Electrolytic Capacitors, 2023-10

Electrolytic capacitors that are not in use undergo a certain change. The ability to handle voltage is lessened. Frequency converters, UPS and similar equipment with large electrolytic capacitor banks cannot be stored indefinitely. Manufacturers recommend that voltage is applied to the appliance for a short time every two years. 

My previous company serviced UPS-systems. You must change capacitors with regular intervals to maintain performance. At one stage I found that I could no longer buy a few electrolytic capacitors when I needed them. I had to buy a lot of 50 or 100 or so and wait for them to be manufactured. Because of this I was left with a large stock of capacitors, that had not been used, when I sold the company. The buyer only bought the stocks he wanted. 

The electrolytic capacitors are not damaged nor degraded by not being used. They just need to be reformed. This is an operation where voltage is applied gradually to keep leakage current down. After an hour or so with voltage applied the capacitor will again be ready for normal use.