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The Importance of Battery Monitoring on a Sailboat

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While spending the day out on the water, the last thing you want to do is attempt to estimate the state of charge of your batteries. For extended peace of mind and ease of use, battery monitors will measure the amount of energy going into and out of your batteries the give you an accurate state of charge measurement. This allows you to enjoy your day on the water without worrying about having enough power.

Why are Battery Monitors Important for your Marine Electrical System?

To ensure your marine electrical system is functioning properly and to keep track of your power usage out on the water, a battery monitor is a key component in your system. They allow you to track how much battery power you have remaining in your house batteries. Although lead acid batteries allowed boaters to escape the need for a monitor as they could estimate the power remaining based on the voltage, battery monitors are essential for lithium battery systems.

lead acid dishcarge curve

Lithium-ion batteries have a much different voltage curve than lead-acid batteries. Although their voltage drops slightly at the beginning of discharge, the voltage remains constant throughout the cycle until the very end, when it drops off dramatically. This means that using voltage to estimate the state of charge of a lithium-ion battery will be extremely inaccurate. A battery monitor is the only way to accurately measure how much power is going in and out of your batteries.

lithium battery discharge curve

Battery Monitoring Methods

There are two main ways that you can monitor the state of charge of your battery system.

Battle Born Battery with Dragonfly IntelLigence and Battery Monitor on a sailboat


A shunt is installed in the negative lead of the house battery bank. This allows the power going in and out of the battery to be forced through that one point and measured. By measuring all the power going into and out of the battery bank and connecting a BMV-712, you can determine your batteries’ current state of charge. A SmartShunt serves the same purpose but can communicate wirelessly. Then, these devices communicate with Cerbo GX, which allows the state of charge to be displayed on a touch screen device like the Victron GX Touch 50.

Smart Batteries

Newer technology has given the boater the option to do away with all the external monitoring components entirely. With Battle Born Batteries equipped with Dragonfly IntelLigence, hardware installed in each of the batteries can monitor the state of charge individually. Along with monitoring a variety of other things, these batteries communicate directly to a mobile app with real-time measurements.

Want to Learn More?

Check out the full Marine 101 series on our YouTube channel or through the Academy page on our website. For further questions or help designing the perfect marine power system, our technical sales team would love to help! You can reach by calling (855) 292-2831 or emailing [email protected].

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