What size battery for Marine Boot?
, From Sally Zhuang, 15 min reading time
Choosing the right marine battery size is an important decision for boaters. Whether you're a first-time boater or a seasoned sailor, understanding the factors that go into selecting the right marine battery size is crucial for optimal performance. This article provides valuable insights and practical tips to help you make an informed decision.
What is a marine battery?
A marine battery is a specially designed deep-cycle battery used to power boats and other watercraft. It is engineered to withstand the challenges of a marine environment, such as vibration, shock, and constant contact with water. Marine batteries are typically deep-cycle batteries, meaning they can be repeatedly discharged and recharged without losing capacity. They provide the energy needed to start the boat's engine, operate electrical systems, and power onboard auxiliary equipment.
What role does the size of the marine battery play?
Marine battery size is important because it directly impacts 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 while 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:
- Boat type and size:Different boat types and sizes have different power requirements. For example, larger boats typically require larger batteries to accommodate their electrical systems and equipment.
- Power consumption: Determine the electrical devices and systems on board that require power. This includes electronics, lighting, pumps, appliances, and other accessories. Calculate the total power consumption to determine the required battery size.
- Climatic conditions:Extreme temperatures, both hot and cold, can affect a battery's performance and lifespan. Depending on the climate in which you operate your boat, you'll need to choose a battery with an appropriate cold cranking amps (CCA) or reserve capacity (RC) to ensure reliable performance in these conditions.
By carefully considering your boat type, power requirements, and climate conditions, you can select the right marine battery size to meet your specific needs and ensure reliable power on the water.
How do you calculate your boat's power needs?
Here are some steps you can take to calculate the boat's power needs:
- Make a checklist of all electrical equipment on your boat, including lights, bilge pumps, trolling motors, and other devices.
- Determine the current consumption of each device. This value is usually listed in amps in the boat's manufacturer's manual. If not available, use a multimeter to measure the amps.
- Note the runtime for each device.This is the length of time you plan to use each device during a charging cycle.
- Calculate the ampere-hour rating of each appliance by multiplying the ampere consumption by the operating time. For example, if a light bulb consumes 1 ampere and runs for 6 hours a day, the power consumption is 6 ampere-hours (Ah).
- Add the ampere-hour values of all devices to determine the total power consumption of the boat.
- Consider adding a margin of 20 to 30% to account for losses and temporarily higher power demands.
- Based on the total power consumption, determine the ampere-hour battery rating that meets your needs. Buy a battery with this Ah rating, as batteries on the market are sorted by ampere-hour.
Another way to express the same meaning is to calculate the total wattage of the electrical load. This is useful if you know the wattage of each appliance. To determine the amp-hour rating, divide the total wattage by the voltage of the boat's 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 watermaker.
- The total wattage would be:
Total power = 20 + 10 + 40 + 10 + 40 + 30 = 150 W
- If you plan to use these devices for six hours on a single charge, the watt-hour number is:
Watt hours = 150 W x 6 hours = 900 Wh
- To determine the ampere-hour rating for a 12V boat system, Divide the watt-hours by the voltage:
Ah = 900 Wh ÷ 12V = 75 Ah
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:
1.Lead-acid battery
Lead-acid batteries are the most common and cost-effective type of marine battery. They have been in use for a long time and come in two types: flooded and sealed. Flooded lead-acid batteries require regular maintenance, including checking the electrolyte level and topping up with distilled water. Sealed lead-acid batteries, also known as valve-regulated lead-acid (VRLA) batteries, are maintenance-free.
2.AGM battery (Absorbent Glass Mat)
AGM batteries are an advanced type of lead-acid battery. They use glass mat separators to contain the electrolyte, resulting in a leak-proof design. Compared to flooded lead-acid batteries, AGM batteries have a longer lifespan and require minimal maintenance. They also have lower internal resistance, allowing for faster charging and discharging.
3.Lithium-ion battery (LiFePO4)
Lithium-ion batteries are the most advanced and expensive option. In marine applications, the lithium battery type is LiFePO4. 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 at a premium. They also deliver 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 are LiFePO4 batteries 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. Here's an explanation of these benefits:
- Weight:LiFePO4 lithium batteries are significantly lighter than conventional lead-acid batteries. This weight reduction can be crucial for marine applications, enabling greater fuel efficiency and more accessible placement within the boat. The lower weight also contributes to improving the vessel's overall performance, particularly in terms of speed and maneuverability.
- Life:LiFePO4 lithium batteries tend to have a longer lifespan than other battery types. They can withstand a higher number of charge cycles, meaning they can be charged and discharged more often before their performance degrades. High-quality LiFePO4 batteries like Power Queen have a lifespan of up to 4,000–15,000 cycles, while lead-acid batteries only last 300–500. This extended lifespan is beneficial for marine applications where reliability and durability are critical, as it reduces the need for frequent battery replacement.
- Depth of discharge:LiFePO4 lithium batteries can be discharged further without causing damage. They can typically be discharged to 80–90% of their capacity without negatively impacting their overall service life or efficiency. This deeper discharge capability provides more usable capacity for marine applications and enables longer operating times on a single charge.
