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Charging a capacitor? 


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 Post subject: Re: Charging a capacitor?
Posted: Fri Dec 17, 2010 2:24 pm 
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One Drone wrote:
You don't have to do this. If you were anal you'd keep a resistor in the car if you had to change batterys or if the battery was dead flat which is rare. But if its a bigger sort of cap like what you probably deal with (maybe above half a farad) then you do charge it slowly is to reduce the possibility of arcing involved with fast charging. High voltages and a small gap between terminals maybe? This arcing won't hurt the cap so much but it might damage the chrome/gold plating on the connectors. Not a biggy.

See we are talking about 14 volts max too here...

So the max discharge will be at 14Volts...

I work with caps in AC so they are seen as a load rather than a storage device... So the charge positive, discharge, charge negative, discharge 50 times a second...

If you put a megohmeter across a cap and charge it to 500 or 1000V DC then yes that can jump a gap, but I can't honestly see 14Volts jumping much of a gap?

foggy wrote:
Guys are you talking about a polarising resistor?
With large caps that are left on the shelf to long a fast charge can cause them to explode, very spectacular to see a 2 farad drive cap go off (not). by doing a slow initial charge the cap can then deal with fast discharges. We used to use a lot of big caps in the lift industry and and found it was normally the new caps that had been sitting on a shelf for a while that would go bang on first power up, after the inital charge no problem with rapid charging.

Are you talking about caps on AC or DC? :? And how many Farads are we talking about?



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 Post subject: Re: Charging a capacitor?
Posted: Fri Dec 17, 2010 2:30 pm 
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These are usually a couple of farads and dc. Used for the supply buffering of elevator motor dives.
 Post subject: Re: Charging a capacitor?
Posted: Fri Dec 17, 2010 3:28 pm 
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wait hang on. when i instilled my cap into my audio setup i just pluged the thing in none of this crap with charging it. i had no fuses blow or anything.



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 Post subject: Re: Charging a capacitor?
Posted: Fri Dec 17, 2010 7:35 pm 
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Dude, I think you're thinking too much about this. I dunno if it's a big deal. Just posting what I know same as you, there is some wiki stuff on a related topic. Under subheading "Benefits of pre-charging" here I can't type a whole lot, quickly with a broken hand. :oops:



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