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### Author Topic: Quick Capacitor question  (Read 3114 times)

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#### HDL_CinC_Dragon

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##### Quick Capacitor question
« on: August 07, 2007, 06:06:32 PM »
Now this is a very simple question but I was surprised that I could not find it on a google search O_o

The voltage that a capacitor can store can only be equal to the voltage being applied to it, correct?
So if lets say I held a 9v battery to a 300 volt capacitor for like 3 days straight, regardless of the time it was applied to it, the 300v capacitor would only store 9 volts right?

I would have to use an inductor to get up to that 300 volts right?

just wanted to get that cleared away... ...
« Last Edit: August 07, 2007, 06:09:03 PM by HDL_CinC_Dragon »
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#### elixier

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##### Re: Quick Capacitor question
« Reply #1 on: August 08, 2007, 12:23:00 PM »
Ya Good Quest.
The out put not be 9V but it will be actually a bit lesser than 9V. Because volate increases exponentially till infinite time in charging of the Capacitor.
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#### HDL_CinC_Dragon

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##### Re: Quick Capacitor question
« Reply #2 on: August 08, 2007, 12:30:07 PM »
uhh I didnt quite understand what you said there...

The output from the battery will be less than 9v? is that what you meant? or did you mean from the capacitor? I know that the capacitor will immediately start to drain its charge and that batteries do in fact lose voltage over time as theyre used and such... but what did you mean?
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#### Del

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##### Re: Quick Capacitor question
« Reply #3 on: August 08, 2007, 01:28:02 PM »

Hi,

I think it just means that the voltage will increase up to "almost" 9V.
The capacitor will never quite reach the battery voltage, but it will get close.

I think, in order to get up to 300V you will need something called a "charge-pump".
I'm not quite sure how it works, but I think it converts a DC voltage to an AC voltage -
then a transformer can be used to change the AC voltage up or down -
finally, the AC voltage gets converted back to DC.

There are also some IC's that will boost an AA (1.5V) up to 3V or 5V.
(such as the MAX756)

#### HDL_CinC_Dragon

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