The Capacitor - Battery question

[Magnethos]

My question is very simple:
I have a High Voltage Capacitor (4.000 Volts) but I need to connect a device that runs on 12 Volts.

2 Simple questions:
A. Is possible to reduce the voltage from 4000 Volts to 12 Volts?
B. If the voltage used is lower, the capacitor discharge time would increase?

[pese]

My question is very simple:
I have a High Voltage Capacitor (4.000 Volts) but I need to connect a device that runs on 12 Volts.

2 Simple questions:
A. Is possible to reduce the voltage from 4000 Volts to 12 Volts?
B. If the voltage used is lower, the capacitor discharge time would increase?

Sure you can use them.
But give attentention that the capacity (mostly in uF) ist still very low.
an 40 vol cap , with the same size have (approx) 100 time cor capacity..

If you look vor very HI-Cap 12volt devices. use the "Boster-Caps"
that is used for Car amplifiers , to hold the peack voltage still in the
car-power-supply. ( 50.000uF abd higer)  15 volts

Gustav Pese

[TinselKoala]

The voltage rating on a capacitor is the maximum working voltage of the cap. It has little or nothing to do with the energy or capacitance.
That is, a 4000 volt capacitor of 1.0 microFarad, charged to 100 volts, will have exactly the same amount of energy in it as a 200 volt 1.0 microFarad capacitor charged to 100 volts.
The voltage rating of the cap is the highest voltage it can take before the dielectric breaks down and the capacitor is ruined.

The more voltage on a cap, the greater its energy content. The relationship is Energy (in Joules) = 1/2 x (Capacitance in Farads x Voltage Squared). This is the applied voltage, not the rated voltage of the cap (which would also be the maximum recommended applied voltage.)

That being said, you should use a cap with a voltage rating only a bit higher (like double) than your applied maximum voltage, as it is inefficient in several ways to use a high-voltage capacitor in low voltage service.

[TinselKoala]

If you charge the 4000 volt capacitor to 4000 volts, it will be VERY DANGEROUS to handle. If you inadvertently take a shock from it, it will likely kill you, if it has any sizeable capacity at all.

How to run your 12-volt inverter from a 4000 volt capacitor? This is what I call the "down-conversion" problem, and it isn't trivial. It can of course be done in various ways, but none of them are very efficient.

One way is to use your big cap to charge a bunch of smaller caps in series, then discharge the smaller caps in parallel.

[Pirate88179]

Why not use two 5.5 volt super caps (5 Fared ea.) and put them in series?  You would have 11 volts and a long time of running just like they were a set of batteries.  I have a small 5.5 volt 2.5 F cap that I can charge from my earth battery and when removed from the EB it lights my led for over two hours.  Just a thought.

Bill