High-power ultracapacitor energy storage pack and method of use

An ultracapacitor energy storage cell pack includes an ultracapacitor assembly including a plurality of parallel ultracapacitors and balancing resistors in series; an enclosure for the ultracapacitor assembly; a controller; one or more temperature sensors; a pack voltage sensor; a GFI sensor; one or more cooling fans carried by the enclosure; 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, the one or more temperature sensors detect an over-temperature condition, or 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, and activated by the controller to cause the pre-charge resistor to limit pack charge current until the ultracapacitor assembly reaches a minimum voltage.

FIELD OF THE INVENTION

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

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.

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.

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.

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.

Packs of batteries and packs of ultracapacitors have been built in various forms and configurations. Various different wiring harnesses, buss 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

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 support plates. Plastic, as a non-conductive material, provides for the safe operation of the high-voltage connections. Two of the plastic plates have wine rack hole cutouts that form the support structure for individual cylindrical ultracapacitor cans and the third plastic plate has pre mounted buss bars and smaller holes for fastening bolts. The first two plastic plates structurally support and separate the ultracapacitors to provide space for cooling airflow along the direction of the plates. The third plate supports and positions the cans by the threaded end terminals that are bolted to the plate. Buss bars are fastened to the inside of the third 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 buss bars.

In a preferred embodiment, 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.

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.

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.

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 automatically discharge 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.

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 automatically discharge 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.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

With reference toFIGS. 1 and 2, an embodiment of an ultracapacitor energy storage cell pack10will now be described.FIG. 1illustrates an exploded view of an embodiment of a half module15of the ultracapacitor energy storage cell pack10.FIG. 2illustrates an embodiment of an assembled ultracapacitor energy storage cell pack module10, which includes two half modules15fastened together. Although each half module15preferably includes eighty ultracapacitors20, each half module may have other numbers of ultracapacitors20. Further, the ultracapacitor pack10may have other numbers of modules15besides a pair (e.g.,1,3,4, etc.).

The ultracapacitor pack10is shown in exploded view inFIG. 1to illustrate the different levels in the half module15that are added during assembly of the half module15. Each of these levels will now be described in turn below followed by a description of the assembly process.

An aluminum base plate25forms a bottom or inner-most level of the half module15. The base plate25includes a welded frame30around edges of the base plate25.

A polycarbonate crate plate35is seated inside the frame30and includes cutouts or holes40with a shape that matches the cross-section of the ultracapacitors20. The base plate25and crate cutouts40form an x, y, and z location and mounting support for the ultracapacitors20. The cutouts40also prevent the ultracapacitors20from rotating during use, e.g., mobile vehicle use.

In the embodiment shown, the individual ultracapacitors20have a general square-can shape (i.e., rectangular parallelpiped). The cross-section of the ultracapacitors20is 2.38 in. by 2.38 in. and the length is about 6 in. On an upper-most or outer-most end of the ultracapacitor20, two threaded lug terminals45and a dielectric paste fill port50protrude from an insulated cover55of the ultracapacitor20. The cover55of the ultracapacitor may include a well encircled by a protruding rim. Shrink plastic that normally surrounds sides or exterior capacitor casing60of the ultracapacitor20is removed to better expose the exterior casing60to circulated cooling

A box frame65ties together the base plate25and frame30with circuit boards70, and a top polycarbonate cover75. The box frame65has elongated lateral cutouts80on two opposing sides to provide for cross-flow air cooling. Bottom flanges85provide a mounting surface to tie two of these box frames65, and, hence, two half modules15, together to form the single ultracapacitor pack module10shown inFIG. 2. The box frame65includes a large upper rectangular opening and a large lower rectangular opening.

The next layer is a first ¼ in. foam rubber insulating and sealing sheet90that covers the ultracapacitors20. The first sheet90has cutouts for the ultracapacitor terminals45and fill port50so that the sheet90can seal tightly against the cover55of the ultracapacitor20.

A second ⅛ in. foam rubber insulating and sealing sheet95may be placed on top of the previous first sheet90. The second sheet95includes rectangular cutouts or holes100. The cutouts100receive copper bar electrical interconnections105. The cutouts100in the sheet95simplify the assembly and proper placement of the copper bar electrical interconnections105. The sheet95also seals the copper bar electrical interconnections105. The copper bar electrical interconnections105include holes that the ultracapacitor terminals45protrude through.

Two identical main circuit boards70(e.g., 40-ultracapacitor main circuit boards) may lay on top of the foam rubber sheets90,95. Each main circuit board70may include holes that the ultracapacitor terminals45protrude through. Each circuit board70may have mounting holes for40(8 by 5) ultracapacitors less two corner positions required for frame structure mounting. Instead of two circuit boards70, a single circuit board70may 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 terminals45and copper bars105to the circuit boards70and compress the foam rubber sheets90,95in between the cover55of the ultracapacitor20and the circuit boards70. Thus, the circuit board70forms the location and mechanical support as well as the electrical connections for the ultracapacitors20. The foam sheets90,95seal around the rim of the ultracapacitor terminals45. A processor and display circuit board mounts on top of the main circuit board70.

