Patent Publication Number: US-6905790-B2

Title: Battery pack having improved battery cell terminal configuration

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. application Ser. No. 09/918,878 filed on Jul. 31, 2001 now U.S. Pat No. 6,811,902. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to battery packs and components thereof. 
     2. Description of the Related Art 
     Conventional lithium polymer soft pack batteries use prismatic or cylindrical cans or rectangular boxes as a package for the battery cells as seen by reference to U.S. Pat. No. 5,639,571 issued to Waters, et al. However, these packages are heavy and expensive, which are disadvantages. In addition, conventional lithium polymer soft pack batteries further use nickel, copper or aluminum terminals to carry current through the package seal to the outside for connection to an overall package connector. These terminals are arranged to exit the same side of the package and are adjacent to each other. The foregoing “same-side” arrangement, however, has shortcomings. 
     One of the problems involves leaking of the electrolyte solution at a seal point of the terminal to the package. Another problem relates to the orientation of the terminals on the same side. Specifically, the terminals are arranged to exit on the same side of the package and are adjacent to each other, making it difficult to electrically connect the packages in a compact configuration. 
     There is therefore a need for an improved battery pack that minimizes or eliminates one or more of the problems set forth above. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a solution to one or more of the above mentioned problems. In one aspect of the present invention, a battery pack is provided that includes a flexible connective circuit containing conductive traces and flaps extending from windows cut from a substrate thereof. One advantage is that these traces and flaps allow for power and control electrical connections between and among a plurality of battery modules in a reduced weight arrangement. Additionally, the flexible circuit allows battery modules to be connected in series (for greater output voltage), or in parallel (for greater ampacity). 
     According to the first aspect, a battery pack is provided that includes a plurality of battery modules each having at least a positive terminal and a negative terminal associated therewith, and a flexible circuit configured to connect the plurality of positive and negative terminals to an overall output of the battery pack. In a preferred embodiment, each module includes a plurality of individual battery units (sometimes referred to as a “soft pack”), each battery unit including a plurality of bicells. 
     In a second aspect of the present invention, a pair of terminals associated with a battery unit are located on opposing sides of the battery unit, allowing the battery unit to be rotated one relative to an adjacent one and placed directly thereon. The process can be repeated to form battery modules. This arrangement allows a compact stacking of battery units. 
     According to the second aspect, a battery unit is provided that includes a (i) plurality of bicells, each bicell containing anodic exposed grids and cathodic exposed grids, the cathodic exposed grids being located across the bicell on the other side of the anodic exposed grids, (ii) a positive terminal, (iii) a negative terminal that is located across the bicell on the other side of the positive terminal, and (iv) a packaging envelope. In a preferred embodiment, a plurality of battery units are each stacked upon the previous battery unit, having been rotated 180 degrees around an axis. 
     In a third aspect of the present invention, a terminal for a battery unit includes a region that contains through apertures along a length dimension of the terminal. The apertures allow an adhesive or the like to flow through the apertures from a first side to a second side of the terminal to thereby form an improved seal. Additionally, in a preferred embodiment, a convoluted arrangement of apertures is used which presents a corresponding convoluted edge path. Such a path would require an electrolyte solution to travel a further distance before it could leak through the individual battery cell package, thereby reducing or eliminating the occurrence of leaking. 
     According to the third aspect, a terminal for a battery unit is provided that includes an electrically conductive body portion having a main axis associated therewith, including a first region configured to be adhered to and in electrical contact with exposed bicell grids, a second region extending along the axis and having a plurality of apertures therethrough, a third region encapsulated by an electrical insulating material, and a fourth region configured for electrical connection to a conductor. 
     Other features, objects, and advantages will become apparent to one of ordinary skill from the following detailed description and accompanying drawing illustrating the invention by way of example but not by way of limitation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is an exploded, perspective view of the battery pack having a plurality of battery modules, according to the invention. 
         FIG. 2  is a schematic and block diagram view of the battery pack of  FIG. 1  coupled to a charger and load. 
         FIG. 3  is a perspective view of an individual battery unit of a battery module. 
         FIGS. 4A-4F  shows the creation of an orientation of stacked battery units of a battery module. 
         FIG. 5  is a perspective view showing, in greater detail, the terminal of FIG.  3 . 
         FIG. 6  is a perspective view showing, in greater detail, apertures of FIG.  5 . 
         FIG. 7  is an enlarged view of a preferred pattern for the apertures of FIG.  6 . 
