Handbook of Energy Storage for Transmission or ... - W2agz.com

EPRI Proprietary Licensed Material
Average Manufacturing Yield (%)
100
90
80
70
60
% CELLS MEETING TOLERANCE
50
1 10 100 1000
Number of Series-Connected Cells
Figure 36 Yield for electrochemical capacitors from two different manufacturing distributions
Cell Failure Modes
The following charts show failure modes for electrochemical capacitors types I, II and
III. There is less experience with type III and no experience with type IV. Figures 12 and
13 charts the common failure mode scenario for these capacitors.
Total capacitance of
string increases
99.0% 99.9%
Internal short in
one cell in string
Increased dissipation
in shorted cell
Temperature rise in
shorted cell
Increase in voltage
In remaining cells
May cause
overvoltage in a cell
May lead to internal
short in second cell
Cascade failure in
short circuit
Figure 37 Possible failure mode scenario for Type I electrochemical capacitors
Overvoltage in
one cell in string
Electrolyte
Decomposition
Impurities increase
leakage current and
self-discharge rate
Gas evolution
Pressure increase
Cell rupture
Venting of gas and
electrolyte
Electrochemical Capacitors 66