Choosing the right marine battery size is an important decision for boaters. Whether you're a first-time boat owner or an experienced sailor, understanding the factors involved in selecting the right size marine battery is critical to optimal performance. This article will provide you with valuable insights and practical tips to help you make an informed decision.
What is a ship's battery?
A marine battery is a specially designed deep cycle battery used to power boats and other watercraft. It is designed to withstand the challenges of a maritime environment such as vibration, shock and constant contact with water. Marine batteries are usually deep cycle batteries, i.e. H. they can be discharged and recharged repeatedly without losing their capacity. They provide the energy necessary to start the boat engine, operate electrical systems and operate additional devices on board.
What role does the size of the naval battery play?
The size of the marine battery is important because it directly affects the performance and reliability of your boat's electrical system. Choosing the right size marine battery ensures you have enough power to start your engine, run your electronics, and meet your power needs when you're on the water.
The size of a marine battery is typically determined by its physical dimensions, weight and electrical capacity. A battery's electrical capacity is measured in ampere-hours (Ah) and refers to the total amount of charge it can deliver over a given period of time.
How to choose the size of a marine battery?
When choosing the size of a marine battery, you need to consider several factors:
Careful consideration of boat type, power requirements and climatic conditions will help you select the right marine battery size to meet your specific needs and ensure reliable power on the water.
How do you calculate the power requirements of your boat?
Here are some steps you can take to calculate the boat's power requirements:
- Make a checklist of all electrical devices on your boat, including lights, bilge pumps, trolling motors and other devices.
- Determine the power consumption of each device. This value is usually specified in the boat's manufacturer's manual in amps. If not available, use a multimeter to measure the amps.
- Note the runtime for each device. This is the length of time you want to use each device during a charging cycle.
- Calculate the amp-hour rating of each device by multiplying the amp consumption by the operating time. For example, if a light bulb uses 1 amp and runs 6 hours a day, the power consumption is 6 amp hours (Ah).
- Add the amp-hour ratings of all devices to determine the boat's total power consumption.
- Consider adding a margin of 20 to 30% to account for losses and temporarily higher power requirements.
- Use total power consumption to determine the amp-hour battery rating that meets your needs. Buy a battery with this Ah rating as the batteries on the market are sorted by amp hours.
Another way to express the same meaning is to calculate the total wattage of the electrical load. This is useful if you have the wattage of each device. To find the amp-hour rating, divide the total wattage by the voltage of the boat system.
For example, let's say you have a 20W light, a 10W navigation system, a 40W autopilot system, a 10W radar, 40W navigation lights and a 30W water purifier. The total wattage would be:
Therefore the battery you need for the boat is at least 12V 75Ah, a 12V 100Ah battery would be suitable.
Types of marine batteries based on chemistry
There are different types of marine batteries based on their chemistry. Here are some common ones:
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Lead-acid battery
Lead-acid batteries are the most common and cost-effective type of marine batteries. They have been in use for a long time and come in two versions: flooded and sealed. Flooded lead-acid batteries require regular maintenance, including checking electrolyte levels and topping up with distilled water. Sealed lead-acid batteries, also known as valve-regulated lead-acid batteries (VRLA), are maintenance-free.
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AGM battery (Absorbent Glass Mat)
AGM batteries are an advanced type of lead-acid batteries. They use glass mat separators to hold the electrolyte, resulting in a leak-proof design. AGM batteries have a longer lifespan compared to flooded lead-acid batteries and require minimal maintenance. They also have lower internal resistance, allowing for faster charging and discharging.
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Lithium-ion battery (LiFePO4)
Lithium-ion batteries are the most advanced and expensive option. For marine applications, the type of lithium battery is LiFePO4 battery. They offer incredible energy density and long cycle life. Li-ion batteries are much lighter and more compact than lead-acid batteries, making them ideal for applications where weight and space are critical. They also provide a constant output voltage throughout the discharge cycle.
These are just a few examples of marine battery types based on their chemistry. Each type has its own advantages and considerations. Therefore, it is important to assess your specific needs and budget before making a decision.
Why LiFePO4 batteries are most recommended?
LiFePO4 lithium batteries are often considered the best option for marine boats because they offer several advantages in terms of weight, lifespan and other important factors. You can find an explanation of these advantages here:
Although their initial cost is higher than other types of batteries, their extremely long lifespan and other advantages make them a worthwhile investment.
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The standard size of Ship Battery
The standard size of marine batteries may vary depending on the specific application and boat size. However, the most common marine battery size is Group 24, which typically has a capacity of around 75-85 amp hours (Ah). Group 27 and 31 batteries are also commonly used in marine applications and offer higher capacities of around 90-105 Ah respectively. 95-125Ah.
These sizes are commonly available in various battery chemistries such as lead-acid, AGM and lithium-ion. Larger boats may require multiple batteries or larger capacity batteries to meet their power needs. It is important to consider factors such as electrical load requirements, expected runtime, and available space before selecting the appropriate battery size for your specific marine application.
