion.

Solar Power: Solar battery chargers are an option if you want to utilise renewable energy. These chargers use solar panels to convert sunlight into electricity to charge your batteries.

• ProNautic offers a range of onboard marine battery chargers with different amp and bank configurations, such as the ProNautic 1240P (40 Amp, 12V, 3-Banks) and the ProNautic 1230P (30 Amp, 12V, 3-Banks).
• Noco Genius provides onboard marine battery chargers with various amp and bank configurations, like the GENPRO10X4 (40 Amp, 12V, 4-Bank) and the GENPRO10X3 (30 Amp, 12V, 3-Bank).
• WaveCharge offers a series of selectable 12V or 6V battery chargers with different amp configurations, including the WaveCharge Pro 2-Bank (12V, 20 AMP) and the WaveCharge 4-Bank (12V or 6V, 12 AMP).
• OPTIMA Batteries High Performance D34M BlueTop Dual Purpose battery, which is a 12-volt marine battery with 750 CCA and is maintenance-free.
• Weize Deep Cycle AGM 12 Volt 100Ah Battery, which is maintenance-free and has a 3% self-discharge rate, making it perfect for RVs, solar panels, trolling motors, and marine use.
• Renogy Deep Cycle AGM 12 Volt 100Ah Battery, featuring a 3% self-discharge rate and 1100A max discharge current, is ideal for RVs, camping, cabins, marine, and off-grid systems.

Frequently asked questions