Abstract:
An ultracapacitor energy storage cell pack including an ultracapacitor assembly including a plurality of ultracapacitors in series; a plurality of interconnections for mechanically and electrically interconnecting the ultracapacitors; and a plurality of balancing resistors, each balancing resistor in parallel with each ultracapacitor to form a resistor divider network that automatically discharges and equalizes each ultracapacitor over time, thereby balancing the ultracapacitors of the ultracapacitor assembly, and each balancing resistor directly mechanically and electrically connected to an associated interconnection.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This patent application is a continuation-in-part of U.S. patent application Ser. No. b  11 / 460 , 738 , filed Jul. 28, 2006, which is a continuation of U.S. patent application Ser. No. 10/720,916, filed Nov. 24, 2003, issued as U.S. Pat. No. 7,085,112 on Aug. 1, 2006, which is a continuation-in-part application of U.S. patent application Ser. No. 09/972,085, filed Oct. 4, 2001, issued as U.S. Pat. No. 6,714,391 on Mar. 30, 2004. These applications/patents are incorporated by reference herein as though set forth in full. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The field of the invention relates to a high-voltage, high-power ultracapacitor energy storage pack composed of a large number of serially connected individual low-voltage ultracapacitor cells that store an electrical charge.  
       BACKGROUND OF THE INVENTION  
       [0003]     The connecting together of individual battery cells for high-voltage, high-energy applications is well known. However, the chemical reaction that occurs internal to a battery during charging and discharging typically limits deep-cycle battery life to hundreds of charge/discharge cycles. This characteristic means that the battery pack has to be replaced at a high cost one or more times during the life of a hybrid-electric or all-electric vehicle. Batteries are somewhat power-limited because the chemical reaction therein limits the rate at which batteries can accept energy during charging and supply energy during discharging. In a hybrid-electric vehicle application, battery power limitations restrict the drive system efficiency in capturing braking energy through regeneration and supplying power for acceleration.  
         [0004]     Ultracapacitors are attractive because they can be connected together, similar to batteries, for high-voltage applications; have an extended life of hundreds of thousands of charge/discharge cycles; and can accept and supply much higher power than similar battery packs. Although ultracapacitors are typically more expensive than battery packs for the same applications and cannot store as much energy as battery packs, ultracapacitor packs are projected to last the life of the vehicle and offer better fuel-efficient operation through braking regeneration energy capture and supplying of vehicle acceleration power.  
         [0005]     During charging and discharging operation of the ultracapacitors, parasitic effects cause the cell temperature to increase. Cooling is required to minimize increased temperature operation that would degrade the energy storage and useful life of each ultracapacitor.  
         [0006]     Low-voltage energy cells, batteries, or ultracapacitors are connected in series to obtain high-voltage energy storage. Because of variations in materials and manufacturing, energy storage cells are not perfectly matched. As the serially connected pack operates through multiple charge and discharge cycles, the cell differences cause the energy storage to become more and more imbalanced among the cells. The energy storage imbalance from cell to cell limits the performance of the overall pack and can shorten the life of the individual cells.  
         [0007]     Packs of batteries and packs of ultracapacitors have been built in various forms and configurations. Various different wiring harnesses, bus bars, and connections have been used for current routing and voltage monitoring. Various different types of circuits for charging, discharging, and equalizing have also been built. Energy storage cells have been mounted in various “egg crate” or “wine rack” style vertical and horizontal support structures. High-voltage packages contain batteries enclosed within a single pack. Batteries have even been connected together by simply touching under some pressure the positive end of one battery against the negative end of another battery such as can be found in flashlights, small toys and appliances. High-energy packs usually include some form of convection air or liquid cooling.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention involves an ultracapacitor high-energy storage pack with structural support, environmental protection, automatic cooling, electrical interconnection of the ultracapacitors, remote ON/OFF switching, a safety pre-charge circuit, a safety and automatic equalizing discharge circuit, a programmable logic controller, a digital interface to a control area data network for control and status reporting, and an optional fire sensing and suppression system. The pack is ideal for high-voltage, high-power applications of electric and hybrid-electric vehicle propulsion systems, fixed site high-power load averaging, and high-power impulse requirements. The pack is housed in an aluminum box enclosure with a detachable access lid. The inside of the box has a thick anti corrosion, electrically insulating coating. The box has holes cut out for the mounting of cooling fans, air intakes, and electrical connections. The air intake cutouts have provision for mounting external replaceable air filters that can be serviced without opening the box. Mounted to the interior of the box are aluminum guide support strips for three plastic crate support plates. Plastic, as a non-conductive material, provides for the safe operation of the high-voltage connections. Two of the plastic crate plates have wine rack type hole cutouts that form the support structure for individual cylindrical ultracapacitor cans and the third plastic crate plate has pre mounted bus bars and smaller holes for fastening bolts. The first two plastic crate plates structurally support and separate the ultracapacitors to provide space for cooling airflow along the direction of the plates. The third crate plate supports and positions the cans by the threaded end terminals that are bolted to the plate. Bus bars are fastened to the inside of the third crate plate to provide connections between adjacent rows of ultracapacitors. The cans, which are arranged in rows of three, are electrically and structurally connected together with threaded studs and bus bars.  
