Capacitor having non-conductive plastic frames

An improved capacitor including a plurality of plastic frame mounted electrode and separator inserts. The plastic frame mounted electrode and separator inserts are oriented in alternating succession, and have a carbon paste placed therebetween. The capacitor includes terminal electrodes through which electric charge may flow. The capacitor also includes a pair of rigid endblocks.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to capacitors, and more particularly, the 
present invention relates to high farad, double-layer capacitors that 
include improved electrodes which are enclosed within a sealed plastic 
case. 
2. Description of the Prior Art 
Conventional double-layer capacitors include two polarizable bodies which 
are made of a paste of activated carbon and sulfuric acid. The individual 
carbon paste bodies are held apart, but disposed in close proximity by a 
porous separator. Electrical contact with each of the carbon paste bodies 
is established by means of conductive electrodes. Double-layer capacitors 
store energy by forming a polarized liquid layer at the surface of the 
conductive electrodes. 
A typical double-layer capacitor contains a single cell. Such a capacitor 
includes a pair of current collectors or current electrodes; a pair of 
polarized electrodes separated by a non-woven fabric or porous separator; 
and a gasket positioned between the current electrodes and surrounding the 
polarized electrodes and the separator. The polarized electrodes of such a 
capacitor are manufactured from activated carbon and are impregnated with 
an electrolyte such as, for example, an acid. 
One of the shortcomings inherent with a polarized capacitor of the 
construction discussed above is its internal electrical resistance. In 
most prior-art capacitors, the individual particles of carbon in the 
polarized electrode are not joined together. This physical environment 
causes the internal resistance of the electrode to be high. In order to 
reduce the internal resistance of the polarized electrode it is necessary 
to bring all the particles of carbon into improved electrical contact with 
each other. 
A further shortcoming with the prior-art construction of polarized 
capacitors is that the internal resistance of conventional double-layer 
capacitors is also greatly affected by the contact resistance between the 
collector electrodes and the polarized electrodes. To reduce the contact 
resistance between the polarized electrodes and the collector electrodes, 
and to further reduce the internal resistance of the polarized electrodes, 
the capacitor cells of the prior art are kept under pressure. Such 
pressure normally brings the particles of activated carbon into improved 
electrical contact with each other. Additionally, the pressure also brings 
the polarized and collector electrodes into improved electrical contact 
with each other. In this regard, conventional double-layer capacitors are 
normally kept under a pressure of about 100 kg/cm.sup.2. Prior-art, 
double-layer capacitors are kept under pressure by deforming their outer 
cases, which are usually made from metal. Another method used to apply the 
appropriate pressure involves bonding the collector electrodes strongly to 
the gaskets. 
The capacitance of a double-layer capacitor may be improved by increasing 
the cross-sectional area of the basic cell. However, when the 
cross-sectional area of the cell is increased, the pressure applied to the 
double-layer capacitor must correspondingly increase. Increasing the 
pressure causes practical problems such as finding a means for applying 
the pressure, and increasing the strength of the outer case which encloses 
the basic cell. 
In addition to the problems noted above, double-layer capacitors suffer 
from additional problems. One such problem is leaking. Double-layer 
capacitors typically use an acid as an electrolyte, and because the casing 
which encloses the capacitor is typically metal, the capacitors corrode 
and subsequently leak. In addition to the identified leaking, the gaskets 
employed in conventional double-layer capacitors are subject to 
degradation, which manifests itself by cracking and wrinkling, and which 
is a result of corrosion, as well as heat induced expansion and 
retraction. Accordingly, conventional capacitors may experience leaking in 
the area around and through their respective gaskets. 
The prior art is replete with numerous examples of assorted devices and 
assemblies which have attempted to improve conventional double-layer 
capacitor design. Many of these prior-art attempts have been directed to 
increasing the capacitance of a double-layer capacitor without increasing 
the external pressure applied to the basic cell. For example, U.S. Pat. 
