Patent Publication Number: US-2017365826-A1

Title: Battery packs and methods for manufacturing battery packs

Description:
RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 62/352,149, filed Jun. 20, 2016, titled “Battery Packs and Methods for Manufacturing Battery Packs” and U.S. Provisional Patent Application No. 62/426,634, filed Nov. 28, 2016, titled, “Low Pressure Molded Printed Circuit Board.” 
     This application also incorporates by reference in their entirety U.S. Pat. No. 9,406,915, issued Aug. 2, 2016, titled “Power Tool System,” and U.S. patent application Ser. No. 15/160,485, filed May 20, 2016, titled “Power Tool System.” 
    
    
     TECHNICAL FIELD 
     This application relates to rechargeable battery packs and methods for manufacturing the battery packs. Furthermore, this application relates to a battery pack including features for protecting electronic and electrical components from contamination including water and a method for manufacturing such a battery pack. In one implementation, the battery pack includes a printed circuit board, a low pressure mold material applied to the printed circuit board which encapsulates a first side of the printed circuit board and creates a perimeter wall around and extending from a second side of the printed circuit board thereby defining a volume and a potting material applied to the printed circuit board to fill the volume. 
     BACKGROUND 
     Cordless power tools generally utilize removable, rechargeable battery packs. It is common for the battery packs to operate in a variety of environments and operating conditions, many of them extremely harsh and often, the battery packs remain in these harsh environments even when not being used. These environments include wet, rainy and snowy conditions where water can get into the battery pack housing. Whether or not the battery packs are coupled to a power tool, water may find its way into the battery pack. As such, have an egress path for the water is very desirable. 
     In addition, when the battery packs are operated continuously or in hot environments, they tend to heat up and it is preferable to have air flow paths into and out of the battery pack. 
     In both of these conditions, it is desirable to include holes in the battery pack housing to allow water to leave the pack and to allow air to flow through the pack. 
     However, these holes in the battery pack housing may allow various contaminants, such as small dust particulates and metal shards from metal grinding to enter the battery pack. These contaminants and particulates can get under the battery cell insulating sleeve or between adjacent terminals or between adjacent battery cell straps and cause high impedance shorting in the electrical systems which may result in a failed battery pack. 
     While closing the holes would prevent the contaminants and particulates from entering the battery pack this also prevents fluids, such as water and air, inside the battery pack from exiting the pack. 
     Various efforts have been made to prevent the negative of effects of contaminants such as water, metal and dust that get inside the battery pack housing. As most of the electronics in the battery pack reside on a printed circuit board (PCB), much attention has been given to protecting the PCB. To this end, injection molded frames or potting boats are precast and attached to the PCB. Thereafter, a potting material is applied to the PCB to encapsulate the electronic components on the PCB. These injection molded frames are costly, require the additional step of molding the frame and applying the frame to the PCB. Furthermore, the injection molded frame cannot be used to encapsulate any portion of the populated PCB. 
     As such, an improved encapsulated PCB is necessary to more effectively and efficiently protect the electronic components that populate the PCB of the battery pack. 
     SUMMARY 
     In order to address the concern of particulates entering the battery pack housing, the battery pack may include one or more features to isolate, insulate or separate the battery cells, terminals and/or battery straps from other battery cells, terminals and/or battery straps in the battery pack. 
     An aspect of the present invention includes an encapsulated printed circuit board, comprising a printed circuit board having a top side, a bottom side and a perimeter wall coupling the top side and the bottom side; a low pressure molded material applied to the printed circuit board such that a portion of the low pressure molded material extends generally perpendicularly to the top side to create a potting wall extending from the top side generally parallel to the perimeter wall. 
     Another aspect of the present invention includes the aforementioned encapsulated printed circuit board, wherein the low pressure molded material encapsulates the bottom side. 
     Another aspect of the present invention includes the aforementioned encapsulated printed circuit board, wherein the low pressure molded material encapsulates a portion of the top side adjacent to an intersection of the top side and the perimeter wall. 
