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Thread: Battery life computation

  1. 28th July 2009 01:18 PM #1
    dpj
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    Default Battery life computation

    hi...

    I have stuck in battery life calculation.
    Will someone validate this??

    I have a 3.3V 1200mAh non rechargable battery;
    my circuit consupmtion is such that for 1 second
    it consumes 6mA and for 10 seconds it consumes
    1mA; I need to compute for how long the battery
    will last???

    I have computed something like this; kindly confirm this for me please...

    Average current consumed will be
    {( 1 sec x 6 mA )+( 10 sec x 1 mA ) } / ( 1 + 10 )
    that will be 16/11= 1.45mA

    So battery life will be 1200 /1.45= 827 hrs
    Is it correct???
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  2. 28th July 2009 01:57 PM #2
    MikeMl
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    Math looks ok. You can slightly improve the battery life by hanging a big capacitor across the battery terminals so as to reduce the ratio of peak to average current out of the battery.
    Mike ML.
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  3. 28th July 2009 05:41 PM #3
    Boncuk
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    Quote Originally Posted by MikeMl View Post
    Math looks ok. You can slightly improve the battery life by hanging a big capacitor across the battery terminals so as to reduce the ratio of peak to average current out of the battery.
    ... and decrease battery life time by the leakage current of the cap.
    Proper Planning Prevents Piss Poor Performance
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  4. 28th July 2009 05:42 PM #4
    MikeMl
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    Quote Originally Posted by Boncuk View Post
    ... and decrease battery life time by the leakage current of the cap.
    Depends on the leakage current.
    Mike ML.
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  5. 28th July 2009 09:25 PM #5
    bountyhunter
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    I am not sure a capacitor would do anything because the load currents are so small that the battery's terminal voltage change will be negligible. I think the cap will just charge up and sleep for the rest of it's life. Maybe if there was an inductor ins eries with the cap, but it would have to be huge due to the long time constants the change occurs over.
    Last edited by bountyhunter; 28th July 2009 at 09:26 PM.
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