         FIG. 8  is a section view taken substantially along lines  8 — 8  of  FIG. 6 , showing, in greater detail, the cut-through pattern of the perforated area of the terminal. 
         FIG. 9  is a section view taken substantially along lines  9 — 9  of  FIG. 5 , showing, in greater detail, a region enclosed by an insulator. 
     
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
     Referring now to the drawings wherein like reference numerals are used to identify identical components in the various views,  FIG. 1  illustrates an improved battery pack  10  according to the invention. The pack  10  may be used for portable or stationary electrical and/or electronic devices, including commercial apparatus such as medical devices. In addition, to enhance understandability, a general overview of the basic stackup of battery components will be set forth. The basic component of the battery pack  10  is a so-called bicell, as know in the art, for example, by reference to U.S. Pat. No. 6,063,519 issued to Jeremy Barker, et al. A plurality of bicells are arranged, as will be seen, to form a battery unit, sometimes referred to as a soft-pack. A plurality of battery units are arranged together to from a battery modules which has terminals for delivering power. Finally, a plurality of battery modules are arranged to form the overall battery pack. Thus, the progression is as follows: bicell→battery unit→battery module→battery pack. 
     Battery pack  10  may include a plurality of battery modules  12   1 ,  12   2 , to  12   n , where n is an integer, a flexible circuit  14 , and a case  16  with a top  18 . 
     The battery modules  12   n  may be rechargeable lithium polymer (LiPo) battery modules configured to provide electrical power. Other chemistries, such as other lithium chemistries, may also be used. Each battery module  12   n  may include a plurality of individual battery units  20  (as shown in FIGS.  3 - 4 A-F), one or more positive terminals  22 , and one or more negative terminals  24 . Each terminal  22 ,  24  may have a respective tang  26 . 
     The flexible circuit  14  is configured to establish control and power connections between and among the individual battery modules  12   n , the case  16  and other electronics to be described below. In the illustrated embodiment, flexible circuit  14  couples the battery modules  12   n  in a series-connected arrangement, and allows electrical power to flow in (charge) and out (discharge) of case  16 . In this regard, flexible circuit  14  may include a substrate  28 , a plurality of windows  30 , a plurality of conductive traces  31 , a plurality of flaps  32 , and one or more jumpers  34 . Flexible substrate  28  may be generally flexible, and may be of a material such as MYLAR® by E. I. Du Pont de Nemours and Company or the like. Substrate  28  is configured to contain a number of conductive traces  31  for establishing the above mentioned connections. Conductive traces  31  may run along the length of the substrate  28  and may be made of copper or another conductive material. Flexible circuit  14  may also include one or more windows  30  cut from substrate  28 . Flaps  32  made of a conductive material, such as copper, fold out from windows  30 , the conductive material being exposed once one side of the flexible substrate  28  is removed from the cut window  30  and the remaining substrate  28  and conductive material are folded to create window  30  and flap  32 . Flaps  32  are electrically connected to conductive traces  31 . 
     Windows  30  may be oversized to allow for thermal expansion of flaps  32  when flaps  32  are electrically connected to terminals  22 ,  24 . In a preferred embodiment, negative terminal  24  of each battery unit  20  is ultrasonically welded to corresponding flap  32  on flexible circuit  14  via tang  26 . Other conventional connection methods may be employed. Flexible circuit  14  may also include one or more jumpers  34 , which allow the connection of battery modules  12   n , in a series-connected arrangement. It should be appreciated that jumpers  34  permit connections over conductive traces  31  without being electrically connected to traces  31  themselves. 
     Flexible circuit  14  may also include a controller connector  36 , a pack connector  38 , a fuse  40 , and a current sensor  42 , all of which are elements known to those with ordinary skill in the art. Controller connector  36  provides electrical and mechanical termination of various power and control signals between a controller (best shown in  FIG. 2 ) dedicated to pack  10  and flexible circuit  14 . Overall pack connector  38  comprises a pair of mating portions  38   1  and  38   2 , and provides power and control from inside battery pack  10  to the outside world. Fuse  40  and sensor  42  provide their conventional functions. Particularly, fuse  40  is configured to “open” electrically when a predetermined current (e.g., a DC current) is being sourced by pack  10 . Sensor  42  generates a current indicative signal representing the level of DC current being provided by pack  10 . Flexible circuit  14  may also include a living hinge  44  which allows flexible circuit  14  to be oriented such that the location of selected windows  30  and flaps  32  can be configured to electrically connect to terminals  22 ,  24  of end module  12   n . There may be, however, no hinges or bends or several, depending on the particular design of the case. 