- Charging efficiency:LiFePO4 lithium batteries have excellent charging efficiency, allowing them to charge much faster than other battery types, such as lead-acid batteries. This faster charging capability is beneficial for marine vessels, reducing downtime and enabling faster turnaround times between trips.
- Size and space efficiency:Lithium-ion batteries have a higher energy density, meaning they can store more energy in a smaller package than other battery chemistries. This compact size allows for greater flexibility in boat design and provides more space for other important onboard equipment.
Although their initial cost is higher than other battery types, they are still a worthwhile investment due to their extremely long lifespan and other advantages.
Learn more about the customer reviews of Power Queen.
The standard size of marine batteries
The standard size of marine batteries can 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 ampere hours (Ah). Group 27 and Group 31 batteries are also commonly used in marine applications and offer higher capacities of around 90–105 Ah and 95–125 Ah, respectively.
These sizes are typically 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 motors
There are several different types of trolling motors you can use on your boat. Here are some of the most common types:
1.Rear mounted trolling motor
This is the most popular type of trolling motor and is mounted on the rear (transom) of the boat. It is easy to install and can be adjusted to various angles. Transom-mounted motors are versatile and suitable for a variety of boat sizes and types.
2.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 windy and rough water conditions. These motors typically include features such as GPS integration and wireless control.
3.Motor-mounted trolling motor
Engine-mounted trolling motors, also called auxiliary motors, are mounted directly on the cavitation plate of an outboard or inboard engine. They are ideal for larger boats and can be used as primary propulsion or as a supplement to the main engine.
4.Hand-controlled trolling motor
These trolling motors feature a tiller handle that allows you to manually control the motor. They are generally more affordable, easier to use, and suitable for smaller boats or anglers who prefer a hands-on approach.
5. Foot-controlled trolling motor
Foot-operated motors are operated via a pedal system, allowing for hands-free operation. They offer precise control and are popular with anglers who want to focus on fishing without having to constantly adjust the motor.
6.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-controlled motors offer convenience and flexibility, especially for anglers who want to move around while operating the motor.
The choice of trolling motor type depends on factors such as boat size, fishing style, water conditions and personal preference.It is 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 impacts the runtime it can provide. It's important to select a lithium battery with sufficient continuous discharge amperage to meet the trolling motor's maximum amperage draw. If you experience issues with your trolling motor when using lithium batteries, it's important to ensure that sufficient continuous amperage is available to allow the motor to operate at its maximum amperage draw. The table below shows the maximum amperage draw based on the motor's thrust.
| Trolling motor thrust/model | Required continuous discharge current |
| 30 lb | 30 |
| 40 lb., 45 lb | 42 |
| 50 lb., 55 lb | 50 |
| 70 lb | 42 |
| 80 lb | 56 |
| 101 lb | 46 |
| Engine Mount 101 | 50 |
| 112 lb | 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 |
Read more about the recommended battery system for trolling motors.
Tips for the maintenance and care of marine batteries
Proper maintenance and care is crucial to ensuring the longevity and performance of your marine battery.Here are some tips to help you keep your battery in good condition:
- Load:When charging your battery, follow the manufacturer's instructions. We generally recommend using a smart marine battery charger, which monitors and adjusts the charging process to prevent overcharging.
- Storage: If you're not using your boat for an extended period, remove the battery and store it in a cool, dry place. Make sure to charge it regularly to maintain its charge level and prevent sulfation.
- Cleanliness: Keep your battery clean and free of dirt, soot, and corrosion. Check the terminals regularly for signs of buildup and clean them as needed with a wire brush or a special battery cleaning solution.
- Connections:Make sure the battery connections are tight and secure. Loose connections can result in poor performance and shorten battery life.
- Electrolyte level (for lead-acid batteries): If you have a lead-acid battery, check the electrolyte levels regularly. If they're low, add distilled water to bring them up to the recommended level.
- Avoid deep discharges: Avoid deep discharging your battery, as this can shorten its lifespan. Charge the battery immediately after use and do not leave it discharged for extended periods.
- Temperature aspects: Extreme temperatures can affect battery performance. Avoid exposing your battery to excessive heat or cold, as this may reduce its capacity and lifespan.
- Regular inspections:Check your battery regularly for signs of damage or wear. If you notice bulges, cracks, or other abnormalities, it may be time to replace the battery.
Remember to always check the manufacturer's guidelines and recommendations for specific care instructions for your marine battery.
Frequently asked questions (FAQs) about marine batteries
- Can battery sizes be mixed on the boat?
Mixing battery sizes on a boat is generally not recommended. It's 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 battery damage. It's best to maintain consistency across your battery bank to optimize performance and extend the life of your batteries.
- What is the most common marine 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's important to note that the appropriate battery size depends on individual power requirements, so it's always best to consult the manufacturer's recommendations for your specific setup.
- 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 engineered to provide a stable and reliable power source over extended periods of time. This makes them ideal for powering electronics, trolling motors, and other accessories on a boat.
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