10

082418

100%Vrated

90%Vrated

80%Vrated

70%Vrated

90

80

70

60

50

40

30

20

10

0

0.1

1.0

10.0

100.0

100%Vrated

90%Vrated

80%Vrated

70%Vrated

0.1

1.0

10.0

100.0

MTTF (years)

POLARITY / REVERSE VOLTAGE

In principal the positive and negative electrodes of the

SuperCapacitors are symmetrical and in theory they should not

have a polarity but for product consistency and for optimum

performance the negative polarity is marked because the

capacitors do not discharge completely when in use. It is

recommended that the polarity should be used as marked. If the

polarity is reversed the circuit will not have a catastrophic failure

but the circuit will see a much higher leakage current for a short

duration of time and the life time of the SuperCapacitors will be

reduced.

LIFE TIME AND TEMPERATURE PERFORMANCE

The life of a SuperCapacitor is impacted by a combination of

operating voltage and the operating temperature according to

the following equation:

time to failure, t ∞ Vn * exp (-Q / k*T)

…………..(1) where V is the voltage of operation, Q is the

activation energy in electron volts (eV), k is the Boltzmann’s

constant in eV and T is the operating temperature in °K

(where K is in degrees

Kelvin). Typical values for the voltage exponent, n, is between

2.5 - 3.5, and Q is between 1.0 - 1.2 eV in the normal

operating temperature range of 40° to 65°C. The industry

standard for SuperCapacitor end of life is when the equivalent

series resistance, ESR, increases to 200% of the original value

and the capacitance drops by 30%. Typically a SuperCapacitor

shows an initial change in the ESR value and then levels off. If

the capacitors are exposed to excessive temperatures the ESR

will show a continuous degradation In the extreme case, if the

temperatures or voltages are substantially higher, than the rated

voltage, this will lead to cell leakage or gas leakage and the

product will show a faster change in the ESR which may increase

to many times the original value.

Expected Lifetime at Various Voltages

SCM Series, 5.4V/5.0V, 6.0V/5.5V, 7.5V, 9.0V/8.1V Rated

Expected Lifetime at Various Voltages

SCM Series, 4.6V/4.2V, 6.4V Rated

MTTF (years)

90

80

70

60

50

40

30

20

10

0

SCM Series

Series-Connected SuperCapacitor Modules