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and only operates to adjust the maximum charging voltage of individual cells, a technique
called monitoring and initializing. The advantage is that the adjusting current for each
capacitor cell will converge to the level of the leakage current, which is negligible in
terms of energy consumption.
The Okamura Laboratory is located in Japan and does not sell capacitors directly. They
partner with other capacitor manufactures, apply their design expertise to the cell design,
and then add active controls to modules. The individual capacitor cells are typically
prismatic geometry, of type II design, and do not contain acetonitrile in the electrolyte.
Okamura has reported that a number of their systems are in use for demonstration
projects associated with vehicular and UPS applications at several hundred volts. Figure
24 shows three of their manufacturing partner’s products.
Figure 11 ECaSS commercial capacitors, from left, Nissan Diesel (346Vdc, 35F, 6.3Wh/kg), Shizuki
Electric “Faradcap” (FML-2A, 54V, 75F, 30Wh), Power Systems (HO2A, 54V, 65F, 6.5Wh/kg)
Panasonic
The Panasonic "Goldcap" capacitor, introduced in 1978, was initially developed for
memory backup applications to replace the unreliable coin cell batteries in use at that
time. It was not until the 1990s that Panasonic began manufacturing much larger
electrochemical capacitor prototypes in Japan. In 1999 Panasonic introduced their
UpCap capacitor for transportation applications, such as needed for hybrid vehicles. One
version of the UpCap is rated at 2000 farads and 2.5 V. It is a type II device that has
been very well engineered. It uses a sophisticated double-seal arrangement in the
crimped package, a lower cost approach than welded construction for preventing water
entry into the package. It has essentially many tabs to the spiral-wound foils at each end
of the package, which helps in reducing the series resistance. Furthermore, this
arrangement helps to extract internally generated heat, which is important for applications
like a hybrid vehicles where there are continuous repetitive charge/discharge cycles. The
UpCap is currently available in high-power and high-energy versions, and under
evaluation for many applications.
These products are available from Panasonic Automotive Electronics Company in
Southfield, Michigan.
Electrochemical Capacitors 31