Choosing The Right Boat Battery: A Guide

Marine batteries are an essential part of your boat's electrical system. They power everything from your boat's engine to electronics and accessories. There are three main types of marine batteries: starting (cranking) batteries, deep-cycle batteries, and dual-purpose batteries. Starting batteries deliver quick bursts of energy to start the boat's engine and are not designed for extended, continuous use. Deep-cycle batteries provide consistent power over a long period and are ideal for electronics, trolling motors, and appliances. Dual-purpose batteries combine the functions of starting and deep-cycle batteries but are less efficient than specialized batteries. When choosing a marine battery, it is important to consider the size and power needs of your boat, the type of battery (starting, deep-cycle, or dual-purpose), and the battery's capacity and reserve power. Additionally, maintenance and proper charging are crucial for extending the life of your marine battery.

Battery type: lead-acid or lithium

When it comes to choosing a battery for your boat, there are two main types to consider: lead-acid or lithium. Both have their own advantages and disadvantages, and the right choice for you will depend on your specific needs and requirements. Here, we will outline the key features of each type to help you make an informed decision.

Lead-acid batteries:

Lead-acid batteries have been a popular choice for boats and marine applications for many years. They are often referred to as the "standard" or "traditional" option and are known for their ruggedness and reliability. Lead-acid batteries are designed to handle deeper cycles than a standard car starter battery, making them suitable for both starting and energy tasks on a boat. They are usually fully sealed to prevent leaks and are vibration-resistant, which is important when operating a boat in choppy waters.

One of the main advantages of lead-acid batteries is their affordability. They typically have a lower initial cost than lithium batteries, making them a more budget-friendly option. Additionally, lead-acid batteries are widely available and can be found at most battery retailers.

However, lead-acid batteries do have some drawbacks. They tend to be heavier than lithium batteries, which can increase the overall weight of your boat and lead to higher fuel consumption. They also have a shorter lifespan and require more frequent replacement than lithium batteries. Lead-acid batteries need to be maintained properly to ensure optimal performance and can be damaged if not handled correctly.

Lithium batteries:

Lithium batteries, on the other hand, offer several advantages that have made them an increasingly popular choice for boat owners. One of the most significant benefits is their lightweight construction. Lithium batteries are known for their low weight, which can reduce the load on your engine and improve fuel efficiency. They also have a longer life cycle, often lasting up to 10 times longer than lead-acid batteries. This means you won't have to replace them as often, saving you time and money in the long run.

Another advantage of lithium batteries is their fast-charging capability. They can charge up to four times faster than lead-acid batteries, which is a significant advantage when you need to get back out on the water quickly. Lithium batteries also provide more usable power, maintaining a consistent voltage throughout their discharge cycle. This ensures that electrical equipment and motors receive a dependable performance.

However, there are some considerations to keep in mind with lithium batteries. They tend to be more expensive than lead-acid batteries, with a higher initial cost. Additionally, lithium batteries may not be suitable for starting applications and are typically recommended for deep-cycle energy applications instead.

In summary, both lead-acid and lithium batteries have their pros and cons. Lead-acid batteries are affordable, widely available, and suitable for both starting and energy tasks, while lithium batteries offer lightweight construction, longer lifespans, and faster charging capabilities. The best choice for your boat will depend on your budget, intended use, and specific requirements.

Battery purpose: starting, deep cycle, or dual-purpose

Marine batteries are available in three main types: starting, deep cycle, and dual-purpose. Each type serves a different purpose, and it's important to understand the differences to ensure you select the right battery for your boat.

Starting batteries, also known as cranking batteries, deliver quick bursts of energy to start the boat's engine. They are not designed for extended, continuous use. When choosing a starting battery, you should consider the engine size and the battery's marine-cranking amps (MCA) or cold-cranking amps (CCA) rating, which indicates its ability to crank the engine in low-temperature conditions.

Deep-cycle batteries, on the other hand, are designed to provide consistent power over a long period, making them ideal for running electronics, trolling motors, and appliances. These batteries have thicker plates and can withstand repetitive discharging and recharging. They are commonly used to power electrical systems such as lights, fish finders, radios, and refrigerators.

Dual-purpose batteries, as the name suggests, combine the characteristics of both starting and deep-cycle batteries. They can deliver the high burst of power needed to start the engine and provide a moderate amount of sustained power for running onboard electronics. Dual-purpose batteries are a good choice for small to mid-size boats that take shorter trips. However, they may not offer the same cranking amps or deep-cycle performance as specialised batteries.

When deciding between these battery types, consider your boat's size and power requirements. Smaller boats with minimal electronics may only need a starting battery, while larger vessels with sophisticated systems may require separate starting and deep-cycle batteries or a dual-purpose battery. Additionally, factors such as reserve capacity (RC), amp-hours (Ah), and battery maintenance should be considered to ensure optimal performance and longevity for your boat's battery.

Battery size: depends on boat's engine size and power needs

The size of the battery you need depends on the size and power requirements of your boat's engine.

