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Battery Size For 912 iS?

in 912iS Technical Questions 7 years ago
I note the installation manual calls for at least 16Ah of battery capacity. Since in the event of a dual alternator failure, the engine will require about 12 amps to run a fuel pump and ECU this is understandable.

Is there any data on the likelihood of a double alternator failure?

Can the engine be started in the "backup battery" emergency mode?

I am trying to decide on a battery size.

  • Re: Battery Size For 912 iS?

    by » 7 years ago

    I am using an Earth X 36C .
    Has 36Ah and 405CCA
    weight 3.9 lb
    Lithium-ion
    Meets Rotax requirement for an internal battery management system in accordance with Rotax service instruction.
    Is the battery selected by Kitfox factory in response to the Rotax instruction for 912iS engines
      
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  • Re: Battery Size For 912 iS?

    by » 7 years ago

    Are you sure about those specs, Richard? I've been looking at the EarthX site for batteries specifications and the 36C says it's 12.4Ah and 320CCA. I'm looking towards the ETX 900, which is 16.0Ah/400CCA and weighs 2.2Kgs.
      
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  • Re: Battery Size For 912 iS?

    by » 7 years ago

    i went for the earthx 1200 - 24.5 Ah. that in theory gives me two hours of flight after total alternator failures. I hope I never have to find out if this is enough.
      
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  • Re: Battery Size For 912 iS?

    by » 7 years ago

    The Ah figure is "lead acid equivalent".
      
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  • Re: Battery Size For 912 iS?

    by » 7 years ago

    Hmmm, I hadn't thought about the lead acid equivalent. But if your 36C is actually chucking out 12.4Ah even though it's the equivalent of 36Ah with a lead acid battery then the engine is only going to get 12.4Ah instead of the 16 recommended by Rotax.

    I will be extremely interested to hear if the 16Ah requirement is 'lead acid equivalent' and that it is okay to 'step down' a Lithium battery to the same (or better) equivalent instead of what it's listed as providing.

    I THINK I'll still need the ETX900 (16.0Ah) but I will be extremely happy to be told I'm wrong. I believe I'm basically getting the 16Ah at 1/3 of the weight of a conventional battery but I'll still need the 900 to satisfy Rotax.
      
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