Marine Battery Voltage Chart (Guide for Your Boat) -
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Marine Battery Voltage Chart

Short on Time? Here’s The Article Summary

The article emphasizes the importance of understanding marine batteries and their voltage charts for boating enthusiasts. It explains the different types of marine batteries, including starting, deep-cycle, and dual-purpose batteries, highlighting their specific functions and benefits.

The article also discusses the relationship between voltage and charge in marine batteries, emphasizing how it determines the amount of electrical energy available. It provides a detailed marine battery voltage chart for 12-volt and 24-volt batteries, showing the voltage levels corresponding to different states of charge. Overall, the article aims to educate readers about marine batteries and their voltage charts, helping them make informed decisions when selecting and maintaining batteries for their boats.


If staying afloat is the number one priority when you’re out on open waters, making sure that your vessel has power is probably number two. Wrapping your head around a marine battery voltage chart is the easiest way to figure out your needs and what equipment is necessary to meet them.

Many new boat owners won’t even consider the batteries in their boats and simply buy the first one they think is suitable without doing any research.

The batteries housed in your boat are crucial and allow you to travel safely and securely when you’re out at sea or in your local lake. Every boat owner has experienced dead batteries at some point on the open water because they can’t handle the boat's electrical load.

Thankfully, this is a mistake you’re only likely to make once and, we hope, that with the help of this article, it’s something you can avoid entirely.

We’ve discussed everything you need to know about marine batteries and their voltage charts. Additionally, we explain the relationship between voltage and charge in marine batteries.

What Is a Marine Battery?

Marine batteries are different from the traditional batteries used in your electrical appliances and are capable of a lot more when it comes to voltage output.

deep cycle battery chart

Marine batteries are designed specifically for marine applications such as boats and other water vehicles. These batteries are designed and built to withstand rough environmental conditions such as high temperatures, exposure to water and salt, and many other corrosive conditions.

Furthermore, deep-cycle marine batteries are often made to deliver a consistent level of power over an extended period rather than a burst of power like standard car batteries. This makes them perfect batteries for running onboard electrical systems including lights, radios, and navigational tools.

There are several marine battery variants on the market, each with its own set of advantages. It is important to do your research before purchasing a battery and your choice of battery will depend on the size of your boat, the amount of power required, and your budget.

This is where the use of modern marine batteries comes into play. The correct marine battery with the correct protection will ensure that your boat runs efficiently.

Understanding the battery discharge voltage charts for marine batteries can be a daunting task in the beginning, but with the correct guidance, you will see how easy it is to navigate these charts.

Benefits of Marine Batteries

There are several added benefits that marine batteries offer that traditional automotive batteries do not, especially when used in marine vehicles.

We already know that these marine batteries have deep cycle capabilities that can deliver consistent power for longer periods, but there are so many more benefits to these powerful batteries.

deep cycle marine battery voltage chart

They are also incredibly durable and constructed to withstand harsh environmental conditions. They are corrosion-resistant, vibration-resistance, and waterproof.

Marine batteries are built in such a way that they do not require any maintenance. They are completely sealed and cannot be accessed making them maintenance-free.

There are also many different types of marine batteries available on the market. They are gel, flood, and lithium-ion marine batteries for you to choose from depending on your electrical requirements and budget.

Marine batteries are built with a ton of safety features making them one of the safest batteries on the market. There are manufactured using flame retardant casing with built-in overcharge protection.

They have an incredibly long-life cycle that can last for several years ensuring that your boat is supplied with durable power for many years to come. Additionally, marine batteries are also compatible with many solar panel systems and you can charge them using a solar-powered deep-cycle battery charger.

deep cycle battery discharge curve

Remember, the most common cause for battery damage is incorrect to use, so as long as you’re caring for your battery, it will care for you.

Three Types of Marine Batteries

Before we get into the voltage charts of marine batteries, it would be a good idea to familiarise yourself with the different types of marine batteries and how each one functions.

Remember these batteries are made with thicker plates and casings that can withstand the beating and vibrations that occur frequently on boats.

Marine Starting Batteries

Marine starting batteries are typically lead acid batteries and have similar functioning to standard car batteries. They are the most common option in boats with alternator engines. Starting batteries have one function and that is to rapidly deliver amps to the engine allowing it to start.

Ultimately marine starting batteries are made to supply high starting currents needed to start engines. They can produce a tremendous amount of power for a short period.

Keep in mind, marine starting batteries are made to deliver brief bursts of high current, so they might not be appropriate for continuously running other electrical equipment on a boat.

A second deep-cycle battery or a dual-purpose battery may be a better option in those circumstances. Ultimately, a starting battery should never be used to up other appliances because of its limited depth of discharge.

Marine Deep-Cycle Batteries

We already touched on marine deep-cycle batteries, but it would be a good idea to provide more insight into these powerful and commonly used marine batteries.

deep cycle battery rating chart

For kayaks, fishing boats, and other water traversal vehicles with trolling motors, a deep-cycle or deep-cell marine battery is utilized as a reliable power source. Due to its high capacity and ability to undergo deep drain, this battery is comparable to those found in RVs and golf carts.

