Life Design

Type EDL supercapacitors have a useful lifetime that decreases with

increasing operating temperature, humidity, applied-voltage, current and

backup-time requirements.

Expected lifetime is the product of four factors:

Expected Life = (Lifetime)•(Temperature Factor)•(Voltage Factor)•(Moisture

Factor)

Lifetime

The minimum rated life at 85 ºC with 5.5 Vdc applied is 1000 hours with

maximum permitted end-of-life capacitance change of –30% and a 4

times increase in internal resistance.

Temperature Factor

To determine the effect of temperature on expected life of a supercapaci-

tor, use the fact that expected lifetime doubles for each 10 ºC that the

operating temperature is reduced. As an illustration, at 85 ºC and full

voltage the rated lifetime is 1000 hours. So, at 40 ºC the expected lifetime

would be multiplied by 2(85-40)/10 = 2^4.5 = 22.6 times. The Tempera-

ture Factor is 22.6, and for 1000-h, 85 °C rated life, the expected 40 °C life

would be 22600 hours.

Voltage Factor

The rate of change of capacitance decreases with decreasing applied

voltage. The effect on life extension is roughly proportional to the voltage

derating, e.g., 5 V applied to 5.5 V rated supercapacitors extends the life

1.1 times.

Moisture Factor

Expected life of these supercapacitors is considerably shortened by

operation in high humidity. The applications discussed here assume that

the relative humidity is no more than 50%.

Expected Life Example

So, for a 5.5 V supercapacitor at 40 °C charged to 5.V in less than 50% RH

the expected life is:

Expected Life = (Lifetime) (Temperature Factor) (Voltage Factor)

(Moisture Factor)

= (1000 h) (22.6) (1.1) (1)

= 24800 hours

= 2.8 years

RoHS Compliant

Type EDL , Electric Double Layer Supercapacitors

Ultra High Capacitance, Small Case Size Options

CDE Cornell Dubilier • 1605 E. Rodney French Blvd. • New Bedford, MA 02744 • Phone: (508)996-8561 • Fax: (508)996-3830

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