First, you need to determine whether you will need one or two batteries. Smaller boats may only require one battery for engine starting and powering a few lights. However, larger boats or boats with high power usage should have two separate batteries: one for starting the boat and another deep-cycle battery to power electronics.

For starting batteries, you should consult your engine manufacturer's recommendations and focus on the battery's marine-cranking amps (MCA). MCA measures the amount of power your battery can deliver in a short burst, and this is vital for knowing you'll have enough power to start your engine in all conditions. A good rule of thumb is to have 1 cranking amp per cubic inch for gasoline engines and 2 cranking amps per cubic inch for diesel engines.

If you are using lead-acid batteries, you will need to double the battery rating as they are damaged by discharges deeper than 50%. Lithium-ion batteries, on the other hand, can be drained completely without suffering damage.

To estimate your boat's power needs, you should make a checklist of all the equipment on your boat and their electric consumption. Multiply the ampere consumption by the number of hours you expect to use each device between charges to determine the amp-hour rating. Then, add the amp-hour rating of each device to find the total power draw for your boat. It's recommended to get a battery that is larger than your baseline watt usage to account for any oversights.

In addition to power needs, you should also consider the weight of the battery as every pound counts on a boat. Lithium-ion batteries are generally lighter than other types of batteries. You should also ensure that the battery fits the dimensions of your battery compartment and that the voltage is compatible with your boat's electrical system.

Lastly, consider the Cold Cranking Amps (CCA) of the battery, which is important for starting your engine in cold conditions. A higher CCA rating will provide better cold-starting performance.

Battery capacity: measured in amp-hours (Ah)

Battery capacity is measured in amp-hours (Ah). This number indicates the battery's capacity to deliver a certain amount of current. The higher the Ah rating, the longer the battery can provide power. A 12v 125Ah battery, for example, has 125 amp-hours, meaning it can theoretically deliver 125 amps per hour.

When selecting a marine battery, it is important to consider the Ah rating to ensure the battery can meet your power requirements. If you are running electronics from your battery, the Ah rating becomes particularly important. A higher Ah rating will provide a longer runtime for your devices.

For deep-cycle batteries, amp-hours are a critical specification. Deep-cycle batteries are designed to provide consistent power over extended periods, making the Ah rating a key indicator of their performance.

When sizing a deep-cycle battery, it is recommended to size it to store three to four times the expected amount of energy used between recharge cycles. This ensures the battery can adequately meet your power needs.

Wet cell batteries, a type of lead-acid battery, typically have an amp-hour capacity ranging from 60 to 200 Ah. In contrast, gel cell batteries, another type of lead-acid battery, have a lower capacity and typically fall in the range of 20 to 101 Ah.

Lithium batteries, such as the Ionic 12V 100Ah and 12V 125Ah, offer dual-purpose functionality, serving as both starter and deep-cycle batteries. These batteries combine the advantages of both battery types, providing ample capacity for your power needs.

When choosing a marine battery, consider the Ah rating to ensure it aligns with your intended usage. This will help you select a battery that can deliver the required amount of current for your boat's electrical systems and accessories.

Battery maintenance: keep terminals clean, prevent vibration, and store correctly

Battery maintenance is crucial to ensure your boat's battery remains in good condition and performs effectively. Here are some detailed instructions to help you keep your battery well-maintained:

Keep Terminals Clean:

• Before taking your boat out on the water, clean the battery terminals and connections using a wire brush to remove any dirt or debris. It is important to do this at the start of each season.
• After cleaning, apply an anti-corrosion spray or terminal protector to provide an additional layer of protection against corrosion. This step is especially crucial for boats exposed to saltwater environments, as salt can accelerate corrosion.
• Check your battery connections and ensure tight terminal connections. You can also use anti-corrosion pads made of fibre between the terminals and cables for added protection.

Prevent Vibration:

• Use a battery protector, such as a battery mat or cushion, to absorb shock and vibration. These protectors are designed to fit under your battery and can be easily trimmed to the desired size. They help to secure the battery and reduce the impact of vibrations, especially when navigating rough waters.
• Ensure your battery is securely fastened in its tray or box. A well-secured battery is less likely to shift during operation, reducing the risk of damage from vibrations.

Store Correctly:

• At the end of the boating season or when the battery will be unused for an extended period, remove the battery and store it in a cool, dry, and well-ventilated place.
• Choose a storage location away from saltwater, freezing temperatures, and excess humidity. Garages or storage facilities with wooden surfaces are recommended.
• Before storing, charge your batteries one final time to reduce the risk of freezing during the off-season.
• Disconnect the negative cable and wait a few hours before checking the specific gravity or voltage.
• Check the specific gravity or voltage using a hydrometer or voltmeter, respectively.
• Disconnect the terminals to remove all electrical loads from the battery. Even when "off," electronics can still draw small amounts of power, slowly draining the battery over time.
• Store the battery in an easily accessible location to facilitate periodic charging.
• Use the correct charger for your battery type. Smart chargers can help prevent overcharging.
• Trickle charge or charge your battery monthly to prevent self-discharge and extend its lifespan. Fully charged batteries are also less likely to freeze.

Frequently asked questions