Patent Publication Number: US-9899658-B2

Title: High current battery pack fusing system

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to battery systems and, more particularly, to a fusing system compatible with the high current, high power battery pack of an electric vehicle. 
     BACKGROUND OF THE INVENTION 
     In response to the demands of consumers who are driven both by ever-escalating fuel prices and the dire consequences of global warming, the automobile industry is starting to embrace the need for ultra-low emission, high efficiency cars. While some within the industry are attempting to achieve these goals by engineering more efficient internal combustion engines, others are incorporating hybrid or all-electric drive trains into their vehicle line-ups. 
     In recent years electric vehicles (EVs) have proven to be not only environmentally friendly, but also capable of meeting, if not exceeding, consumer desires and expectations regarding performance, range, reliability, and cost. In order to insure both vehicle reliability and user safety, electric vehicles use a variety of techniques to prevent battery pack abuse as well as mitigate the effects of an unavoidable abusive event (e.g., battery pack damaged during a collision, etc.). Fuses, which may be employed at the battery level, the battery pack level, or both, are one of the primary means of protecting an EV&#39;s battery pack. Unfortunately while fuses may be used to provide very effective protection in a low current circuit, due to the high current levels common in an EV the response time of a fuse may be too slow to provide the desired level of protection. This phenomenon is illustrated in  FIG. 1  which provides the cutoff current characteristics for a variety of conventional high current fuses ranging from a 300 amp fuse to an 800 amp fuse. As expected, as the current rating of the fuse increases, so does the time it takes to blow the fuse for a given current level. Thus for the set of exemplary fuses shown in  FIG. 1 , a 300 amp fuse subjected to 1000 amps of current will take approximately 8 seconds to blow while a 600 amp fuse may take as much as 200 seconds to blow at the same current level. Subjecting an EV&#39;s electrical system to an overcurrent of such magnitude and for such an extended period of time may damage the battery pack. To avoid this problem, the fuse within an EV&#39;s power train is typically undersized to insure that the fuse will blow quick enough to protect the various battery pack and drive train components. For example, assuming that the EV battery pack uses wire bond battery interconnects that typically are only capable of withstanding 1000 amps for approximately 10 seconds, based on the above fuse data a 300 amp fuse would be required to insure adequate protection. 
     Unfortunately while undersizing the fuse may provide the desired level of protection for the battery pack, under certain routine conditions the fuse may blow prematurely. In part this is due to the thermal characteristics of the wire bond versus those of the fuse.  FIG. 2  graphically illustrates the heat-up and cool-down cycling of a wire bond interconnect (curve  201 ) versus that of a 300 amp fuse (curve  203 ) as the system is subjected to a series of aggressive current pulses as illustrated in  FIG. 3 . Such a pulse pattern may be due, for example, from an aggressive driving pattern such as those that may occur during street racing or otherwise spirited driving. As shown, eventually the fuse becomes too hot, resulting in the system going into an overheat protection condition, i.e., the fuse blows prematurely. 
     Accordingly, what is needed is a fuse that provides a rapid response to excessive currents while still insuring that the fuse will not blow during normal vehicle operation. The present invention provides such a system. 
     SUMMARY OF THE INVENTION 
     The present invention provides an electric circuit comprised of a battery pack, a fuse assembly and an electrical load. The battery pack includes a plurality of batteries, a first battery pack bus bar, and a first plurality of wire bond interconnects that electrically connect the plurality of batteries to the first battery pack bus bar, where a first end portion of each wire bond interconnect is attached to the first battery pack bus bar, where a second end portion of each wire bond interconnect distal from the first end portion is attached to a first battery terminal of a corresponding one of the plurality of batteries, and where each of the first plurality of wire bond interconnects is fabricated from a first material and is of a first wire gauge. The fuse assembly, which is configured to blow during a current spike and prior to the first plurality of wire bond interconnects being damaged, is comprised of a first fuse bus bar, a second fuse bus bar, and a second plurality of wire bond interconnects that electrically connect the first fuse bus bar to the second fuse bus bar, where the second plurality of wire bond interconnects are connected in parallel between the first and second fuse bus bars, where each of the second plurality of wire bond interconnects is fabricated from the first material and is of the first wire gauge, and where the total number of wire bond interconnects of the fuse assembly (i.e., the second plurality of wire bond interconnects) is less than the total number of parallel connected wire bond interconnects of the battery pack (i.e., the first plurality of wire bond interconnects). 