         [0009]     In an aspect of the invention, the triple can connections are arranged four rows deep and twelve rows along the top to efficiently package one-hundred and forty four ( 144 ) cylindrically shaped ultracapacitor cans with threaded polarized connections at each end of the can. For different design requirements, the longitudinal dimension of the box may be shortened or lengthened to respectively delete or add one or more layers of twelve ( 12 ) ultracapacitors. Similarly, the depth dimension of the box may be shortened or lengthened to respectively delete or add a layer of thirty-six ( 36 ) ultracapacitors. Again similarly, the width dimension of the box may be shortened or lengthened to respectively delete or add a layer of forty-eight ( 48 ) ultracapacitors.  
         [0010]     In addition to the ultracapacitors, the box houses and has mounting provision for other electrical components. Temperature sensors and controllers switch the forced-air cooling fans on and off for thermal management of the ultracapacitor environment. A pre-charge resistor is automatically switched in series with the power charge circuit when first turned on to prevent overloading the charging energy source. High-power relays called contactors provide remote controlled switching of the energy storage pack into and out of the charge and load circuits. An integral Control Area Network (CAN) controller is connected to multiple pin electronics connectors to report status parameters and control the switching of the energy storage pack through a CAN digital data network. The pack also contains integral Ground Fault Interrupter (GFI) and fire sensing automatic safety shutoff systems.  
         [0011]     Finally, a balancing or drain resistor is mounted in parallel around each ultracapacitor to safely discharge the pack to an inactive state over a period of time. This periodic discharge function also serves to equalize all the ultracapacitors energy storage to a balanced condition.  
         [0012]     A further aspect of the invention involves an ultracapacitor energy storage cell pack including an ultracapacitor assembly having a plurality of parallel ultracapacitors and balancing resistors in series, each balancing resistor in parallel with each ultracapacitor to form a resistor divider network that automatically discharges and equalizes each ultracapacitor over time, thereby balancing the ultracapacitors of the ultracapacitor assembly; an enclosure to enclose and protect the ultracapacitor assembly; a controller for the ultracapacitor assembly; one or more temperature sensors to monitor temperature of the ultracapacitor assembly and coupled to the controller; a pack voltage sensor to monitor voltage of the ultracapacitor assembly and coupled to the controller; a GFI sensor to monitor for a ground fault interrupt condition of the ultracapacitor assembly and coupled to the controller; one or more cooling fans carried by the enclosure and controlled by the controller to cool the ultracapacitor assembly based upon temperature sensed by the one or more temperature sensors; an on/off relay coupled to the ultracapacitor assembly and the controller, the on/off relay activated by the controller during normal operation of the ultracapacitor assembly and deactivated by the controller when the GFI sensor detects a ground fault interrupt condition, when the one or more temperature sensors detect an over-temperature condition, or when the pack voltage sensor detects an over-voltage condition; and a pre-charge resistor and a pre-charge relay coupled to the ultracapacitor assembly and the controller, the pre-charge relay activated by the controller to cause the pre-charge resistor to limit pack charge current until the ultracapacitor assembly reaches a minimum voltage.  
         [0013]     Another aspect of the invention involves a method of using an ultracapacitor energy storage cell pack including the steps of providing an ultracapacitor energy storage cell pack including a ultracapacitor assembly having a plurality of parallel ultracapacitors and balancing resistor in series, each balancing resistor in parallel with each ultracapacitor to form a resistor divider network that automatically discharges and equalizes each ultracapacitor over time, thereby balancing the ultracapacitors of the ultracapacitor assembly and assuring a safe condition for service personnel; an enclosure to enclose and protect the ultracapacitor assembly; a controller for the ultracapacitor assembly; one or more temperature sensors to monitor temperature of the ultracapacitor assembly and coupled to the controller; a pack voltage sensor to monitor voltage of the ultracapacitor assembly and coupled to the controller; a GFI sensor to monitor for a ground fault interrupt condition of the ultracapacitor assembly and coupled to the controller; one or more cooling fans carried by the enclosure and controlled by the controller to cool the ultracapacitor assembly based upon temperature sensed by the one or more temperature sensors; an on/off relay coupled to the ultracapacitor assembly and the controller, the on/off relay activated by the controller during normal operation of the ultracapacitor assembly and deactivated by the controller when the GFI sensor detects a ground fault interrupt condition, when the one or more temperature sensors detect an over-temperature condition, or when the pack voltage sensor detects an over-voltage condition; and a pre-charge resistor and a pre-charge relay coupled to the ultracapacitor assembly and the controller, the pre-charge relay activated by the controller to cause the pre-charge resistor to limit pack charge current until the ultracapacitor assembly reaches a minimum voltage; automatically discharging the ultracapacitors of the ultracapacitor energy storage cell with the balancing resistors to balance ultracapacitors of the ultracapacitor assembly and assure a safe condition for service personnel; cooling the ultracapacitor assembly with the one or more cooling fans based upon temperature sensed by the one or more temperature sensors; activating the on/off relay with the controller during normal operation of the ultracapacitor assembly and deactivating the on/off relay with the controller when the GFI sensor detects a ground fault interrupt condition, when the one or more temperature sensors detect an over-temperature condition, or when the pack voltage sensor detects an over-voltage condition; and activating the pre-charge relay with the controller to cause the pre-charge resistor to limit pack charge current until the ultracapacitor assembly reaches a minimum voltage.  
