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Hi everyone! My 10 year-old daughter wants to do a science fair experiment on the classic "Which battery lasts the longest?" I need a little help from the gurus...
My plan is to use a 2-battery AA holder to power a small clock and some sort of load device (motor, fan, light, etc). We'll set the clock to 12:00, and start the test. When the battery can no longer power the circuit, the clock will stop, and she can record the time the battery lasted. Simple enough!
However, I'm having trouble finding a device that will have the right load to drain the batteries in a reasonable amount of time. Ideally, the batteries would last LESS than 12 hours, so there's no confusion on whether the clock wrapped past 12:00, and she can just read the time directly off the clock every morning for however many batteries she wants to test. I need some ideas for a device that will do *something* (so it is interesting - a resistor load that just sits there and gets warm is too boring for a 10 year old), will work off 3v, and will draw enough current to drain AAs in less than 12 hours.
I tried a small hobby motor, but it was still running after almost 24 hours. I'm currently testing a small 12v computer fan, but I'm not hopeful. Darn it - too many things have been made too efficient!
Does anyone have any ideas for a cool (CHEAP) device that would fit the requirements?
My plan is to use a 2-battery AA holder to power a small clock and some sort of load device (motor, fan, light, etc). We'll set the clock to 12:00, and start the test. When the battery can no longer power the circuit, the clock will stop, and she can record the time the battery lasted. Simple enough!
However, I'm having trouble finding a device that will have the right load to drain the batteries in a reasonable amount of time. Ideally, the batteries would last LESS than 12 hours, so there's no confusion on whether the clock wrapped past 12:00, and she can just read the time directly off the clock every morning for however many batteries she wants to test. I need some ideas for a device that will do *something* (so it is interesting - a resistor load that just sits there and gets warm is too boring for a 10 year old), will work off 3v, and will draw enough current to drain AAs in less than 12 hours.
I tried a small hobby motor, but it was still running after almost 24 hours. I'm currently testing a small 12v computer fan, but I'm not hopeful. Darn it - too many things have been made too efficient!
Does anyone have any ideas for a cool (CHEAP) device that would fit the requirements?