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How To Install A Battery Monitor In A Camper Van (Wiring Diagrams)

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Knowing how much charge remains in your batteries is a crucial part to enjoying your van life experience. Without this information, you run the risk of running out of juice to power your electronics, lights, fridge, and more. Furthermore, without knowing your battery levels, you can easily over-discharge your batteries, which leads to premature reductions in their lifespan.

Unfortunately, most modern camper batteries do not display their remaining power. So, how can we get this ‘percentage charge’ information if these batteries don’t provide it?

Battery monitor showing 100% charge
Victron BMV-712 battery monitor

That is where battery monitors come in.

These devices are installed next to your batteries and record the electrical power as it flows into and out of your batteries. These battery monitors then display the percentage charge remaining. This is perfect for peace of mind.

In this post, you will learn why batter monitors are important and how to install them in your camper van’s electrical system. We also provide:

  • step-by-step guidance,
  • helpful diagrams, and
  • material lists

So if you’re ready, let’s get to it!

Table of Contents
    Add a header to begin generating the table of contents

    Why Are Battery Monitors Important?

    Battery monitors are like fuel gauges for your vehicle. They tell you when your batteries are fully charged, half charged, and near empty. Without a fuel gauge, you’d likely often run out of gas in your car. Battery monitors provide the exact same benefit.

    Prolong The Lifespan Of Battery

    Battery monitors are important because they help inform the user what actions to take to prolong the service life of their batteries.

    Two of the largest factors that shorten battery life are excessively deep discharges and extended periods of time at 100% charge. 

    • Continually discharging AGM batteries past 50% drastically shortens their lifespan
    • Constantly keeping lithium (LiFePO4) batteries at 100% also shortens their lifespan

    So whichever type of batteries you have, battery monitors help you to keep those batteries in their operational sweet spot for a longer lifespan. Doing so not only prolongs a battery’s service life, but it also saves you money by not having to buy new batteries prematurely.

    In many cases, battery monitors end up paying for themselves in the long run.

    Recommended Battery Monitors

    While there are lots of different monitor brands available, we recommend purchasing a battery monitor that has Bluetooth capabilities. With Bluetooth, you can connect your smartphone to the battery monitor and display all the battery information right on your phone. The included physical display for most battery monitors is usually clunky and old. So being able to display the monitor’s user interface on your phone is convenient and very nice.

    That is why we recommend the Victron BMV-712. With the Victron mobile app, you get a fantastic user interface on your phone that displays not only the current percentage charge but also the net flow of amps into and out of the batteries.

    Victron Smartphone App For
    Victron mobile app

    But at over $200, the Victron BMV-712 is a higher end unit and may not be appropriate for everyone. If you’re looking for a comparable product for half the price, both the Renogy monitor and AiLi monitor are popular alternatives.

    ➡ Download our electrical eBook (with diagrams) to learn how to wire an electrical system in a camper van.

    For More DIY Electrics Info: Visit our complete camper van electrical system guide to get started.

    How To Install A Battery Monitor In A Camper Van

    Below is our step-by-step battery monitor installation guide. Though the installation method specifically refers to our Victron monitor, these steps should be similar no matter which brand monitor you have.

    Step 1: Identify All The Individual Components Of A Battery Monitor

    The complete battery monitor package often includes several individual components. These usually include:

    Battery Monitor Shunt

    The battery monitor ‘shunt’ is the device that measures the electrical current as it enters and exits the batteries. Because the shunt is installed in-line next to the batteries, the device can easily record the data to send to the display monitor.

    Battery monitor shunt
    Shunt

    Battery Monitor Display

    The battery monitor display is a separate unit that receives the electrical data from the shunt and displays the information on the screen for the user to see. The monitor display is able to show a wide range of battery-related information, such as percentage charge, voltage, net flow of amps, and more.

    Battery monitor display unit
    Display

    Shunt-Monitor Connection Cable

    Each battery monitor brand provides their own proprietary cable to connect the shunt to the display.

    For our Victron BMV-712, they call this the “RJ12 cable”.

    RJ12 cable for battery monitors
    RJ12 cable

    Temperature Sensor Wire

    Some battery monitors come with an additional wire to connect the shunt to a positive terminal (at the battery or bus bar).

    This temperature sensor wire, which is provided with the Victron BMV-712, helps to improve battery charging accuracy by monitoring the overall temperature of the batteries.

    Temperature sensor wire for Victron battery monitor
    Temperature sensor cable

    Step 2: Connect Battery Monitor Shunt To Negative Battery Terminal

    Installation Materials Table

    Product

    Purpose

    Where To Buy

    Shunt

    Measures electrical data to and from the batteries.

    Included with battery monitor package

    2/0 AWG Wire (Black)

    Wire size used to install the battery monitor shunt.