Although the ultracapacitor pack10and the half modules15are 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.

A top aluminum frame110and the transparent polycarbonate cover75may attach to the frame structure to complete the half module15. The transparent cover75allows observation of a light emitting diode (LED) failure detection display that indicates the active/inactive status of the ultracapacitors20.

Together, the bottom base plate25, crate plate35, box frame65, sealing sheets90,95, and circuit board(s)70, and ultracapacitor terminal fasteners form an ultracapacitor mounting assembly112for the ultracapacitors20. The ultracapacitor mounting assembly112provides a mounting surface for the copper bar interconnects105, maintains the position and spacing of the ultracapacitors20in the X, Y, and Z directions, does not allow the ultracapacitors to rotate when connected, and the main circuit board(s)70provides a mounting platform for the cell equalization, failure detection, processor, and LED display systems. Attaching the ultracapacitors20to the mounting assembly112by the terminals45instead of the exterior ultracapacitor casing60allows the ultracapacitors20to be more effectively cooled because the majority of the surface area of the ultracapacitors20is in the cooling air stream supplied by the cross-flow air cooling assembly115. Sealing along the cover55and around the terminals45protects the terminals45from water, dust, and other contaminants.

An exemplary method of assembling the ultracapacitor half module15will now be described. The ultracapacitors20are first placed onto the bottom base plate25, with the bottoms of the ultracapacitors20extending through the square cutouts40of the crate plate35. The box frame65is applied over the ultracapacitors20, so that the ultracapacitors extend through the large lower and upper rectangular openings of the box frame65. The ¼ in. foam rubber insulating and sealing sheet90is placed on top of the ultracapacitors20, with the ultracapacitor terminals45and fill port50protruding through cutouts in the sheet90. The ⅛ in. foam rubber insulating and sealing sheet95is placed on top of the previous sheet90and the copper bar electrical interconnections105are placed into the rectangular cutouts100of the sheet95. The ultracapacitor terminals45also protrude through holes in the copper bar electrical interconnections105. The main circuit boards70are layered on top of the foam rubber sheets90,95so that the threaded ultracapacitor terminals45protrude through the corresponding holes in the circuit boards70. Lug nuts are screwed onto the threaded terminals45, compressing the foam rubber sheets90,95in between the cover55of the ultracapacitor20and the circuit boards70, and securing the ultracapacitors20and copper bars105in position. The processor and display circuit board is mounted on top of the main circuit board70. The top aluminum frame110and the transparent polycarbonate cover75are placed over the circuit boards and attached to the frame structure to complete the half module15. A pair of half modules15may be positioned back to back (i.e., facing opposite directions with the bottoms of the aluminum base plates25touching) and a cross-flow air cooling assembly115may be attached to the frame structure, adjacent the elongated lateral cutouts80on one side of the box frames65. The half modules15may be bolted or otherwise fastened together at the respective bottom flanges85to complete the ultracapacitor pack module10.

To determine if one or more ultracapacitors20in the pack10need to be replaced, a user observes the light emitting diode (LED) failure detection display through the transparent cover75. The LED failure detection display includes an array of LEDs that correspond to the array of ultracapacitors20, each LED indicating the status of a corresponding ultracapacitor20. Each unlit LED indicates a corresponding failed LED. An ultracapacitor20in the pack10can quickly and easily be replaced by simply unfastening the frame and unbolting only the failed ultracapacitor20that had been previously identified by the LED display. The replacement ultracapacitor is put into position and the procedure reversed.

With reference toFIGS. 3–8, and initially,FIGS. 3 and 4, an ultracapacitor energy storage cell pack (hereinafter “ultracapacitor pack”)200constructed in accordance with another embodiment of the invention will now be described. The ultracapacitor pack200includes a ultracapacitor cell and winerack support assembly (hereinafter “ultracapacitor assembly”)210, an ultracapacitor pack box enclosure (hereinafter “box enclosure”)220, a metal lid230, an air filter bracket240(w/ air filter), cooling fans250, fan finger guards260, higher-power precharge resistor270, Programmable Logic Controller module (hereinafter “PLC”)280, high power relays (kilovac contactors)290, electrical connectors300,310,320and other discrete components mounted within the box enclosure220.

The ultracapacitor assembly210includes one-hundred and forty-four (144) ultracapacitors330connected in series to provide a nominal 360 volts DC, 325 watt-hours energy storage. The value of each ultracapacitor330is 2600 Farads. In alternative embodiments, the ultracapacitor assembly210may have other numbers of ultracapacitors, different types of ultracapacitors, and/or an overall different amount of voltage and/or power. Each ultracapacitor330is connected with a parallel drain resistor340(FIG. 5). The ultracapacitor assembly210includes a first wine rack middle support plate350, a similar second wine rack middle support plate360, and a wine rack end support plate370for supporting the ultracapacitors330.

