Capattery Double-Layer Capacitor Life
presented at the 11th Capacitor & Resistor Technology Symposium,
John R. Miller, David A Evans, Nancy H. Clark, W.E. Baca, and Thomas B.
Double layer capacitors (DLCs) have
received increased use in computer memory backup applications for
consumer products during the past ten years. Their extraordinarily high
capaci tance density along with their maintenance-free operation makes
them particularly suited for these products. These same features also
make DLCs very attractive in military type applications. Unfortunately,
lifetime performance data has not been reported in the literature for
any DLC component.
Our objective in this study was to
investigate the effects that voltage and temperature have on the
properties and performance of single and series connected DLCs as a
function of time.
Evans model RE110474, 0.47 farad, 11.0
volt Capatteries were evaluated. These components have a tantalum
package, use welded construc tion, and contain a glass-to-metal seal,
all incorpo rated to circumvent the typical DLC failure modes of
electrolyte loss and container corrosion.
A five-level, two-factor "Central
Composite Design" was used in the study. Single and series connected
Capatteries rated at 85°C, 11.0 volts operation were subjected to
test temperatures between 25 and 95°C, and voltages between 0 and
12.9 volts (9 test conditions). Measured responses included
capacitance, equivalent series resistance, and discharge time. Data
were analyzed using a regression analysis to obtain response functions
relating DLC properties to their voltage, tempera ture, and test time
history. These results are de scribed and should aid system and
component engineers in using DLCs in critical applications.
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