1.EDLC may fail under the following circumstances:
Initial issues such as leaks or short circuits are usually detected during the manufacturer’s routine inspections, so they are not considered in the Weibull distribution model.
The opening of the explosion-proof valve is caused by the increase in internal pressure within the product. Voltage and temperature generate a certain amount of gas within the product, and the gas quantity increases as the operating time increases. When the internal pressure reaches the set threshold, the explosion-proof valve opens and releases pressure, preventing the product from exploding. The functionality of the EDLC is not compromised, but the rate of capacity decay will accelerate.
When the capacity decays to 80% of the nominal value or the ESR increases to 200% of the nominal value, it is defined as EDLC functional failure, indicating that the capacitor has reached the end of its lifespan.
2.Simple life equation
The performance of EDLC is significantly influenced by the operating voltage and environmental temperature. Generally speaking, EDLC follows the 10°C principle, which means that reducing the temperature by 10°C doubles its lifespan. This principle is particularly applicable when the temperature is near the maximum operating temperature and voltage of the product. For the voltage aspect of EDLC, the principle is approximately that for every 0.1V decrease in voltage, the lifespan increases by 1.3 times. Therefore, the simplified lifespan equation for EDLC can be expressed as follows: where τ(T0 , V0) represents the lifespan under known conditions of temperature T0 and voltage V0.
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