       FIG. 1  also shows a case  16  and top  18  which cooperate to enclose and protect the interior components of battery pack  10 , namely modules  12  and flexible circuit  14 . The case  16  includes a bottom  46 , two end walls  48 ,  50  and two side walls  52 ,  54  which form an interior  56 . Interior  56  houses, in effect, modules  12  and flexible circuit  14 . Case  16  and top  18  may comprise electrical insulating material, for example a polyester or a plastic. 
       FIG. 2  shows, in schematic and block diagram form, battery pack  10  in greater detail as employed in a preferred environment, specifically further including a battery controller  58 , package connector  38  comprising a positive polarity (+) terminal  60  and a negative polarity (−) terminal  62 , communication terminals such as a transmit (Tx) terminal  64  and a receive (Rx) terminal  66 , and a control terminal such as a charge circuit line  68 .  FIG. 2  further shows a master controller  70 , a charger  72 , a power source  74 , and an electrical load  76 . 
     In operation, pack  10  may be used to provide (discharge) power to a load  76  or to receive power (recharge) through a charger  72 . Positive polarity terminal  60  is connected to charger  72 , which is also connected to current sensor  42 . Both charger  72  and current sensor  42  are connected to battery controller  58  through battery controller connector  36 . Negative polarity terminal  62  is also connected to charger  72  and fuse  40 . Transmit terminal  64  is connected to battery controller  58  through controller connector  36  and to master controller  70  through pack connector  38 . Receive terminal  66 , which is connected to battery controller  58  through controller connector  36  and is also connected to master controller  70  through pack connector  38 . Charge circuit line  68 , which is connected to battery controller  58  through controller connector  36 , is also connected to master controller  70  through pack connector  38 . 
     When the battery pack is providing power to a load  76 , master controller  70  allows the positive and negative polarity terminals  60 ,  62  to pass through charger  72  to power load  76 . When battery pack  10  needs recharging, as determined by master controller  70 , the terminal leads  60 ,  62  are reconfigured so as to be recharged by charger  72  connected to power source  74 . Master controller  70  determines charge or recharge configuration dependent upon information supplied by battery controller  58 . Voltage information is supplied to battery controller  58  via controller connector  36 , which is connected to transmit terminal  64  and receive terminal  66 . Transmit terminal  64  and receive terminal  66  send and obtain voltage information about individual battery units  20 , individual battery modules  12 , and the overall battery pack  10 , information which has been collected via the electrical connection of terminals  22 ,  24  of battery units  20  (plurality of units  20  comprising battery modules  12 ) to flexible circuit  14  via flaps  32 . 
     In a preferred embodiment, battery units  20  are electrically connected in a series-connected arrangement (shown best by FIG.  4 ). Each negative terminal  24  of the individual battery units  20  (which is electrically connected to positive terminal  22  of adjacent battery unit  20 , connected in series) is electrically connected to flexible circuit  14  via flaps  32 . This is accomplished by ultrasonically welding tang  26  of negative terminal  24  to corresponding flap  32  in flexible circuit  14 . As previously discussed each flap  32  corresponds to electrically conductive trace  31  running through flexible circuit  14 . Traces  31  connect to controller connector  36 . Because each battery unit  20   n  is connected to flexible circuit  14  and adjacent battery unit  20   n+1 , a voltage lead for each battery unit  20   n  is produced, which allows the voltage level of each battery unit  20   n  to be read individually by battery controller  58 . The voltage level information may be transmitted and received, via transmit terminal  64  and receive terminal  66 , respectively to overall controller  70 . Therefore, both the overall battery pack  10  voltage as well as the voltages of the individual battery cells  20  may be monitored. Positive terminal  22  of the end battery unit  20  is connected to the flexible circuit  14  although positive terminal  22  does not include a tang  26  in this embodiment. This connection is accomplished by ultrasonically welding negative terminal  24  to positive terminal  22  and ultrasonically welding tang  26  of negative terminal  24  to corresponding flap  32  of flexible circuit  14 . 
     Battery controller  58  may be configured to request recharge of battery pack  10  or one or more individual battery units  20  via charge circuit line  68 , dependent upon the voltage readings of the individual components and overall battery pack  10 . Use of the flexible circuit  14  to electrically connect battery modules  12 , allows acquisition of information about each battery unit  20 , each battery module  12 , and battery pack  10  while providing a reduced-weight arrangement for electrically connecting the individual battery units  20  and battery modules  12 . 