     In one aspect, the battery pack may further comprise a second battery pack bus bar and a third plurality of wire bond interconnects that electrically connect the plurality of batteries to the second battery pack bus bar, where a first end portion of each wire bond interconnect is attached to the second battery pack bus bar, where a second end portion of each wire bond interconnect distal from the first end portion is attached to a second battery terminal of a corresponding one of the plurality of batteries, and where each of the third plurality of wire bond interconnects is fabricated from the first material and is of the first wire gauge. The first plurality of wire bond interconnects may be coupled to the plurality of batteries and to the first battery pack bus bar utilizing a bonding technique selected from the group consisting of ultrasonic bonding, resistance bonding, thermocompression bonding, thermosonic bonding and laser bonding. The second plurality of wire bond interconnects may be coupled to the first and second fuse bus bars utilizing a bonding technique selected from the group consisting of ultrasonic bonding, resistance bonding, thermocompression bonding, thermosonic bonding and laser bonding. The third plurality of wire bond interconnects may be coupled to the plurality of batteries and to the second battery pack bus bar utilizing a bonding technique selected from the group consisting of ultrasonic bonding, resistance bonding, thermocompression bonding, thermosonic bonding and laser bonding. The first and second battery pack bus bars may be fabricated from aluminum or copper. 
     In another aspect, the total number of wire bond interconnects corresponding to the second plurality of wire bond interconnects is equivalent to between 70 and 99 percent of the total number of wire bond interconnects corresponding to the first plurality of wire bond interconnects; alternately, the total number of wire bond interconnects corresponding to the second plurality of wire bond interconnects is equivalent to between 80 and 95 percent of the total number of wire bond interconnects corresponding to the first plurality of wire bond interconnects; alternately, the total number of wire bond interconnects corresponding to the second plurality of wire bond interconnects is equivalent to between 85 and 90 percent of the total number of wire bond interconnects corresponding to the first plurality of wire bond interconnects. 
     In another aspect, the fuse assembly may further comprise an electrically insulating base (e.g., a plastic base), where the first and second fuse bus bars are attached to a surface of the base. The fuse assembly may be configured such that the upper surface of the base is coplanar with both the upper surface of the first fuse bus bar and the upper surface of the second fuse bus bar. The first and second bus bars may be molded into, or bonded to, or otherwise attached to, the surface of the base. 
     A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       It should be understood that the accompanying figures are only meant to illustrate, not limit, the scope of the invention and should not be considered to be to scale. Additionally, the same reference label on different figures should be understood to refer to the same component or a component of similar functionality. 
         FIG. 1  illustrates the cutoff current characteristics of a variety of conventional high current fuses; 
         FIG. 2  graphically illustrates the thermal characteristics of a wire bond versus a fuse; 
         FIG. 3  illustrates the current pulse pattern used to obtain the thermal characteristics shown in  FIG. 2 ; 
         FIG. 4  provides a schematic diagram of a battery pack with bus bars above and below the battery cells in accordance with the prior art; 
         FIG. 5  provides a schematic diagram of a battery pack with both bus bars adjacent to one end of each of the battery cells in accordance with the prior art; 
         FIG. 6  provides a detailed perspective view of the bus bars in a particular layer stack configuration in accordance with the prior art; 
         FIG. 7  provides a top view of a battery module utilizing a series of non-overlapping bus bars of alternating polarity in accordance with the prior invention; 
         FIG. 8  provides a schematic diagram of a battery pack utilizing a plurality of the battery modules shown in  FIG. 7  combined in a series configuration; 
         FIG. 9  provides a schematic diagram of a battery pack utilizing a plurality of the battery modules shown in  FIG. 7  combined in a parallel configuration; 
         FIG. 10  provides a perspective view of a portion of a battery module such as that shown in  FIG. 7 ; 
         FIG. 11  provides a top view of a fuse assembly in accordance with the invention; 
         FIG. 12  provides a first side view of the assembly shown in  FIG. 11 ; 
         FIG. 13  provides a second side view of the assembly shown in  FIG. 11 ; 
         FIG. 14  provides a side view of the fuse assembly of  FIG. 11 , similar to that shown in  FIG. 13 , except that the bus bars are integrated into the base such that the top surfaces of the bus bars are coplanar with the top surface of the base; 
         FIG. 15  provides a top view of a fuse assembly in accordance with an alternate embodiment of the invention; 
         FIG. 16  provides a first cross-sectional view of the assembly shown in  FIG. 15 ; 
         FIG. 17  provides a second cross-sectional view of the assembly shown in  FIG. 15 ; 
         FIG. 18  provides a top view of the fuse assembly shown in  FIG. 15  after the wire bond interconnects and the fusible links have blown and the arc suppression member has moved into place; 
         FIG. 19  provides a first cross-sectional view, similar to that shown in  FIG. 16 , after the wire bond interconnects and the fusible links have blown and the arc suppression member has moved into place; and 
         FIG. 20  provides a second cross-sectional view, similar to that shown in  FIG. 17 , after the wire bond interconnects and the fusible links have blown and the arc suppression member has moved into place. 