     Another aspect of the present invention includes the aforementioned encapsulated printed circuit board, wherein the potting wall extending from the top side extends from the top side from the portion of the top side adjacent to the intersection of the top side and the perimeter wall. 
     Another aspect of the present invention includes the aforementioned encapsulated printed circuit board, wherein the low pressure molded material is a thermoplastic polyamide. 
     Another aspect of the present invention includes the aforementioned encapsulated printed circuit board, wherein the potting wall and the top side form a volume and a potting material fills the volume. 
     Another aspect of the present invention includes the aforementioned encapsulated printed circuit board, further comprising at least one lead wire coupled to the printed circuit board and wherein the low pressure molded material encapsulates a portion of the at least one lead wire coupled to the printed circuit board. 
     Another aspect of the present invention includes an encapsulated printed circuit board, comprising a printed circuit board having a top side, a bottom side and a perimeter wall coupling the top side and the bottom side; a low pressure molded material molded about a majority of the bottom side and at least a portion of the perimeter wall such that a potting wall extends generally perpendicularly to the top side and generally parallel to the perimeter wall at the at least a portion of the perimeter wall. 
     Another aspect of the present invention includes the aforementioned encapsulated printed circuit board, wherein the low pressure molded material is a thermoplastic polyamide. 
     Another aspect of the present invention includes the aforementioned encapsulated printed circuit board, wherein the potting wall and the top side form a volume and a potting material fills the volume. 
     Another aspect of the present invention includes a method of encapsulating a printed circuit board, comprising the steps of providing a printed circuit board having a top side, a bottom side and a perimeter wall coupling the top side and the bottom side; populating the printed circuit board with a plurality of electronic components; applying a low pressure molded material to at least a portion of the perimeter wall such that a portion of the low pressure molded material extends generally perpendicularly to the top side thereby creating a potting wall extending from the top side at the at least a portion of the perimeter wall and generally parallel to the perimeter wall. 
     Another aspect of the present invention includes the aforementioned method of encapsulating a printed circuit board, wherein creating the potting wall extending from the top side forms a volume defined by the top side and the potting wall and further comprising the step of filling the volume with a potting material. 
     Another aspect of the present invention includes a method of encapsulating a printed circuit board, comprising the steps of providing a printed circuit board having a top side, a bottom side and a perimeter wall coupling the top side and the bottom side; populating the printed circuit board with a plurality of electronic components; molding a low pressure molded material about a majority of the bottom side and at least a portion of the perimeter wall to form a potting wall that extends generally perpendicularly to the top side and generally parallel to the perimeter wall at the at least a portion of the perimeter wall. 
     Another aspect of the present invention includes the aforementioned method of encapsulating a printed circuit board, wherein the potting wall and the top side define a volume and further comprising the step of filling the volume with an encapsulating material. 
     Another aspect of the present invention includes a battery pack comprising a plurality of battery cells, a plurality of battery straps coupling the plurality of battery cells, and a cell holder holding the plurality of battery cells in a fixed position relative to each other. The cell holder includes a plurality of cutouts exposing the plurality of battery straps. The battery pack includes a room temperature vulcanized material applied to at least one of the recesses to cover at least a portion of the corresponding battery strap. 
     The RTV material provides the advantage of protecting the battery strap from water, dust, metal shards and/or other contaminants. 
     These and other advantages and features will be apparent from the description and the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an exemplary embodiment of a battery pack of the present disclosure. 
         FIG. 2  is an exploded view of the exemplary battery pack of  FIG. 1 . 
         FIG. 3A  is a perspective view of an exemplary core pack of the battery pack of  FIG. 1  without potting material. 
         FIG. 3B  is a top view of the exemplary core pack of  FIG. 3A . 
         FIG. 4A  is a perspective view of an exemplary populated printed circuit board of the core pack of  FIG. 3A . 
         FIG. 4B  is a top view of the populated printed circuit board of  FIG. 4A . 