     Connecting battery modules  12  to each other via flexible circuit  14  allows flexibility of battery pack  10  in at least two ways. First, there exists electrical flexibility. Terminals  22 ,  24  which connect modules  12  to flexible circuit  14  also provide a voltage lead for each individual battery unit  20 . Additionally, terminals  22 ,  24  enable voltage sensing of individual modules  12  and the overall battery pack  10 . Moreover, the flex circuit  14  can be configured to couple the plurality of battery modules in parallel, thereby increasing amperage capacity (ampacity). Alternatively, flexible circuit may be configured to couple the plurality of modules in series, thereby increasing output voltage. Still further, the flex circuit can be configured to allow one tier, two tiers, or more of battery modules. The foregoing can be accomplished via appropriate routing and interconnection of traces  31  and/or jumpers. 
     Second, a mechanical flexibility exists. Due to the flexibility of substrate  28 , modules  12  can be oriented easily in various heights, widths, and depths. Flaps  32  in flexible circuit  14  may be oriented to correspond with terminals  22 ,  24  for electrical connection. The first aspect of the invention shows a battery pack  10  that is simpler to assemble, that uses electrical connections to both connect battery modules  12  and battery units  20  and obtain voltage information about individual modules  12  and battery units  20 , and that allows numerous orientations and sizes of the battery pack  10  because of the use of the flexible circuit  14 . 
     In another aspect of the invention,  FIG. 3  shows an individual battery unit  20  in greater detail, and in various phases of constructions. A plurality of units  20  make up a module  12 . An exploded view is designated  20   START , an intermediate phase of construction is designated  20   INT , and a finished phase of construction is designated  20   FINISH .  FIG. 3  shows a plurality of bicells  78 , a packaging envelope  80 , an axis  82 , adhesive layer  83 , a first side of the battery unit  84 , a second opposing side of the battery unit  86 , a cover strip  85 , positive polarity exposed grids  88 , and negative polarity exposed grids  90 , a vent  92 , and a direction of rotation  94  relative to axis  82 . 
     Bicells  78  may comprise conventional bicells known to those of ordinary skill in the art, for example as seen by reference to U.S. Pat. No. 6,063,519, issued to Barker, et al., hereby incorporated by reference. As to the present invention, bicells  78  of battery unit  20  are connected in a parallel electrical relationship. The exposed grids  88 ,  90  are current carriers. The cathodic grids  88  are ultrasonically welded together leaving just an overall top and bottom surface thereof exposed. The anodic grids  90  are ultrasonically welded together leaving just an overall top and bottom surface exposed. 
     As described in the Background, a problem with conventional arrangements (i.e., terminals on the “same side” of a battery unit), is that it becomes more difficult to connect multiple battery units in a compact, series-connected arrangement. According to the invention, each individual battery unit  20  has a positive terminal  22  located at a first end  84  of the battery unit  20  and a negative terminal  24  located at a second end  86 . The second end  86  is located on an opposing side of battery unit  20  from first end  84 , relative to a horizontal axis  82 . In the illustrated embodiment, negative terminal  24  is ultrasonically welded to the remaining exposed top surface of anodic grids  90 . In the illustrated embodiment, the positive terminal  22  is ultrasonically welded to the remaining exposed bottom surface of cathodic grids  88 . The cover strip  85  is made of the same material as the corresponding terminal (positive or negative)  22 ,  24  and grid (positive or negative)  88 ,  90  and is placed above the grids  88 ,  90  or below the grids  88 ,  90 , depending upon whether the terminal  22 ,  24  is either welded on the top of the stack of grids  88 ,  90  or below the stack of grids  88 ,  90 . That is, the cover strip is placing on the opposing side relative to the terminal. That way, an electrosonic welding horm has opposing, reaction surfaces to grip. The strips minimize damage to the relatively fragile grid portion during welding. 