     
    
    
     DESCRIPTION OF THE SPECIFIC EMBODIMENTS 
     As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises”, “comprising”, “includes”, and/or “including”, as used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, process steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” and the symbol “/” are meant to include any and all combinations of one or more of the associated listed items. Additionally, while the terms first, second, etc. may be used herein to describe various steps, calculations or components, these steps, calculations or components should not be limited by these terms, rather these terms are only used to distinguish one step, calculation or component from another. For example, a first calculation could be termed a second calculation, and, similarly, a first step could be termed a second step, without departing from the scope of this disclosure. 
     In the following text, the terms “battery”, “cell”, and “battery cell” may be used interchangeably and may refer to any of a variety of different battery configurations and chemistries. Typical battery chemistries include, but are not limited to, lithium ion, lithium ion polymer, nickel metal hydride, nickel cadmium, nickel hydrogen, nickel zinc, and silver zinc. The term “battery pack” as used herein refers to an assembly of batteries electrically interconnected to achieve the desired voltage and capacity, where the battery assembly is typically contained within an enclosure. The terms “electric vehicle” and “EV” may be used interchangeably and may refer to an all-electric vehicle, a plug-in hybrid vehicle, also referred to as a PHEV, or a hybrid vehicle, also referred to as a HEV, where a hybrid vehicle utilizes multiple sources of propulsion including an electric drive system. 
       FIG. 4  illustrates a portion of an exemplary battery pack  400  utilizing a conventional battery pack configuration in which the battery interconnects (e.g., wire bonds) are attached to both the upper and lower portions of the batteries. As shown, battery pack  400  includes a first group of batteries  402  and  404  connected in parallel, a second group of batteries  406  and  408  connected in parallel, and a third group of batteries  410  and  412  connected in parallel. The first, second and third groups of batteries are connected in series. Bus bars  414 ,  416 ,  418 ,  420 ,  422 ,  424  are used to connect the batteries in this parallel and series arrangement. Each of the bus bars is coupled to the respective batteries with one or more interconnects  425  (e.g., wire bonds). A relatively thick wire  426  couples the second bus bar  414  to the third bus bar  422 , making a series connection between the first and second battery groups, while a second relatively thick wire  428  couples the fourth bus bar  416  to the fifth bus bar  424 , making a series connection between the second and third battery groups. As a result, the first bus bar  420  is the negative terminal while the sixth bus bar  418  is the positive terminal for battery pack  400 . 
     The use of bus bars at both ends of the batteries as illustrated in  FIG. 4  requires a relatively complex manufacturing process in order to (i) attach the battery interconnects  425  between the battery end surfaces and the bus bars, and (ii) attach the wires (e.g., wires  426  and  428 ) that couple the upper bus bars to the lower bus bars. Wires  426  and  428  are also problematic in the sense that they can introduce parasitic resistance into the current path, which in turn can introduce a voltage drop under high current drain conditions. Additionally this configuration prevents, or at least limits, the ability to efficiently remove battery pack heat by affixing a heat sink to a battery end surface. 
