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Thread: Configure Shunt Amperage

  1. #1
    Junior Member
    Join Date
    May 2010
    Auckland, New Zealand

    Configure Shunt Amperage

    I am running the AF3500 and have the shunt wired into the right place (between the main bus and the battery.
    On start up I'm showing about 30amps for a few minutes (seems ok). If the battery has been running all my IFR equipment on the ground for a while and the engine has been shut down when I start the engine I'm getting over 60amps displayed. Sometimes 70 amps which must be wrong.
    I have the 60amp regulator in my Vans RV7a.
    To reduce the 60 plus amps I turn on other items like landing lights, pitot heat and the amps displayed is halved. As this drops the amps due to the other electrics drawing power means less available to the battery. Again that seems fine.
    I think it is over reading.

    Why is it that on a 2 hour flight me EFIS is still showing around 20amps going to the battery. By then I would expect the battery is fully charged and the EFIS should be showing zero amps?

    1/ Max top of range 80.0
    2/ Red high at 60.0
    3/ Yellow high at 40.0
    4/ Yellow low at 0.00
    5/ Red Low at 0.00
    7 Audio ON
    8/ Instruement PRIMARY
    9/ Display Units AMPS
    10/ Shift Adjust 0.0
    11/ Num Cal Points 2

    Display (amps) AD VALUE
    0.00 2497
    0.00 0

    1/ How do you create a few Number of Calibration Points (easy to do with a gas tank, just add a few gals at a time and record Ad Values etc so you end up with many cal points across the measurement range)?
    2/ How many Calibration Points are people inputting?
    3/ I think my 2 x Calibration Points are wrong. Do I get rid of the 0.00 0 entry as that's confusing the other 0.00 2497 entry?
    4/ I could simply take the plane for a 1 hour flight and see how many amps are showing (say it's still showing 20amps when I know the battery is charged). Then set 11/ Shift Adjust to -20.0 and that will fix the over read?
    5/ Why am I getting such an over read of amps?
    6/ Do I need a few more calibration points than the 2 I have now?


  2. #2

    Shunt between Alternator and main bus

    Are you sure that the shunt is between the battery and main bus, not between the alternator and main bus? Your readings sound correct if it is between the alternator and main bus. That's how I have it installed on my -8 (however I use the hall effect sensor).

    My fuel calibration points are every 2 gallons and top out at 14gln for one tank and 16 on the other. So I have 10 calibration points: 0,2,4,6,8,10,12,14,16 & 18 (16+) glns. Since mine is a taildragger I did the calibration with the tail up and tail down.

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