No. 5,086,373 ("the '373 patent"), which issued to Kurabayashi, discloses 
a double-layer capacitor which has a construction where the carbon 
particles in the polarized electrode are joined together by sintering the 
electrode. In such a sintered electrode arrangement, the individual 
particles of carbon are joined together, but the polarized electrode 
remains relatively porous. Accordingly, the internal resistance of the 
electrode is reduced, while the surface area of the respective electrodes 
remains relatively high. To further improve the electrical contact between 
the polarized electrodes and the collector electrodes, the device 
described in the '373 patent employs individual collector electrodes which 
are manufactured by a technique which includes hot curing a mixture of 
rubber and conductive particles and applying it to the polarized 
electrodes. The hot curing process results in the rubber flowing into the 
porous polarized electrode and, thereby, increasing the area of contact 
between the polarized electrodes and the collector electrodes. 
While the process disclosed in the '373 patent results in an improved 
capacitor which eliminates some of the shortcomings attributed to 
conventional designs, it is still unsatisfactory for applications where a 
capacitor having a very large capacitance is desirable. Such applications 
include so-called "SLI" or starting, lighting, and ignition applications. 
Typically, in such applications a relatively large capacitance capacitor 
is electrically coupled to a battery, or other voltage source, which is 
used to start a machine such as an industrial engine or motor. In these 
circumstances, the starting of the engine requires a significant amount of 
current early in the starting process, and then less current as the 
starting proceeds. Capacitors are used to provide the initial current in 
such an application, thereby reducing the current demands on the battery 
coupled to it. The battery provides the rest of the current necessary to 
start the engine. 
In addition to their unsatisfactory operation in SLI applications, 
conventional double-layer capacitors, are generally expensive, heavy, and 
difficult to dispose of or recycle once they have reached the end of their 
commercial usefulness. 
As noted, the capacitance of a capacitor may be increased by increasing the 
area of the basic cell. As described, most double-layer capacitors utilize 
a paste consisting of carbon powder and an electrolyte. Another factor 
upon which the capacitance of double-layer capacitors depends is the 
active surface area of the carbon powder used in the paste. If an improved 
powder could be developed for use in such pastes, the performance of 
capacitors could also be improved. 
Accordingly, it would be desirable to have a double-layer capacitor having 
even greater capacitance than prior-art devices. It would also be 
desirable to have a capacitor which is relatively lightweight and 
relatively inexpensive. It would also be desirable to have a capacitor 
which has an advantageous combination of capacitance, weight, and cost 
characteristics, unachieved heretofore, and to have a capacitor which is 
substantially leak-free and which can be enclosed within a 
corrosion-resistant container. Finally, it would be desirable to have a 
capacitor which is manufactured from materials which can be readily 
recycled. 
OBJECTS AND SUMMARY OF THE INVENTION 
Therefore, it is an object of the present invention to provide an improved 
capacitor having a high farad capacity. 
A further object of the present invention is to provide a double-layer 
capacitor having a low internal electrical resistance. 
A further object of the present invention is to provide a double-layer 
capacitor which avoids many of the problems associated with the prior-art 
practice of applying external pressure to the components thereof. 
A further object of the present invention is to provide a double-layer 
capacitor which is lightweight in relative comparison to prior-art 
devices. 
A further object of the present invention is to provide a double-layer 
capacitor having a substantially leak-free and corrosion-resistant 
container or casing. 
A further object of the present invention is to provide a double-layer 
capacitor which is relatively easy to dispose of once it has reached the 
end of its commercial usefulness. 
A further object of the present invention is to provide a double-layer 
capacitor that is manufactured from recyclable materials. 
A further object of the present invention is to provide a double-layer 
capacitor having a novel, gasket-free construction. 
These and other objects and advantages are achieved in an improved 
capacitor of the present invention and which includes a plurality of 
non-conductive plastic frames. The frames are constructed in a manner 
which permits the positioning or mounting of various components in various 
orientations therein. In this regard, a plurality of carbon-filled 
conductive electrode inserts are mounted on a predetermined number of the 
non-conductive plastic frames. Further, each carbon-filled conductive 
electrode insert has a first surface and an opposite second surface. Two 
conductive electrode inserts are normally mounted in an adjacent position 
one to the other within one plastic frame, thereby forming an electrode. 
The improved capacitor of the present invention also includes first and 
second terminal electrodes. Each terminal electrode includes at least one 
plastic frame mounted, carbon-filled conductive electrode insert which has 
a metal screen imbedded therein, and a metal stud terminal which is 
electrically coupled to the metal screen. 
