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BMV-712 Battery monitor showing current draw when master shutoff switch turned off.

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  • BMV-712 Battery monitor showing current draw when master shutoff switch turned off.

    This is going to be embarrassing, but here goes.

    Just replaced my 4 ea. 6V AGM battery bank with a new 4 ea. 12V Lithium battery bank -- and added a BMV-712 battery monitor. I was pretty sure I only needed a single battery bank shutoff switch to completely isolate the battery bank from my 12 volt loads. But after I completed the install, I tested the shutoff switch by switching it off (along with my solar circuit breakers and inverter/charger on/off switch), then monitored the current draw via the BMV-712 monitor.

    With all switches off, the monitor was showing a current load of 4.8 amps! Time remaining on my fully charged Lithium bank: around 4 days.

    Here's a simplified block diagram of my system:

    SimplifiedElectrical.pdf

    (Not shown on the diagram is the 12V circuit between the battery and the BMV-712. But the manual says that load is milliamps, not amps.)

    I don't know how the BMV-712 could be seeing a load with all switches off.

    The only thing I can guess is the inverter/charger is not working like I thought.

    Is my problem obvious to anyone?

    Thanks.

    -Steve
    2018 Solitude 310GK, disc brakes
    Morryde SRE4000/XFactor with heavy duty shackles, V-Brackets in spring hangers
    2012 Ram 3500 SRW 6.7 Diesel, air bags
    18k B&W Companion, non-slider
    640 watts solar, 400 amp-hour Lion Safari UT 1300 battery bank
    Aims 1500 watt inverter/charger with ATS
    Somerset, WI

  • #2
    To totally isolate any draw on the battery bank the shut off switch needs to be before any loads. Your switch in your diagram is only removing the 12 v loads and not the inverter/charger. The inverter charger will draw some kind of amps even when not in use.

    Brian
    Brian & Michelle
    2018 Reflection 29RS
    2022 Chevy 3500HD

    Comment


    • #3
      Steve,

      I have been working to wire in my new Lithium system and I believe I have a simple solution to this issue.

      On the battery cut off switch, move the battery feed to the load side of the switch. So you are moving both wires to one side of the switch. From there, run a new and separate heavy battery feed to the switch. This method will turn off ALL functions at the switch and will back feed power to the brake switch and CO detector when the switch is in the on position. After this is done, the converter charger would still operate all 12V DC functions in the rig while plugged into AC and would also allow you to turn off the switch when you do not want battery charging to occur.

      A main breaker would need to be added to the positive battery feed and as close as possible to the battery, while the BMV712 would need to be added on the negative side of the battery before any chassis ground or components.

      Jim
      Last edited by Guest; 04-01-2020, 07:04 AM.

      Comment


      • #4
        Originally posted by steve&renee View Post
        This is going to be embarrassing, but here goes.

        Just replaced my 4 ea. 6V AGM battery bank with a new 4 ea. 12V Lithium battery bank -- and added a BMV-712 battery monitor. I was pretty sure I only needed a single battery bank shutoff switch to completely isolate the battery bank from my 12 volt loads. But after I completed the install, I tested the shutoff switch by switching it off (along with my solar circuit breakers and inverter/charger on/off switch), then monitored the current draw via the BMV-712 monitor.

        With all switches off, the monitor was showing a current load of 4.8 amps! Time remaining on my fully charged Lithium bank: around 4 days.

        Here's a simplified block diagram of my system:

        [ATTACH]n15784[/ATTACH]

        (Not shown on the diagram is the 12V circuit between the battery and the BMV-712. But the manual says that load is milliamps, not amps.)

        I don't know how the BMV-712 could be seeing a load with all switches off.

        The only thing I can guess is the inverter/charger is not working like I thought.

        Is my problem obvious to anyone?

        Thanks.

        -Steve
        The inverter should draw <1.2 amps. See spec sheet on page 23 of the Magnum manual (pic below). Note the manual says the on/off switch on your inverter is not a battery disconnect switch.

        Easy enough to test the amperage draw due to the inverter--remove the negative wire (at the BMV's shunt) that is going to the inverter.


        Click image for larger version

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        Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

        2017 Ford F-350 DRW, '19 315RLTSPlus

        Comment


        • #5
          howson Country Campers

          Thanks for your replies. Couple of missremembers / misstatements I made:

          1. The amperage was 2.8, not 4.8

          2. The current flow was *into* the battery. The 2.8 was showing positive flow, not negative!

          Jim:

          1. I know the main cutoff-switch is removing only 12V loads, but the inverter/charger switch was off when I checked the BMV-712. I don't see how a switched-off inverter/charger could have been affecting the battery. That's what switches are for, aren't they? Moreover, the inverter/charger has led-indicators that tell me whether the inverter/charger is in invert-mode, charge-mode, fast charge, slow charge, etc. None of these lights was on -- because the inverter/charger power switch was off.

