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  1. #1
    King Pin
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    Victron BMV-712 Smart Battery Monitor - Like a Fuel Gauge for your Batteries.

    As many of you know, I do a lot of boondocking, and rely heavily on my battery bank. I currently have 300 amp hours of Battle Born LiFePo4 (lithium) batteries installed. When using lead acid batteries, you can get a ballpark estimate of their state of charge by referring to a state of charge chart. However, with the flat discharge curve of a lithium battery bank, a state of discharge chart is not very accurate.

    At the Las Vegas Rally, the Battle Born representatives suggested purchasing a Victron battery meter in order to monitor the status of the battery bank. They offered a rally discount, so I ordered one. Wow! What a useful tool it turned out to be. Now, I can monitor my battery usage down to the amp hour. I equate it to having the equivalent to a fuel gauge for my batteries.

    The model of meter I selected is the Victron BMV-712 Smart Battery Monitor. I like this model because it has Blue Tooth capability which allows it to be programmed and monitored right from your smart phone.

    Installation is fairly straightforward. There are four parts that must be connected.

    1. Meter
    2. Shunt
    3. Power Connection (or alternate temperature probe/power connection)
    4. Control Cable

    Meter Installation.The meter should be installed in an area that is out of the weather and can be seen by the owner. If you purchase a meter that does not have Blue Tooth, you should install the meter inside the RV in a convenient location that you can use to monitor the status. If you purchase a Blue Tooth dongle, you can pair it with earlier versions of meters, or you can purchase the 712 model with built in Blue Tooth capability. If using the Blue Tooth version, you can install the meter in your basement or front battery storage compartment because you'll be able to monitor battery status directly from your phone.

    I elected to install my meter in the basement of my travel trailer near my solar controller monitor. The meter is designed to be panel mounted. I used a project box to mount my meter as can be seen in the following photo. (List of materials at the end of this thread)



    Shunt Installation.
    The shunt is where the measuring takes place. The 712 comes with a 500A/50mV shunt. One end of the shunt is connected to the most negative battery post and the other end goes to the negative battery cable. It is important that no other negative connections be made to the batteries or the measurements will not be accurate. If necessary, some minor rewiring might be warranted.

    The shunt must be in a weather proof enclosure. On a fifth wheel, this is easy. Just mount it inside the battery storage area. However, if you have a travel trailer, it's a little more tricky. I elected to mount the shunt on the back side of the TT A-frame in a weather resistant enclosure. You can see from this image how it was done.



    Power ConnectionThere are two types of power connections available for the 712 meter. The unit is shipped with a standard 12V connection. I elected to purchase a separate power connection/temperature sensor. Simply mount the power (temperature) connection to an available 12V source, and clip the leads into the appropriate connections on the printed circuit board that is already mounted on the shunt. You can see where the wires connected to the shunt in the previous picture, and where I mounted my power/temperature sensor in this picture. (look for the yellow tag).



    Control Cable.The control cable plugs into the shunt circuit card and the back of the meter. It is approximately 30 feet long which allows you to mount the meter inside your coach if desired and still have plenty of cable.


    SET UP
    Once the unit was powered up, I linked to it with my smart phone via Blue Tooth. It immediately updated the firmware to the most recent version. That took about three minutes.

    Then, I used the settings mode to adjust the parameters for my particular battery bank. If you have lead acid or AGM batteries, most of the parameters are already set, and you just have to let the system know how many usable amp hours you have. For example, it you have two 12V AGM batteries in parallel and each is 90 amp hours, you have 180 amp hours. However, you do not want them to discharge below 50% state of charge, so you'd program the Victron settings for 90 amp hours. (180aH * 50%).

    In my case, Battle Born has a page on their website for several parameter changes that are needed with LiFePo4 batteries. I set my usable amp hours to 300. Note: Previously, BB suggested setting the meter to 99aH per battery, but now recommends the full 100aH per battery.

    The next two sections of the thread will deal with usage and parts sources.

    Jim

  2. #2
    King Pin
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    Victron BMV-712 Smart Meter usage


    Once the meter was installed as detailed above, it was time to start monitoring usage. The main screen shows detailed usage as it is occurring, and the secondary screen shows statistical usage over time.

    We took a boondocking trip to Utah last week, and used the meter to closely monitor our usage. The primary goal was to determine if your battery bank is sufficient for our needs, and if my solar charging system is adequate to recharge the batteries in a reasonable time frame (4-5 hours). Our typical usage is 3-4 hours of satellite television in the evening, followed the next morning with brewing coffee, making toast and running the microwave for 5-10 minutes through my 2000 Watt Pure Sine inverter. And if it's cold outside, we keep the furnace set at 68°F while sleeping.

    The image below shows the status of the batteries at a given point in time. As you can see, I'd used 145 amp hours of battery power which equates to 52% remaining power. This was much more than I anticipated. But as you can see from the temperature reading at the bottom of the screen, it was 39.2°F when the image was captured. The furnace ran quite a bit over night and used a lot of battery power. You can also see that the current flow was a +37.1 Amps. This is because I was running the generator at the time.