The improved capacitor of the present invention also includes a plurality 
of microporous separator inserts which are mounted in a predetermined 
number of the plastic frames. In this regard, each of the plastic frame 
mounted separator inserts is oriented or otherwise positioned in 
sandwiched relation between two adjacent carbon-filled conductive 
electrode inserts. The gaps between each of the carbon-filled conductive 
electrode inserts and each of the microporous separators are filled with a 
carbon paste. The plurality of plastic frames, in which the conductive 
electrode and the microporous separator inserts are mounted, are joined to 
one another by thermal welding, or a similar technique, to form a 
substantially fluid impervious outer enclosure or case. 
The improved capacitor of the present invention includes first and second 
endblocks which are of rigid design. In this respect, the endblocks 
maintain pressure on the plurality of plastic frames thereby preventing 
deformation of the plastic frames and further maintain good internal 
electrical contact between the internal components of the capacitor, 
thereby facilitating a lower internal resistance. In an alternative 
embodiment of the present invention, conductive electrode inserts, each 
having a metal screen imbedded therein and a metal stud terminal which is 
electrically coupled to the metal screen, are mounted in the first and 
second rigid endblocks. Such endblocks function as terminal electrodes 
and, therefore, in a capacitor having such endblocks the necessity of 
having separate terminal electrodes is eliminated. 
The improved capacitor of the present invention may also include a carbon 
coating in the form of a carbon powder or carbon cloth applied to the 
surfaces of the individual carbon-filled conductive electrodes. 
These and other objects and advantages of the present invention will become 
more apparent from the following detailed description of the preferred 
embodiment of the present invention taken in combination with the 
accompanying drawings.

DETAILED DESCRIPTION 
First Embodiment 
Referring more particularly to the drawings, the capacitor of the present 
invention is designated generally by the numeral 10 in FIG. 1. The 
capacitor 10 includes a first endblock 20 and a second or opposite 
endblock 30. The first endblock 20 includes an end plate 21 and a cover 
22. Similarly, the second endblock 30 includes an end plate 31 and a cover 
32. The specifics of the construction of the endblocks 20 and 30 are 
explained in further detail in U.S. Pat. No. 5,308,718, which is 
incorporated by reference herein. 
The endblocks 20 and 30 each include a pair of openings. The openings in 
endblock 30 are not seen in the drawings. The openings 23 and 24 of the 
endblock 20 each receive therethrough individual metal stud terminals. 
These stud terminals will be discussed in greater detail hereinafter. 
Oriented in sandwiched relation between the respective endblocks 20 and 30 
is a plurality of individual components 50. The components 50 of the 
capacitor 10 include individual nonconductive frames 100 which are 
constructed so as to permit the mounting of various additional 
subcomponents therein. The nonconductive frames are typically manufactured 
from a synthetic, polymeric based material. 
As more clearly seen in the exploded view of FIG. 2, each of the frames 100 
includes a first opening 101 and an adjacent, second opening 102 of 
substantially the same size and dimensions. The first opening 101 is 
defined by a peripheral edge 103, and the second opening 102 is defined by 
a peripheral edge 104. Each frame 100 includes a center rib 105 which 
includes weld beads (not shown). The frames 100 are designed to achieve a 
capacitor 10 which has two side-by-side capacitors cells which are 
discussed in greater detail hereinafter. The frames 100 are manufactured 
by an injection molding technique which utilizes a glass-filled, high 
density polyethylene. The individual frames 100, as are the rest of the 
synthetic components described herein, are constructed in accordance with 
conventional plastic manufacturing processing techniques. In view of the 
fact that the capacitor 10 of the present invention is manufactured of 
plastic, it is relatively lightweight as compared to the prior-art devices 
which have traditionally been manufactured from metal. In addition, and 
because many of the components of the capacitor 10 may be manufactured 
from a source of high density polyethylene, the several capacitor 
components are readily recyclable into products such as plastic lumber, 
plastic planters, traffic bumps, and other useful objects. 
