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

Knowing how much charge remains in your batteries is a crucial part of 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 overcharge your batteries, leading to premature lifespan reductions.

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?

That is where battery monitors come in.

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

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

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

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 prolongs a battery’s service life and saves you money by not buying new batteries prematurely.

In many cases, battery monitors pay for themselves in the long run.

Recommended Battery Monitors

While there are lots of different monitor brands available, we recommend purchasing a battery monitor with 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, displaying 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 the current percentage charge and the net flow of amps into and out of the batteries.

Victron | Battery Monitor

Prolong your battery's lifespan. Knowing your battery's state-of-charge (SOC) is a critical factor in preventing it's premature death. This monitor displays percentage charge, voltage, instantaneous power flow, and more. Bluetooth capable means easy connection to any smartphone.

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But at $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.

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 regardless of your brand monitor.

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
Battery monitor 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 can show a wide range of battery-related information, such as percentage charge, voltage, net flow of amps, and more.

Battery monitor display unit
Battery monitor display

Shunt-Monitor Connection Cable

Each battery monitor brand provides its 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 have an additional wire to connect the shunt to a positive terminal (at the battery or bus bar).

This temperature sensor wire, provided with the Victron BMV-712, helps 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 the Battery Monitor Shunt To The Leisure Battery (Negative Post)

In this step, we will connect one end of the battery monitor shunt to the negative terminal post of your leisure battery. Below, we list the materials you’ll need and the step-by-step procedure.

Installation Materials Table

You’ll need the battery monitor shunt and the five materials and tools below to complete this wiring step.

  • 2/0 AWG Wire – Our recommended wire size for maximum electric safety
  • Copper Lugs – Crimps onto 2/0 wire and attaches to shunt
  • Cable Cutter – Heavy duty cutter for 2/0 AWG wires
  • Hydraulic Crimper – Crimps copper lugs onto 2/0 wire end
  • Heat Gun – Activates heat shrink around copper lugs

Step-By-Step Procedure

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

The materials you will need to attach the battery monitor shunt to the negative bus bar are exactly the same as in Step 2. If you haven’t bought your bus bars yet, we recommend the ones we use in our van below.

Bus Bars

Bus bars are power distribution centers that collect and distribute electricity to/from multiple sources. They simplify the wiring process and help keep electric wiring clean and orderly. Connects to batteries, solar charger, inverter, and DC-DC charger.

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Step-By-Step Procedure

  1. Cut the 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 the 2/0 wire to the battery monitor shunt.
  5. Connect the other end of the 2/0 wire to the 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

Next, connect the battery monitor shunt to the display unit using the provided cable from the manufacturer. If you have a Victron-branded battery monitor, this is the RJ12 cable.

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 the 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

Remember To Recalibrate The Battery Monitor Occasionally

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 ensure 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 displays 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 met 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 being overcharged and kept at 100% for long periods. That’s why manufacturers of laptops and phones whose devices use lithium batteries recommend not charging their devices to 100% to prolong their usable life.

However, because standard 12V batteries do not display a percentage charge, 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 Electrical Info: Visit our complete camper van electrical system guide to start.

Final Thoughts

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

If you have any questions, please reach out in the comments section below.

Happy building!

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