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Old 11-07-2010, 09:34 PM
ibpointless2 ibpointless2 is offline
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Join Date: Sep 2010
Posts: 829
Originally Posted by sseti View Post
hello ibpointless2

Must say great finding.
Today I put un test your circuit and as you said with two dead 9V batteryes (one 7,01V and second 1,2 V), connected in series. When I put it in test, I noticed voltage drop to 4,6 V and still droping (think due so big difference in batterys voltage).

Will see tomorrow
till then
Yes that is way to big of a difference in battery voltage. The 7 volt battery is charging the 1.2 volt battery and that is the reason for the loss. Try it with the 7 volt battery only.

What i suggest is a series of dead batteries that add up to around 20 volts and just let it run non stop to see how long your LED will run for. The LED will get dimmer but should not go out.

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Oh and one important thing i should note if you're trying to replicate this experiment! I used brand new 1uF @ 400 capacitors and before i hook up all the wires to the capacitor i pre-charge the capacitors + and - with a battery, you can use your source battery or a another battery with a voltage close to the source battery. The light sometimes will not turn on unless you pre-charged the capacitor. And a pre-charge is just a mere tap of the capacitor terminals to the battery.
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