         FIG. 5A  is a perspective view of the exemplary printed circuit board of  FIG. 4A  with various lead wires coupled to the printed circuit board. 
         FIG. 5B  is a top view of the exemplary printed circuit board of  FIG. 5A . 
         FIG. 6  is a top view of the exemplary printed circuit board of  FIG. 5B  partially encased in low pressure molded material. 
         FIG. 7  is a perspective view of the exemplary printed circuit board of  FIG. 5A  partially encased in low pressure molded material. 
         FIG. 8  is a bottom view of the exemplary printed circuit board of  FIG. 6 . 
         FIG. 9A  is a perspective view of the exemplary printed circuit board of  FIG. 7  with a conformal coating material applied. 
         FIG. 9B  is a top view of the exemplary printed circuit board of  FIG. 9A . 
         FIG. 10A  is a perspective view of the exemplary core pack of  FIG. 3A  with potting material applied. 
         FIG. 10B  is a top view of the exemplary core pack of  FIG. 10A . 
         FIGS. 11A and 11B  are additional views of the circuit board of  FIG. 6  encased in low pressure molded material and connected to various lead wires. 
         FIG. 12  is a side view of an exemplary embodiment of a core pack of the battery pack of  FIG. 1 . 
         FIG. 13  is a side view of another exemplary embodiment of a core pack of the battery pack of  FIG. 1 . 
         FIG. 14  is a side view of another exemplary embodiment of a core pack of the battery pack of  FIG. 1 . 
         FIG. 15  is a cross sectional view of the core pack of  FIG. 14 . 
         FIG. 16  is a perspective view of another exemplary embodiment of a core pack of the battery pack of  FIG. 1 . 
         FIG. 17  is another exemplary embodiment of a core pack of the battery pack of  FIG. 1 . 
         FIG. 18A  is a top view of a terminal block of the battery pack of  FIG. 1 . 
         FIG. 18B  is a bottom/interior view of an exemplary embodiment of the top housing of the battery pack of  FIG. 1 . 
         FIGS. 19A and 19B  are interior views of another exemplary embodiment of the top housing of the battery pack of  FIG. 1 . 
         FIG. 20A  is a top view of an exemplary embodiment of a converting element of the battery pack of  FIG. 1 . 
         FIG. 20B  is a bottom view of the converting element of  FIG. 20A . 
         FIG. 21  is a plan view of an exemplary embodiment of a jumper link of the battery pack of  FIG. 1 . 
         FIG. 22  is a forward view of an exemplary embodiment of a terminal block of the battery pack of  FIG. 1 . 
         FIG. 23A  is a perspective view of a conventional terminal block. 
         FIG. 23B  is a plan view of the terminal block of  FIG. 23A . 
         FIG. 24A  is a perspective view of a conventional power terminal of the terminal block of  FIG. 23A . 
         FIG. 24B  is a plan view of the terminal of  FIG. 24A . 
         FIG. 25A  is a perspective view of an exemplary embodiment of a terminal block of the battery pack of  FIG. 1 . 
         FIG. 25B  is a top plan view of the terminal block of  FIG. 25A . 
         FIG. 26A  is a perspective view of a power terminal of the terminal block of  FIG. 25A . 
         FIG. 26B  is a top plan view of the terminal of  FIG. 26A . 