    In the next image, the top of the page shows the most recent discharge, the deepest discharge and the average discharge. These numbers are vital when determining what size battery bank you need along with how much solar charging you need to keep them topped off.



    Lessons Learned

    My analysis indicated that my battery bank provides plenty of power for our typical usage. We plan on camping in the Northern U.S. and Canada in the summer, and the Southern U.S. in the winter. This should minimize the need for air conditioning which will require running a generator or camping in an RV park with hook ups.

    However, this experiment indicated that I do not have enough solar charging capacity to top off the batteries each day. I had to run a generator for an hour a day to get them topped back off. My solar array produces about 16 amps at noon. Of course it's less efficient in the morning or evening. If I'm using an average of 132 amp hours per day, and want the system to charge in five hours, I'll need to produce 26.4 amp hours on average to complete the task. So, I'm going to double my solar array in order to meet or exceed my requirements. My current array is three 100 watt panels in series. I plan on adding another three panels in series and then running both arrays in parallel to the controller.

    Jim
    Last edited by TucsonJim; 04-14-2019 at 05:46 PM.

  3. #3
    King Pin
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    SOURCES

    Victron BMV-712 Meter
    $206.55

    Victron Energy Temperature Sensor
    $20.40

    Project Box for Shunt
    $21.99

    Project Box for Meter
    $10.99

    I also used miscellaneous screws and battery cables I had on hand.

    LINKS

    Victron 712 Page
    Last edited by TucsonJim; 04-14-2019 at 06:00 PM.

  4. #4
    Long Hauler Paul & Deb's Avatar
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    Agreed. I've had mine installed for a few years now.

    Paul "Poppy" and Deb Cervone
    2022 Imagine XLS 22MLE
    2021 Imagine XLS 17MKE - SOLD ; 2015 Grand Design Reflection 337RLS - SOLD
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  5. #5
    Site Sponsor Cate&Rob's Avatar
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    Quote Originally Posted by Poppy's 5th Wheel View Post
    Agreed. I've had mine installed for a few years now.
    And . . . I know where that idea came from . . . .

    Rob
    Cate & Rob
    2015 Reflection 303RLS

  6. #6
    Seasoned Camper Hwktlg8's Avatar
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    Thanks for the detailed write up. This has been on my eventual to do list as well.
    Ryan and Alison
    2017 Solitude 377MBS-R
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  7. #7
    King Pin
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    Quote Originally Posted by Poppy's 5th Wheel View Post
    Agreed. I've had mine installed for a few years now.
    Paul - Time to upgrade to the new Blue Tooth version.

    Jim

  8. #8
    Seasoned Camper
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    Quote Originally Posted by TucsonJim View Post
    As many of you know, ...
    Jim

    I installed the BMV-712 this weekend in my 297RSTS. I took a different approach with mounting of the shunt as I installed in next to my inverter in the pass-through. I am curious on you decision to mount the temperature sensor as you did. I am assuming this is a simple thermocouple so I connected mine directly to the positive terminal of one of my batteries. I believe the actual temperature of the batteries could be higher then ambient since they are housed in black boxes on the front of the trailer and could be exposed to the sun.
    Last edited by howson; 04-14-2019 at 08:06 PM.
    2018 297RSTS
    2018 GMC Denali HD

  9. #9
    King Pin
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    Quote Originally Posted by srobins View Post
    Jim

    I installed the BMV-712 this weekend in my 297RSTS. I took a different approach with mounting of the shunt as I installed in next to my inverter in the pass-through. I am curious on you decision to mount the temperature sensor as you did. I am assuming this is a simple thermocouple so I connected mine directly to the positive terminal of one of my batteries. I believe the actual temperature of the batteries could be higher then ambient since they are housed in black boxes on the front of the trailer and could be exposed to the sun.
    I installed the temp sensor under the A-frame as shown. I did it more just for general information of the local temperature. BB batteries do very well in high temperatures. They will actually have more capacity at high temp, but if they were drained frequently at a high temp, it could shorten their life span. In reality, they are where they are, and I'm not going to make any changes due to sunshine. If you have AGM and/or Lead Acid batteries, temperature monitoring is more important.

    Jim

  10. #10
    Site Sponsor Cate&Rob's Avatar
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    Quote Originally Posted by TucsonJim View Post
    Paul - Time to upgrade to the new Blue Tooth version.

    Jim
    Hi Jim,

    September 2015 . . . post 44 - 48 . . . the first conversation between Paul and I about Victron battery monitors .
    https://www.mygrandrv.com/fo...3864#post43864 When I installed the one on my boat, no one had even heard of “blue tooth” LOL .
    (Victron builds quality stuff to marine standards . . . which is way beyond typical RV expectations)

    Rob
    Cate & Rob
    2015 Reflection 303RLS

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