The box enclosure220is preferably made of metal and includes square end cutouts380in rear wall382to accommodate air flow therethrough and circular cutouts390in front wall392to accommodate the cooling fans250. The front wall392and rear wall382are joined by opposite parallel side walls394. The filter(s) of the air filter bracket240is externally serviceable and fits over the square cutouts380of the rear wall382. The interior of the box enclosure220and underside of the lid230is coated with a thick material that provides electrical insulation and corrosion protection as an additional level of safety for the box enclosure220. The inner bottom of the box enclosure220includes support plate guides for mounting the wine rack middle support plates350,360and end support plate370.

FIG. 4shows an exploded view of the ultracapacitor assembly210. The ultracapacitors330are cylindrical canisters with aluminum female threaded connections at each end, which receive male threaded aluminum interconnection studs400for connecting the ultracapacitors330in senes. Aluminum bus bars410and aluminum interconnection washers are also used to interconnect the ultracapacitors330in series at the ends of the rows. Providing electrical connections made of aluminum metal prevents any corrosive galvanic effects from dissimilar metals. Additionally, the threaded connections are covered with a silicon dielectric grease to prohibit environmentally caused corrosion.

The wine rack middle support plates350,360and end support plate370are 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 middle support plates350,360and end support plate370are different in construction to allow ease of assembly and replacement of any canister row.

With reference toFIG. 6, the wine rack middle support plates350,360include a pattern of generally circular cutouts430for receiving the ultracapacitors330. The cutouts430include an additional semi-circular recess440to accommodate and support the drain resistors340. The drain resistors340are preformed with ring terminals442(FIG. 5) attached to leads of the drain resistors340for simplicity of mounting and electrical connection. Additional semi-circular recesses450along a top edge460and bottom edge470of the wine rack middle support plates350,360provide clearance for the attaching rivets of support guides on a bottom of box enclosure220and the lid230. The wine rack middle support plates350,360are made of 3/16″ thick polycarbonate plastic for strength and electrical insulation.

With reference toFIG. 7, the wine rack end support plate370includes a pattern of circular holes480for receiving threaded bolt fasteners for mounting the ultracapacitors330. Additional semi-circular recesses490along a top edge500and a bottom edge510of the wine rack end support plate370provide clearance for the attaching rivets of support guides on a bottom of the box enclosure220and the lid230. The wine rack end support plate370is 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 bars410are affixed in place to the wine rack end support plate370with 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 bars410are pre-positioned to avoid confusion that could cause assembly mistakes.

FIG. 8is a general block diagram of the ultracapacitor pack200. As indicated above, each ultracapacitor330is connected in parallel with the drain resistor340. 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 ultracapacitor330is2600Farads and the value and power of the drain resistor340is selected to completely discharge the ultracapacitor330over a number of hours during an inactive period of the ultracapacitor pack200. The energy drain action is slow enough so as not to interfere with the normal operation of the ultracapacitor pack200. The discharge is also slow enough so as not to cause any significant temperature increase from the drain resistors340within the ultracapacitor pack200. The chemical composition of the ultracapacitor330allows charge to build up across the ultracapacitor330over a period of time after the ultracapacitor330is shorted and left open. The drain resistors340allow a safe discharge of the high voltage of the ultracapacitor pack200to eliminate any shock danger from the ultracapacitor “memory” to personnel servicing the ultracapacitor pack200.

Because the ultracapacitors330can 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 resistor270with its own heat sink is mounted inside the box enclosure220and used to limit the initial charging current. Based on input to a pack voltage sensor520, the PLC280controls a pre-charge contactor relay540to engage the pre-charge resistor270until the ultracapacitors330reach a minimum safe voltage level.

The PLC280is the control center for additional features. Through a Control Area Network (CAN) bus interface (e.g., SAE standard J1939), the PLC280offers remote ON/OFF control and status reporting of: the control relay positions for on/off relay550and precharge relay540, pack voltage sensor520, ground fault interrupt (GFI) sensor560, cooling fans250, box temperature sensor570, over temperature sensor580, optional fire sensor590, and optional fire suppression system600. The PLC280also uses input from the box temperature sensor570to turn on and off the cooling fans250. During normal operation of the ultracapacitor pack, the on/off relay550is activated. The on/off relay550is deactivated by the PLC280when the GFI sensor560detects a ground fault interrupt condition, when the over temperature sensor580detects an over-temperature condition, or the pack voltage sensor520detects an over-voltage condition. The fire suppression system600is activated by the PLC280in the event a fire condition is detected by the fire sensor590to extinguish any fire in the ultracapacitor pack200. A 360 VDC+stud feed thru610is an external power cable attachment for the positive side of the ultracapacitor pack200. A 360 VDC− stud feed thru620is an external power cable attachment for the negative side of the ultracapacitor pack200. A 24 VDC+, 24 VDC− power connector630provides the positive and negative dc power connections for the PLC280. A digital data interface connector640includes the wires that connect to the CAN buss network and is also the port by which the PLC280is programmed.

The ultracapacitor pack200includes 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.

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.