    3/8” Copper Lugs

    Attaches to 2/0 AWG wire ends to connect wire to shunt and batteries.

    Lug Crimper

    Crimps lugs onto 2/0 wire ends

    Heat Shrink

    Covers exposed copper wires after lugs are attached.

    Step-By-Step Procedure

    1. Cut appropriate length of black 2/0 AWG wire.
    2. Crimp copper lug on both ends of the 2/0 wire.
    3. Apply head shrink over 2/0 wire and lug.
    4. Connect one end of 2/0 wire to negative battery terminal.
    5. Connect other end of 2/0 wire to battery monitor shunt.
    Connecting battery to battery monitor shunt
    Connecting battery to battery monitor shunt

    Step 3: Connect Shunt To Negative Bus Bar

    Additional Materials Table

    Product

    Purpose

    Where To Buy

    Bus Bar

    Electrical current collection and distribution centers.

    Step-By-Step Procedure

    1. Cut appropriate length of black 2/0 AWG wire.
    2. Crimp copper lug on both ends of the 2/0 wire.
    3. Apply head shrink over 2/0 wire and lug.
    4. Connect one end of 2/0 wire to battery monitor shunt.
    5. Connect other end of 2/0 wire to negative bus bar.
    Connecting the battery monitor shunt to the bus bar
    Connect shunt to bus bar

    Step 4: Wire Display to Shunt With RJ12 Cable

    Additional Materials Table

    Product

    Purpose

    Where To Buy

    Battery Monitor Display

    Displays battery percentage charge.

    Included with battery monitor package.

    RJ12 Cable

    Connects battery monitor shunt to display

    Included with battery monitor package.

    Step-By-Step Procedure

    1. Take the provided connection cable and connect the shunt to the display.
    Connecting the battery monitor shunt to the display unit.
    Connecting to the battery monitor display unit

    Step 5: Access Monitor Display via Bluetooth

    If you have the Victron BMV-712, which is Bluetooth enabled, you can take additional steps to connect your smartphone to the battery monitor.

    1. Download the VictronConnect app through Apple or Android.
    2. Ensure your phone’s Bluetooth is turned on.
    3. Select Bluetooth monitor device on the app and enter the access PIN, usually “00000”
    4. Marvel at all the information now displayed on your phone.
    5. Customize battery monitor information to fit your system
      1. Battery bank size (total amps)
      2. Low voltage alarm

    Camper Van Electrics Guide

    ➡ Download our electrical eBook (with diagrams) to learn how to wire an electrical system in a camper van.

    Remember To Occasionally Recalibrate The Battery Monitor

    A battery monitor estimates the battery’s current charge percentage by measuring the total amps that have flowed into and out of the battery.

    But simply measuring amps in and amps out is not a perfectly accurate way to measure percentage charge. And over time, the percentage that is displayed on the monitor becomes more and more inaccurate.

    In our experience, the Victron battery monitor loses about 1% of accuracy every day.

    Therefore, we like to make sure that our batteries reach 100% charge at least once a week. When plugged into shore power, the provided electricity is enough to force the monitor to auto-synchronize back to 100%.

    But with solar panels, sometimes the battery monitor will not auto-synchronize due to the drastic voltage fluctuations from the ever-changing intensities of the sun.

    Therefore, if we are sure that our batteries are near 100% charged but our monitor is displaying a wildly different amount, we will manually synchronize the monitor back to 100%.

    Showing how to syncronize a battery monitor back to 100%
    Synchronizing a battery monitor back to 100%

    How A Battery Monitor Can Help You Save Money

    If you have been doing van life long enough, you have almost certainly meet other camper van travelers who have had to deal with dead batteries. And many times, these batteries have died prematurely.

    Oftentimes, prematurely dead batteries occur because the user unknowingly over-discharged their AGM batteries. The more you discharge AGM batteries, the fewer charge cycles and lifespan that battery has.

    That’s why it is recommended not to discharge an AGM battery past 50%

    Lithium batteries are similar but in the opposite sense. These batteries do not like the be overcharged and kept at 100% for long periods of time. That’s why manufacturers of laptops and phones, whose devices uses lithium batteries, recommend to not charge their devices to 100% to prolong their usable life.

    But because standard 12v batteries do not come with a percentage charge display, it is too easy to ignore a battery’s current charge.

    That’s why battery monitors are important. By displaying the charge percentage, battery monitors help keep you informed about your battery’s state of charge so that you know what actions you need to take.

    For More DIY Electrics Info: Visit our complete camper van electrical system guide to get started.

    Final Thoughts

    We hope you learned a little bit more about battery monitors, why their important, and how to install them in your own van conversion.

    If you have any questions, please send us an email or reach out in the comments section below.

    Happy building!

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