Referring now to FIGS. 2, 3, and 7, mounted within the openings 101 and 
102, which are defined by the individual plastic frames 100, are 
individual carbon-filled, conductive electrode inserts which are 
designated generally by the numeral 120. The conductive electrode inserts 
120 are manufactured from a carbon-plastic combination, such as 
carbon-filled, high density polyethylene. Each carbon-filled conductive 
electrode insert has a first surface 121, an opposite second surface 122, 
and a peripheral edge 123. The peripheral edge 123 of each of the 
individual conductive electrode inserts 120 is secured to the peripheral 
edges 103 or 104 of one of the openings 101 or 102, respectively. The 
conductive electrode inserts 120 may be mounted, or otherwise secured in 
the individual frames 100 by infrared-type thermal welding or 
ultrasonic-type thermal welding, for example. Electrode inserts of desired 
characteristics may be constructed using the teachings of U.S. Pat. No. 
4,169,816, which is incorporated by reference herein. Electrode inserts 
useful in the present invention have a thickness in the range of about 
0.001 inches to about 0.005 inches. 
In addition, and as can best be seen by reference to FIG. 7, each 
carbon-filled conductive electrode insert 120 may have its outwardly 
facing surfaces 121 and 122 coated with active carbon particles. The 
carbon particles form a carbon coating 160. The carbon coating 160 
increases the surface area of the conductive electrode insert 120. The 
active carbon particles may be applied to the electrode insert surface by 
means of an adhesive. It has been found that an adhesive under the 
tradename Eccocoat 258A, available from Emerson and Cuming, and another 
adhesive under the product number #W101894-3, available from Advanced 
Polymer Concepts, are suitable adhesives. The adhesive may be applied 
manually by rolling, brushing, or spraying it on the surface of the 
electrode. The electrode insert is then placed in a tray filled with 
active carbon particles, or carbon powder, so that a layer of carbon 
particles, approximately 0.003 of an inch thick, is formed on each of the 
outwardly facing surfaces 121 and 122. In addition, the carbon powder may 
be sprinkled or sprayed on the surfaces 121 and 122. The carbon covered 
electrode insert is then placed in a heated press and the carbon particles 
are hot-pressed into the surfaces 121 and 122. A carbon powder suitable 
for forming the carbon coating of the present invention is available from 
the Calgon Carbon Corporation under the designation TOGLF 80.times.325. 
In addition to applying carbon particles, the surface area of the 
conductive electrode inserts may also be increased by laminating a high 
surface area carbon cloth to the respective surfaces 121 and 122. 
Structurally, each individual conductive electrode insert 120 may include a 
metal screen 140 which is embedded therein. In addition, a plastic screen 
170 may be mounted on either or both of the surfaces 121 and 122. As 
should be understood, two conductive electrode inserts 120, are 
individually mounted within each of the openings 101 and 102 and thereby 
form an electrode 180 (FIG. 3). Each capacitor 10 includes a plurality of 
electrodes 180 which are spaced a predetermined distance apart and are 
disposed in substantially parallel relation one to the other. 
As noted in the previous paragraph, the conductive electrode inserts 120 
may include various components and coatings. The most simple configuration 
of the present invention is shown in FIG. 9, where the conductive 
electrode inserts 120 consist only of a sheet of carbon plastic, or 
carbon-filled polyethylene. The conductive electrode inserts 120 may or 
may not include the carbon coating 160, the metal screen 140, or the 
plastic screen 170. The coating 160 and plastic screen 170 may be on 
either or both sides of the conductive electrode inserts 120. 
Preferably, about 98% of the area of the plastic screen 170 is open. The 
plastic screens help ensure uniform spacing between adjacent components of 
the capacitor. The screen has nodes at points where horizontal and 
vertical members of the mesh meet. The nodes have a thickness of about 
0.025 inches, thus with the screen in place a spacing of about 0.025 
inches is maintained between adjacent components. 
As can best be seen by further reference to FIG. 4, within the openings 101 
and 102 of a predetermined number of non-conductive frames 100 are mounted 
a plurality of microporous separators 200. The microporous separator 
inserts 200 are preferably manufactured from a material such as 
silica-filled, high density polyethylene. 
Each of the microporous separator inserts 200 has a first surface 201, an 
opposite second surface 202, and a peripheral edge 203. The peripheral 
edge 203 of any one of the microporous separator inserts 200 may be welded 
to one of the peripheral edges 103 or 104 of one of the openings 101 or 
102. As with the conductive electrode inserts 120, the microporous 
separator inserts 200 may be mounted in the frames 100 by thermal welding, 
or similar techniques. A plastic frame 100 having two microporous 
separator inserts 200, each of which is individually mounted within the 
openings 101 and 102, respectively, constitutes a single separator 220. 
