Author Topic: Fun with cheap Chinese tantalum capacitors  (Read 2215 times)

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Jbub

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Fun with cheap Chinese tantalum capacitors
« on: January 05, 2018, 04:36:54 PM »
+1
I finally got around to testing my caps from eBay / China. 
They are 25v 220uF and pretty cheap. I got (2) 20 packs for 8.54 each plus 1.20 shipping, about 50 cents a piece.

Having discussed these caps in another thread @peteski suggested a burn in period to eliminate any bad caps. @Steveruger45 did so and had some blow up. Knowing this was most likely going to happen I thought I should get video of some flaming caps.

Sorry about the shaky video and wrong aspect. I didn't realize until after I had tested all the caps.

I think I had 4 actually blow up but since I was stupid and put them to close together I had to discard another 6 for a total of 10 lost. The remainder are 'burning' in so if I have any more failures I'll update the thread.

Testing these is a good thing, just imagine one going boom in a nice new model.
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Steveruger45

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Re: Fun with cheap Chinese tantalum capacitors
« Reply #1 on: January 05, 2018, 06:27:26 PM »
0
Great post.  Yeah, seems you got exactly the same caps I did and getting much the same failure rate of 20%.
I put 18v across them from one of my power tool batteries.   I'm guessing you put about the same voltage across too?
Steve
Atascocita, Texas

Jbub

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Re: Fun with cheap Chinese tantalum capacitors
« Reply #2 on: January 05, 2018, 06:34:44 PM »
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Great post.  Yeah, seems you got exactly the same caps I did and getting much the same failure rate of 20%.
I put 18v across them from one of my power tool batteries.   I'm guessing you6 put about the same voltage across too?
I took a voltage reading on the battery close to 19v iirc. I can't be for sure on the failure rate because I discarded anything that was burned. I didn't want to risk a damaged one going up in flames after installation. I do think I could have kept more if I hadn't spaced them so close together.
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Steveruger45

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Re: Fun with cheap Chinese tantalum capacitors
« Reply #3 on: January 05, 2018, 06:49:51 PM »
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thanks and yes. I threw out any suspect ones after my first testing too.  BTW I spaced mine at about 1.5 inches on my first test ladder which was ok for any adjacent caps next to those going ballistic but I would suggest a min of 2 inch spacing to be safe if testingin this way.

What I am doing now is selecting two caps for an install after a close visual inspection first and then testing them individually on separate power tool batteries and like you did and Pete suggested do all this on a ceramic tile or concrete floor and stand well back.

I'm just wondering if anyone that has the more expensive quality branded caps has done a test like this so we could establish if the more expensive ones are really better?
Steve
Atascocita, Texas

Point353

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Re: Fun with cheap Chinese tantalum capacitors
« Reply #4 on: January 05, 2018, 06:53:07 PM »
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Now try applying 25V to see if any of these caps survive.

Steveruger45

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Re: Fun with cheap Chinese tantalum capacitors
« Reply #5 on: January 05, 2018, 07:06:57 PM »
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I pretty sure none would.  But they only have to survive operating volts of about 13v.
Steve
Atascocita, Texas

Jbub

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Re: Fun with cheap Chinese tantalum capacitors
« Reply #6 on: January 05, 2018, 07:07:59 PM »
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I've read in places that if using tantalum caps on new designs to use only 50% of the rated voltage. I suspect going 25v would blow all but maybe a couple of them. I think the emotion of seeing these blowing up like that makes me want to test them further also. I'm not sure if that is logical or not.
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Point353

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Re: Fun with cheap Chinese tantalum capacitors
« Reply #7 on: January 05, 2018, 07:27:41 PM »
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Given that the 25V rating of these parts seems dubious, one might also question whether the actual capacitance meets the claimed value of 220µF, as well.

tehachapifan

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Re: Fun with cheap Chinese tantalum capacitors
« Reply #8 on: January 05, 2018, 07:34:36 PM »
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Yikes! :scared:
Russ

Steveruger45

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Re: Fun with cheap Chinese tantalum capacitors
« Reply #9 on: January 05, 2018, 07:36:26 PM »
+1
Yep, I read the same thing about using tantalum caps with about twice the voltage rating than that you were going to apply to them, which was why I went for 25v caps in the first place and not the 16v variety.

