BMV 700 install Help, Tech not figuring it out !

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scott-n asked Jul 26, '19

BMV 700 install Help, Tech not figuring it out !

BMV 700 w/ blue tooth dongle installed into a 5th Wheel RV with 4 Wet cell 6V golf cart batteries wired series/parallel to a 2500w inverter/charger. When the inverter is turned off, the RV runs off the DC battery bank, when I need AC power the inverter is turned on and AC is throughout the entire RV. His first attempt resulted in moniter reading discharge from batteries only ( inverter off ) and no absorbson readings from shore power or when the inverter was on no discharge readings, second attempt resulted in discharge readings from inverter only, but when inverter was off no readings from the battery bank. Tech is now saying I possibly need another shunt ? The desired outcome is for the moniter to read my battery status from the 4 battery bank charging and discharging when using the batteries alone or when using the inverter is on. I dry camp alot and when I switch on the inverter to watch TV or wife uses a AC kitchen appliance the moniter keeps an accurate account of the battery status. When plugged into shore power or the generator the moniter can read absorption recharging the batteries and account for the difference.

The inverter is a brand new Xantrez Freedom 458 modified sine 2500w inverter/charger with automatic 30 amp transfer.

Little worried that the tech is going to damage my electricial system just changing things and hoping it will work? Any help is appreciated. I have searched for a wiring diagram for the 700 using 4 batteries and an inverter with no success.

Thanks

BMV Battery Monitor installation inverter current draw

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Answer 1 · 2019-07-27T07:07:56Z

JohnC answered · Jul 27, 2019 at 07:07 AM

Hi Scott. It sounds like your shunt is wired incorrectly.

https://www.victronenergy.com/upload/documents/Quickinstallsheet_BMV70x_part1_2.pdf

Note it's a battery monitor, and not designed specifically for separating loads or sources. Wired to the -ve side of your batteries, and could be considered the actual batt pole, with no wires bypassing it. Bypassed wires don't get measured.

If this isn't clear or applicable, perhaps post some pics of the shunt or a wiring layout.

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scott-n commented · Jul 27, 2019 at 06:22 PM

Thanks JohnC for responding, I'm not doing the install personally, The RV tech is having problems and I just wanted to make sure that BMV 700 can be connected to monitor my 4 batteries....discharge and absorption rates ...using an inverter/charger. Last spoke to them yesterday and they were thinking I needed another Shunt. Is there a wiring diagram somewhere that will show the correct connections when using an inverter?

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JohnC ♦ scott-n commented · Jul 28, 2019 at 06:41 AM

This might cover you. Don't be confused by the 'little' wires that are just sensors/comms. But it does show you where they go.

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scott-n JohnC ♦ commented · Jul 28, 2019 at 02:19 PM

Does the BMV still calculate the battery draw when the inverter is off? and again when the batteries are charging in this configuration?

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JohnC ♦ scott-n commented · Jul 29, 2019 at 05:00 AM

Yes it will. The BMV/shunt is a 2-way device, the current into/out of the batts indicated by +/- notations.

Your DC loads (the -ve terminal of) would be added to the 2 wires already on the rhs of the shunt pictured. The idea being that 'nothing' bypasses the shunt, with the only -ve connection to the batts being the shunt lhs terminal.

It's a nett reading of course, relevant to the batts alone. To derive individual charge/discharge (ac or dc) figures you'd need to look perhaps at additional kit.

But get your BMV up correctly first, and see what else you really 'can't do without'.

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scott-n JohnC ♦ commented · Jul 29, 2019 at 01:41 PM

Thanks again John, didnt think it needed another shunt. I passed the Info to the techs with the diagram.

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