         [0014]     An additional aspect of the invention involves an ultracapacitor energy storage cell pack including an ultracapacitor assembly having a plurality of ultracapacitors in series; a plurality of interconnections for mechanically and electrically interconnecting the ultracapacitors; and a plurality of balancing resistors, each balancing resistor in parallel with each ultracapacitor to form a resistor divider network that automatically discharges and equalizes each ultracapacitor over time, thereby balancing the ultracapacitors of the ultracapacitor assembly, and each balancing resistor directly mechanically and electrically connected to an associated interconnection.  
         [0015]     One or more implementations of the aspect invention described immediately above includes one or more of: the plurality of interconnections include a plurality of generally rectangular block-shaped bus bars; each bus bar includes a side with one or more taps, and the balancing resistor is directly mechanically and electrically connected to the bus bar interconnection at the one or more taps on the side of the bus bar; and/or a screw and ring terminal directly mechanically and electrically connects the balancing resistor to the bus bar interconnection.  
         [0016]     Another aspect of the invention involves an ultracapacitor energy storage cell pack including an ultracapacitor assembly having a plurality of ultracapacitors in series, the ultracapacitors including ends with end terminals having male externally threaded studs; a plurality of interconnections for mechanically and electrically interconnecting the ultracapacitors; an end support plate having a pattern of holes to receive the male externally threaded studs of the ultracapacitors; and a fastening arrangement for mounting the end support plate and the interconnections to the end terminals so that the interconnections are mechanically and electrically directly connected to the end terminals, and the interconnections are disposed between the end support plate and the ends of the ultracapacitors.  
         [0017]     One or more implementations of the aspect invention described immediately above includes one or more of: the fastening arrangement includes bus bars with a holes therethrough for receiving the male externally threaded stud of the ultracapacitors, the end support plate with the holes therethrough for receiving the male externally threaded stud of the ultracapacitors, and internally threaded fasteners for threadably engaging the male externally threaded studs of the ultracapacitors; and/or wave washers are disposed between at least part of the internally threaded fasteners and the end support plate.  
         [0018]     Another aspect of the invention involves an ultracapacitor energy storage cell pack including an ultracapacitor assembly including a plurality of parallel ultracapacitors and balancing resistors in series, each balancing resistor in parallel with each ultracapacitor to form a resistor divider network that automatically discharges and equalizes each ultracapacitor over time, thereby balancing the ultracapacitors of the ultracapacitor assembly; two or more wine rack style support plates with hole cut outs to locate and support each ultracapacitor; electrical and mechanical connections between each ultracapacitor; an enclosure to enclose and protect the ultracapacitor assembly; one or more temperature sensors to monitor temperature of the ultracapacitor assembly; a pack voltage sensor to monitor voltage of the ultracapacitor assembly; a ground fault isolation sensor to monitor for a ground fault condition of the ultracapacitor assembly; a cooling system to cool the ultracapacitor assembly; and an on/off relay coupled to the ultracapacitor assembly and an external control input, the on/off relay activated during normal operation of the ultracapacitor assembly and deactivated by the external control input to terminate normal operation.  
         [0019]     One or more implementations of the aspect invention described immediately above includes one or more of: the pack includes a controller either internal or external to the enclosure; the controller is coupled to one or more of a pack temperature sensor(s), a pack voltage sensor, a ground fault isolation sensor, a fire sensor, a fire suppression sensor, a cooling system control input, an on/off relay control input, and a precharge resistor control relay input; the controller includes an algorithm to control one or more of the cooling system, precharge resistor control relay input, and on/off relay from one or more of pack temperature sensor input, voltage sensor input, ground fault isolation input, fire sensor input, and fire suppression input; the controller includes one or more algorithms for monitoring and reporting the sensor inputs to the control network interface, and includes one or more algorithms for controlling the cooling system, precharge resistor control relay input, and on/off relay in response to commands from the network interface; the cooling system is a forced air refrigeration unit; and/or the cooling system is an liquid cooled cold plate attached to one or more external surfaces of the enclosure.  
