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Why Do Capacitors Age?
Capacitor aging is essentially the degradation of the electrolyte. That’s the substance that fills in the space between the layers of insulation inside the component. Capacitors are made using different materials with different properties. Therefore, the rate and severity of degradation vary depending on the type of capacitor in question.
In the late 90s and early 2000s, the computing world experiences a “capacitor plague” which caused millions of dollars in damage as capacitors with defective electrolytes rapidly aged and capacitors failed. While new capacitors don’t have this problem, it demonstrates what eventually happens to all capacitors.
Liquid vs. Solid Capacitors
There are many different ways to make a capacitor (and even supercapacitors), and two common types of capacitors use either a liquid electrolyte or a solid organic polymer. Liquid electrolyte capacitors experience evaporation and can even develop leaks. Temperature plays a role as well. The hotter a capacitor runs, the shorter its lifespan. According to Gigabyte, at 85c a liquid polymer capacitor only has a lifespan of around 8000 hours.
Solid capacitors do much better and can last many times longer. That’s especially true at lower temperatures comparatively. If solid capacitors are so much more resilient to aging and catastrophic failure, why not simply use them exclusively in power supplies? It turns out that different capacitors have different electrical characteristics, and liquid electrolyte capacitors have an important role to play in PSU design. This means at least some of those capacitors will use a liquid electrolyte. There’s also a difference between high-quality liquid electrolytes and less expensive ones.
The Negative Effects of Aged Capacitors
Aged capacitors show two main symptoms. First, their capacitance drops over time. Eventually, it can fall outside of the minimum specifications for that capacitor. This makes the power supplied through the capacitor unstable. The second symptom is an increase in the ESR or Equivalent Series Resistance. When electrical resistance becomes too high, it can cause component damage and failure.
In the context of Power Supply Units in a computer, a PSU with aged capacitors can’t provide its full rated wattage or, at the very least, can’t provide it in a stable fashion.
Choose a PSU That Takes Aging Into Account
While you can’t do anything about the fact that capacitors age, you can keep it in mind when you buy your next PSU. It’s a good idea to use a power supply calculator so that you know how much wattage you need at a minimum. The calculator will give you a recommended PSU wattage. If the calculator in question doesn’t take aging into account, add 10% (or go one model up) from that number to ensure that the PSU can keep supplying enough power for your computer to run reliably.
If you buy a PSU with significantly more capacity than your system needs, it should run under less strain and at lower temperatures. Which should also make capacitors age more slowly.
You can also make your current PSU last longer by making sure it has enough airflow and not running it at high temperatures.
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