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Thread: Additional Alternator on 912is?

  1. #1
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    Default Additional Alternator on 912is?

    Looking for some experience in adding an additional alternator to a 912is. I am looking at the 30 amp one from Edge Performance but know there is another one that is interfaced to the engine with a fan belt and believe it actually fits inside the cowling without mods. Specifically looking at what kind of penalty in horsepower do I pay when using either one.

    Thanks ahead of time

    Gary
    Gary (Geek) Phenning
    Leavenworth (Not the Prison), WA
    Kitfox STi in Building Stage

  2. #2
    Senior Member efwd's Avatar
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    Default Re: Additional Alternator on 912is?

    Gary, you must have quite an extensive list of power consuming items. I thought I was loaded up, I don't need a second alternator for my 912is.
    Eddie Forward
    Flying
    SS7, 912iS, Garmin G3X

  3. #3
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    Default Re: Additional Alternator on 912is?

    Eddie, Thanks. This is exactly the kind of input I was looking for. One thing I have learned working on aircraft electrical systems is that there is the theoretical load in the books and the real load when actually operating. My experience is that the latter one is less than what the enginerds quoted cause they were required to put in some safety margins. So I was looking for some real experience numbers. With your set up, how much current is your electrical system indicate that it's pulling?

    I went through the loading listed in the books and got some "nominal" numbers (again engineers adding some safety numbers even when not at full load). Here's what I got

    Garmin system (not transmitting the radio came in at 6A.
    Landing, Nav and Strobe lites take 10.6A
    Boost pumps (9A per pump) 18A

    So that was a 35A pull. Before everyone jumps in to point this out, yeah I realize that these aren't pulling their loads at the same time and that the battery itself will make up the deficit and go back to getting a charge as the load comes off - a non event really. But that 30A alternator actually only puts out about 28A at higher RPM so regardless, that alternator will be running at almost full capacity just in normal flight. I also have a heated pitot tube that while I don't expect to use it that much or be flying at an altitude where it's cold enough for it to pull a full 20A, it will pull 10A if I do use it. Back when Orville and Wilbur were teaching me to fly, I was taught to turn on your pitot heat if you fly into rain and while I don't expect to operate that much in rain - it wouldn't be the first time if it does. Last but not least I am not really a fan of the Rotax system that will take over the 30A alternator if the 18A alternator that it uses to drive its critical systems dies. Again, I do realize that if it didn't, the fan in the front of the aircraft will stop turning which is bad. Sorry for the long winded answer but it just seems like I could avoid all this with an alternate alternator and the stock 30A could be my back up. But I'm still in the thinking process.

    Again thanks for the input.

    Gary
    Gary (Geek) Phenning
    Leavenworth (Not the Prison), WA
    Kitfox STi in Building Stage

  4. #4
    Senior Member 109JB's Avatar
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    Default Re: Additional Alternator on 912is?

    When I did my load analysis for my 912UL, I found that the conventional landing/strobes drew a bunch. I opted to replace with Kuntzelman LED nav/strobe lights that draw about 2 amps total. Also, I've seen some people calculate loads based on peak currents or what the breaker requirements are. Really need to use the running or average currents that the component manufacturer lists.
    John Brannen
    Morris, IL
    Sonerai IIL (Single Seat)
    Kitfox 3/4 1050 - Rotax 582 (Back Flying and sold)
    Kitfox IV 1050 - Rotax 582 (sold)
    Kitfox IV 1200 Speedster - Rotax 912 UL (project)
    Piper Twin Comanche (Sold)
    Glasair 1 FT (Waiting to start)

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    Default Re: Additional Alternator on 912is?

    Geek Do you know the 30 amp from Edge will not fit between the flywheel and the engine mount . Without cutting the cross bar out of the mount. Maybe Dustin will chime in to ,that's what I had to do when I insalled there EP912 STI.

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    Default Re: Additional Alternator on 912is?