Group |
Size (inches) |
24 |
10.25 x 6,81 x 8,88 |
24F |
10,75 x 6,81 x 8,88 |
24H |
10,25 x 6.81 x 9.38 |
24R |
10,25 x 6.81 x 9 |
24T |
10.25 x 6.81 x 9.75 |
27 |
12.06 x 6.81 x 8.88 |
27F |
12.5 x 6.81 x 8.94 |
27H |
11.75 x 6.81 x 9.25 |
31 |
13 x 6.72 x 9.44 |
8D |
20.75 x 11.13 x 9.88 |
Different types of trolling motor
There are different types of trolling motors you can use for your boat. Here are some of the most common types:
Rear mounted trolling motor
This is the most popular type of trolling motor and is mounted on the back (transom) of the boat. It is easy to install and can be adjusted to different angles. Transom mount motors are versatile and suitable for different sizes and types of boats.
Bow-mounted trolling motor
Bow mount trolling motors are mounted on the front (bow) of the boat. They offer better maneuverability and control, especially in wind and rough water conditions. These motors usually have features like GPS integration and wireless control.
Motor Mounted Trolling Motor
Motor-mounted trolling motors, also called auxiliary motors, are mounted directly to the cavitation plate of an outboard or inboard motor. They are ideal for larger boats and can be used as primary propulsion or as a supplement to the main engine.
Hand controlled trolling motor
These trolling motors have a tiller handle that allows you to control the motor manually. They are generally cheaper, easier to use and suitable for smaller boats or anglers who prefer a hands-on approach.
Foot controlled trolling motor
Foot-controlled motors are operated via a pedal system, allowing hands-free operation. They offer precise control and are popular with anglers who want to concentrate on fishing without having to constantly adjust the motor.
Remote controlled trolling motor
These trolling motors come with a wireless remote control that allows you to control the motor from anywhere on your boat. Remote control motors offer convenience and flexibility, especially for anglers who want to move around while operating the motor.
Choosing the type of trolling motor depends on factors such as boat size, fishing style, water conditions and personal preference. It's important to consider your specific needs and the features that will enhance your boating and fishing experience.
Recommended size for trolling motor
The amp-hour rating of a battery directly affects the runtime it can provide. It is important to select a lithium battery with sufficient continuous discharge current to accommodate the maximum amp draw of the trolling motor. If you experience problems with your trolling motor when using lithium batteries, it is important to ensure that there is enough continuous power available to allow the motor to operate at its maximum current draw. The table below shows the maximum current draw based on motor thrust.
Trolling Motor Thrust/Model |
Required continuous discharge current |
30lb |
30 |
40 lb., 45 lb |
42 |
50 lb., 55 lb |
50 |
70lb |
42 |
80lb |
56 |
101lb |
46 |
Engine Mount 101 |
50 |
112lb |
52 |
Engine Mount 160 |
116 |
E-drive |
40 |
Talon Shallow Water Anchor |
30 |
Raptor Shallow Water Anchor |
70 |
Note: A starter battery is not suitable for use with an electric trolling motor.
Thrust range |
LiFePO4 battery capacity |
Recommended battery |
30 to 55 pounds |
50-100 Ah |
|
55 to 80 pounds |
100-150 Ah |
|
80 to 100 pounds |
150-200 Ah |
|
200 to 300 pounds |
200-300 Ah |
Power Queen 12V 410Ah |
Tips for maintenance and care of marine batteries
Proper maintenance and care is critical to ensuring the longevity and performance of your marine battery. Here are some tips to help you keep your battery in good condition:
Remember to always follow the manufacturer's guidelines and recommendations for specific care instructions for your marine battery.
Frequently asked questions (FAQs) about marine batteries
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Can battery sizes be mixed on the boat?
It is generally not recommended to mix battery sizes on a boat. It is best to have batteries of the same size, type, and age in the same battery bank. Mixing different sizes or capacities can cause imbalances in the charging and discharging process, resulting in reduced performance and possible damage to the batteries. It is best to maintain consistency in the battery bank to optimize performance and extend the life of your batteries.
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What is the most common ship battery size?
The most common marine battery size is typically Group 24. Group 24 batteries are widely used in a variety of marine applications, including starting batteries for smaller boats and general-purpose batteries for boats with moderate power requirements. These batteries offer a good balance of size, capacity, and affordability, making them a popular choice for many boaters. However, it is important to note that the appropriate battery size depends on individual power requirements. Therefore, it is always best to consult the manufacturer's recommendations for your specific setup.
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Does a boat need a deep cycle battery?
Deep cycle marine batteries are specifically designed for continuous discharge and cyclic use, making them an essential component for boaters. Unlike starter batteries, which are optimized for starting an engine, deep cycle batteries are designed to provide a stable, reliable power source over an extended period of time. This makes them ideal for running electronics, trolling motors and other accessories on a boat.