The capacitor 10 of the present invention includes a plurality of 
separators 220 which are positioned in sandwiched relation between 
adjacent electrodes 180 or between one electrode 180 and a terminal 
electrode, discussed in further detail below. Separators useful in the 
present invention have a thickness in the range of about 0.001 inches to 
about 0.005 inches. As should be understood, the microporous separators 
are ion-selective membranes, and various ion-selective membranes known in 
the art may be mounted in the frames described above, or otherwise welded 
between adjacent electrodes 180. 
As can best be seen by reference to FIG. 2, a series of alternating 
electrodes 180 and separators 220 forms a cell stack 240. Thus, the 
capacitor 10 of the present invention has a multi-layer construction. The 
frames 100 of the electrodes 180 and separators 220 are joined, or 
otherwise sealed one to the other by vibration-type thermal welding, or by 
similar fastening techniques. 
Fastened to the stack 240 by a thermal welding technique, or the like, are 
two terminal electrodes which are designated generally by the number 260. 
As can best be seen by reference to FIGS. 5 and 7, a terminal electrode 
has a construction somewhat similar to the electrodes 180. In this regard, 
a terminal electrode 260 includes a non-conductive frame 100; two 
conductive electrode inserts 120; each of which is individually mounted in 
the opening 101 and 102 of the frame 100; and two metal screens 140, each 
of which is embedded in the individual conductive electrode inserts. Each 
metal screen acts as a current collector, and could, for example, take the 
form of a perforated metal sheet or other thin layer of conductive 
material. Electrically coupled to, and centrally positioned on each metal 
screen 140 is a metal stud terminal 300, which as described above is 
adapted to be received through the individual openings found in the 
endblocks. The metal screens 140 and metal stud terminals 300 are 
preferably made from copper. The metal stud terminals 300 provide a path 
through which electric charge may leave the capacitor 10. In addition, 
they provide points across which an electric potential may be applied in 
order to charge the capacitor 10. 
In an alternative embodiment, seen more clearly by reference to FIG. 2, 
conductive electrode inserts, each having a metal screen imbedded therein 
and a metal stud terminal which is electrically coupled to the metal 
screen, are mounted in the first and second rigid endblocks. Such 
endblocks function as terminal electrodes and, therefore, in a capacitor 
having such endblocks the necessity of having separate terminal electrodes 
is eliminated. 
As should be understood the endblocks 20 and 30; electrodes 180; separators 
220; and terminal electrodes are welded or fastened together to form a 
sealed case. As noted above, the capacitor 10 of the present invention may 
be constructed using thermal welding techniques. The method employed to 
construct a capacitor 10 is similar to the method of constructing the 
battery which is disclosed in U.S. Pat. No. 4,945,019, the specification 
of which is incorporated by reference herein. Adjacent components are 
welded together into a welding machine (not shown). The first weld is 
accomplished by placing an endblock in the lower fixture of a welding 
machine and placing a terminal electrode in the upper fixture of the 
machine. The lower fixture moves along a predetermined course of travel 
until physical contact is made between the two components. Vibration of a 
predetermined magnitude is imparted to the objects and a weld is achieved 
thereby. 
The process continues when the component in the upper fixture, which during 
the first weld is the terminal electrode, is disengaged and the lower 
fixture moves in a direction away from the newly welded component. Another 
component is then secured to the top fixture and the process is repeated. 
When the desired number of components are welded to the stack, which is 
located on the bottom fixture, an endblock is placed in the upper fixture 
and welded to the end of the stack to complete the process. Thus, the 
components of the capacitor 10 are welded together to form a fluid 
impervious and substantially leak-proof case. The components are welded in 
an alternating fashion as depicted in FIG. 2, wherein alternate layers of 
electrodes 180 and separators 220 make up the stack of cells 240. One of 
the key features of the present invention is the rib 105 of each of the 
frames 100. Each of the ribs divides the frame such that it has two or 
more openings. The ribs are welded together, providing structural strength 
at the center of each electrode and separator. This design helps reduce 
bowing or deformation of the electrodes and separators compared to a 
design where a single, large electrode or separator insert is mounted 
within a one-opening frame. In addition, the frame design and welding 
techniques eliminate the need to apply external pressure to the capacitor 
components as is the case with prior-art devices. 