    Quote Originally Posted by 109JB View Post
    When I did my load analysis for my 912UL, I found that the conventional landing/strobes drew a bunch. I opted to replace with Kuntzelman LED nav/strobe lights that draw about 2 amps total. Also, I've seen some people calculate loads based on peak currents or what the breaker requirements are. Really need to use the running or average currents that the component manufacturer lists.
    Good info on the lights. They are certainly bright but something has to drive them to get that. The numbers I was listing were the nominal numbers from the Garmin book. The radio for example had something along the lines of 1.5A when receiving, 3.8A average when transmitting and 7.5A peak. I used the 1.5 number because the others are a short amount of time and that's where we get to the part about letting the battery take care of the short term high current draw and then charge it back. Guess my real draw towards the extra/higher amp alternator is having one that isn't running full out and not having an electrical system that can be taken over without warning by the Rotax. The battery back up is another option I'm looking at. That at least would give me about an hour and half (without the lights) to still have avionics and find a place to land and fix the issue.

    Quote Originally Posted by 3 tracks View Post
    Geek Do you know the 30 amp from Edge will not fit between the flywheel and the engine mount . Without cutting the cross bar out of the mount. Maybe Dustin will chime in to ,that's what I had to do when I insalled there EP912 STI.
    Dustin and I have talked. What a great asset he is and really willing to give you the value of his experiences. I am aware of the interference between the engine mount and the alternator (thanks to Dustin). That cross bar is a required support if you have a nose wheel configured aircraft. I understand removing it for a tail dragger is not a problem and believe I read somewhere that John McBean had verified that.

    Thanks all for the inputs.

    Geek
    Gary (Geek) Phenning
    Leavenworth (Not the Prison), WA
    Kitfox STi in Building Stage

  7. #7
    Robthend's Avatar
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    Default Re: Additional Alternator on 912is?

    I was doing research today and came up with the exact same question that Geek had. Did a form search on the topic and this one popped up. Answered a lot of my questions.....and created more. I'm building a tri-gear so adding an Edge Performance accessory alternator on my EP914Ti won't work. I had seen briefly some other options for an accessory case, gear driven alternator and another one using a belt driven. Anyone with experience with these other options?

    Robert
    El Paso

    PS Hi Gary. (I'm TJ's father-in-law)
    Robert Henderson
    El Paso, Tx
    SS7 Tri gear N87KF
    EP914Ti, Airmaster, Garmin G3x, GNX375

  8. #8
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    Default Re: Additional Alternator on 912is?

    Going to be interesting to see what comes up here. I do know that the Edge Performance alternator won't work for you as you said. I do believe I have read that the Rotax belt driven external alternator will fit inside the Kitfox cowling without modification which is certainly a plus. It also puts out much more current - somewhere along the lines of 40A which I thought was also a bonus. Haven't sat down and figured out the draw to the horsepower of the engine. That will take a bit of time for me as well as bourbon.

    Give TJ my best. They have snow over there on the West side and that causes some real fun times over there.

    G
    Gary (Geek) Phenning
    Leavenworth (Not the Prison), WA
    Kitfox STi in Building Stage

  9. #9

    Default Re: Additional Alternator on 912is?

    Quote Originally Posted by Robthend View Post
    I was doing research today and came up with the exact same question that Geek had. Did a form search on the topic and this one popped up. Answered a lot of my questions.....and created more. I'm building a tri-gear so adding an Edge Performance accessory alternator on my EP914Ti won't work. I had seen briefly some other options for an accessory case, gear driven alternator and another one using a belt driven. Anyone with experience with these other options?

    Robert
    El Paso

    PS Hi Gary. (I'm TJ's father-in-law)
    i think Edge’s smaller alternator will work with the crossbar, but best check with them.

  10. #10
    Robthend's Avatar
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    Default Re: Additional Alternator on 912is?

    Not 30 minutes ago, i opened an email from Mike at Stolcreek (Edge Performance dealer) who did confirm, after sending multiple photos of my engine mount, that he believed the 15 amp WOULD fit. Mike said the photos of Kitfox Rotax engine mount appears identical to Just aircraft engine mount and had successfully mounted 15 amp alternator to that air frame. So....I have a request into Stolcreek for 15 amp, add-on alternator to install before mounting my engine. Should now give me adequate power.....just need to figure out how to wire all this.

    Robert
    Robert Henderson
    El Paso, Tx
    SS7 Tri gear N87KF
    EP914Ti, Airmaster, Garmin G3x, GNX375

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