         [0020]     One or more implementations of the aspect invention described immediately above may include threaded electrical connections between each capacitor and the threaded connections may include a liquid, paste, or gel to enhance the electrical and thermal conductivity, and/or protect against corrosion and thread connection loosening.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]     The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the principles of this invention.  
         [0022]      FIG. 1  is an exploded perspective view drawing of an embodiment of a half module of an ultracapacitor energy storage cell pack.  
         [0023]      FIG. 2  is a perspective view of an embodiment of an ultracapacitor energy storage cell pack.  
         [0024]      FIG. 3  is a top plan view of an embodiment of a circuit board for the half module illustrated in  FIG. 1  and ultracapacitor energy storage cell pack illustrated in  FIG. 2 .  
         [0025]      FIG. 4  is an exploded perspective view of an alternative embodiment of a ultracapacitor energy storage cell pack.  
         [0026]      FIG. 5  is an exploded perspective view of the ultracapacitors and support plates of the ultracapacitor energy storage cell pack of  FIG. 4 .  
         [0027]      FIG. 6  is perspective detail view taken of detail  6  of the ultracapacitors, threaded interconnections between the ultracapacitors, and parallel drain resistors mounted with ring terminals of the ultracapacitor energy storage cell pack of  FIG. 5 .  
         [0028]      FIG. 7  is a side-elevational view of an embodiment of a middle support plate of the ultracapacitor energy storage cell pack illustrated in  FIG. 4 , and the middle support plate is shown with cutouts for the ultracapacitors and the drain resistors.  
         [0029]      FIG. 8  is a side-elevational view of an embodiment of an end support plate of the ultracapacitor energy storage cell pack illustrated in  FIG. 4 , and the end support plate is shown with cutouts for the mounting bolts and the support guide mounting rivets.  
         [0030]      FIG. 9  is a block diagram of the ultracapacitor energy storage cell pack illustrated in  FIG. 4 .  
         [0031]      FIG. 10  is a partial perspective view of another embodiment of a ultracapacitor energy storage cell pack.  
         [0032]      FIG. 11  is a perspective view on an embodiment of a bus bar interconnection of the ultracapacitor energy storage cell pack of  FIG. 10 .  
         [0033]      FIG. 12  is an exploded side elevational view of an embodiment of a fastening arrangement for one side of a ultracapacitor energy storage cell pack.  
         [0034]      FIG. 13  is a side elevational view of the fastening arrangement of  FIG. 12  shown in an assembled configuration. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0035]     With reference to  FIGS. 1 and 2 , an embodiment of an ultracapacitor energy storage cell pack  10  will now be described.  FIG. 1  illustrates an exploded view of an embodiment of a half module  15  of the ultracapacitor energy storage cell pack  10 .  FIG. 2  illustrates an embodiment of an assembled ultracapacitor energy storage cell pack module  10 , which includes two half modules  15  fastened together. Although each half module  15  preferably includes eighty ultracapacitors  20 , each half module may have other numbers of ultracapacitors  20 . Further, the ultracapacitor pack  10  may have other numbers of modules  15  besides a pair (e.g., 1, 3, 4, etc.).  
         [0036]     The ultracapacitor pack  10  is shown in exploded view in  FIG. 1  to illustrate the different levels in the half module  15  that are added during assembly of the half module  15 . Each of these levels will now be described in turn below followed by a description of the assembly process.  
         [0037]     An aluminum base plate  25  forms a bottom or inner-most level of the half module  15 . The base plate  25  includes a welded frame  30  around edges of the base plate  25 .  
         [0038]     A polycarbonate crate plate  35  is seated inside the frame  30  and includes cutouts or holes  40  with a shape that matches the cross-section of the ultracapacitors  20 . The base plate  25  and crate cutouts  40  form an x, y, and z location and mounting support for the ultracapacitors  20 . The cutouts  40  also prevent the ultracapacitors  20  from rotating during use, e.g., mobile vehicle use.  
         [0039]     In the embodiment shown, the individual ultracapacitors  20  have a general square-can shape (i.e., rectangular parallelpiped). The cross-section of the ultracapacitors  20  is 2.38 in. by 2.38 in. and the length is about 6 in. On an upper-most or outer-most end of the ultracapacitor  20 , two threaded lug terminals  45  and a dielectric paste fill port  50  protrude from an insulated cover  55  of the ultracapacitor  20 . The cover  55  of the ultracapacitor may include a well encircled by a protruding rim. Shrink plastic that normally surrounds sides or exterior capacitor casing  60  of the ultracapacitor  20  is removed to better expose the exterior casing  60  to circulated cooling air. The shrink plastic may be left on the bottom of the ultracapacitor  20 .  
         [0040]     A box frame  65  ties together the base plate  25  and frame  30  with circuit boards  70 , and a top polycarbonate cover  75 . The box frame  65  has elongated lateral cutouts  80  on two opposing sides to provide for cross-flow air cooling. Bottom flanges  85  provide a mounting surface to tie two of these box frames  65 , and, hence, two half modules  15 , together to form the single ultracapacitor pack module  10  shown in  FIG. 2 . The box frame  65  includes a large upper rectangular opening and a large lower rectangular opening.  
