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Backup battery switch?

in 912iS Technical Questions 8 years ago

  • Re: Backup battery switch?

    by » 8 years ago

    I got this from the supplier:

    "Please find attached correct wiring diagrams and Rotax´s check list of the 912iS installation, based on which we received their authorization to make installations of this engine. Everything is in compliance with the diagram from 2012 and Rotax did not find any discrepancy and such installations are still fully functional."

    I still cannot believe "such installations are still fully functional".

    Are you saying out is output from pin 1? Is that from ALTA or B?
      
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  • Re: Backup battery switch?

    by » 8 years ago

    So they do not ever correct any issues? they still use out of date instructions? Sorry but in aviation everyone has the responsibility to update publications and make changes as necessary. Otherwise the system does not work: Rotax, Continental, Lycoming, MT propellers, Hartzell etc cannot send workers to each of the thousands of aircraft manufactures every year to make sure they are following the most recent publications. That is putting the responsibility in the wrong place (aviation does not use quality control anymore, quality assurance is better: It puts the responsibility on each person in the process, not some poor sucker trying to oversee everyones elses work)
    I messed up the pin input/output tasks(I hate Mondays). Let me get some help with that.

    Here is what happens.
    The ECU decides what generator to use:
    During engine-start the ECU switches all relays to Gen B. If the ECU is happy with GEN B the engine will continue to run. Once the rpm goes past 2300, for more than 3 seconds, the ECU tries Gen A. If Gen A is OK then the ECU switches to Gen A for the ignition and injection and allows Gen B (30 amps) to charge the battery.
    If one Gen fails the ECU will switch to the other Gen and at the same time it will stop charging the battery (primary concern is keeping the engine running).
    If both gens fail the pilot must turn on the Backup-power and the ECU will run off the battery power.
      
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  • Re: Backup battery switch?

    by » 8 years ago

    Thanks
    And what is available at pin 1 and 2? It cannot only be power inputs for start and "backup". Where are the power put from the generators going? I guess it is ALT-B on pin 3, and then ALT-A on pin 1 and 2. Is that true or is that unknown?
      
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  • Re: Backup battery switch?

    by » 8 years ago

    not sure; they would not be 12 AWG wires if they did not carry a large load.
    Again, the ECU decides what generator to use so you cannot say pin-1 = Gen-B, etc.
      
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  • Re: Backup battery switch?

    by » 8 years ago

    The pin (female) is I think 66740 - 6. These pins are gold plated and not cheap!

    Data sheet : http://www.farnell.com/datasheets/492503.pdf?_ga=1.40535970.1605293683.1469085568

    I note that the B alternator output is up to 28? Amps and that the Rotax wiring diagram specifies 12 AWG for the wire and provides a 12 AWG terminal. The rule of thumb for a 35C wire temperature rise for 12 AWG is I think about 20 Amps, which is less than rated alternator output. The "aero electric" book says that the wire for the alternator output should be rated for maximum output.

    Question: has Rotax run into any problems with recommending 12 AWG for that wire? Does the fuse box connector ever get too hot? I am using aircraft grade wire, not PVC insulated stuff. I know that maximum amperage on that wire should only be transitory anyway and my average load should be no more that 12 Amps continuous.

    I have ordered a connector pin that takes 10 AWG wire (66741 - 6) from element14.com which I am considering using for that wire instead of 12 AWG , But maybe I am way too cautious.
      
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