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Registered Member #1774
Joined: Wed Oct 22 2008, 02:51AM
Location:
Posts: 135
As the title says I have some second-hand electrolytic capacitors that rattle! I have 20 of them for my 20 stage coilgun project and about 7 or so rattle when shaken lightly. All show above rated capacitance using a capacatance meter, but i havnt tried to use them to fire anthing yet. Any idea's why?
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
I had some big electrolytics that rattled, and while they seemed to work fine, and held a charge at their 450V rating, I ended up throwing them away. I was worried that they were dried out and might overheat and blow up under high ripple current.
Registered Member #1774
Joined: Wed Oct 22 2008, 02:51AM
Location:
Posts: 135
Well that sucks, im going to see if I can get a refund. Guess that puts an end to my project, I cant find any other capacitors close to this size for any less than $50 each.
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
What size do you want each capacitor to be? Alltronics has some nice computer grade caps for really cheap. They are 3900uf and 400 volts each and for 4 of those capacitors it is only ~25 bucks! That amounts to 312 joules each!
Top link is for 4 of them and the bottom link is for one.
They may not be made for pulse discharge but they sure as hell do hold quite alot! I bought two of them and i say they are quite good! I discharged them into a dead short at full voltage a few times and they didn't die. I also exploded some wire with them. And all of that was without a protection diode! I thought one died at one point because it would charge to like 12 volts and stay there, but it turns out the diode i used to rectify the charger died, and the capacitor still works to this day.
Registered Member #1774
Joined: Wed Oct 22 2008, 02:51AM
Location:
Posts: 135
Wow thanks, thats insanely cheap, the caps I was going to use were only 50joules each and cost only $10 less for 4. Im going to try and order 4 now! You may have just saved my project.
Edit: well ill have to think about it, shipping is rediculous. For 20 shipping is $240 for only 1 its $40!!!! Thats almost 6 times the cost of the capacitor.
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
El_Roberto wrote ...
Wow thanks, thats insanely cheap, the caps I was going to use were only 50joules each and cost only $10 less for 4. Im going to try and order 4 now! You may have just saved my project.
Edit: well ill have to think about it, shipping is rediculous. For 20 shipping is $240 for only 1 its $40!!!! Thats almost 6 times the cost of the capacitor.
Wow, i am sorry to hear that, that really bugs me that it costs SOOOOO MUCH. it only costed me like maybe 10 bucks for a 5 pound bag of capacitors and 2 of those capacitors from that place... Keep a look on ebay, they sometimes have similar caps and you may get away with cheap shipping.
Update: Those are the same ratings, but have some aesthetic damage. It may also be high shipping and they may not even ship to you.
I will keep looking.
edit. And one more thing, thank you teslacoolguy for the link to alltronics, he is the one that gave me the link when i wanted to make a coilgun.
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Rattling capacitors!!!