         FIG. 27  is a plan view of the terminal of  FIG. 26B  being welded to a wire. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , there is illustrated an exemplary embodiment of a battery pack  10  of the present disclosure. This exemplary battery pack  10  is a convertible battery pack capable of switching between a low voltage configuration (for example, a 20 volt output) and a medium voltage configuration (for example, a 60 volt output) similar to the battery pack disclosed in U.S. Pat. No. 9,406,915 herein incorporated by reference and sold as FlexVolt™ battery packs by DeWalt™. The battery pack  10  includes a housing  12  for holding a battery core pack  14  and other components. The housing  12  includes a mechanical interface  16  for coupling with an associated powered device, such as a cordless power tool, e.g., circular saw, drill. The mechanical interface  16  includes a plurality of slots  18  in an upper portion  20  of the housing  12 . A first group of these slots  22  are positioned so as to allow terminals of the associated powered device to enter the battery pack housing  12  and mate with corresponding terminals (discussed below) of the battery pack  10 . The housing  12  also includes an opening that receives a latch  24  for latching the battery pack  10  to the associated power device. By necessity, the slots  22  and latch opening provide access for contaminants, such as water and dust and metal shards, into the battery pack housing  12 . The mechanical interface  16  of the battery pack housing  12  also includes a set of rails  29  that form a set of grooves  31 . The rails  29  and grooves  31  are configured to mate with a corresponding set of rails and grooves on the various power devices that are designed to mate with the battery pack  10 . The mechanical interface  16  also includes a second set of slots  23   a ,  23   b . These slots are configured and designed to mate with a corresponding converter element of a subset of the various power devices, e.g. 60 volt cordless power tools. 
     Referring also to  FIG. 2 , there is illustrated an exploded view of the battery pack  10  of  FIG. 1  and  FIGS. 3A and 3B , there is illustrated a side perspective view and a top view of an exemplary core pack of the present disclosure. In this particular exemplary battery pack  10 , the housing  12  includes a forward portion  25 , a top portion  26 , a rearward portion  27  and two side portions  28   a ,  28   b . The battery pack also includes the core pack  14 . The core pack  14  includes a cell holder  30 , a plurality of battery cells  78  held in a fixed position relative to each other by the cell holder  30 , a terminal block assembly  32 , a converter element housing  31 , and a printed circuit board  34 . The core pack  14  also includes a plurality of lead wires  40  coupling the battery cells (via various battery straps) to the PCB  34  and the PCB  34  (via board flag terminals) to the battery pack terminals  46  of the terminal block assembly  32 . The PCB  34  is populated with a plurality of various electronic components  48 , such as resistors, integrated circuits, capacitor, etc. This illustration does not include any potting material applied to the PCB  34 . When assembled, the top portion  26  is placed on the core pack  14  and the two side portions  28   a ,  28   b  of the housing  12  are placed on either side of the core pack  14 . In this example, the cell holder  30  serves as a front and rear portion of the housing  12 . The side portions  28   a ,  28   b  hold the top portion  26  in place and the side portions  28   a ,  28   b  are fastened to the cell holder  30  by a plurality of fasteners  36 , such as screws. 
     As will be discussed in more detail below, a low pressure molded material  66 , for example, a thermoplastic polyamide such as that sold by Henkel under the tradename Technomelt PA646, partially encapsulates the PCB  34 . One side of the PCB  34  is positioned on the core pack  14  to abut the converter element housing  38  for the converter element. A portion of a second side of the PCB  34  is positioned on the core pack  14  to abut a standoff  52 . The standoff  52  may be used to position the top housing  26  relative to the core pack  14 . The standoff  52  and the converter element housing  38  assist in positioning the PCB  34  on the core pack  14  and help define a volume along with a top side  60  of the PCB  34  and a potting wall  68  created by the low pressure molded material, as discussed in further detail below. 
     In addition, several lead wires  40  connect the various battery straps  42  to the PCB  34 . A first end of the lead wire  40  is coupled, typically by soldering or welding, to the battery strap  42 . A second end of the lead wire  40  is connected to a connector  58  on the PCB  34 . The connector  58  may include a set of pins to fix the end of the lead wire  40  to the connector  58 . The PCB connector  58  and the second end of the lead wire  40  are encapsulated by the low pressure molded material  66  during the molding process. This seals the wire connections at the PCB connector  58  and protects the exposed wires and connectors  58  from contaminants. 
     As described in more detail below, the PCB assembly including the populated PCB  34 , the PCB connectors  58 , the lead wires  40  and low pressure molded material  66  are placed on the cell holder to provide the core pack  14  illustrated in  FIGS. 3A and 3B . 
