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#41 | |
Badcaps Veteran
Join Date: Dec 2008
Posts: 4,841
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![]() Quote:
How do you achieve the rated voltage on certain caps? An LM317 or its variants will go up to 50 volts or so, how do you get to say 400v if you need to? Also, which method are you using to test the leakage? Thanks
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#42 | |
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Join Date: Jul 2005
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![]() Quote:
Have not had time to install it because it's summer though ![]() It was very big though so it might look a bit odd, but I think it will work fine...
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"The one who says it cannot be done should never interrupt the one who is doing it." |
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#43 | |
Badcaps Veteran
Join Date: Jun 2014
City & State: hell
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![]() Quote:
So say the capacitor has 1000uf printed on it. Does that mean that it is likely leaky, and would require reforming if its measured capacitance is over 1200uf? What about capacitors that measure lower then their specified capacitance? Will reforming be of any help to these? Can capacitors loose their capacitance over time, in storage? i got some 1500uf 16v MBZ Rubycons, that i believe are old stock, but they all measure around 1400uf Their ESR is in the ballpark of 10 - 20 mOhms |
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#44 | |
Badcaps Veteran
Join Date: Dec 2008
Posts: 4,841
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![]() Quote:
One would think in a climate like Sweden summer would be the only time you'd want to do it, or at least that's the case here in Canada... Can't do any electronics projects in the dead middle of the winter, just way too darn cold indoors. |
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#45 |
Super Moderator
Join Date: Jul 2005
City & State: ----
My Country: Sweden
Line Voltage: 230v 50Hz
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![]() There are a couple on eBay, I bought one like these but they seem popular so the price can be higher on them.
http://www.badcaps.net/forum/showpos...2&postcount=35 The winters are made comfy here in Sweden by my computers ![]() |
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#46 | |
Badcaps Veteran
Join Date: Dec 2008
Posts: 4,841
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![]() Quote:
In the description they state: A 10A 75mV Shunt (not included, available in our store) must be added if the meter is used to measure current / amps; otherwise the meter will be damaged. Just curious, the resolution on this 20V/10A model is 0.01 for both the voltage and the amperage. So the last digit is µA. How many microamps does the circuit need to draw for the last digit to switch from a 0 to a 1? Also, would a current shunt be necessary for such low current draw? |
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#47 |
Yup it's me
Join Date: Nov 2016
City & State: Carabobo
My Country: Venezuela
Line Voltage: 110v 60hz
I'm a: Hobbyist Tech
Posts: 284
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![]() Hi, I have close to 200 caps that are in spec but on the high side of capacitance don't have ESR meter so don't know high might be, it's kind of a big job to reform all those caps, a big part can hold voltage for days
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#48 |
a fake rubycon
Join Date: Jan 2017
City & State: california
My Country: USA
Line Voltage: 122.5VAC 59.9Hz
Posts: 512
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![]() i have TONS of old caps that are so old that some do not even have vents
here are some of the old caps i have #1 [old ventless elna 470uf 63vdc] [marcon 470uf 63vdc] and [nippon chemi-con 1000uf 16vdc] #2 [nippon chemi-con 680uf 16vdc] [a weird ventless nichicon 470uf 35vdc] [no-name ventless 680uf 16vdc] [Illinois capacitor 2200uf 10vdc] #3 [Illinois capacitor with marcon style vent 470uf 25vdc] [ventless rubycon cap 470uf 10vdc] [Illinois capacitor with older jamicon style vent 470uf 10vdc] #4 [old bellcon cap 2200uf 25vdc] |
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#49 |
Yup it's me
Join Date: Nov 2016
City & State: Carabobo
My Country: Venezuela
Line Voltage: 110v 60hz
I'm a: Hobbyist Tech
Posts: 284
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![]() 40 of the ones I talked about don't have vents, they are Ruby's and nichicon
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#50 |
a fake rubycon
Join Date: Jan 2017
City & State: california
My Country: USA
Line Voltage: 122.5VAC 59.9Hz
Posts: 512
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![]() Hello, i'm here to reform a old 330uf cap, the cap is rated for 35V but my PSU can't go above 28V.
Will 28V still work for a 35V cap? thank you ![]() |
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#51 |
New Member
Join Date: Oct 2017
City & State: VA
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![]() So I've read a fair bit on here, and a bunch of other places on reforming caps, and while a lot of it is useful knowledge, there seems to be a ton of misinformation going around.
This thread was hugely helpful in setting me straight. My use-case has been hard to pin down. I have 11 18,000uf 19v GE electrolytics (they're enormous, like mini soda can size) that I'm working on reforming. I want to make a battery tab spot welder with them, and they've been in storage for at least 20 years, according to the surplus company I got them from. I put the first one on my bench PS at 19v and 250mA for around 13 hours over several sessions. Each afternoon when I reconnected it, I'd check the voltage before reconnecting it. It seemed to hold a bit more charge each time. After 13 hours, I thought surely it's done, and did a few "fast" charge cycles at 5A (max current on the PS) to see what would happen. I think it has developed an internal short, as the residual charge after a few hours is now only a volt or so, where before, it was holding 9 and 10 volts overnight. The second try, I have had at 19v and 250mA for over 24 hours in multiple sessions, and I'm still hesitant to put it to work. I just put another one on, but held the current down at 10mA, and it's been cooking for about 6 hours so far. My questions: Is that first one dead, or can I revive it? Is 250mA too much, even for such a big cap as this? Without any special equipment, is there any way to test the ESR of them? I have a multimeter and a CC/CV PSU, but that's about it. Oh, I also have a subwoofer board that I could probably scrounge a few components out of. It's mostly 56v caps of varying uf, with a few resisters thrown in, and some SMD stuff. As far as my electrical knowledge, I know there's a formula that goes like P=I/R, and it relates power, inductance, and resistance, which are somehow related to volts, amps, and current? ![]() ![]() Any ideas? Thanks! Acer Last edited by acercanto; 10-18-2017 at 07:59 PM.. Reason: clarification |
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#52 |
Badcaps Veteran
Join Date: May 2008
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![]() Yes, probably.