       FIG. 5  illustrates a battery pack  500  utilizing an alternate conventional battery pack configuration in which all the bus bars are proximate to one end of the battery pack, thus enabling efficient heat removal from the other end of the battery pack. Furthermore, by locating bus bars  514 ,  516 ,  518  and  522  proximate to one end of the batteries, fewer bus bars are required than in battery pack  400 . The relatively thick wires  426  and  428  from the upper bus bars to the lower bus bars are also eliminated in the embodiment shown in  FIG. 5 . 
     Access to both the positive and negative terminals in battery pack  500  is at one end of the cells, i.e., at the top end of the cells, where the bus bars are coupled to the positive and negative terminals using battery interconnects (e.g., wire bonds). As in the prior arrangement, the first group of batteries  402  and  404  are connected in parallel, the second group of batteries  406  and  408  are connected in parallel, and the third group of batteries  410  and  412  are connected in parallel. The first, second and third groups of batteries are connected in series. Bus bars  514 ,  516 ,  518 ,  522  are used to couple the batteries in this parallel and series arrangement. Specifically, starting with the negative terminal of battery pack  500 , a first bus bar  514  is connected to the negative terminals of the first group of batteries  402  and  404  while a second bus bar  522  is connected to the positive terminals of the same group of batteries  402  and  404 , both at the top end portion  438  of each of the batteries. The first and second bus bars  514  and  522  couple the first group of batteries  402  and  404  in parallel. Similarly, the second bus bar  522  and the third bus bar  516  couple the second group of batteries  406  and  408  in parallel, while the third bus bar  516  and the fourth bus bar  518  couple the third group of batteries  410  and  412  in parallel. Series connections between battery groups are formed by the bus bars, specifically the second bus bar  522  connects the positive terminals of the first group of batteries  402  and  404  to the negative terminals of the second group of batteries  406  and  408 ; and the third bus bar  516  connects the positive terminals of the second group of batteries  406  and  408  to the negative terminals of the third group of batteries  410  and  412 . The fourth bus bar  518  is the positive terminal of the battery pack  500 . 
     In battery pack  500  the bus bars are arranged in a layer stack  550 . In this stacking arrangement first bus bar  514  and third bus bar  516 , which are separated by an air gap or other electrical insulator to prevent short circuiting, are placed in a first layer  530 . Similarly, second bus bar  522  and fourth bus bar  518 , which are also separated by a gap or insulator, are placed in a third layer  534 . Disposed between layers  530  and  534  is an electrically insulating layer  532 . To simplify fabrication, the layer stack may be formed using layers of a circuit board, e.g., with the bus bars made of (or on) copper layers or other suitable conductive metal (such as aluminum) and the insulating layer made of resin impregnated fiberglass or other suitable electrically insulating material. 
     The batteries shown in  FIGS. 4 and 5  have a projecting nub as a positive terminal at the top end of the battery and a can, also referred to as a casing, that serves as the negative battery terminal. The batteries are preferably cylindrically shaped with a flat bottom surface, for example utilizing an 18650 form factor. Typically a portion of the negative terminal is located at the top end of the cell, for example due to a casing crimp which is formed when the casing is sealed around the contents of the battery. This crimp or other portion of the negative terminal at the top end of the battery provides physical and electrical access to the battery&#39;s negative terminal. The crimp is spaced apart from the peripheral sides of the projecting nub through a gap that may or may not be filled with an insulator. 
     Preferably in a battery pack such as battery pack  500  in which the battery connections are made at one end of the cells (e.g., end portions  438 ), a heat sink  552  is thermally coupled to the opposite end portions  440  of each of the batteries. This approach is especially applicable to a co-planar battery arrangement which provides a relatively flat surface to attach a heat sink. Heat sink  552  may be finned or utilize air or liquid coolant passages. If heat sink  552  is air cooled, a fan may be used to provide air flow across one or more heat sink surfaces. In some configurations, heat sink  552  may be attached or affixed to the bottom of a battery holder. 
