Electrolytic Capacitors: What You Need To Know

This short article will discuss why electrolytic capacitors fail and steps you can take to prevent or prolong the timeframe before this happens. We will not “reinvent the wheel” in this article since much has been written on this subject. Where applicable, I’ll include links to information the reader should review.

Some things to know:

  • Capacitors degrade overtime “in the field” even if the circuit card or module they are installed on, is NOT in service! I know this is hard to believe, but it’s true.
  • Capacitors are used to maintain DC voltages constant, when they start to degrade, the voltage can change!
  • If not replaced, they will eventually fail which could cause other system problems.

What To Look For:

electrolytic capacitor


As you can see on this electrolytic capacitor, it has started to “bulge” on the top. This is indicative of an over pressure inside the cap due to aging. This capacitor is bad! Replace it!



What A User Can Do To Extend Capacitor Life:

  • Keep out of service components stored in a temperature controlled area.
  • When installed, make sure all installations are operating within temperature specs, preferably at the low-end.
  • Inspect Capacitors for signs of aging like bulging frequently during outage periods

For More Detailed Information, Some Useful Links Are:

Cover page of helpful capacitors article
(this is a great detailed article)

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