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How to step up amps and step down current from a 20,000 v dc down to 144 v and up 1-3 amps from capacitor?

Hi, I am trying to run a 28hp motor for an electric vehicle conversion. The controller uses 500amp and 144 volts dc max. I am building a capacitor with 20,000 volts and 1to3amps, I wish to use the capacitor in place of batteries, for a # of reasons. So I am wondering how to step the volts down and up the amps. Or if the controller does that for me. I know normally a converter is used for battery packs, but this is different. I was thinking by using certain gauge wires and one way diodes I could do this. What do you think?
If I have done the correct calculations the pico farads are 450,000,000 . The formula is so
A capacitor’s ability
to store energy is measured in either
microfarads ( uf ), nanofarads (nF) or
picofarads (pF). Micro means one mil
lionth, nano stands for one billionth
and pico for one trillionth (farads are
also used, but in high voltage work
they are impractically large units).
Several factors affect capacitance.
The formula for determining capacitance
where C is the capacitance in
picofarads. K is a constant that depends
on the insulator (or dielectric)
between the plates (called the dielectric
constant), A is the area of one
conductive plate in square inches, d is
the separation between adjacent
plates in inches, and n is the number
of plates. As you may know, different
insulators have different dielectric
constants. Table 1 shows the values of
K for some common materials and
the peak voltage they can withstand
per 1/1000th inch (called a mil) of thickness.
10mill Mylar has a punture rate per .001 of 7,500 volts so times 10 75000 volts Dc for safety I will only have 70% of capacitor stored with energy.

Asked by:fusion man


  1. billrussell42 says:

    How are you making this 20000 volt capacitor? Capacitors do NOT have current ratings, they have capacitance ratings, in farads. How are you going to charge it?

    No, the controller will not work with voltages above 144 volts, and will be damaged.

    It is very difficult to step down DC voltages from 20kV to 140 volts, as semiconductors tend to die above 500 volts.

    diodes and wires won’t help.

    I think you need to take some courses in basic electricity and circuits before you kill yourself.

    If you are serious about this, work with 100 volts, not 20000 volts. Capacitors are much more efficient at that voltage, and your controller will work with it fine.

    I’ve answered similar questions from you before. You are going off in some strange directions, with limited knowledge. Last time it was a 2000 amp capacitor.

    I repeat, capacitors do not have current ratings, they have capacitance ratings in farads, microfarads, nanofarads, etc.

  2. JavaScript_Junkie says:

    72000 watts ?
    I hope you have the power company behind you !
    LOL !

  3. Martyn G says:

    If you try to engineer this with a 20,000V supply, you will most certainly kill yourself.

    I used to work in an electric vehicle development lab. Believe me.. you do not want to be doing that at 20,000V.

    As it is, there are no sensible semi-conductor devices that can handle switching voltages like that. If you have a 20KV supply, you will get transient in excess of 60KV. This means ANY inductance other than that you intentionally put there will be radiating radio spectrum interference and causing horrendous unreliability.

    It is much easier, safer and reliable to use a 135V battery pack (10 x 12V batteries, which have 13.5V unloaded, hence 135V) .

    The converter will do the conversion to the motor operating voltage. I assume you have selected a motor that suits the controller.

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