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Battery Capacity for Ignition and Flight Controls

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  • Battery Capacity for Ignition and Flight Controls

    How much battery capacity do I need for my tow plane ignition?

    How much battery capacity do I need for the flight controls in my tow plane?

    These are common questions and we had a chance to do some flight testing at the last several aero tow events to determine the answers.

    We are currently operating two tow planes, a TopModel 3.37M Porter and a Hangar 9 3.5M Super Decathlon. Both are powered with twin cylinder DA-120 engines. Both are using a combination of Hitec HS-5645, HS-7954, and HS-7955 digital servos and 2-cell 6.6 volt, 2500 mA LiFe A123 battery packs. Each plane has three batteries on board, one for the ignition and two for the radio gear.

    Each plane has a 100 oz DuBro fuel tank, and each plane will operate for over one hour per tank of fuel. We set our transmitter timer for 60 minutes and did consecutive tow circuits for one hour without stopping (approximately 20 launch/landings per hour). Then we recharged the batteries using CellPro Multi 4 chargers and logged the mA put back into the packs.

    The results were very consistent between the two tow planes.

    Ignition = 550 mA per hour

    Flight Controls = 600 mA per hour (the two flight packs run in parallel so current is drawn from both packs at 300 mA per pack)

    So, our total energy demand is 1150 mA per hour. Our Harbor Freight 15 Watt solar panel supplies 1250 mA per hour, so our 12 volt lead acid source battery is maintained and can keep up with the charging demand from continuous flight operations.

    At busy events, we fly one plane for two hours (with one stop for fuel) and then put it on recharge, switch planes, and then fly that plane for two hours.

    A Site for Soar Eyes

  • #2
    Great info, Jim. This is the sort of testing and verifying that is really useful. Much appreciated. BTW, I like your choice of servos. I'll be piggy-backing off your choice for the Bidule 111.

    Comment


    • JimD
      JimD commented
      Editing a comment
      Asher,

      I have been working through the servo options for the Bidule 111 and will be posting a build thread shortly.

      Jim

  • #3
    Hi Jim,

    Interesting to see your effort here.

    I would like to confirm your numbers against ours, as we have checked the same information.

    You saw our Pawnee at Stephane's gathering and it is set up very close to the same as you listed here on your Porters. Our servos are Spectrum 6030 Titanium gear.

    Our Numbers are 500mah per hour on both flight packs and 560mah per hour on ignition. These are rounded to what's shown and are so close as to be non-important. Two hours towing.

    The receiver is a 9ch power safe JR.

    Rich

    Comment


    • #4
      Jim, Rich, Thanks for the very useful info in power consumption. Would anyone think these values would be much different for 150-200cc engines?

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      • #5
        Not really, as almost all engines use a CM6 style spark plug. I think I remember reading that a twin ignition system will draw about 1.6 amps at full throttle.

        Scott
        Last edited by MarnochS; 04-25-2016, 07:00 PM.

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