On Sat, 30 Jun 2007 04:42:13 -0700, wrote:

Hi,
need a little help with some math, If I have an impossibly perfect
battery that provides a constant voltage right up untill it dies and
the battery for example is 3500mAh, how long would the battery power
say a 20mA led ?

Would it be, 3500 / 20 = 175 hours ?

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Yes
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Sorry if the post seems a bit to simple... Just need to be sure about
it.

Thanks for your help.

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You're welcome.

if you have a perfect device which can supply 3500mAH and a perfect
load which draws a constant 20mA, then:


3500 milliamperes * hours
Time = --------------------------
20 milliamperes


The milliamperes will cancel out, and you'll be left with:


3500 * hours
Time = -------------- = 150 hours
20


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JF