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Grid Capacitors or Other Surplus Caps? Answered

I am looking for some extremely powerful capacitors, I know that you can buy old grid transformers and I wondered if there was some kind of capacitor they use one the grid which could also be available.  If not, what industry would have old capacitors cheap that still work, I'm looking around 300 volts 1 Farad or more 

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user
mpilchfamily (author)2013-01-29

Be careful getting old capacitors. Capacitors don't age well. The electrolyte used in them does dry out over time. While you may be able to get the caps for a good price you may find a high failure rate.

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iceng (author)mpilchfamily2013-01-29

Gradually raising the voltage on long unused EL caps allows the
chemistry to reestablish the plate dielectric insulation and so far
I have not been a capacitor explosion victim :-)

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iceng (author)2013-01-29

Actually the very most powerful capacitors ( C×V2 ÷2 ) are being
manufactured today.

Back in the vacuum tube days they were called condensers and a big metal
can electrolytic condenser was 40 micro-farads at 350 Working VDC

You can buy an ultra-cap 25uF at 2.7VDC for $7.50...
or 5800mfd at 300vdc for $ 30,00

IF you put 173 of the 5800mfd caps in parallel then you will have
a 1 Fared 300 VDC capacitor.

A

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user
iceng (author)iceng2013-01-29

CORRECTION

You can buy an ultra-cap 25 uF Farad at 2.7VDC for $7.50...

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user
steveastrouk (author)iceng2013-01-29

I always read mfd as microfarad. What did you mean ?

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iceng (author)steveastrouk2013-01-29

25,000,000mfd @ 2.7vdc for $7.50  91 J .....  8.3¢ / JOULE

      or

      5800mfd
       × 173
 ------------------
1,003,400mfd @ 300vdc for $ 51,900.oo  45153 J ....  $1.15 / JOULE

That is the web pricing of capacity ;-)

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