Shunt Wiring

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tr0y
tr0y Solar Expert Posts: 99 ✭✭✭
in Caravan, Recreational Vehicle, and Marine Power Systems #1
Hi All - 

Wiring  a shunt into my system for proper monitoring and have a quick question. Do I need to with both the battery Negative to and from the inverter and the Battery Negative from the charge controller to both run across the shunt for proper readings ? Thanks 
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  • Tecnodave
    Tecnodave Registered Users Posts: 437 ✭✭✭✭
    #2
    Yes......every negative goes to one end of the shunt and only the battery negative goes to the other end...the sensing device or connections for the sensing device go to the small #6-32 screws, multiple sensors can be used togather, I use MidNite WhizbangJr as well as Bogart Engineering Tri-Metric monitors on my system , they do not interfere with each other, I also maintain a system where I have a MagnaSine BMK and a Whizbang Jr working togather sharing the same shunt,
    2 Classic 150, 2 Kid, 5 arrays 7.5 kw total  2ea.  2S6P Sharp NE-170/NE-165, 1ea. 12P Sanyo HIT 200,  2ea. 4/6P Sanyo HIT 200, MagnaSine MS4024AE, Exeltech XP-1100,  2 Banks L-16 battery, Rolls-Surette S-530 and Interstate Traction, Shunts with whizbangJr and Bogart Tri-Metric, iCharger i208B  dc-dc buck/boost converter with BMS for small form lithium 8S 16650 or LiFePO4,
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,694 admin
    #3
    As Tecnodave said, you want "all battery current" to flow through the shunt (all negative "bus connections" on one side, battery only on the other side).

    If you connect any loads to the "battery side" of the shunt, those loads will be "invisible" to the shunt and battery SoC will be much less accurate.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • tr0y
    tr0y Solar Expert Posts: 99 ✭✭✭
    #4
    Thanks guys, so just because I'm slow, negative out of the Midnight Classic to the shunt and inverter negative to the same pole on the shunt.  And then from there to the Victron 712 and WhizBang Jr to monitor. 
    Thanks   
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,694 admin
    #5
    You got it. ALL negative connections on one side of shunt. Battery negative (all batteries negative if you have parallel battery strings) on the other side of shunt.

    Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Estragon
    Estragon Registered Users Posts: 4,498 ✭✭✭✭✭
    #6
    To clarify, the classic negative output wire, inverter, and any other loads or power sources are attached to one of the big bolts on the shunt.  The only thing on the big bolt on the other side of the shunt should be a wire to the battery/bank negative.

    WbJr and any other monitor sense wires go via small wires to the small bolts.

    The big bolts carry full current in/out of the bank.  Sense currents and voltages are tiny, and go to the small bolts.  For sense devices, refer to wiring instructions for the particular device on how to wire the sense & power connections for that device.
    Off-grid.  
    Main system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • speedbrake
    speedbrake Registered Users Posts: 10 ✭✭
    #7
    Agree with "all negative connections on one side of the shunt" advice, but let me put a finer point on it because I struggled with this in my install.  I had about six different negative wires, large and small, all needing to go to the 'one side of the shunt'.  Those fat (3/8") shunt bolts are quite short and can only handle one or two thick ring terminals before you run out of threads to secure it.  My solution: buy a bus bar (I used a blue sea 6 x 5/16" posts, but any bus bar will do), attach all 6 of my negative wires to it, then run ONE wire from that negative bus bar to the shunt.  Caveats: make sure the bus bar is rated for the number of amps you plan to put thru it, especially if you have an inverter because those can be HIGH amp.  Make sure that one wire going from the neg bus bar to the shunt is of sufficient gauge to handle the max amp load.  I used 4/0 welding wire, your setup may be different.  Also, I had  other "negative wires" in my travel trailer that I was concerned about connecting to the shunt. Specifically, my converter wiring.  Positive wire ran from my converter 25' forward to the battery bank, but the converter's negative wire ran to the frame (ground) about 4' from the converter.  I thought I was going to have to 'add a wire'.  After consulting with Bogart Engineering (they make the Trimetric battery monitor) I was told that as long as I have a frame ground going to that "one side of the shunt", then I don't need to extend my converter's negative wire.  Essentially, the frame is acting as an alternative circuit path instead of running another negative wire. So, battery's negative wire on one side of the shunt, all the other negative wires (including a frame/ground) on the other side.
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