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Thread: Backup Battery Check Before Takeoff

  1. #1
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    Question Backup Battery Check Before Takeoff

    When I do the Backup Battery (Ignition) check in the before takeoff checklist here is what happens.
    When I go Ignition right, left ignition light illuminates as it should, no RPM drop. When I switch the Backup Battery to "Emergency", the engine quits. However if I switch the ignition to Left and turn the Backup Battery to Emergency, the engine continues to run.

    Backwards from what the checklist describes......is this an easy fix??

    Jon

  2. #2
    Senior Member carlconti's Avatar
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    Default Re: Backup Battery Check Before Takeoff

    Sounds like a bad or disconnected backup battery.
    Carl

  3. #3
    Member DRL's Avatar
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    Default Re: Backup Battery Check Before Takeoff

    Quote Originally Posted by txcub View Post
    When I do the Backup Battery (Ignition) check in the before takeoff checklist here is what happens.
    When I go Ignition right, left ignition light illuminates as it should, no RPM drop. When I switch the Backup Battery to "Emergency", the engine quits. However if I switch the ignition to Left and turn the Backup Battery to Emergency, the engine continues to run.

    Backwards from what the checklist describes......is this an easy fix??

    Jon
    If the main battery fails, the engine will quit unless the emergency switch is moved to the emergency position AND the ignition switch is in either right or both. So, if the alternator fails, continued flight will depend on how long the main battery will last.

    The backup battery is only connected to the right ignition box when the switch is in emergency. With the ignition in left, the right box is not working in either emergency switch position.

    It could be a bad backup battery or bad connectors.

    There is a pdf file available that is called "Ign module ops check - Backup Battery" it will ensure that the backup system is wired correctly.

  4. #4
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    Default Re: Backup Battery Check Before Takeoff

    The push on connectors used on the back up battery are a really crappy way to wire an emergency battery.
    They can fall off under vibration and after several removals and reinstalations will loosen.
    you DO replace the emergency battery every year, don't you?
    I had my terminals fall off and soldered them in place to ensure a good secure connection.
    If you solder be careful not to damage the battery.
    Bill

  5. #5
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    Default Re: Backup Battery Check Before Takeoff

    OK - problem solved. Turns out as discussed, it was an almost dead backup battery (1.5 volts). Replaced the battery and checks out normal now.

    Thanks for the help!

    Jon
    Last edited by txcub; 08-24-2016 at 08:54 AM.

  6. #6
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    Default Re: Backup Battery Check Before Takeoff

    Quote Originally Posted by txcub View Post
    OK - problem solved. Turns out as discussed, it was an almost dead backup battery (1.5 volts). Replaced the battery and checks out normal now.

    Thanks for the help!

    Jon
    A reminder that the Condition Inspection Form calls out for the Ignition Battery Backup to be replaced annually.

    Chuck
    Chuck Hull
    L70 Agua Dulce, CA

  7. #7
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    Default Re: Backup Battery Check Before Takeoff

    Yes, I am aware of that but I just got it....

    Quote Originally Posted by Charles View Post
    A reminder that the Condition Inspection Form calls out for the Ignition Battery Backup to be replaced annually.

    Chuck

  8. #8
    Senior Member ceslaw's Avatar
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    Default Re: Backup Battery Check Before Takeoff

    Follow up and new question.

    When doing the run up and checking the emergency backup battery, its voltage quickly drops from over twelve down to about six or seven volts in about a minute, at which point I switch off the emergency function. It shows a normal voltage when not in the emergency mode, so the charging circuit is presumably working properly.

    The obvious answer is a bad battery, and I am going to change it forthwith. But it is less than a year old and it seems odd it would go south in such a short time.

    Has anyone noticed anything similar??

    Chuck

  9. #9
    Senior Member ceslaw's Avatar
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    Default Re: Backup Battery Check Before Takeoff

    Question answered. It was a bad battery. Which underscores two points.

    1. Need to always check the ignition back up battery on runup

    2. Need tp replace the back up battery at the annual condition inspection per CC specs even if it seems to be okay.

    This back up battery went bad quickly after ten months.

  10. #10
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    Default Re: Backup Battery Check Before Takeoff

    Thanks for the follow up and info Chuck!

    Quote Originally Posted by ceslaw View Post
    Question answered. It was a bad battery. Which underscores two points.

    1. Need to always check the ignition back up battery on runup

    2. Need tp replace the back up battery at the annual condition inspection per CC specs even if it seems to be okay.

    This back up battery went bad quickly after ten months.
    Dave Embry
    "You only live once.....
    ..but if you do it right.....
    ....once is enough."..

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