I don't think further testing is illogical at all, what ever it takes to make you feel comfortable using them.

In my case, I am comfortable with a three step quality test.
A) close visual inspect, I have found one or two with partly broken terminals.
B) batch test on 18v for 2 hours spaced 2 inches a part.
C) individual test on 18v for 2 hours that passed a and b before using them.

Steve
Steve
Atascocita, Texas

peteski

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Re: Fun with cheap Chinese tantalum capacitors
« Reply #10 on: January 05, 2018, 07:39:44 PM »
+2
If you are interested in safe use of tantalum caps I recommend watching this tutorial.  In general, it is recommended to use tantalum caps at 50% of their rated voltage.  This tutorial is from KEMET (one of the well-known manufacturers of quality capacitors).

Also, since you guys are doing the burn-in tests on multiple caps, make sure not to inhale the nasty smoke/fumes emanating from the destroyed caps.

For people not wanting to go through the tutorial's technical mambo-jumbo, here is the recommendation from that tutorial:



As you can see, polymer tantalum caps can be used closer to their rated voltage, but they are more expensive (of course).
« Last Edit: January 05, 2018, 09:03:07 PM by peteski »
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Steveruger45

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Re: Fun with cheap Chinese tantalum capacitors
« Reply #11 on: January 05, 2018, 08:10:40 PM »
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Hi again Pete,
Thanks the link.  Very interesting.
You know, these cheapo caps look just like the expensive ones.  I don't know if my suspicion is correct but I would not be surprised if these are made at the same place as the expensive ones but just haven't gone through the branded makers quality control. 
Just a thought.
Steve
Atascocita, Texas

peteski

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Re: Fun with cheap Chinese tantalum capacitors
« Reply #12 on: January 05, 2018, 08:48:45 PM »
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Hi again Pete,
Thanks the link.  Very interesting.
You know, these cheapo caps look just like the expensive ones.  I don't know if my suspicion is correct but I would not be surprised if these are made at the same place as the expensive ones but just haven't gone through the branded makers quality control. 
Just a thought.

The dimensions of SMD components are well defined and manufacturers all follow that standard. There is also a fair amount of copying going on in China. On the other side of the coin, KEMET probably has their components made in China, so those cheap caps could possibly be manufactured at the same factory. Nowadays you never know.
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Point353

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Re: Fun with cheap Chinese tantalum capacitors
« Reply #13 on: January 05, 2018, 11:17:43 PM »
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You know, these cheapo caps look just like the expensive ones.  I don't know if my suspicion is correct but I would not be surprised if these are made at the same place as the expensive ones but just haven't gone through the branded makers quality control. 
There are numerous "look-a-like" sources in the far east.
Just two examples:
http://www.betop-components.com/
http://www.china-jinpei.com/tantalum-capacitor/

Also, see this report:
https://www.electronicproducts.com/Passive_Components/Capacitors/How_to_spot_counterfeit_passive_components.aspx
« Last Edit: January 05, 2018, 11:19:46 PM by Point353 »

Steveruger45

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Re: Fun with cheap Chinese tantalum capacitors
« Reply #14 on: January 06, 2018, 12:37:04 AM »
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Many thanks the post with those links. Excellent.
The last link, the report with the photos of the AVX cap and the fake caps, in particular.
I just checked my dubious quality caps and they compare exactly, visually, to the genuine AVX one in every way.
This  is firming my earlier stated suspicion of same manufacturer but no branded quality control.
« Last Edit: January 06, 2018, 12:38:41 AM by Steveruger45 »
Steve
Atascocita, Texas