Trying to guess how much current is "too much" or "too little" can prove a little hard. This is one reason why I suggested in my first post to use a series resistor of 1 kOhms or greater - it simplifies the process. And after all, that was the recommendation in some Panasonic datasheets too. With a 1-kOhm resistor, the initial current will be limited as follows: Supply Voltage --------- Current Limit 10 V ------------------- 10 mA 20 V ------------------- 20 mA 30 V ------------------- 30 mA ... 100 V ------------------ 100 mA ... etc. However, this initial current above will decrease as the capacitor chargers up and the voltage across its terminal increases. So in the first case with 10V supply voltage: once the capacitor charges up to 5V, the 1-kOhm will limit the current to 5 mA, and once the capacitor charges up to 9V, the 1-kOhm resistor will limit the current down to 1 mA. However, if the capacitor is leaky for some reason and it want to draw 2 mA of leakage current, then the voltage across its terminals will never be able to go past 8V with that 10V supply and 1-kOhm resistor. That said, most capacitor datasheets give a worst-case leakage current formula for each capacitor series. It is usually given as: I = 0.01 * C * V or I = 0.03 * C * V where I is the capacitor's internal leakage current in uA, C is the capacitance of the capacitor in uF, and V is the voltage across the capacitor. I didn't want to include that formula in my first post, as I wanted to make the cap reforming process as simple as possible for people. However, I do recommend to run through this calculation, as it will give a worst-case scenario of what to expect for the leakage current from any given capacitor. In your case with the 19V, 18000 uF capacitors, the maximum leakage current for each capacitor should be: I = 0.03 * 18000 * 19 = 10260 uA = 10.26 mA Thus, if any of your reformed capacitors draw more than about 11 mA after fully charging them to 19V, they may be too out-of-spec to use. As for this: See how much current it draws after charging up. If it's 10x more than the leakage current above, I definitely wouldn't use it. You can do a "spark" test. Charge the cap to at least 5V and short its leads on a metal surface. Do beware that for a large 18000 uF cap like that, you *will* get a lot of sparks and possibly pit whatever metal you touch. So keep away from flammable surfaces and substances. And probably a good idea to wear safety glasses/goggles too, just in case some hot piece of metal try to go anywhere. Last edited by momaka; 10-19-2017 at 08:13 PM.. |
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#53 |
Badcaps Veteran
Join Date: Dec 2009
City & State: Prague, 50°4'52.22"N, 14°23'30.45"E
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![]() With such energy, I think ESR meter will be a better choice
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#54 |
New Member
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![]() Wow, thanks, Momaka. I didn't realize the current through the resistor would diminish as the voltage went up. It makes sense, but I hadn't thought about it.
The power supply shows the amp draw, and when it is fully charged, it shows less than 1mA on all of them, even the potentially dead one, but I haven't put my multimeter inline yet. What will the spark test tell me? Also, is it bad for them to do it before it is fully reformed? Sorry for the dumb questions, I really need to learn more about electricity. For someone that's been building computers and taking things apart since he was a kid, you'd think I would have picked up more. Acer |
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#55 | |||
Badcaps Veteran
Join Date: May 2008
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![]() Quote:
Sometimes, an electrically leaky cap can fool an ESR meter into showing that the ESR is fine. With the spark test, you can verify if that is true. If the cap is electrically leaky, it won't spark too well (if at all). Likewise, if a cap has high ESR but you don't have an ESR meter to check it, the spark test can be used to determine only if the ESR is really bad (but it won't be able to determine marginal or just slightly out-of-spec ESR). Don't get me wrong, the spark test is hardly useful and it takes a ton of experimenting with different caps to know what is considered "good" spark and what isn't. So overall, you don't really need to do it. But in a situation without much equipment, it can come handy. That said, you probably don't need to do it, as you will be building a tab welder, which will essentially do the same thing as the spark test does: short-circuit the capacitor as it is charged. Quote:
Only when the caps have been sitting for too long and you try to apply full voltage is when you really need to do the reform procedure. Quote:
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#56 |
Badcaps Veteran
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![]() Shorting the two terminal of charged capacitor is also bad for the cap due to high discharging current.
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#57 |
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![]() RC Time constant:
http://www.electronics-tutorials.ws/rc/rc_1.html So when you are using the resistor you can see how long it will take to charge up the capacitor. |
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#58 |
Badcaps Veteran
Join Date: May 2008
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#59 |
Badcaps Veteran
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![]() Because you are overstepping the rated ripple current by several magnitudes?
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#60 | |
Badcaps Veteran
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![]() Quote:
Think of it like pushing 5 Watts of power through a resistor rated for only 1 Watt. Can you do it? The answer is YES - however, only if you limit the duration of that power level so that the AVERAGE power dissipation does not exceed the 1 Watt rating. In other words, you can dissipate 1 Watt of power through the 1-Watt resistor continuously. But if you want to dissipate 5 Watts, then you can only do it for 1/5 of a second every second... or 1/10 of a second twice a second... or 1/20 of a second four times in a second.... and etc. Last edited by momaka; 10-22-2017 at 02:14 AM.. |
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