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  1. #1
    Senior Member Richard Cranium's Avatar
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    Nice juicy word problem - battery life comparison

    If I'm using a light that gets 2.5 hours of run time using 4x2450mAh "AA" batteries before tripping a low-current warning led, how much run time would I get before tripping the warning led if I used a battery pack with 4x5000mAh "C" cell batteries?

    Sorry, I can't offer any more exacting spec, other than the light is a Stella 120 by light and motion. I don't the spec for the low current warning led, nor do I know for sure which which brand of batteries I would buy.

    Thanks for any insights.

  2. #2
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    Should give you about twice the run time - so about 5 hours.

  3. #3
    Senior Member Richard Cranium's Avatar
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    Should give you about twice the run time - so about 5 hours.
    That's what I figured, I was wondering if there is anything else involved to indicate otherwise. Not to mention whether or not battery specs are accurate......

  4. #4
    Senior Member kf5nd's Avatar
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    5.1 hours

  5. #5
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    The larger batteries would be drained at a lower rate (%C) and have relatively greater capacity than 2 sets of the AAs.

    For these reasons you should get considerably longer than twice the runtime.
    Making a Pilom Triple LED Headlight ? I have parts available :)
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  6. #6
    Senior Member Richard Cranium's Avatar
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    I agree with the "5.1 hour math" using simple math. What I don't know or understand is how battery cell size effects the "roll off" or drain curve of usable energy.

    In other words, what is known about how clusters of cells and cell sizes produce favorable drainage per use with respect to weight or overall capacity.

    I've constructed a remote battery pack for a simple headband headlight that used to produce 3 hours of usable light per three alkaline 1,5 vol "AAA" batteries. By substituting a 4-cell "AA" battery pack I have quadrupled usable run time. In a test the headlight produced usable light for over 10 hours! of course i may end up damaging the "led" - I'm supplying 4.8 (4x1.2) volts instead of 4.5 (3x1.5)

    That just what I wanted, no more worry about changing batteries - even if i ride all night. Now I want the same for a Stella 120.....
    Last edited by Richard Cranium; 04-14-09 at 08:00 PM.

  7. #7
    Member 24X18's Avatar
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    Standard Lantern(6volt)

    I use this....


    Standard..Lantern Battery..like $$3.00 for the Lantern.
    Last edited by 24X18; 10-26-09 at 02:26 AM.

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