         [0041]     The next layer is a first ¼-in. foam rubber insulating and sealing sheet  90  that covers the ultracapacitors  20 . The first sheet  90  has cutouts for the ultracapacitor terminals  45  and fill port  50  so that the sheet  90  can seal tightly against the cover  55  of the ultracapacitor  20 .  
         [0042]     A second ⅛-in. foam rubber insulating and sealing sheet  95  may be placed on top of the previous first sheet  90 . The second sheet  95  includes rectangular cutouts or holes  100 . The cutouts  100  receive copper bar electrical interconnections  105 . The cutouts  100  in the sheet  95  simplify the assembly and proper placement of the copper bar electrical interconnections  105 . The sheet  95  also seals the copper bar electrical interconnections  105 . The copper bar electrical interconnections  105  include holes that the ultracapacitor terminals  45  protrude through.  
         [0043]     Two identical main circuit boards  70  (e.g., 40-ultracapacitor main circuit boards) may lay on top of the foam rubber sheets  90 ,  95 . With reference additionally to  FIG. 3 , each main circuit board  70  may include holes  107  that the ultracapacitor terminals  45  protrude through. In the embodiment shown, each circuit board  70  may have mounting holes  107  for 40 (8 by 5) ultracapacitors less two corner positions required for frame structure mounting. Instead of two circuit boards  70 , a single circuit board  70  may be used. Thus, as used herein, the word “circuit board” means one or more circuit boards. Fasteners such as lug nuts fasten the individual ultracapacitor terminals  45  and copper bars  105  to the circuit boards  70  and compress the foam rubber sheets  90 ,  95  in between the cover  55  of the ultracapacitor  20  and the circuit boards  70 . Thus, the circuit board  70  forms the location and mechanical support as well as the electrical connections for the ultracapacitors  20 . The foam sheets  90 ,  95  seal around the rim of the ultracapacitor terminals  45 . A processor and display circuit board mounts on top of the main circuit board  70 .  
         [0044]     Although the ultracapacitor pack  10  and the half modules  15  are shown as being generally rectangular in shape, either or both may have shapes other than generally rectangular such as, but not by way of limitation, circular, oval, other curvilinear shapes, other rectilinear shapes, and other polygonal shapes.  
         [0045]     A top aluminum frame  110  and the transparent polycarbonate cover  75  may attach to the frame structure to complete the half module  15 . The transparent cover  75  allows observation of a light emitting diode (LED) failure detection display that indicates the active/inactive status of the ultracapacitors  20 .  
         [0046]     Together, the bottom base plate  25 , crate plate  35 , box frame  65 , sealing sheets  90 ,  95 , and circuit board(s)  70 , and ultracapacitor terminal fasteners form an ultracapacitor mounting assembly  112  for the ultracapacitors  20 . The ultracapacitor mounting assembly  112  provides a mounting surface for the copper bar interconnects  105 , maintains the position and spacing of the ultracapacitors  20  in the X, Y and Z directions, does not allow the ultracapacitors to rotate when connected, and the main circuit board(s)  70  provides a mounting platform for the cell equalization, failure detection, processor, and LED display systems. Attaching the ultracapacitors  20  to the mounting assembly  112  by the terminals  45  instead of the exterior ultracapacitor casing  60  allows the ultracapacitors  20  to be more effectively cooled because the majority of the surface area of the ultracapacitors  20  is in the cooling air stream supplied by the cross-flow air cooling assembly  115 . Sealing along the cover  55  and around the terminals  45  protects the terminals  45  from water, dust, and other contaminants.  
         [0047]     An exemplary method of assembling the ultracapacitor half module  15  will now be described. The ultracapacitors  20  are first placed onto the bottom base plate  25 , with the bottoms of the ultracapacitors  20  extending through the square cutouts  40  of the crate plate  35 . The box frame  65  is applied over the ultracapacitors  20 , so that the ultracapacitors extend through the large lower and upper rectangular openings of the box frame  65 . The ¼-in. foam rubber insulating and sealing sheet  90  is placed on top of the ultracapacitors  20 , with the ultracapacitor terminals  45  and fill port  50  protruding through cutouts in the sheet  90 . The ⅛-in. foam rubber insulating and sealing sheet  95  is placed on top of the previous sheet  90  and the copper bar electrical interconnections  105  are placed into the rectangular cutouts  100  of the sheet  95 . The ultracapacitor terminals  45  also protrude through holes in the copper bar electrical interconnections  105 . The main circuit boards  70  are layered on top of the foam rubber sheets  90 ,  95  so that the threaded ultracapacitor terminals  45  protrude through the corresponding holes in the circuit boards  70 . Lug nuts are screwed onto the threaded terminals  45 , compressing the foam rubber sheets  90 ,  95  in between the cover  55  of the ultracapacitor  20  and the circuit boards  70 , and securing the ultracapacitors  20  and copper bars  105  in position. The processor and display circuit board is mounted on top of the main circuit board  70 . The top aluminum frame  110  and the transparent polycarbonate cover  75  are placed over the circuit boards and attached to the frame structure to complete the half module  15 . A pair of half modules  15  may be positioned back to back (i.e., facing opposite directions with the bottoms of the aluminum base plates  25  touching) and a cross-flow air cooling assembly  115  may be attached to the frame structure, adjacent the elongated lateral cutouts  80  on one side of the box frames  65 . The half modules  15  may be bolted or otherwise fastened together at the respective bottom flanges  85  to complete the ultracapacitor pack module  10 .  