     The plurality of bicells  78  is enclosed in packaging envelope  80 . Packaging envelope  80  may comprise a single sheet which is folded to enclose the bicells  78 . Packaging envelope  80  may be a type of laminated, aluminized flexible material which contains four layers. The outside layer exposed to the environment is an electrical insulating material, for example, a polyester. The next underlying layer is metallic, for example, aluminum. This metallic layer reduces or eliminates the amount of moisture outside of the packaging envelope  80  to which the battery unit  20  is exposed (i.e., provides a bidirectional moisture barrier). The third layer is of the same material as the outside layer. The fourth layer, layer  83 , comprises an adhesive such as a conventional sealing hot melt adhesive, for example ethylene acrylic acid (EAA). The part of a sheet of packaging envelope  80  is placed under the individual battery unit  20  and a remaining part of the packaging envelope  80  is folded over the battery unit  20  such that the hot melt adhesive layer  83  comes in contact with itself in three locations. It comes in contact with itself on a first end  84  and a second end  86  and edge  91  along the axis of the fold. Packaging envelope  80  contains a vent  92 , which allows any gas due to overcharging or other conditions to escape. 
     In another aspect of the present invention, opposing terminals  22 ,  24  allow the individual battery units  20  to be bussed as battery modules  12  in a compact form. An individual battery unit  20  can be rotated around horizontal axis  82  in a clockwise direction  94  by 180 degrees and placed on top of another battery unit  20 . 
       FIGS. 4A through 4F  show one construction process for a preferred embodiment of the invention. A first battery unit  201 , and additional battery units  20 , are configured the following way. Positive terminals  22  (e.g., aluminum) and negative terminals  24  (copper) of battery units  20  are oriented such that negative terminal  24  is electrically connected to the top surface of ultrasonically welded anodic exposed grids  90  and positive terminal  22  is electrically connected to the bottom surface of the ultrasonically welded cathodic exposed grids  88 . A second battery unit  20   2  is placed adjacent first battery unit  20   1  ( FIG. 4A ) such that positive terminal  22  on bottom surface of second battery unit  20   2  is electrically connected to negative terminal  24  on top surface of first battery unit  20   1  (FIG.  4 B). Second battery unit  20   2  is rotated clockwise about 180 degrees  94  around horizontal axis  82  such that negative terminal  24  of second battery unit  20   2  is oriented above positive terminal  22  of first battery unit  20   1  (FIG.  4 C). A third battery unit  20   3  may be placed on second battery unit  20   2  such that positive terminal  22  on bottom surface of third battery unit  20   3  is electrically connected to negative terminal  24  on top surface of second battery unit  20   2  (FIG.  4 D). No rotation  94  of third battery unit  20   3  is required. A fourth battery unit  20   4  may be oriented as second battery unit  20   2  such that positive terminal  22  on bottom surface of fourth battery unit  20   4  is electrically connected to negative terminal  24  on top surface of third battery unit  20   3  (FIG.  4 E). Fourth battery unit  20   4  is rotated clockwise about 180 degrees  94  around horizontal axis  82  such that negative terminal  24  of fourth battery unit  20   4  is oriented above positive terminal  22  of third battery unit  20   3  and first battery unit  20   1  (FIG.  4 F). This “stacking” of successive battery units  20  can be repeated for a plurality of battery units  20 . Note, in a constructed embodiment, positive terminal  22  does not generally include a tang  26 . However, respecting  FIG. 4F , the bottom terminal designated T BOTTOM , may include a tang electrically connected thereto so as to facilitate connection to flexible circuit  14 . The overall positive terminal of module  12  in T BOTTOM , while the overall negative terminal of module  12  is designated T TOP . Each node, it should be appreciated, also includes at least one tang, owing to the presence of a negative terminal. This allows voltage sensing for each unit  20 . 
     By placing negative terminal  22  on a second end  86  opposing positive terminal  24  with respect to a horizontal axis  82 , a more compact stacking of battery units  20  to create a battery module  12  is available. This is another aspect of the invention. 
     In another aspect of the invention,  FIG. 5  shows terminal  24  in greater detail. Terminal  24  comprises an electrically conductive tab and may be formed of copper or aluminum material. Terminal  24  allows individual battery unit  20  to be electrically connected to another individual battery unit  20 , the flexible connection  14 , or another electrical connection. The terminal  24  has a first region  96 , a second region  98  having apertures  99   a , a third region  100 , a fourth region  102 , a first locating hole  104  and a second locating hole  106 . In the illustrated embodiment, terminal  24  has a tang  26  protruding from one edge of third region  100  along a lengthwise axis  101 . The first region  96  may be welded to the exposed grids  90  of the plurality of bicells  78 . 
     In a first embodiment, apertures  99   a  in region  98   a  are arranged in a repeating pattern and comprise a standard slot, I-shape through aperture. This allows adhesive to flow therethrough. 
