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Thread: Best battery replacement advice from Cubcrafters?

  1. #31
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    Default Re: Best battery replacement advice from Cubcrafters?

    Quote Originally Posted by Pete D View Post
    The wires that carry all of the starter current are 4 gauge.

    I don't have the data for our starter current testing in front of me, but what I remember is as the engine was cranking you could see the compression strokes in the current. The peaks were something like 200 or 220, right about what the CCA rating of the battery is, but the average amperage while cranking was lower at about 180 amps.

    Pete D.
    Thanks Pete
    Bill

  2. #32
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    Default Re: Best battery replacement advice from Cubcrafters?

    If I assume about the equivalent of 8' of number 4AWG wire and an average of 200 Amps starter current then ---

    .0002485 Ohms/foot X 8 feet X 200 amps = .3976 Volts drop

    The two solenoids and airframe ground return will probably double that to about .8 Volts
    That is acceptable for a 12 Volt system.

    I doubt that you could get much improvement with larger wire.
    The fact is we are pushing the little battery and the starter to their limits.

    Maybe the lithium iron technology will solve our problem.

    I built a small 115 Volt AC forced air heater for the engine and use a blanket.
    That keeps the engine warm to the touch and has made starting easy on our 15/20 degree mornings so far.

  3. #33
    Senior Member turbopilot's Avatar
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    Default Re: Best battery replacement advice from Cubcrafters?

    Quote Originally Posted by randylervold View Post
    I don't think I'd run another wire, but a heavier gauge wire would have less resistance and pass the current better. But it would also be HEAVIER... light is right!
    Been thinking more about the hot start issue. Since I have not experienced this situation I am guessing we have a fully charged battery which cannot deliver enough amps to the starter to get best the compression stroke. This could be because the battery does not have enough capacity, the wire between the battery and the starter has too much resistance or a combination of the two.

    How about installing a "gang" circuit/switch between the ignition backup battery and the main battery. When the main battery cannot get past the compression stroke in cold conditions or on a hot start, then activate the gang switch to combine both batteries to starter circuit.
    Bob Anderson, CC11-00316, N382RA

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