         [0048]     To determine if one or more ultracapacitors  20  in the pack  10  need to be replaced, a user observes the light emitting diode (LED) failure detection display through the transparent cover  75 . The LED failure detection display includes an array of LEDs that correspond to the array of ultracapacitors  20 , each LED indicating the status of a corresponding ultracapacitor  20 . Each unlit LED indicates a corresponding failed LED. An ultracapacitor  20  in the pack  10  can quickly and easily be replaced by simply unfastening the frame and unbolting only the failed ultracapacitor  20  that had been previously identified by the LED display. The replacement ultracapacitor is put into position and the procedure reversed.  
         [0049]     With reference to  FIGS. 4-9 , and initially,  FIGS. 4 and 5 , an ultracapacitor energy storage cell pack (hereinafter “ultracapacitor pack”)  200  constructed in accordance with another embodiment of the invention will now be described. The ultracapacitor pack  200  includes a ultracapacitor cell and wine rack style crate support assembly (hereinafter “ultracapacitor assembly”)  210 , an ultracapacitor pack box enclosure (hereinafter “box enclosure”)  220 , a metal lid  230 , an air filter bracket  240  (w/air filter), cooling fans  250 , fan finger guards  260 , high-power precharge resistor  270 , Programmable Logic Controller module (hereinafter “PLC”)  280 , high power relays (kilovac contactors)  290 , electrical connectors  300 ,  310 ,  320  and other discrete components mounted within the box enclosure  220 .  
         [0050]     The ultracapacitor assembly  210  includes one-hundred and forty-four (144) ultracapacitors  330  connected in series to provide a nominal 360 volts DC, 325 watt-hours energy storage. The value of each ultracapacitor  330  is 2600 Farads. In alternative embodiments, the ultracapacitor assembly  210  may have other numbers of ultracapacitors, different types of ultracapacitors, and/or an overall different amount of voltage and/or power. Each ultracapacitor  330  is connected with a parallel balancing and drain discharge resistor  340  ( FIG. 6 ). The ultracapacitor assembly  210  includes a first wine rack middle crate support plate  350 , a similar second wine bottle rack type middle crate support plate  360 , and a wine bottle rack type end crate support plate  370  for supporting the ultracapacitors  330 .  
         [0051]     The box enclosure  220  is preferably made of metal and includes square end cutouts  380  in rear wall  382  to accommodate air flow therethrough and circular cutouts  390  in front wall  392  to accommodate the cooling fans  250 . The front wall  392  and rear wall  382  are joined by opposite parallel side walls  394 . The filter(s) of the air filter bracket  240  is externally serviceable and fits over the square cutouts  380  of the rear wall  382 . The interior of the box enclosure  220  and underside of the lid  230  is coated with a thick material that provides electrical insulation and corrosion protection as an additional level of safety for the box enclosure  220 . The inner bottom of the box enclosure  220  includes support plate guides for mounting the wine rack middle support plates  350 ,  360  and end support plate  370 .  
         [0052]      FIG. 5  shows an exploded view of the ultracapacitor assembly  210 . The ultracapacitors  330  are cylindrical canisters with aluminum female threaded connections at each end, which receive male threaded aluminum interconnection studs  400  for connecting the ultracapacitors  330  in series. Aluminum bus bars  410  and aluminum interconnection washers are also used to interconnect the ultracapacitors  330  in series at the ends of the rows. Providing electrical connections made of aluminum metal prevents any corrosive galvanic effects from dissimilar metals. Optionally, the threaded connections are covered with a silicon dielectric grease to prohibit environmentally caused corrosion or with other liquid, paste, or gel grease to enhance the electrical and thermal conductivity, and/or protect against corrosion and loosening of the threaded connection.  
         [0053]     The wine bottle rack type middle crate support plates  350 ,  360  and end crate support plate  370  are made of nonconductive plastic material to prevent any high-voltage arcing or other high-voltage leakage effects that could occur over time due to vibration and shock. The wine rack style middle crate support plates  350 ,  360  and end crate support plate  370  are different in construction to allow ease of assembly and replacement of any canister row.  
