Choosing The Right Battery Size For Your 28Hp Boat

Choosing the right battery for your boat is essential to ensure optimal performance and avoid damage to the boat's electrical system. The size of the battery will depend on several factors, including the boat's engine size, power requirements, and physical dimensions of the battery compartment.

It is crucial to select a battery that meets the minimum power requirements and has sufficient cranking amps (CA) or cold-cranking amps (CCA) to start the engine, especially in cold conditions. Additionally, the battery's reserve capacity, typically measured in amp hours (Ah), is important to consider for running electrical devices for extended periods.

For a 28hp boat engine, it is recommended to refer to the manufacturer's specifications and choose a battery that meets or exceeds their recommendations for cranking amps and reserve capacity. The physical dimensions of the battery compartment will also play a role in determining the suitable battery size, ensuring a proper fit without modifying the battery tray.

Battery type: Marine vs standard

Marine batteries are designed to handle the unique challenges of the marine environment. They are built to provide power to the boat's engine, electronics, and accessories. On the other hand, standard car batteries have a very specific role: to provide enough amperage to turn over a gasoline or diesel engine. Marine batteries are designed to discharge energy over a longer period, while car batteries discharge large amounts of energy in a short period of time.

Marine batteries feature thicker internal lead plates than car batteries, allowing them to discharge energy over a longer period. Their housings are also typically larger, with extra plastic protection, as boating environments can be rough due to choppy currents and wake from other watercraft. Marine batteries are also designed to be sturdier, with elevated electrical connectors to prevent them from getting wet and short-circuiting.

When it comes to battery type, marine batteries use ""marine cranking amps" (MCA) instead of the standard automotive "cold cranking amps" (CCA). Boat batteries are tested at the freezing point, while car batteries are tested below freezing. This is because pleasure boats typically operate in warmer waters rather than icy conditions.

In terms of maintenance, marine batteries require proper charging to extend their life. It is important to only use a charger designed for marine batteries, as overcharging or undercharging can reduce their lifespan. Different types of marine batteries also require different charging voltages. For example, a 12-volt deep-cycle marine battery should be charged to around 14.4-14.8 volts. Additionally, it is recommended to use a trickle charger to maintain battery health when the boat is not in use.

In summary, while standard car batteries can be tempting due to their availability, it is important to understand the key differences between them and marine batteries. Marine batteries are designed to handle the specific demands of the marine environment, featuring thicker lead plates, larger housings, and elevated electrical connectors. They also use different ratings, such as MCA instead of CCA, and require proper maintenance and charging to ensure optimal performance and longevity.

Battery function: Starting vs deep cycle

When it comes to choosing the right battery for your 28hp boat, it's important to consider its specific function: starting or deep cycle. Here's a detailed comparison to help you make an informed decision:

Starting Batteries

Starting batteries, also known as cranking batteries, are designed to deliver a quick burst of high power to crank and start your boat's engine. They provide a short burst of high current for a brief period, which is essential for powering the starter motor and ignition system. Starting batteries have thinner plates and a larger surface area to facilitate this rapid energy discharge.

The primary advantage of a starting battery is its ability to provide an instant surge of electric current, making it ideal for jumpstarting your boat's engine. They also tend to be relatively portable, coming in different sizes, and offer a large power-to-weight ratio.

However, one of the drawbacks of starting batteries is their sensitivity to deep-cycle tasks. Additionally, the battery charging process can be slow, and they typically have a shorter service life compared to deep cycle batteries.

Deep Cycle Batteries

Deep cycle batteries, on the other hand, are engineered for prolonged energy delivery at a lower, steady rate. They are built with thicker plates and denser active material to withstand deeper discharge cycles. Deep cycle batteries are capable of being discharged down to 20% of their capacity and then recharged, making them ideal for powering electrical appliances and accessories in boats and other applications requiring sustained power supply.

