Suppose the current drain (on average) of a LED is 2mA at 4.5v. Now suppose that 250 mAH 1.5v cells are being used to power this thing. I want to keep this LED powered for 504 hours (3 weeks), how many cells are needed and how should they be arranged?(adsbygoogle = window.adsbygoogle || []).push({});

Now, here is my stab at the problem.

There is a voltage requirement of 4.5v, right? So, place 3 1.5v cells in a series to add the voltage up to 4.5v. So far I know that there will be a series of 3 cells.

There is a mAH requirement of 250 mAH, right? So there will be cells in parallel to each other to meet this requirement (since putting cells in parallel adds current). At this point, I get stuck, because I am not sure how to compute how many I will need in parallel.

I do know that battery life = capacity / current though...

Any help?

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# Homework Help: Problem dealing with mAH, mA, and volts

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