     In a typical battery pack in which all battery interconnects are attached to one end of the cells, typically a multi-layer stack (e.g., stack  550 ) is used in order to provide bus bars for both terminals as well as a suitable insulator located between the bus bars. This approach results in a relatively complex bus bar arrangement. For example,  FIG. 6  from co-assigned U.S. patent application Ser. No. 14/203,874, the disclosure of which is incorporated herein for any and all purposes, illustrates a multi-layer bus bar configuration in which the bus bars are stacked with an interposed insulator, and in which each bus bar includes multiple contact fingers  601 . 
     In order to simplify bus bar design and configuration, thereby significantly reducing material and fabrication costs as well as overall battery pack complexity, the battery pack may be configured with a series of non-overlapping bus bars of alternating polarity. Such a configuration is disclosed in co-assigned U.S. patent application Ser. No. 14/802,207, filed 17 Jul. 2015, the disclosure of which is incorporated herein for any and all purposes. Although this approach may be used throughout the entire battery pack, preferably it is used to form battery modules, where the battery modules are then electrically coupled to form the battery pack. Assuming the battery pack is used in an electric vehicle as preferred, the individual battery modules may be contained within a single battery pack enclosure, or within multiple enclosures, the latter approach allowing subsets of modules to be distributed throughout the vehicle in order to obtain a particular weight distribution or to fit within the confines of a particular vehicle envelope or structure. 
       FIG. 7  provides a top view of a battery module  700  utilizing a series of non-overlapping bus bars of alternating polarity. Visible in  FIG. 7  is the end portion of each of a plurality of batteries  701 , where the end portions are accessible through corresponding apertures in an upper tray member  703 . Tray member  703  is prepared and/or treated to provide electrical isolation between the batteries, for example by fabricating the tray member from an electrically insulative material such as a plastic, or coating the tray member with an electrically insulative material. The batteries are divided into a plurality of rows  705 , where each row  705  includes sixteen batteries  701 . Even though module  700  is shown with seven rows  705 , it should be understood that this design is not limited to configurations utilizing this number of battery rows, and therefore is equally applicable to configurations utilizing a fewer number, or a greater number, of battery rows  705 . Similarly, the design is not limited to configurations in which each battery row is comprised of sixteen batteries, rather the design may be used with configurations using a fewer number, or a greater number, of batteries  701  per battery row  705 . 
     In the configuration illustrated in  FIG. 7 , interposed between battery rows  705  are linear bus bars  707 , where each bus bar  707  is devoid of the contact fingers utilized in the prior art approach shown in  FIG. 6 . Bus bars  707  are preferably made of copper, although other suitable electrically conductive materials such as aluminum may be used. Although this approach may utilize any battery type that provides access to both terminals at a single end portion of the battery, in the illustrated assembly batteries  701  are cylindrical, preferably utilizing an 18650 form factor. 
     The batteries within a single row  705  form a group with all terminals of a first polarity being electrically connected to a single bus bar on one side of the battery row, and all terminals of the second polarity being electrically connected to a single bus bar on the other side of the battery row. For example, all positive terminals of battery row  705 A are electrically connected to bus bar  707 A and all negative terminals of battery row  705 A are electrically connected to bus bar  707 B. As a result of this approach, each group of batteries represented by a single row are electrically connected in parallel while the battery rows within a single module  700  are electrically connected in series. By varying the number of batteries within a single row, as well as the number of rows within a single module, the desired voltage and current capabilities of the module may be configured as desired to meet the design criteria for a specific application. 
     Preferably module  700  uses wire bond interconnects  709  to electrically couple the batteries  701  to the bus bars  707 . Wire bond interconnects  709  may be attached using any wire bonding technique suitable for the selected wire gauge, wire material and bus bar material. Typical wire bonding techniques include, but are not limited to, bonding, resistance bonding, thermocompression bonding, thermosonic bonding and laser bonding. 
     As previously noted, module  700  may be configured as the entire battery pack. For some applications, however, multiple modules  700  may be electrically interconnected in order to achieve the desired battery pack output characteristics. For example, modules  700  may be electrically interconnected in series as illustrated in  FIG. 8 , or electrically interconnected in parallel as illustrated in  FIG. 9 . Other series/parallel arrangements may be used with the invention. 
