help with capacitors please?

i am trying to double the output of a 1.5v battery to 3v i have setup a capacitor parallel circuit like this

               --------------+ capacitor - -------------+ capacitor - ---------------
                                                                                                                       
         +                                                                                                            
        Battery                                                                                                   -------   + Multimeter 
         -                                                                                                             -------    - Multimeter

              ------------------------------------------------------------------------------- 

However i am not getting the output of 3v, i did this yesterday and had 3v but today im only getting 1.5 i tested the battery on its own and that is 1.5 so why is it that i am not getting 3?

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framistan6 years ago
What probably occured, was you measured both capacitors with the OHMS function or the DIODE test function. This places a small current from your meter into the capacitor.. and each capacitor charged up to 1.5 volts. This charge takes a few minutes to dissipate out of the capacitor. Then you connected the capacitors in series and measured the 3 volts that was still present in the caps which came from your meter during the previous test. Modern digital voltmeters do not require much amperage to register a reading. Just microamps of voltage will register on the meter.
connorfrancis (author)  framistan6 years ago
Thanks your probably right. il keep experimenting anyway, just wondering too do you know anyway to double the voltage without using a joule thief cheers Connor.
frollard6 years ago
The way you've drawn it that isn't a parallel circuit, that's series. You can't just add passive components to a dc circuit to get more voltage out, doesn't work that way.

You can search for 'voltage doubler' -- but again that only works with an oscillator (AC or pulsed) circuit.
connorfrancis (author)  frollard6 years ago
but i still dont get it because yesterday i did the exact same thing and recieved 3v from a 1.5v battery.
If you charge both caps separately then put them in series you'll get the 3 volts, but that's a mechanically switched process. You get more voltage but less capacitance.
connorfrancis (author)  frollard6 years ago
Thanks for the reply, can you draw me a simple circuit for a parallel circuit, i have done this once just using 2 x 10v 1000uf capacitor a multimeter and a 1.5aa battery, i know that the voltage will be high but less capacitance but once i can see the 3v on my multimeter i will be able to test a device i have created to give it more amps. please help.
So the 10v on your cap is the maximum before it explodes. You should always have a 2x safety factor (never charge a 10v above 5v) if you want the caps to last.

Again, i can't draw you one, there are plenty of voltage doublers here on ibles and elsewhere on the net, but they will take MORE than just a few caps.
connorfrancis (author)  frollard6 years ago
Thanks everyone for all your answers :)
You can't "double" the voltage without some electronics, first of all to chop your DC to AC and then to boost it.

The Joule thief is NOT the only circuit that can do that, but it is, if you can wind the transformer, one of the simplest.

Steve
connorfrancis (author)  steveastrouk6 years ago
Thanks Steve appreciate the input, why do you suggest to change from DC to AC
Because you can't do it otherwise is the simplest way to explain it.

Steve
because every voltage increase application relies on a CHANGE in current, not just direct current -- so you have to pulse your dc on and off -- or fully invert it to a sine wave -- to get it to induce a change you can use in a transformer.