What Is a Battery Monitor and Why Do You Need One?
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You can make many upgrades to your RV or off-grid battery system, but one of the simplest and most powerful is adding a battery monitor. Often thought of as the fuel gauge for your batteries, a good battery monitor helps RVers, boaters, and off-grid homeowners get the most out of their RV batteries and avoid unexpected shutdowns and potential damage.
What Is a Battery Monitor?
Battery monitors are essential in RVs, sailboats, and off-grid properties, where knowing your remaining power can make the difference between comfort and scrambling for backup power. People often think of battery monitors as the fuel gauge of a battery. However, they do much more than just provide the state of charge of your battery system. Battery monitors also collect and display helpful data such as battery voltage, power consumption, estimated remaining runtime, current consumption, battery temperature, and more.
Battery monitors come in many forms; this advanced display shows all the details of a power system.
How a Battery Monitor Works
There are two types of battery monitors, shunt-based and voltage-based. One measures actual ammount of charge consumed or added and the other measures the current state only.
Voltage-Based Battery Monitors
The simplest type is the voltage-based monitor and frequently comes standard on most mobile power applications. This type of monitor just measures the real-time voltage of the battery and uses it to estimate its state of charge.
Voltage-based monitors are not very accurate because the real-time voltage of a battery will fluctuate based on temperature changes and other environmental conditions. If you change the battery type the voltage meter may even be completely inaccurate altogether. However, knowing the voltage of your batteries is better than nothing!
This is a voltage battery monitor, its very simple but only provides a rough estimate of actual battery percentage left.
Shunt Battery Monitors
The shunt-type monitor is much more accurate because it measures the actual energy flowing into and out of the battery and knows the actual charge. These battery monitors require a shunt inline with the battery terminals. The shunt measures the real-time voltage of your battery system as well as the current draw.
The battery monitor uses these measurements to calculate the state of charge, power consumption, estimated remaining runtime, and other beneficial information about your battery system. For most modern power systems, we highly recommend using a shunt-based battery monitor. Many modern monitors can also send this information to a phone or external monitoring system.
In this image, the shunt labeled passes all the system power through it, allowing it to measure actual battery charge and send the information to a monitor screen for you to read.
Battery Monitor Vs. Battery Management System (BMS)
Lithium batteries have an integrated battery management system (BMS) that helps optimize their performance and protect them from operating outside of safe conditions. The BMS is the control center for individual batteries in a system, not the system as a whole.
The main function of the BMS is to prevent overcharging and over-discharging, which can damage a battery and shorten its life. The BMS also calculates the remaining charge, watches the battery’s temperature, keeps an eye on the battery’s health and safety by checking for loose connections and internal shorts, and balances the charge across all of the cells in the battery.
If unsafe conditions are detected, the BMS shuts the battery down to protect the lithium-ion cells and the user.
BMS In Smart Batteries
In the past, an external monitor was the only way to know what was happening inside your batteries. But with modern lithium smart batteries like Battle Born’s Smart models, the batteries themselves can now provide real-time data directly to your phone or monitoring system.
When paired with the Battle Born HUB, you can view system-wide data (state of charge, voltage, current, temperature, and more) without installing a separate shunt or monitor. This makes monitoring simpler than ever.
These smart monitors are equivalent to a shunt-based monitor and, depending on the model, can be paired with other systems to communicate the data.
Why You Need a Battery Monitor
The BMS collects data and uses it to optimize each individual battery. On the other hand, your battery monitor collects information and displays it so that you can know optimize the performance of your entire battery system.
One of the most basic functions of a battery monitor is to display the remaining charge of your battery system.
In lead-acid batteries, the battery voltage drops significantly as you use them. This voltage drop typically gives some indication that your batteries are running low. For example, your lights may dim as the batteries get low.
Conversely, lithium batteries do not experience a significant voltage drop as they drain. Without a battery monitor, there is no warning your batteries are dying until they are dead and the BMS shuts them off.
If you don’t have an accurate state of charge on your batteries, you risk shutting down your system without warning and possibly damaging your batteries depending on type.
Helps You Take Better Care of Your Batteries
Battery monitors do much more than just display the state of charge of your system. Your battery monitor also provides you real-time and historical information on voltage, power consumption, temperature, and more. This data allows you to make better decisions on how to optimize your battery usage and charging.
A good example is deciding when to switch the fridge in your RV from battery power to propane. Perhaps it’s early evening, and your battery monitor says you have four hours of runtime left. However, if you switch your RV fridge to propane, you can make it through the night without needing to run your generator.
If using lead-acid batteries they should not be drained past 50 percent state of charge for optimum longevity. Using an accurate shunt-based monitor will let you know when you are reaching the 50% mark and that they will need to be charged. Lead-acid batteries also take a long time to charge and need to make it through an absorption cycle. Without a battery monitor you may not know when your batteries reach full charge. If they don’t make it to a full charge before draining you will shorten their lifespan.
Pairing a battery monitor with solar lets you track how much energy your panels are truly producing and whether your bank is keeping up with daily consumption. This information is critical when sizing solar upgrades.
Switching to lithium solves all these problems, but the battery monitor is still critical to know how much energy you have left, or how much you have charged the batteries.
When it comes to monitoring your battery system, you now have more options than ever. The best choice depends on whether you’re running Battle Born Smart Batteries or building a system around Victron components.