       FIG. 10  provides a perspective view of a portion of a battery module such as the module shown in  FIG. 7 . For clarity only a portion of the illustrated batteries shown in  FIG. 10  are interconnected to adjacent bus bars. This figure shows a clearer view of the access apertures  1001  fabricated into upper tray member  703 , apertures  1001  allowing access to the battery terminals located at the ends of the batteries. The access apertures  1001  utilized in the illustrated embodiment are continuous slots that provide easy electrical access to all of the batteries within a single row while still holding the batteries in place. Thus in this configuration there is a single access aperture per battery group. It should be understood, however, that access apertures  1001  may utilize an alternate shape and may be configured to allow access to more or less than a battery group. For example, the access apertures may be configured with a circular or elliptical shape with one opening per battery, or one opening per sub-group of batteries (e.g., two or more batteries). 
     Upper tray member  703 , which may be molded, cast, printed using a 3D printer, or fabricated using an alternate technique, is preferably fabricated from a plastic material, although other materials may also be used to fabricate the tray member. In a preferred embodiment, bus bars  707  are integrated into upper tray member  703 , for example by molding the bus bars into the tray member during tray member fabrication. Alternately, bus bars  707  may be bonded into slots molded into the upper tray member  703 . Integrating the bus bars into the upper surface of tray member  403  insures that the bus bars are properly positioned during the battery interconnection process and that they remain in position after pack fabrication, thus minimizing stress and damage to the battery interconnects. 
     In accordance with the invention, a high current fuse with a short time constant is provided for use in an EV. The fuse is designed to exhibit thermal characteristics that are similar to, if not substantially identical to, those of the wire bond interconnects used in the EV&#39;s battery pack. As a result, the system does not go into an overheat protection condition when the system is subjected to repetitive high current cycles, such as those common during aggressive and/or spirited driving. 
       FIG. 11  provides a top view of a fuse assembly  1100  in accordance with one embodiment of the invention.  FIGS. 12 and 13  provide orthogonal side views of the same assembly  1100 . Base  1101  of fuse assembly  1100  is fabricated from an electrically insulative material, typically plastic (e.g., polycarbonate, acrylonitrile butadiene styrene (ABS), polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), nylon, etc.), although other materials may be used as long as the material is electrically insulating. Attached to, or integrated into, top surface  1103  of base  1101  are two bus bars  1105  and  1106 , the bus bars fabricated from copper, aluminum or other suitable electrically conductive material. Bus bars  1105  and  1106  may be bonded, bolted or otherwise attached to surface  1103  of base  1101 . Alternately, bus bars  1105  and  1106  may be molded into base  1101 . Alternately, bus bars  1105  and  1106  may be bonded into slots molded into surface  1103  of base  1101 . Integrating the bus bars into the upper surface  1103  of base  1101  insures that the bus bars are properly positioned during fuse fabrication and remain properly positioned during the life of the fuse assembly. Additionally, if the top surfaces of the bus bars and base  1101  are coplanar, the risk of arcing is reducing when the fuse blows.  FIG. 14  provides a cross-sectional view of an embodiment of the fuse assembly with the bus bars integrated into the base such that the top surfaces of each are coplanar. 
