can i use an AC capacitor on DC?

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  #1  
Old 02-08-05, 05:26 PM
Sparkadelic
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can i use an AC capacitor on DC?

Been awhile since I really cared(school i guess, lol) usually I just replace them, and on my way. But I wanted to add some caps to my car stereo system and I have some fairly large ones from some electric motors. 1 cap is rated at 850-1020MFD at 110-125VAC. Is it possible to use this for 12 VDC? I guess i should be pulling my books out for a refresher!
 
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Old 02-09-05, 12:15 AM
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Isn't a capacitor pretty much an open circuit when used on DC? Why do you want to do this?
 
  #3  
Old 02-09-05, 05:38 AM
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They store energy for the loud parts in the music, I don't know if they are made the same way as a motor cap, you can try it but I think the ones sold for car stereo are reasonably priced, I wouldn't take a chance frying my car stereo wiring or components.
 
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Old 02-09-05, 06:05 AM
Sparkadelic
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Ya it is for tighter/crisper bass. And reasonably priced has different meanings to different people. I would not go out and spend any money on a cap. It really isn't that important to me. I just thought I might mess around a bit with the ones I have if possible.........I wont try until I know for sure. Thanks anyways.
 
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Old 02-09-05, 09:46 AM
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Just did a search, cheapest I could find is a 1.2 farad by Pyramid for $55. Read you need about .5 farad for ea 500 watts.
 
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Old 02-09-05, 01:51 PM
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Doubtful...

Originally Posted by Sparkadelic
Been awhile since I really cared(school i guess, lol) usually I just replace them, and on my way. But I wanted to add some caps to my car stereo system and I have some fairly large ones from some electric motors. 1 cap is rated at 850-1020MFD at 110-125VAC. Is it possible to use this for 12 VDC? I guess i should be pulling my books out for a refresher!
Usually, MFD stands for microfarad (aka uF).

Since a typical car audio capacitor is in the 1F range, I'm afraid your electric motor capacitor won't be nearly large enough.
 

Last edited by arcas; 02-09-05 at 01:54 PM. Reason: bad grammar
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Old 02-09-05, 05:01 PM
Sparkadelic
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Ya, I understand the whole capacitance deal. That is why car audio caps are usually the size of a small thermos. But I have a lot of these caps and was considering paralleling them to see what effect they had. I understand now that I cant find my answer here, I will do more reading and take it from there. Thanks for all input. Like I said it isn't something I need, I just wanted to muck around.
 
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Old 02-09-05, 05:14 PM
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If I remember correct from college an AC is sort of 2 DC caps connected together in series +-/-+. I would not use it for DC.
 
  #9  
Old 02-09-05, 09:17 PM
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Very large capacitors for DC filtering are often electrolytic, and are for DC only. Polarity matters. Motor capactors would be AC But you would need 1000 of these babies to get 1 F.
 
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Old 02-10-05, 08:10 PM
Sparkadelic
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Thanks all. Ya a million to one. That sure would be a whack of caps. 1000 caps wired together..........where could I put them out of the way?........lol. I wont bother you anymore with this, thanks again!
 
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