One of the key advantages of deep cycle batteries is their ability to provide a consistent power supply over extended periods. They are designed to be deeply discharged and recharged many times, making them highly durable. Additionally, newer technologies such as lithium-ion models offer longer-lasting performance and are gaining popularity.

However, it is important to note that deep cycle batteries are not suitable for starting applications as they do not have the high cranking power required. Using them as starters will compromise their strength and they may not be able to start the engine.

Dual-Purpose Batteries

In some cases, you may opt for dual-purpose batteries that serve both starting and deep cycle functions. These batteries provide a compromise for applications requiring both quick energy bursts and sustained power delivery. While they may not excel in either function, they can be useful when space and weight savings are crucial, such as in marine and recreational vehicle use.

Choosing the Right Battery

When selecting the appropriate battery for your 28hp boat, consider your specific energy needs. Determine whether your primary requirement is engine starting or powering appliances and electronics. Also, take into account the energy consumption of your boat and choose a battery with adequate capacity. For marine applications, choose batteries designed to withstand harsh conditions, such as those with sturdy construction and elevated electrical connectors to prevent water damage.

Battery size: Engine starting requirements

When it comes to engine-starting requirements, the size of the battery you need will depend on the size of your engine. The best way to determine the right battery size is to consult the manufacturer's recommendations for your specific engine. They will provide specifications for cranking amps (CA), which can also be measured in marine cranking amps (MCA) or cold-cranking amps (CCA). These measurements indicate the amount of energy your battery can deliver in a short burst, typically to start the engine.

Most boat engine manufacturers will list the required cranking amps in one of these forms (CA, MCA, or CCA), and this information can usually be found online or by contacting the manufacturer directly. It is important to meet or exceed the manufacturer's recommendations to ensure your engine has enough power to start. However, you don't need to overspend on a battery with significantly higher cranking amps than what is recommended.

As a general rule of thumb, for gasoline engines, aim for 1 cranking amp per cubic inch, while for diesel engines, you'll need 2 cranking amps per cubic inch. For example, if you have a 6.0-liter gasoline engine with 366 cubic inches, you'll need a minimum of 400 MCA. The same engine in diesel would require 800 MCA.

In addition to cranking amps, another specification to consider is the battery's reserve capacity, typically measured in amp hours (Ah) or reserve capacity (RC). This specification describes the amount of energy the battery can deliver over an extended period, and it is important to meet or exceed the manufacturer's recommendations in this regard as well.

When choosing a battery, it is also crucial to consider the physical size and weight of the battery. Make sure it fits within the designated battery storage area on your boat and that the weight does not exceed any limitations.

If space and weight are not a concern, opting for a larger battery can be beneficial. This is because lead-acid batteries tend to have a shorter lifespan when they are deeply discharged. By choosing a larger battery, you can reduce the depth of discharge and prolong the battery's lifespan.

In terms of battery type, marine batteries are specifically designed for boats and offer several advantages over standard car batteries. They are fully sealed to prevent leaks and are built to withstand vibrations and impacts. Marine batteries also have a longer charge retention time and a longer lifespan than car batteries.

When it comes to battery chemistry, lithium-ion batteries offer several benefits over traditional lead-acid batteries. They are lighter in weight, have higher energy density, and can reduce the load on your engine. Lithium-ion batteries also have a longer lifecycle, saving you from frequent replacements.

In summary, when considering engine-starting requirements for your 28hp boat, consult the manufacturer's recommendations for cranking amps and reserve capacity. Opt for a marine battery that meets or exceeds these specifications, taking into account physical size and weight limitations. If possible, consider choosing a larger battery or a lithium-ion option to enhance performance and longevity.

Battery power: Auxiliary or house battery requirements

The power requirements of your boat will depend on the number and nature of the appliances and devices you have on board. To determine the correct battery power, you should first list all the electrical equipment on your boat, including lights, bilge pumps, trolling motors, and other electrical devices.

