Uncharged capacitor = much reduced lifetime?

[Peroxyde]

Hi,

I have learnt in this thread that an uncharged capacitor will have its life span significantly reduced.

Yeah most people believe that the caps wear out and die due to age, this is only true if they are uncharged and sitting for prolonged periods of time. If they are being used on a regular basis the caps can last upwards of 20 years. If you check the specsheets on most caps there lifetime if in use is very high, they just dont have a really long shelf life.

Can you please clarify how this apply to the following scenarios?

Q1- The Power supply is plugged into the electric outlet but is not connected to a motherboard. Would its capacitors remain uncharged?

Q2- The computer is fully functional, it is plugged in to the electric outlet. But the computer is turned off for a long period of time. Would this leave the capacitors uncharged?

Q3- A motherboard, removed from a computer and stored on shelf for a long period. Would its capacitors also suffer?

Thanks in advance for any advice.

 

[Modelworks]

Q1 - input side which runs about 200volts would be charged anytime the psu is plugged into the wall. Output side caps would remain uncharged except for those that generate the 5V standby.

Q2 - Same as Q1
Q3 - those would be uncharged and will degrade with time

Realize that time here is not a week or a month but years. It isn't like leaving a motherboard in the closet for a year will cause the capacitors to fail. After 4-5 years of no use you might have some degradation.

 

[Red Squirrel]

This thread gave me a super funny idea. My IT manager who is a total nut job constantly comes in our office to give us a soap box. While doing this he always picks up random components and twirls it in his hands. Hard drives, ram, printer parts, screws... you name it.

We need to keep charged capacitors laying around. :twisted:

 

[Peroxyde]

We need to keep charged capacitors laying around. :twisted:

Hope this will help to increase his life span

 

[Red Squirrel]

Hope this will help to increase his life span

It should keep him on his toes anyway, and he might actually stop bothering us so much, and then productivity will go up. :awe:

They are also fun to throw at friends. :twisted:

 

[Peroxyde]

Thanks for the clarification. Just to be complete on the subject, some more questions.

Q4- How long does it take approximately for a capacitor to degrade to a point it becomes unsafe?

Q5- Are the solid capacitors also subjected to this phenomenon?

 

[Modelworks]

Thanks for the clarification. Just to be complete on the subject, some more questions.

Q4- How long does it take approximately for a capacitor to degrade to a point it becomes unsafe?

Q5- Are the solid capacitors also subjected to this phenomenon?

http://www.wa4bpj.com/Ham_Radio/Ham_Radio_Tech_Info/capacitor.htm

The following time limits apply to shelf life at 35°C 60%RH for all styles of CDE Aluminum Electrolytic capacitors:
1Year - Will meet initial parameters.
3 Years - Recommend testing before use to determine if re-aging is required to meet initial parameters of DCL (leakage).
4 Years - Re-aging is usually required before use.
5 Years - Typically expect to meet all parameters after re-aging.
10 Years - Typically end of useful shelf life, but subject to many variables.

RE - AGING PROCEDURE

1. This re-aging procedure is performed at room temperature.
2. Connect capacitor to a voltage source with a resistor in series. 10K ohms for 75VDC and below. 100K ohms above 75VDC.
3. Slowly increase voltage to the rated WVDC while monitoring the charge current. Do not allow the charge current to any individual unit to exceed 1mA.
4. After reaching full voltage, continue to apply full voltage for a minimum of 4 hours.
5. Re-test DCL (leakage) after re-aging is complete.

I assume caps are okay within 4 years , at 5 years I test. Just depends on how they were stored.


Q5 - solid caps are less susceptible ,all depends on the internal makeup.

 

[C1]

I wouldnt worry about. By the time your capacitors go you probably wont want the part anyway as it has been superceded.

I see shelf life for non-aluminum capacitors spec'ed at 3yrs. Otherwise operationally, it is a function of temperature, case size, ripple current & voltage rating. This link has a discussion along with formulae:

http://docs.google.com/viewer?a=v&q...DCBIl5&sig=AHIEtbTjxSvXMpT2Sx2czfk97edvSKJSow

 

[Compman55]

Computers today will outdate themselves before it becomes a problem. However high quality CRT/LCD/LED monitors that you become attached to may need some caps some day.

As I see it the only industry that needs to worry is aviation / medical. All the other uses, its just a given that over time they will age.

 

[GotNoRice]

I think this issue might be a bit overblown. I have a 240wpc Yamaha Stereo Amp that was built in 1979 and continues to function perfectly over 30 years later. I have several other receivers from the 70's that are also still running with all original parts. The Yamaha amp in particular has a very large power supply and gets nearly too hot to touch with usage so these capacitors haven't had an easy life.

As far as computer components go, I have a 550w EPS12v powersupply that I bought back in 2003 for the dual-xeon rig I was building at the time. The powersupply proved to have a lot of longevity since the 24/8-pin connectors it has (only common on servers back then) were ultimately adopted in the latest ATX specification. I've run that powersupply with 4 or 5 different computers and it's still going strong in a Core2Quad rig today.

 

[kaytaro]

I'm an Avionics Bench Tech, I repair aircraft radios/instruments/radars.... ect, mostly general aviation stuff. Most of the equipment I work on is 20+ years old ( Bendix King / ARC / Collins / Nacro Brands) and 99% of their 100's of caps are fine. While caps are a common item to fail, this is way out of proportion, its not something you should worry about. As GotNoRice said by the time your caps get to the point they affect the function of your PC it would be outdated.

 

[C1]

If you are worried about bringing up a long idled electrolytic, then my old RCA electronics training manuals, state that to "reform" the capacitor, apply normal full working voltage, but current limit the component. So I suppose in the case of a modern PSU, this might be the equivalent of plugging it in, but not actually using it for a few days. Even after powering the PSU on, the number of PC components might be minimized & then added over a week's time.