         [0054]     With reference to  FIG. 7 , the wine bottle rack type middle support plates  350 ,  360  include a pattern of generally circular cutouts  430  for receiving the ultracapacitors  330 . The cutouts  430  include an additional semi-circular recess  440  to accommodate and support the body and leads of the individual drain resistors  340 . The balancing and discharging drain resistors  340  are preformed with ring terminals  442  ( FIG. 6 ) attached to leads of the drain resistors  340  for simplicity of mounting and electrical connection. Additional semi-circular recesses  450  along a top edge  460  and bottom edge  470  of the wine bottle rack type middle crate support plates  350 ,  360  provide clearance for the attaching rivets of support guides on a bottom of box enclosure  220  and the lid  230 . The wine bottle rack type middle crate support plates  350 ,  360  are made of 3/16′ thick polycarbonate plastic for strength and electrical insulation.  
         [0055]     With reference to  FIG. 8 , the wine bottle rack type end crate support plate  370  includes a pattern of circular holes  480  for receiving threaded bolt fasteners for mounting the ultracapacitors  330 . Additional semi-circular recesses  490  along a top edge  500  and a bottom edge  510  of the wine bottle rack type end crate support plate  370  provide clearance for the attaching rivets of support guides on a bottom of the box enclosure  220  and the lid  230 . The wine bottle rack type end crate support plate  370  is made of 3/16′ thick Grade G-10/FR4 Garolite glass fabric laminate with an epoxy resin that absorbs virtually no water and holds its shape well. Inside-mounted aluminum bus bars  410  are affixed in place to the wine rack end crate support plate  370  with silicon RTV (Room Temperature Vulcanizing, which is a common jelly-like paste that cures to a rubbery substance used in various applications as adhesive and/or sealer). The bus bars  410  are pre-positioned to avoid confusion that could cause assembly mistakes.  
         [0056]      FIG. 9  is a general block diagram of the ultracapacitor pack  200 . As indicated above, each ultracapacitor  330  is connected in parallel with the drain resistor  340 . One-hundred and forty-four (144) of these parallel connections are connected in series to provide a nominal 360 volts DC, 325 watt-hours energy storage. The value of each ultracapacitor  330  is 2600 Farads and the value and power of the drain resistor  340  is selected to completely discharge the ultracapacitor  330  over a number of hours during an inactive period of the ultracapacitor pack  200 . The balancing drain resistors form a resistor divider network to equalize each ultracapacitor and balance the pack assembly. The energy drain action is slow enough so as not to interfere with the normal operation of the ultracapacitor pack  200 . The discharge is also slow enough so as not to cause any significant temperature increase from the drain resistors  340  within the ultracapacitor pack  200 . The chemical composition of the ultracapacitor  330  allows charge to build up across the ultracapacitor  330  over a period of time after the ultracapacitor  330  is shorted and left open. The drain resistors  340  allow a safe discharge of the high voltage of the ultracapacitor pack  200  to eliminate any shock danger from the ultracapacitor “memory” to personnel servicing the ultracapacitor pack  200 .  
         [0057]     Because the ultracapacitors  330  can accept hundreds of amperes of electrical current during charging, a connection to an energy source would appear as a short circuit to the energy source. To accommodate this problem, a high-power pre-charge resistor  270  with its own heat sink is mounted inside the box enclosure  220  and used to limit the initial charging current. Based on input to a pack voltage sensor  520 , the PLC  280  controls a pre-charge contactor relay  540  to engage the pre-charge resistor  270  until the ultracapacitors  330  reach a minimum safe voltage level.  
         [0058]     The PLC  280  is the control center for additional features. Through a Control Area Network (CAN) bus interface (e.g., SAE standard J1939), the PLC  280  offers remote ON/OFF control and status reporting of: the control relay positions for on/off relay  550  and precharge relay  540 , pack voltage sensor  520 , ground fault interrupt (GFI) sensor  560 , cooling fans  250 , box temperature sensor(s)  570 , over temperature sensor(s)  580 , optional fire sensor  590 , and optional fire suppression system  600 . The PLC  280  also uses input from the box temperature sensor  570  to turn on and off the cooling fans  250 . During normal operation of the ultracapacitor pack, the on/off relay  550  is activated. The on/off relay  550  is deactivated by the PLC  280  when the GFI sensor  560  detects a ground fault interrupt condition, when the over temperature sensor(s)  580  detects an over-temperature condition, or the pack voltage sensor  520  detects an over-voltage condition. The fire suppression system  600  is activated by the PLC  280  in the event a fire condition is detected by the fire sensor  590  to extinguish any fire in the ultracapacitor pack  200 . A 360 VDC+stud feed thru  610  is an external power cable attachment for the positive side of the ultracapacitor pack  200 . A 360 VDC−stud feed thru  620  is an external power cable attachment for the negative side of the ultracapacitor pack  200 . A 24 VDC+, 24 VDC−power connector  630  provides the positive and negative dc power connections for the PLC  280 . A digital data interface connector  640  includes the wires that connect to the CAN bus network and is also the port by which the PLC  280  is programmed.  