Next, you need to calculate the total power draw of your boat. To do this, you must list the electric consumption of each electrical device, preferably in amps, and the running time for each device. Then, multiply the ampere consumption and running time for each device to determine the amp-hour rating. Finally, add up the amp-hour ratings of all the devices to find the total power draw of your boat.

It is recommended to add a 20% to 30% margin to the total electrical consumption to account for losses in the electrical system and higher power requirements at certain times.

Another method to determine the total power requirements of your boat is to calculate the total wattage of the load. This can be done by dividing the wattage of each appliance by the voltage to find the amp-hour rating. Then, add up the amp-hour ratings of all the appliances to find the total wattage.

Once you have determined the total power draw or wattage of your boat, you can select a battery with a suitable amp-hour rating. It is generally recommended to choose a battery that exceeds your baseline power usage to accommodate any unexpected increases in power demand.

When selecting a marine battery, it is also important to consider the chemistry of the battery. Lithium batteries, for example, have a higher depth of discharge (DoD) than lead-acid batteries, meaning they can provide a higher percentage of their stored power. Lithium batteries are also lighter, more durable, and quicker to recharge than lead-acid batteries.

In addition to power requirements, you should also consider the physical dimensions of the battery to ensure it fits within the available space on your boat. The weight of the battery is also an important consideration, especially for smaller boats, as each additional pound can affect the performance of the boat.

Finally, it is crucial to choose a battery with the correct voltage that matches your boat's electrical system. Most boats use a 12-volt electrical system, but some may use 6-volt or 24-volt systems.

By carefully considering your power requirements, battery chemistry, dimensions, weight, and voltage, you can select the right auxiliary or house battery for your boat.

Battery maintenance: Charging and longevity

To ensure your boat battery lasts as long as possible, it's important to follow some basic maintenance and charging practices. Here are some tips to help you maximise the lifespan of your boat battery:

• Keep it fully charged: A healthy, fully charged lead-acid battery should have a reading of around 12.7 to 12.8 volts. If your battery's voltage drops to 12.0 volts, it is fully discharged, and this will have a severe impact on its lifespan. After using your boat, connect a battery charger to ensure it is fully charged before your next trip.
• Avoid overcharging: While keeping your battery charged is important, you should also avoid overcharging it as this can negatively affect its lifespan. Follow the manufacturer's instructions for proper charging procedures.
• Store in a cool, dry place: When your boat is not in use for extended periods, store the battery in a cool, dry place to maintain its condition.
• Regularly inspect connections and terminals: It's important to regularly inspect the connections and terminals for any signs of corrosion or dust and keep the battery clean. Corroded terminals can affect the battery's efficiency and shorten its life.
• Wear gloves: Always wear gloves when working with batteries to protect your hands from acid.
• Stick to one type of battery: Using different types of batteries can lead to underperformance of your boat electronics and shorten the lifespan of the battery bank.
• Turn off the battery master switch: When leaving the vessel, remember to turn off the battery master switch. If you won't be using your boat for a long time, disconnect the batteries and store them in a cool, dry place.
• Proper installation and wiring: Ensure your boat is correctly wired, and the battery is properly installed and securely mounted to protect it from excessive vibration and physical shocks, which can reduce its lifespan.
• Maintain optimal state of charge: Keep your battery fully charged after each use, and use a trickle charger or battery maintainer during periods of inactivity to prevent degradation.
• Temperature considerations: Higher temperatures can accelerate chemical reactions inside the battery, leading to potential damage. Colder conditions can also affect batteries by slowing down chemical reactions, which may cause faster discharge rates.
• Keep battery terminals clean: Regularly check and clean battery terminals to prevent corrosion and ensure optimal performance.
• Maintain proper electrolyte levels: For batteries that allow it, maintain adequate electrolyte levels to ensure the electrolyte covers the plates adequately, especially for deep cycle marine batteries.

Frequently asked questions