COSEL Co., Ltd.

Q&A(FAQ) What is the Expected Lifetime of an Electrolytic Capacitor?

1. Expected Lifetime of Power Supplies

Among the components used in power supplies, aluminum electrolytic capacitors are among those with the shortest service life. Therefore, they are critical components from the standpoint of power supply reliability, and by estimating the expected lifetime of aluminum electrolytic capacitors, the overall lifetime of the power supply can also be predicted.
The lifetime of an aluminum electrolytic capacitor is determined by factors such as the amount of excess electrolyte, the rate at which the electrolyte evaporates through the rubber seal, and the operating temperature,which has a major influence on evaporation. The relationship between ambient temperature and capacitor lifetime follows the Arrhenius law.

Expected Lifetime of an Electrolytic Capacitor: L = Lo x 2 ^{(T1-T2) / 10}

Lo : Lifetime Under Maximum Rated Operating Temperature
T1 : Allowable Maximum Temperature
T2 : Capacitor Temperature on operation

The actual life expectancy is then determined by applying the temperature-dependent coefficient based on Lo.

2. Influence to Power Supplies

The expected lifetime of an aluminum electrolytic capacitor is defined by criteria such as:

1. -A reduction in capacitance beyond the allowable limit
2. -An increase in tan δ
3. -An increase in leakage current

Electrolytic capacitors are used in various parts of a power supply—such as input/output smoothing circuits, auxiliary power supply circuits, and phase compensation circuits—and the impact of their degradation varies depending on the application.
Table 1 shows typical examples of how the locations where aluminum electrolytic capacitors are used can affect the performance of a power supply.

3. Note

Since the lifetime of aluminum electrolytic capacitors depends on environmental conditions—especially ambient temperature—power supplies must be operated in an environment where heat does not accumulate.