       FIG. 6  shows a second embodiment of second region, designated  98   b . The second region  98   b  contains apertures  99   b  cut through terminal  24 . In the illustrated embodiment, apertures  99   b  run substantially the length of terminal  24 . Packaging envelope  80  seals to itself through the apertures of second region  98   b  at the sides  84 ,  86  because of the hot melt adhesive flows from above and below the apertures  98   b  to adhere to itself The apertures  98   b  reduce or eliminate leaks of electrolyte solution from bicells  78  in at least two ways. First, the apertures  98   b  allow packaging envelope  80  to more effectively seal because the hot melt adhesive binds with itself. Second, the design of the apertures  98   b  creates a convoluted path by which the electrolyte solution must travel in order to leak from bicell  78 . 
       FIG. 7  shows an enlarged view of a repeating pattern of apertures  98   b  referred to in the encircled region designated “ 7 ” in FIG.  6 .  FIG. 7  shows a first axis  108 , a transverse axis  110 , L-shaped apertures  112 , and I-shaped apertures  114 . I-shaped apertures  114  are cut along a horizontal axis  108 . I-shaped apertures  114  are located between sets of L-shaped apertures  112 , wherein the long leg of the L-shaped aperture is located along the direction of transverse axis  10 . There may be four orientations of L-shaped apertures  112   a ,  112   b ,  112   c ,  112   d . A first orientation  112   a  is oriented as the letter “L” in the conventional manner. A second orientation  112   b  is the mirror image of the first orientation  112   a , the image being reflected with respect to transverse axis  110 . This second orientation resembles a backward letter “L”. A third orientation  112   c  is the mirror image of  112   a , the image being reflected through horizontal axis  108 . A fourth orientation  112   d  is the mirror image of second orientation  112   b , the image being reflected through horizontal axis  108 . As viewed along transverse axis  110 , a first pattern  113  is located above a second pattern  115 . As described along horizontal axis  108 , first pattern  113  may include one third orientation L-shaped aperture  112   c , followed by one fourth orientation L-shaped aperture  112   d . Between the long legs of two L-shaped apertures  112   c ,  112   d  is located one I-shaped aperture  114  aligned along the horizontal axis  108 . As described along horizontal axis  108 , second pattern  115  may include one first orientation L-shaped aperture  112   a , followed by a second orientation L-shaped aperture  112   b . Between the long legs of the two L-shaped apertures  112   a ,  112   b  is located one I-shaped aperture  114  aligned along the horizontal axis  108 . 
       FIG. 8  is a section view taken substantially along lines  8 — 8  in FIG.  6  and shows a first side  120  and a second side  122  of terminal  24  in second region  98 . This better illustrates how the apertures  98 , allow the hot melt adhesive of the packaging  80  to seal with itself. 
       FIG. 9  is a section view taken substantially along lines  9 — 9  in FIG.  5  and shows an electrical insulator  124  applied to the fourth region  102  of the terminal  24 . Insulator  124 , such as a polyester, may be applied in the form of a tape or may be applied at the time of manufacture of terminal  24 . These methods are known to those of ordinary skill in the art. Insulator  124  is applied to first side  120  of terminal  24 , second side  122  of terminal  24 , and edge  126  of terminal  24 . Placement of insulator  124  reduces or eliminates shorting of terminal  24  that could be created if terminal  24  comes in contact with the aluminum layer of packaging envelope  80 . 
     Terminal  24  may contain first locating hole  104  and second locating hole  106 . These holes  104 ,  106  may aid in welding of terminal  24  to exposed grids  88 ,  90  of plurality of bicells  78  and manufacture of battery unit  20  by aiding in alignment of components for sealing. 
     It should be understood that although  FIG. 5  illustrates tang  26 , tang  26  is not required for the invention. In a preferred embodiment, positive terminal  22  excludes tang  26 , and negative terminal  24  includes tang  26 , tang  26  being the location of electrical connection of battery units  20  to flexible circuit  14 . 
     Terminal  24  (including or excluding tang  26 ) aids in the sealing of packaging envelope in at least two ways. Apertures  99   a ,  99   b  allow hot melt adhesive of packaging envelope  80  to seal to itself. Further, apertures  99   b  create a convoluted path, making it more difficult for electrolytic solution to leak from packaging envelope  80 . In one embodiment, terminal  24  may include a tang  26  that aids in connection of battery unit  20  to flexible circuit  14 . Terminal  24  is another aspect of the invention.