The active area of a capacitor of the present design may be adjusted in two 
ways. First, the size of the electrode inserts may be varied. For example, 
an electrode having a width of about 9 inches and a length of about 10 
inches may be easily constructed. Electrodes of greater size can also be 
constructed. The larger the electrodes the greater the capacitance of an 
individual cell. Second, the number of electrodes may be adjusted by 
simply welding more components to the stack of cells. Capacitors having 
tens of cells can be readily and easily constructed. Accordingly, the 
capacitance of the capacitor is readily adjusted. Each cell is 
electrically coupled in series, therefore, the more cells the lower the 
capacitance of the capacitor. The total capacitance, C.sub.T, may 
determined according to the following equation: 
##EQU1## 
As can be best seen in FIG. 6, the capacitor 10 of the present invention 
includes a carbon paste 400 which is positioned between the electrodes 120 
and separators 200. The carbon paste 400 may be directly applied to the 
electrodes during the welding process. This step may be achieved by both 
automated and manual application techniques. 
The carbon paste 400 consists of a mixture of carbon powder and sulfuric 
acid. Various types of carbon powder have been found suitable for making 
the paste 400. Carbon powder under the tradename Carbon Black Pearls 2000 
may be mixed with sulfuric acid having a specific gravity of approximately 
1.85 in a ratio of about 86 percent acid to about 14 percent carbon 
powder, by weight, to form a suitable paste. Carbon powder under the 
tradename Osaka M-15 may be mixed in a ratio of about 72 percent acid to 
about 28 percent carbon, by weight, to form another suitable paste. 
As noted above, the carbon paste 400 is placed between the electrodes 180 
and separators 220 during the welding process. The paste may be run or put 
through a coining machine which rolls the paste into a flexible stratum of 
substantially uniform thickness. Preferably, the paste is about 0.002 
inches to about 0.050 inches thick. In order to improve the electrical 
contact between the paste 400 and the electrode inserts 120, and as was 
discussed above, the carbon coating 160 is applied to the surface of the 
electrode insert 120. It has been found that the presence of the carbon 
coating increases the capacitance of the capacitor, as is exemplified in 
the table below which compares the capacitance of two three-cell 
capacitors having 145 cm.sup.2 electrode inserts prepared with the carbon 
coating 160 on both surfaces of their electrode inserts and without the 
carbon coating 160. 
TABLE 1 
______________________________________ 
Effect of Applying Carbon Powder 
To The Paste/Plastic Interface 
On Capcitor Performance 
Discharge 
Capacitance Capacitance Percent 
Current w/o Carbon Layer 
w/Carbon Layer 
Increase 
(AMPS) (Farads) (Farads) (%) 
______________________________________ 
2 48.63 53.06 9.1 
6 47.65 53.57 12.4 
14 50.2 54.26 8.1 
20 51.95 58.33 12.3 
______________________________________ 
As should be understood, a paste-filled and operational capacitor 10 
includes two capacitor cells 420 and 425 (FIG. 1) due to the side-by-side, 
dual opening configuration of the frames 100. The capacitor cells 420 and 
425 are in side-by-side position to one another. Each capacitor cell is 
electrically isolated from the other. As should be understood charge flow 
through each cell is from end to end. In other words, during discharge, 
charge flows directly from one metal terminal stud positioned in the end 
block 20, through a load, and then to the corresponding metal terminal 
stud in the end block 30. Of course, charge flows in the opposite 
direction during charge. Thus, the capacitor 10 includes two parallel 
current paths 426 and 428 (FIG. 2). 
Initially, the capacitor 10 of the present invention is uncharged, that is, 
when first constructed the capacitor 10 holds no electric energy. The 
capacitor 10 may charged by applying an electric voltage across its 
terminal studs. In particular, each cell 420 and 425 may be charged by 
applying a voltage across the metal stud terminals. In order to charge the 
cell 420 of the capacitor 10 a voltage must be applied across the metal 
stud terminal positioned in the end block 30 and the metal stud terminal 
in the end block 20. Likewise, a voltage must be applied across the two 
metal stud terminals of the cell 425. Once charged, the capacitor may be 
allowed to hold its charge, or the capacitor 10 may be discharged by 
appropriately coupling a load to the metal stud terminals. 