          2. I *really* don't understand your rewiring suggestion. Seems like it wouldn't switch the battery bank off at all.

          I took the trailer to storage last night. I'm going back today to try to do some testing.

          Thanks again.

          -Steve
          2018 Solitude 310GK, disc brakes
          Morryde SRE4000/XFactor with heavy duty shackles, V-Brackets in spring hangers
          2012 Ram 3500 SRW 6.7 Diesel, air bags
          18k B&W Companion, non-slider
          640 watts solar, 400 amp-hour Lion Safari UT 1300 battery bank
          Aims 1500 watt inverter/charger with ATS
          Somerset, WI

          Comment


          • #6
            Originally posted by steve&renee View Post
            howson Country Campers

            Thanks for your replies. Couple of missremembers / misstatements I made:

            1. The amperage was 2.8, not 4.8

            2. The current flow was *into* the battery. The 2.8 was showing positive flow, not negative!

            Jim:

            1. I know the main cutoff-switch is removing only 12V loads, but the inverter/charger switch was off when I checked the BMV-712. I don't see how a switched-off inverter/charger could have been affecting the battery. That's what switches are for, aren't they? Moreover, the inverter/charger has led-indicators that tell me whether the inverter/charger is in invert-mode, charge-mode, fast charge, slow charge, etc. None of these lights was on -- because the inverter/charger power switch was off.

            2. I *really* don't understand your rewiring suggestion. Seems like it wouldn't switch the battery bank off at all.

            I took the trailer to storage last night. I'm going back today to try to do some testing.

            Thanks again.

            -Steve
            Could it be possible the BMV needs to be calibrated? Under SETTINGS > BATTERY there's a CALIBRATE setting for the amperage (see pic below). If everything is disconnected from the system (except the BMV, obviously) you'd click this setting. (Honestly I've never done it, but that sure appears like the right sequence.) This forum conversation seems to confirm what I'm writing: https://community.victronenergy.com/...libration.html

            Regarding your inverter--it *will* draw some amperage even with the ON/OFF switch in the "off" position. All that does is turn off the output, not the "brains" inside the unit. (At least that's my interpretation of what the manual is stating.)

            Click image for larger version

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            Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

            2017 Ford F-350 DRW, '19 315RLTSPlus

            Comment


            • #7
              Originally posted by howson View Post

              Could it be possible the BMV needs to be calibrated?

              . . .

              Regarding your inverter--it *will* draw some amperage even with the ON/OFF switch in the "off" position. All that does is turn off the output, not the "brains" inside the unit. (At least that's my interpretation of what the manual is stating.)
              I think you're definitely onto something about the need to calibrate the BMV. Just in the last few hours, I've started thinking about whether something was amiss with the monitor's setup. Especially since I realized that current flow was indicated by the sign of the readout. There's no way I could have had current flow into the battery bank: *Everything* was off and there was no shore power. I was thinking about calling Victron, but I'll try the calibration first.

              I still don't believe your last statement -- at least with my AIMS unit. It *does* have a power save/monitor mode, but you have to explicitly activate that with a switch. In the off position, my remote display is dead. When you power the unit on, the display lights with a splash screen and it chimes.

              Thanks for thinking of the calibration.

              -Steve

              2018 Solitude 310GK, disc brakes
              Morryde SRE4000/XFactor with heavy duty shackles, V-Brackets in spring hangers
              2012 Ram 3500 SRW 6.7 Diesel, air bags
              18k B&W Companion, non-slider
              640 watts solar, 400 amp-hour Lion Safari UT 1300 battery bank
              Aims 1500 watt inverter/charger with ATS
              Somerset, WI

              Comment


              • #8
                Originally posted by steve&renee View Post
                I still don't believe your last statement -- at least with my AIMS unit. It *does* have a power save/monitor mode, but you have to explicitly activate that with a switch. In the off position, my remote display is dead. When you power the unit on, the display lights with a splash screen and it chimes.
                There's a lot of electronics that draw power even when "off". But no point in debating as it is easy to test--use a "real" multimeter to measure if there is any amperage going into the inverter with it connected, but with the switch off. (The goal is to know the parasitic power draw sources in your camper, not whether I'm right or not!)
                Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

                2017 Ford F-350 DRW, '19 315RLTSPlus

                Comment


                • #9
                  Originally posted by howson View Post

                  Could it be possible the BMV needs to be calibrated?
                  That was it. I'm totally convinced. I completely isolated the battery bank from all loads (with the master shutoff switch), and disconnected the system side of the shunt. This according to Victron's advice in the link you provided: https://community.victronenergy.com/...libration.html

                  That has to be a zero load condition. At that point I hit the Zero Calibrate button on the BMV app, and just like the zero-button on a digital caliper, the monitor displays 0 for current in or out of the bank.

                  Hooked it all back up, and with the master shutoff still off, the BMV app shows 0 current draw or charge.

                  I'm confident now that I'm good to go.

                  Thank you, Howard.

