Determination of Capacitor Life as a Function of Operating Voltage and Temperature

Potentiostatically charged Hybrid capacitors age predictably by a mechanism involving electrochemical reactions that reduce the efficiency of the cathode and consume electrolyte. One of these reactions results in the formation of hydrogen at the cathode which reacts irreversibly with the tantalum foil substrate. The material formed is much less conductive than the original. The consequence to capacitor performance is an increase in ESR and a decrease in capacitance.

It has been assumed that the rate of this wear-out mechanism is directly related to the leakage current in the capacitor. This means that the relative age of a capacitor is proportional to the quantity of charge passed as leakage current. If one knows what quantity of charge a capacitor can pass over its useful life, capacitor life can be easily estimated by determining the leakage current under any proposed operating conditions.