Battle Born Smart Batteries + HUB
Our Battle Born Smart Batteries include built-in monitoring electronics that measure voltage, current, state of charge, and temperature. When paired with the Battle Born HUB, you can access all of this information directly from your phone or tablet.
Best For:
RVers, boaters, or off-grid users who want simple, direct battery monitoring without extra components
Battle Born customers who prefer an all-in-one lithium solution
Systems where batteries are the main focus (fewer external devices like large inverters/chargers)
Key Benefits:
Real-time monitoring directly from your batteries
Safety alerts for temperature, voltage, and over-current conditions
HUB integration for multi-battery banks
App-based access — no extra displays or wiring needed
Tip: If you’re running an all-Battle Born system, Smart Batteries + HUB may give you everything you need without adding a separate battery monitor.
Victron BMV-712
The BMV-712 is one of the most widely used battery monitors in RV, marine, and off-grid applications. It combines a physical display with Bluetooth connectivity, giving you the best of both worlds.
Best For:
RVers who want an always-on display panel inside their rig
Installers building Victron-based systems
Users who want both visual and app-based access
Key Benefits:
Tracks voltage, current, amp-hours, and state of charge
Programmable alarms and relay for automatic load shedding
Bluetooth built-in, compatible with VictronConnect
Can monitor a second battery or midpoint voltage
Victron, battle born, Cell Phone, Electronics, Mobile Phone, Phone
Victron SmartShunt
The SmartShunt is a streamlined alternative to the BMV-712. Instead of a display, it connects via Bluetooth and uses the VictronConnect app as your interface. This makes it easier to install and more budget-friendly.
Best For:
Minimalist RV and marine systems where space is limited
Users who are comfortable with app-based monitoring
Installers who want faster installation with fewer wires
Key Benefits:
Compact, simple to install
Lower cost than the BMV-712
Full Bluetooth monitoring via VictronConnect
Integrates seamlessly with other Victron products
Victron Lynx Shunt VE.Can
For larger, more complex power systems, the Victron Lynx Shunt is the professional-grade option. It connects directly into the Victron Lynx distribution system and integrates with GX devices for complete visibility.
Best For:
Multi-battery, high-power systems (marine, industrial, off-grid property)
Installers working with Victron GX devices (Cerbo GX, Color Control GX)
Users who want detailed system-wide monitoring and remote access via the VRM Portal
Key Benefits:
Full integration into Victron Lynx power distribution busbars
VE.Can communication for seamless system data sharing
Works with GX devices for remote monitoring and control
Ideal for large, professional installs
Which Battery Monitor Is Right for You?
If you’re running Battle Born Smart Batteries, start with the built-in monitoring and HUB for a simple, reliable solution.
If you’re building a Victron-based system, we recommend the BMV-712 or SmartShunt for most RV and marine applications.
For large-scale installs, the Victron Lynx Shunt provides the highest level of system integration.
No matter which option you choose, having accurate battery monitoring ensures you get the most out of your Battle Born Lithium Batteries — protecting your investment and giving you peace of mind off-grid.
Optimize Your Battery System
The more information you have on your battery system, the better decisions you can make to optimize its usage. If you’re looking to get the most out of your battery system, a battery monitor is a simple, inexpensive, and fantastic upgrade to consider.
Want To Learn More About Electrical Systems and Lithium Batteries?
We know that building or upgrading an electrical system can be overwhelming, so we’re here to help. Our Reno, Nevada-based sales and customer service team is standing by at (855) 292-2831 to take your questions!
Also, join us on Facebook, Instagram, and YouTube to learn more about how lithium battery systems can power your lifestyle, see how others have built their systems, and gain the confidence to get out there and stay out there.
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5 thoughts on “What Is a Battery Monitor and Why Do You Need One?”
hooking up the victron 700 to a Battleborn 100Ahr, with solar only via a victron mppt charger. I’ve changed the efficiency and Peukert’s exponent as suggested. Can you recommend other changes to improve accuracy of the monitor?
Hi Jim! Thank you so much for reaching out, we are more than happy to help answer this question! Changing the battery capacity, the discharge floor option to 0%, and the charge voltage to 14.4 will be the best things to implement for your monitor.
Is the location of the battery monitor important relative to the actual battery bank? Mine are on a boat with about 15feet between battery and the monitor.
Thanks
The shunt itself should be very close to the batteries. The little communication cable that plugs into the back of the round gauge can be far away, mine came with a 50 foot cable. I swapped it for one that is about 6 feet long to make it look neater.
5 thoughts on “What Is a Battery Monitor and Why Do You Need One?”
hooking up the victron 700 to a Battleborn 100Ahr, with solar only via a victron mppt charger. I’ve changed the efficiency and Peukert’s exponent as suggested. Can you recommend other changes to improve accuracy of the monitor?
Hi Jim! Thank you so much for reaching out, we are more than happy to help answer this question! Changing the battery capacity, the discharge floor option to 0%, and the charge voltage to 14.4 will be the best things to implement for your monitor.
Is the location of the battery monitor important relative to the actual battery bank? Mine are on a boat with about 15feet between battery and the monitor.
Thanks
The shunt itself should be very close to the batteries. The little communication cable that plugs into the back of the round gauge can be far away, mine came with a 50 foot cable. I swapped it for one that is about 6 feet long to make it look neater.
Aᴡesome post.