         [0059]     The ultracapacitor pack  200  includes structural support, environmental protection, automatic cooling, electrical interconnection of the ultracapacitors, remote ON/OFF switching, a safety pre-charge circuit, a safety and automatic equalizing discharge circuit, a programmable logic controller, a digital interface to a control area data network for control and status reporting, and an optional fire sensing and suppression system. The pack is ideal for high-voltage, high-power applications of electric and hybrid-electric vehicle propulsion systems, fixed site high-power load averaging, and high-power impulse requirements.  
         [0060]     Additional embodiments of the ultracapacitor packs will be described.  
         [0061]     In one or more embodiments of the ultracapacitor packs described herein, in addition to, or instead of cooling fan(s), the ultracapacitor pack includes a cooling system that is a forced-air refrigeration system or a liquid cooled cold plate attached to one or more external surfaces of the ultracapacitor pack enclosure.  
         [0062]     In one or more embodiments of the ultracapacitor packs described herein, the controller (e.g., processor) for the ultracapacitor pack is either internal to or external to the ultracapacitor pack enclosure.  
         [0063]     In one or more embodiments of the ultracapacitor packs described herein, the controller (e.g., processor) includes control algorithms and/or reporting algorithms. For example, but not by way of limitation, in one embodiment, the controller includes an algorithm to control one or more of the cooling system, precharge resistor control relay input, and on/off relay from one or more of the pack temperature sensor or sensors input, the voltage sensor input, the ground fault isolation input, the fire sensor input, and the fire suppression input. For example, but not by way of limitation, in another embodiment, the controller includes one or more algorithms for monitoring and reporting the sensor inputs to the control network interface, and/or includes one or more algorithms for controlling the cooling system and on/off relay in response to commands from the network interface.  
         [0064]     With reference to  FIG. 10 , a partial perspective view of another embodiment of an ultracapacitor energy storage cell pack  700  is shown. In this embodiment, passive balancing drain resistors  710  are attached directly to bus bar interconnects  720  via a small screw  730  and ring terminal  740 . As shown in  FIG. 11 , the bus bar interconnect  720  includes a substantially flat, rectangular block configuration with vertical holes  740  near opposite ends to couple interconnection studs of adjacent ultracapacitors together in series. One or more laterally extending taps  750  extend into side  760  of the bus bar interconnect  720 . The screw  730  and ring terminal  740  attach to the bus bar interconnect  720  at the taps  750  for attaching the passive balancing drain resistors  710  directly to the bus bar interconnects  720 . Thus, in this embodiment, the ring terminal  740  at one end of the resistor  710  is fastened directly to the bus bar  720  with a screw  730  rather than placed around the threaded bolt between the capacitor can and the bus bar  720 . Fastening the ring terminal  740  of the balancing resistor  710  to the bus bar  720  rather than across the connection bolt as was previously done removes that ring terminal  740  from the high current path through the ultracapacitors and results in a more consistently lower interconnect resistance between the ultracapacitor and the bus bar  720  for the high current path of the pack assembly  700 .  
         [0065]     With reference to  FIGS. 12 and 13 , an embodiment of a fastening arrangement  800  at one side of an ultracapacitor energy storage cell pack is shown. In this embodiment of the ultracapacitor energy storage cell pack, ultracapacitor cans  810  include end terminals  820  that are male externally threaded studs rather than female internally threaded studs. In the fastening arrangement  800 , a bus bar  830  is on the inside of an insulated wine rack support rack structure  840  with fastener  850  attaching to the externally threaded surface of the end terminal  820 . The wine rack support structure  840  is somewhat similar to wine rack end support plate  370  shown and described above with respect to  FIGS. 5 and 8 . In the embodiment shown in  FIGS. 12 and 13 , the fastener  850  is a hexagonal internally threaded nut. A wave washer  860  is disposed between a flange of the fastener  850  and an outer side of the insulated support rack structure  840  to act as a lock washer and provide structure stability for wine rack support sheet  840 . The fastening arrangement  800  ensures a solid electrical connection between the ultracapacitor  810  and the bus bar  830 , and is important for keeping the connection resistance at a minimum between the ultracapacitor  810  and the bus bar  830 .  
         [0066]     The fastening arrangement  800  may be applied to the other ultracapacitor energy storage cell packs described herein. Thus, in alternative embodiments, the female internally threaded studs of the other ultracapacitor energy storage cell packs and fastening arrangements described herein are replaced with male externally threaded studs and the fastening arrangement  800 .  
         [0067]     While embodiments and applications of this invention have been shown and described, it would be apparent to those in the field that many more modifications are possible without departing from the inventive concepts herein. The invention, therefore, is not to be restricted except in the spirit of the appended claims.