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Subject: Re: Error in Battery FAQ - Pause vs. shutdown & restart
From: Björn Stenberg (bjorn_at_haxx.se)
Date: 2003-04-23


Brent Geery wrote:
> This in incorrect! mA (a measure of power) does not equal mAh (a
> measure of energy.) Power can tell you what the player is drawing,
> but not what it has consumed. Another way to look at it, is to equate
> mA to the speedometer in you car, and mAh to the odometer.
>
> Using the example power draw examples shown above, lets look at the
> example given-- power-down and restart vs. paused for 15 minutes.:
>
> Pause will draw 94mA / 60 minutes X 15 minutes = 23.5mAh used.
>
> Power-down and restart will draw about (800mA / 3600 seconds X 3
> seconds = 0.6666 mAh) + (600 mA /3600 seconds X 6 seconds = 1.0 mAh) +
> (195 mA / 3600 seconds X 3 seconds = 0.1625 mAh) = 1.83 mAh total
> used.
>
> 94 mAh / 3600 seconds = 0.0261-e
> 1.83 mAh / 0.0261-e = 70.085 seconds
>
> Thus, if planning on pausing more than about 1 minute 10 seconds, a
> shutdown and restart saves more power! I'm a little shocked, but the
> numbers don't lie.

I have now updated the battery faq with a calculation like the above. Slightly different numbers, slightly different wording, but the conclusion is the same.

-- 
Björn



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