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Thread: Current shunt

  1. #21
    Junior Member JohnC's Avatar
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    Default Re: Current shunt

    Thanks for your input. I considered the wire size but thought since the run from the alternator to the OV relay was several feet and with 10 gauge, I'd be OK with 2 - 3 feet of 10 gauge to the shunt and back. I think your right in that the halo would have been easier. Thanks again.

  2. #22
    Senior Member Andy's Avatar
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    Default Re: Current shunt

    Quote Originally Posted by JohnC View Post
    Thanks for your input. I considered the wire size but thought since the run from the alternator to the OV relay was several feet and with 10 gauge, I'd be OK with 2 - 3 feet of 10 gauge to the shunt and back. I think your right in that the halo would have been easier. Thanks again.

    The Gamin shunt drops 50 mV (corrected from 40 mV) at 100A. Why do you need the shunt if the link will drop more voltage than the shunt does? Why not tailor the link length so it acts as the shunt and measure the voltage across the link? You'd eliminate the shunt, 2 crimp terminals, and two bolted terminals and have a functionally equivalent solution.

    My back of the envelope calculation shows 0.126 V per foot at 100 A for M22759/16-10 so, if my calculation is correct, less than a foot could replace the Garmin shunt. If I went that way I'd remove the existing 10 AWG link and make a new link with the GEA 24 fuse leads crimped in the link terminals. The only down-side I can see is you'd have to determine the scale factor rather than use a published value.

    ref - https://cdn.glenair.com/wire-and-cab.../m22759-16.pdf
    Last edited by Andy; 04-21-2021 at 03:32 PM.

  3. #23
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    Default Re: Current shunt

    Came across this today:

    https://www.youtube.com/watch?v=XsJOAq0KYN8

    Interesting electrical monitor from circa 2013. I assume all of this is monitored in the G3X now?
    Last edited by hawgdrvr; 04-26-2021 at 01:49 PM.

  4. #24
    Senior Member Andy's Avatar
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    Default Re: Current shunt

    Quote Originally Posted by hawgdrvr View Post
    Interesting electrical monitor from circa 2013.
    Still standard fit for an FX-3 with World VFR panel but I don't think many were/are built that way. Additional electrical monitoring was provided by the CGR-30P engine monitor.

    (edited to delete comment on redundancy - too far removed from the thread topic)
    Last edited by Andy; 04-27-2021 at 12:54 PM.

  5. #25
    Senior Member Andy's Avatar
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    Default Re: Current shunt

    It cooled down enough in Phoenix for me to install my emergency ignition current sensor. I used an AMP25 Hall effect sensor fitted on the negative lead at the battery.

    I then ran my second in flight emergency ignition discharge test and again demonstrated 30 minutes operation. Current draw was 1.3 - 1.4 Amps during discharge with a peak charging current of 3.1 A when the test was terminated.

    The addition of this current sensor caused another change in the engine pages and they now look like this:
    Attached Images Attached Images

  6. #26
    Senior Member turbopilot's Avatar
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    Default Re: Current shunt

    Quote Originally Posted by Andy View Post
    It cooled down enough in Phoenix for me to install my emergency ignition current sensor. I used an AMP25 Hall effect sensor fitted on the negative lead at the battery.

    I then ran my second in flight emergency ignition discharge test and again demonstrated 30 minutes operation. Current draw was 1.3 - 1.4 Amps during discharge with a peak charging current of 3.1 A when the test was terminated.

    The addition of this current sensor caused another change in the engine pages and they now look like this:
    Good idea. Can never have too much information in an all electric airplane.
    Bob Anderson, CC11-00435, N94RA

  7. #27
    Senior Member Andy's Avatar
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    Default Re: Current shunt

    Quote Originally Posted by turbopilot View Post
    Can never have too much information in an all electric airplane.
    Well you can if you are a worrier! The initial charge current of 3.1 A greatly exceeds the 0.3 C maximum specified in the Panasonic Technical Manual. The in-flight discharge test with in-flight re-charge may reduce battery life.

    If the ignition battery has not been discharged, a typical peak charging current after engine start seems to be about 0.4 A. 0.3 C for a 2 AH battery is 0.6 A so that's within limits.

    The peak charge current after a routine emergency ignition test during run-up was 0.7 A. How long the 0.3 C limit is exceeded with depend on how long the test was run. I don't consider a brief rpm drop test to be adequate and usually monitor the voltage for a 10 second test. The 0.7 A charge was observed after a 7 second test.

    These recorded peaks are almost certainly lower than the instantaneous peaks as G3X indicated and logged current and voltage are heavily lagged.

    Still pondering what, if anything, to do about this.

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