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f.pelosa 12th February 2013 04:09 PM

old caps
 
hi all,

does an electrolytic capacitor get "old" if never used?

I have these caps, 20 years old but still virgin, and I wonder what to do.
I've read one can reform them to bring them back to the original capacitance by slowly increasing the input voltage, but I wonder if other properties, such as ESR for instance, are conserved or not.

In particular, these are 22000uF 63V Siemens Sikorel, dated 03.1990.

Thanks all
AC

Elvee 12th February 2013 04:19 PM

Quote:

Originally Posted by f.pelosa (Post 3366921)
hi all,

does an electrolytic capacitor get "old" if never used?

In theory yes, but anyway it is completely reversible

Quote:

I have these caps, 20 years old but still virgin, and I wonder what to do.
I've read one can reform them to bring them back to the original capacitance by slowly increasing the input voltage, but I wonder if other properties, such as ESR for instance, are conserved or not
.
Yes, see this thread for information:
http://www.diyaudio.com/forums/parts...t-goodies.html
Note that the capacitance doesn't change, only the leakage current is affected by a prolonged storage.
Reforming them is the sensible thing to do (I never follow my own advice though)

Quote:

In particular, these are 22000uF 63V Siemens Sikorel, dated 03.1990.
I bet they are in pristine condition: Siemens Elytics are of exceptional quality.

f.pelosa 15th February 2013 03:34 PM

thanks
 
thanks a lot

DF96 15th February 2013 04:02 PM

1990 isn't old! 1960 might be old. Old electrolytics can, if not properly sealed, dry out and lose capacitance or have raised ESR.

oz7aff 15th February 2013 04:57 PM

Try searching for shelf life electrolytic capacitors

It will bring op some interesting papers to read.

Panasonic say that there is some aging, but it
can be dealt with:

Under normal conditions, storage life can exceed 10
years.
It is recommended that the leakage current be checked
for conformance to the specified limit if the capacitor has
been stored for four years or more.
Storage may require reforming of the capacitor to
reduce leakage current below the specified limit. This
can be accomplished by applying rated voltage in series
with a 1000 resistor for a time period of 30 ~ 60 minutes.

AMV8 15th February 2013 07:42 PM

Hi
I also have some Siemens Sikorel capacitors of the same value as yours. They are excellant quality capacitors and I have found them to be the equal of any capacitors I have used.
I do not know the condition of your capacitors but mine have all been ok when used.
When first using old capacitors I have reformed them as described in detail on the "Kendeil Capacitors" website. Kendeil also give information about storage of capacitors and expected life and deterioration that you might find interesting.
Don


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