Unlike starting batteries, these deep-cycle batteries can be deeply discharged repeatedly with no damage to the battery’s integrity.

The unique feature of these batteries is that are made with fewer and thicker plates which enables them to be steadily discharged over longer periods. Additionally, marine deep-cycle batteries can tolerate high temperatures and still produce strong electrical currents, all thanks to the thicker plates.

Marine Dual-Purpose Batteries

As the name suggests, marine dual-purpose batteries give you the best of both worlds. Marine dual-purpose batteries are designed to serve two purposes – they start the engine of the boat, and they provide power to boating equipment, such as the lights, radios, and navigational systems.

Marine dual-purpose batteries function as a perfect compromise between starting and deep-cycle batteries. They are the perfect choice if you require a battery with dual functioning.

These batteries are a lot cheaper than devoted deep cycle or starting batteries but they shouldn’t be used in boats that require high power demands. Marine dual-purpose batteries are suitable for medium-sized boats that go on short trips.

If you are interested in getting a marine battery for your boat, then you can visit Shop Solar Kits. We stock a wide range of marine batteries that are suited for all types of boats and other water vehicles.

Voltage Chart

The functioning of marine batteries makes them significantly different from other locomotive batteries and this is the same for their associated voltage charts. Unlike an RV battery voltage chart, marine battery voltage charts are a little more complex but are still easy to understand.

marine battery voltage vs state of charge chart

The table below will help you determine the capacity, also known as the state of charge (SoC) for your marine battery. It is a useful table to have so make sure you get comfortable and familiarise yourself with it to ensure that you get accurate readings.

The table below displays a 12-volt battery chart and a 24-volt battery voltage chart, as well as their corresponding voltages and charge capacities. Bear in mind that because of the way these systems work, these values aren’t the same as you will find on a 12-volt deep-cycle battery charging chart

State of Charge (%)

Voltage (12 Volt Battery)

Voltage (24 Volt Battery)





























































0 (fully discharged)



The Relationship Between Voltage and Charge

As we know, marine batteries are capable of storing a large amount of energy that can be used to power boats and boating equipment.

The relationship between the voltage and charge of these batteries is of paramount importance, as it determines the amount of electrical energy available at a given time.

12v marine battery voltage chart

To give you a recap, voltage is the measure of the difference in electrical potential between two points. However, in the case of a marine battery, the voltage represents the stored amount of energy in the battery.

As you can see, a fully charged marine battery has a voltage of 12.70 volts for a 120-volt battery, and 25.40 volts for a 24-volt battery. A fully discharged or depleted battery will be 11.90 volts for the same 12-volt battery, and 23.80 volts for the 24-volt battery.

There is a common misconception that charge is referring to the voltage, but this is not at all the case. Charge refers to the amount of electrical energy stored inside. The charge is typically measured in ampere-hours and this measurement represents the amount of electrical charge that is available.

For example, a marine battery with an ampere capacity of 100Ah can deliver 5 amps of electrical current for 20 hours.

The Importance of This Relationship

The voltage charge relationship for marine batteries is important because it determines the amount of power that can be delivered by the battery.

In marine batteries, a higher voltage means that more electrical energy is available to be used, while a higher charge means that the battery can deliver that energy over a certain period.

To put it in perspective, let's take a marine battery that has a voltage of 12 volts and a capacity of 100Ah. To determine its electrical energy, you would take the voltage and multiply it by the ampere-hours. In this case, it would be 12 volts x 100Ah, which would give us an answer of 1200 watt-hours.

Now, let’s say the same battery has been discharged to 50% capacity. If we use the same formula above, then we would get 600 watt-hours of electrical energy (12 volts x 50Ah).

deep cycle marine battery voltage and capacity chart

To sum it up, the link between marine batteries' voltage and the charge is crucial because it establishes the amount of usable electrical energy, which in turn affects how well electrical equipment and devices operate.

To prevent running out of power when it's most required, it's critical to routinely check the voltage and charge level of marine batteries and to make sure they are kept well-maintained and charged. 


Marine batteries are made specifically to run your boat's motor and a few additional devices you might install onboard.

These batteries will provide you with hours of enjoyment while you go fishing, have fun at sea, or engage in any other activity with your boat.

Hopefully, this article has provided you with the correct insight into the functioning of these marine batteries, as well as help you understand the voltage chart.

If you require further assistance, then you can always reach out to Shop Solar Kits. They can give you professional advice on marine batteries and which one will work for your boat's system. Make sure that you also familiarise yourself with a solar panel voltage chart before installation. 

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Article by

Cody Oehm

Cody is the Head of Marketing at Shop Solar, and joined the company in spring of 2022. 

He has an entrepreneurial background and has been in the ecommerce industry since 2015. With 4 businesses under his belt and a drive to make a bigger impact, he decided to team up with Shop Solar on their mission to make solar simple and affordable. You can browse best seller's here.

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