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how to drain a AA battery? Answered

Hi, im doing a science project for school and i need to find what type of AA batteries last the longest (Duracell, Energizer, ect..) but i need to monitor it while it is draining so that i can tell which one goes out first, so a fairly quick technique would be ideal...
thanx :)


I'd go with a flashlight of some kind. Plus I'd put some meters on it to measure voltage and current, and record those measurements plus an observation of how much light the flashlight is emitting. Do this at regular time intervals, like every 10 minutes or 30 minutes or so, while the battery is discharging. That way you'll be able to make some nice graphs later, and more importantly these graphs will show you which battery is delivering more total energy.

BTW, this data sheet, here:
should give you an idea of how much energy you can get out of a typical AA alkaline battery.

Here's an interesting idea: Are the total amounts of energy delivered the same if you discharge fast or slow ?

Hook a resistor across the terminals, hook a voltmeter across both, watch for it to hit zero.

Or: Hook a resistor in series with an ammeter across the terminals, watch for it to hit zero.

As long as you use the same equipment (including the same resistor, to avoid variation from one to another) for all the tests, you should get consistent results.

This ignores the fact that different kinds of batteries have different discharge profiles. Alkies and old-fashioned carbon batteries lose voltage as they run down; some of the newer versions stay at or near their top voltage until they're almost dead, then fall off suddenly. To get _that_ information, you'll need to look at the voltage many times and draw a plot of exactly how it drops off over time.

There are other ways to do this, of course, but that's probably the most basic approach.

May be cheating, but I'm leaving him to work out the details, and I'm posing him the additional challenge of doing it _right_. On this kind of project, more than half the assignment is collecting and interpreting the data.

(I used to get top grades on some of my high-school science labs -- despite having klutzes for lab partners -- by quite literally doing the problem "forward and backward". If we couldn't get anything resembling decent data, I would start from the ideal response, backward-calculate to ideal lab results, introduce reasonable amounts of error from reasonable sources, and calculate it forward again -- explaining exactly what kinds of error were injected and why they were reasonable. The teacher knew I wasn't reporting actual observations, but he was satisfied that I had fully demonstrated that I knew the material he was trying to teach; making it work in the lab wasn't really the point of the exercise.)

The quickest way to drain the batteries would be to simply connect both terminals with a short length of thick wire.

As to how you monitor it...

Now, that would be telling, wouldn't it?

(I don't think you need to drain the batteries completely to get a reasonable answer to your question, though.)

The idea of the science project is to explore how YOU can do the science.

If we help, you'll be cheating.

What have you already thought of ?


He would indeed be cheating.

How about you make a list of goals and read about the subject. This particular problem shouldn't be too hard to find a solution to. Just make sure you keep the right goals in mind.

Good luck with your project. Keep us up to date ;-)