     Electrically connecting bus bar  1105  to bus bar  1106  is a plurality of wire bond interconnects  1107 . Wire bond interconnects  1107  may be attached to bus bars  1105  and  1106  using any wire bonding technique suitable for the selected wire gauge, wire material and bus bar material. Typical wire bonding techniques include, but are not limited to, ultrasonic bonding, resistance bonding, thermocompression bonding, thermosonic bonding and laser bonding. Wire bond interconnects  1107  are configured to exhibit similar thermal characteristics to those of the wire bonds used in the fabrication of the EV&#39;s battery pack (e.g., wire bonds  425  in  FIGS. 4 and 5 , wire bonds  709  in  FIG. 7 , etc.) and as such are preferably fabricated from the same material, and of the same gauge wire, as the battery pack interconnects. The number of wire bond interconnects  1107  used in fuse assembly  1100  is selected to provide the desired current handling capability for the EV&#39;s electrical system, thereby insuring that fuse assembly  1100  blows when intended, i.e., before any components within the battery pack or drive train can sustain damage. In order to insure that fuse assembly  1100  blows before any of the interconnects used in the EV&#39;s battery pack can be damaged, the total number of interconnects connected in parallel between fuse bus bars  1105  and  1106  is less than the total number of wire bond interconnects installed in parallel within the battery pack, or within a battery module of the EV&#39;s battery pack. For example, assuming a battery pack with 70 batteries connected in parallel such that there are 70 parallel battery interconnects to a first bus bar and 70 parallel battery interconnects to a second bus bar, then the number of wire bond interconnects  1107  in fuse assembly  1100  would be set to a value of less than 70, e.g., 65 wire bond interconnects  1107 . In a battery pack using both parallel and serially connected batteries, the number of battery pack wire bonds used as the baseline in determining the number of wire bond interconnects in the fuse assembly is the total number of parallel interconnects corresponding to a single group of parallel connected batteries. Thus in the assembly shown in  FIG. 7  where there are 7 sets of 16 parallel batteries, the number of wire bond interconnects installed in parallel is 16, i.e., 16 parallel coupled batteries with 16 parallel wire bond interconnects to a first bus bar and 16 parallel wire bond interconnects to a second bus bar. Thus in this example the number of interconnects  1107  in fuse assembly  1100  would be set to a value of less than 16. Preferably the total number of wire bond interconnects in fuse assembly  1100  is between 70 and 99 percent of the total number of parallel connected wire bond interconnects in the EV&#39;s battery pack, or battery pack module; alternately, the total number of wire bond interconnects in fuse assembly  1100  is between 80 and 95 percent of the total number of parallel connected wire bond interconnects in the EV&#39;s battery pack; alternately, the total number of wire bond interconnects in fuse assembly  1100  is between 85 and 90 percent of the total number of parallel connected wire bond interconnects in the EV&#39;s battery pack. As a result of this design, fuse assembly  1100  would blow before any of the battery interconnects are damaged during a current spike. 
       FIGS. 15-20  illustrate an alternate embodiment of the invention, this embodiment adding an arc suppression member to the fuse assembly shown in  FIGS. 11-14 . As shown, arc suppression member  1501  is held within a channel  1503  fabricated within base  1505 . As in fuse assembly  1100 , base  1505  is fabricated from an electrically insulative material such as a plastic. Arc suppression member  1501  is held within base  1505  by a plurality of fusible links  1507 . Fusible links  1507  are fabricated from a material with a much higher electrical resistance than wire bond interconnects  1107 , thus during normal operation very little current passes through them. Preferably the resistivity of fusible links  1507  is at least 2 times the resistivity of wire bond interconnects  1107 ; alternately, the resistivity of fusible links  1507  is at least 10 times the resistivity of wire bond interconnects  1107 ; alternately, the resistivity of fusible links  1507  is at least 100 times the resistivity of wire bond interconnects  1107 ; alternately, the resistivity of fusible links  1507  is at least 1,000 times the resistivity of wire bond interconnects  1107 . Once fuse assembly  1500  blows, however, all of the current passes through fusible links  1507 , causing them to immediately fuse. After fusible links  1507  fuse, spring assembly  1509  forces arc suppression member  1501  partially out of the base  1505  as illustrated in  FIGS. 18-20 . Preferably stops  1511  are used to prevent arc suppression member  1501  from being forced completely out of the fuse assembly. As arc suppression member  1501  is fabricated from an electrically insulative material, such as a plastic or a ceramic, arcing between bus bars  1105  and  1106 , or between portions of the blown wire bond interconnects  1107  and/or fusible links  1507 , is suppressed. 
     Systems and methods have been described in general terms as an aid to understanding details of the invention. In some instances, well-known structures, materials, and/or operations have not been specifically shown or described in detail to avoid obscuring aspects of the invention. In other instances, specific details have been given in order to provide a thorough understanding of the invention. One skilled in the relevant art will recognize that the invention may be embodied in other specific forms, for example to adapt to a particular system or apparatus or situation or material or component, without departing from the spirit or essential characteristics thereof. Therefore the disclosures and descriptions herein are intended to be illustrative, but not limiting, of the scope of the invention.