SmartShunt to monitor charge current from a (vehicle) alternator

DIY
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Just wanting to check if I’ve missed something.

If I connect an isolated battery, ex. a bank of AA batteries, 1.5v x 9 for 13.5VDC, in the follow manner, is this going to work as I am thinking?

  • the (-)negative of AA battery bank is connected to the MINUS of the SmartShunt.

  • the (+)positve of the AA battery bank is connected to the SmartShunt Red Wire marked as VBatt+. (but I’m also putting a diode to block any reverse current going into the AA battery bank (13.5 - 0.7 = ~12.8VDC powering the SmartShunt).

  • the “charging wire” that is connected to the alternator, is connected to the LOAD terminal of the SmartShunt.

  • a wire from the MINUS of the SmartShunt is connected to the (positive) of the vehicle/car battery.

So, in effect, I have inserted the SmartShunt into the charging wire that normally runs directly from the alternator to the POSITIVE terminal of the vehicle/car battery.

But I’ve also powered the ShartShunt from a separate isolated DC power supply.

Is this going to work correctly to allow me to monitor the charge current between the alternator and the vehicle/car battery?

Any voltage the SmartShunt is going to report will be the AA battery bank, but the current measured and shown is going to be the alternator current… correct?

note: the Aux connector and the VE Connect lines are not going to be connected to the vehicle battery, or the vehicle ground, either directly or through a tempuratute/sensor connection, to help keep isolation.

edit: post went up before I’d finished correcting grammar, etc.

edit2: picture coming if visualization will help

SAMPLE - SKETCH
SAMPLE - SKETCH1153×700 178 KB

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Sorry, the Smartshunt has to be connected in the MINUS path of the battery…

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It is an interesting idea, I can understand where you are coming from on this. The battery + and alternator connections may need reversing to get the correct direction of current flow. It would work from a theoretical point of view but I am not going to say it will definitely work try st your own risk.

However, you must not connect the VE Direct cable to a GX device as the voltages will be wrong and you will blow something. You would only be able to monitor it by Bluetooth. I think you understand this.

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Why would you not just put the SmartShunt into the alternator ground path as designed?

Editing to add: an alternator cannot charge a battery that’s isolated from it. DC requires a complete circuit, so if a second battery is installed, intended for charging from the alternator, the second battery must share a common negative return path with the alternator.

If you want to charge an isolated battery, you need an isolated charger like an Orion-Tr Smart Isolated DC-DC charger, that’s connected between both batteries. Then, if you want to monitor the charge current going in to the second (isolated) battery, you install a SmartShunt on the negative return wire between the Orion and second battery (to monitor current going into the second battery) or between the first battery and the Orion (to measure the current being drawn from the first battery, supplied by the alternator).

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