In a double-layer capacitor, such as the one of the present invention, it 
is important that the active materials and components, that is the carbon 
paste and electrodes, be kept under substantially uniform compression. For 
example, when two components of the capacitor 10 are joined by a thermal 
weld, the components are compressed evenly and uniformly while the weld is 
being made. In the welding process, the welding machine itself does the 
compression. Under some circumstances the parts may be compressed in a 
jig. Once the weld is made, the parts stay in compression, thereby 
assuring proper electrical contact between the carbon paste and the 
individual electrodes. Typically, components are welded together under a 
compression pressure in a range of about 50 to about 200 lbs per square 
inch. 
Accordingly, the construction of the present invention results in a 
capacitor which has extremely low internal resistance. In addition, the 
components are welded in a manner where they are substantially 
hermetically sealed to each other. Accordingly, the capacitor 10 of the 
present invention, as noted earlier, is substantially leak-proof because 
there are no seals through or around which a fluid may flow. In addition, 
the capacitor 10 of the present invention is made substantially leak-proof 
because the high density polyethylene components are highly corrosion 
resistant. 
OTHER EMBODIMENTS 
The frames 100 may be of various geometric configurations. Thus, a frame 
having one, two, three, four, or more openings could be manufactured and 
subcomponents, such as electrode inserts and separators, could be mounted 
therein. 
In a second embodiment of the present invention, the frame 100 includes 
three openings and two ribs 440 so as to permit the construction of a 
three-cell capacitor. A terminal electrode 450 for a three-cell capacitor 
is shown in FIG. 11. 
A third embodiment of the present invention is shown in FIGS. 10, 12, and 
13. In the third embodiment, the frame 100 includes four openings and four 
ribs 460 so as to permit the construction of a four-quadrant capacitor 
having four capacitor cells. A terminal stud of terminal electrode 500 of 
the four-quadrant capacitor may be electrically coupled by means, for 
example, of a metal bus bar to another terminal stud of the same 
electrode. The terminal electrodes may be electrically coupled so as to 
electrically couple the capacitor cells in parallel, as in FIG. 12, or in 
series as in FIG. 13. The choice of parallel or series coupling depends on 
the voltage and capacitance desired from the capacitor. In order to couple 
the cells of the four-quadrant capacitor in parallel, the connections 
shown in FIG. 12 would be the same for the terminal electrode at the 
opposite end of the capacitor. In order to couple the cells in series, 
there is a bus bar connection between two terminal studs of the terminal 
electrode of the opposite end of the capacitor as shown in phantom lines 
in FIG. 13. 
OPERATION 
In summary, the capacitor 10 of the present invention includes a plurality 
of electrodes and separators. Further, the electrodes and separators are 
oriented or otherwise disposed in alternating succession and further have 
a carbon paste placed therebetween. A large number of capacitor cells may 
be incorporated into a single capacitor. Proportionally greater voltage 
can be achieved in capacitors having 50 to 60 or more cells. Such 
capacitors would have usefulness for SLI applications in which previous 
capacitors were unsuitable. In addition, the size of the electrode inserts 
may be relatively large. Therefore, a high farad capacity may be achieved. 
As can be seen from Table 1, a relatively small, three cell capacitor of 
the present invention has a capacitance of about 53 to 58 farads. 
Thus, the present invention provides a new and novel capacitor which is 
manufactured from a corrosion resistant material such as plastic, which 
further is of a gasket-free design, and which avoids the problems 
attendant with the prior-art practice of applying external pressure to 
these same assemblies. In particular, the present invention provides a 
capacitor having relatively low internal resistance, and a high farad 
capacity. The present invention also provides a capacitor that is 
lightweight in relative comparison to the prior-art assemblies. The 
present invention also provides a capacitor which is substantially 
leak-free and corrosion resistant. Lastly, the present invention provides 
a capacitor which is easy to dispose of once it has reached the end of its 
life cycle and which is made from recyclable materials. It is to be 
understood that the invention is not confined to the particular 
construction and arrangement of the components herein illustrated and 
described, but embraces such modified forms thereof as come within the 
scope of the following claims.