                  -Steve
                  2018 Solitude 310GK, disc brakes
                  Morryde SRE4000/XFactor with heavy duty shackles, V-Brackets in spring hangers
                  2012 Ram 3500 SRW 6.7 Diesel, air bags
                  18k B&W Companion, non-slider
                  640 watts solar, 400 amp-hour Lion Safari UT 1300 battery bank
                  Aims 1500 watt inverter/charger with ATS
                  Somerset, WI

                  Comment


                  • #10
                    Originally posted by howson View Post

                    There's a lot of electronics that draw power even when "off". But no point in debating as it is easy to test--use a "real" multimeter to measure if there is any amperage going into the inverter with it connected, but with the switch off. (The goal is to know the parasitic power draw sources in your camper, not whether I'm right or not!)
                    I'll measure.
                    2018 Solitude 310GK, disc brakes
                    Morryde SRE4000/XFactor with heavy duty shackles, V-Brackets in spring hangers
                    2012 Ram 3500 SRW 6.7 Diesel, air bags
                    18k B&W Companion, non-slider
                    640 watts solar, 400 amp-hour Lion Safari UT 1300 battery bank
                    Aims 1500 watt inverter/charger with ATS
                    Somerset, WI

                    Comment


                    • #11
                      [QUOTE=steve&renee;n15821]

                      That was it. I'm totally convinced. I completely isolated the battery bank from all loads (with the master shutoff switch), and disconnected the system side of the shunt. This according to Victron's advice in the link you provided: https://community.victronenergy.com/...libration.html

                      This is what I was describing to do, but may have not got that across so well. To move all loads (both wires on the switch moved to one side) to one side of the battery switch and to run a new feed from the battery to the open side of the switch. To not do this and your batteries will still be powering the CO detector, brake switch, and in some cases the radio memory.

                      The nice thing about doing this is you can control when you want your batteries to be charged or not. For instance I can keep my batteries at a storage SOC of 50% and with the battery switch turned off can still power the rig with the converter charger. If I'm boondocking, I turn the switch on and charge the batteries from the converter/charger while on the generator.



                      Jim
                      Last edited by Guest; 04-01-2020, 12:25 PM.

                      Comment


                      • #12
                        Originally posted by MidwestCamper View Post
                        ...move all loads to one side of the battery switch and to run a new feed from the battery to the open side of the switch.
                        Jim
                        I guess this is why someone invented the "picture is worth a thousand posts" saying. Man, I'm having a hard time seeing what you're saying.

                        I think my diagram shows all loads on the load side of the shutoff switch, and a single feed from the battery bank to the shutoff switch. I guess you are suggesting that the inverter/charger is a battery load, so the inverter/charger (+) lead should come into the battery either via the bus-bar -- or via the load-side of the shutoff switch. (In fact, before I installed the BMV-712, that's how my old setup was configured.)

                        As I've suggested to Howard, I don't believe the inverter/charger is a battery *load*. (I'm going to measure it with a meter to confirm -- 'cause Howard is making me.)

                        If the inverter/charger is indeed not a load, then I like my current configuration -- because it lets me run 2/0 wire from the inverter/charger to the battery, but 1/0 or less wire to the shutoff switch.

                        Now: I'm completely out of ammo. Done. Finished. Kaput.

                        -Steve
                        Last edited by steve&renee; 04-01-2020, 05:18 PM.
                        2018 Solitude 310GK, disc brakes
                        Morryde SRE4000/XFactor with heavy duty shackles, V-Brackets in spring hangers
                        2012 Ram 3500 SRW 6.7 Diesel, air bags
                        18k B&W Companion, non-slider
                        640 watts solar, 400 amp-hour Lion Safari UT 1300 battery bank
                        Aims 1500 watt inverter/charger with ATS
                        Somerset, WI

                        Comment


                        • #13
                          See drawing.
                          Attached Files

                          Comment


                          • #14
                            Originally posted by MidwestCamper View Post
                            See drawing.
                            I get it. If the inverter/charger is indeed a battery load when it is switched off, your configuration allows one to eliminate battery drain when you turn the relocated "master" switch off -- mine doesn't. I'll measure the switched-off load, and if there's any load, I'll probably make your configuration change.

                            Thanks for following up.

                            -Steve
                            2018 Solitude 310GK, disc brakes
                            Morryde SRE4000/XFactor with heavy duty shackles, V-Brackets in spring hangers
                            2012 Ram 3500 SRW 6.7 Diesel, air bags
                            18k B&W Companion, non-slider
                            640 watts solar, 400 amp-hour Lion Safari UT 1300 battery bank
                            Aims 1500 watt inverter/charger with ATS
                            Somerset, WI

                            Comment


                            • #15
                              Steve,

                              The nice thing about having a switch to kill the battery entirely is to be able to run your converter/charger to power the rig while on AC and not keeping your batteries at 100% SOC. See the RV Battery section in how to make your lithium batteries last longer.

                              Take care,

                              Jim

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