     After the PCB assembly is placed on the cell holder  30 , the PCB assembly may be affixed to the cell holder  30  by various fasteners, as is well known in the art. The lead wires  40  are coupled to the associated, corresponding battery straps  42 , and the terminal flags  44  are coupled to the associated, corresponding battery terminals  46 . 
     As illustrated in  FIGS. 4A and 4B , the printed circuit board  34  for the battery pack  10  includes a top surface  60 , a bottom surface  62  and a perimeter wall  64  coupling the top surface  60  and the bottom surface  62 . Both the top surface  60  and the bottom surface  62  may be populated with a plurality of various electronic components  48 , such as integrated circuit, resistors, capacitors, etc., as is well known in the art. In the illustrated exemplary embodiment, a pair of connectors  58  are populated on the bottom surface  62  of the PCB  34  for receiving lead wires  40 . 
     As illustrated in  FIGS. 5A and 5B , the lead wires  40  are coupled to the connectors  58 . 
     As illustrated in  FIGS. 6, 7, and 8 , a low pressure molded (LPM) material  66 , such as a thermoplastic polyamide, is applied to the PCB  34 . The LPM material  66  may be applied to the bottom side  62  of the PCB  34  as is illustrated in  FIG. 8 . In this instance, the LPM material  66  encapsulates the wire connectors  58  and the ends of the wires  40  and provides a seal around the wires  40  thereby preventing contaminants, such as water, from entering the wire connectors  58 . As illustrated in  FIGS. 6 and 7 , the LPM material  66  may be applied along and encapsulate a portion of the perimeter wall  64  of the PCB  34 . In this instance, the LPM material  66  may overlap and encapsulate a portion  67  of the top surface  60  of the PCB  34  adjacent to the intersection of the top surface  60  of the PCB  34  and the perimeter wall  64  of the PCB  34 . Furthermore, the LPM material  66  may be molded such that a potting wall  68  is formed around and encapsulates a portion of the perimeter of the PCB  34 . The potting wall  68  extends generally perpendicularly to the top surface  60  of the PCB  34  and generally parallel to the perimeter wall  64  of the PCB  34 . The potting wall  68  along with the top surface  60  of the PCB  34  form a volume  70 . The potting wall  68  and the top surface  60  of the PCB  34  may be referred to as a potting boat  72 . 
     In a first process, as illustrated in  FIGS. 9A and 9B , after the LPM material  66  is molded onto the PCB  34 , a potting material or conformal coating material  74  may be applied to the top surface/side  60  of the PCB  34  in the volume  70  created by the potting wall  68  and the top side  60  of the PCB  34 . Thereafter, the PCB assembly with the potting material  74  is coupled to the cell holder  30  and the lead wires  40  are attached to the appropriate straps, as illustrated in  FIGS. 10A and 10B . 
     In a second process, the PCB assembly is joined with the cell holder  30  and then a potting material (such as thermosetting plastics or silicone rubber gels) or a conformal coating material (such as an acrylic, an epoxy, polyurethane, or a silicone) is applied to a top surface  60  of the PCB  34  in the volume  70  defined by the potting boat  72  comprising the LPM material  66  and the top surface  60  of the PCB  34 . 
     In this second process, as illustrated in  FIGS. 10A and 10B , the converter element housing  38  and the standoff  52  along with the potting wall  68  and the top surface  60  of the PCB  34  may serve to define the potting boat volume  70 . In alternate embodiments, the LPM material  66  may be molded about the PCB  34  to form a potting wall  68  about the entire perimeter of the PCB  34 . This will depend upon the particular battery pack and core pack to which the PCB is being used. 
     By using a LPM material  66  to create the potting wall  68 , the volume  70  for a potting material or conformal coating material  74  can be created in a much more efficient process than if an insert molded plastic part is created which is then attached to the PCB to create a potting volume. 
       FIGS. 11A and 11B  illustrate enhanced views of the lead wires  40  coupled to the connectors  58  as they are encapsulated in the LPM material  66 . 
     Referring to  FIG. 12 , an exemplary embodiment of the core pack  14  includes a plurality of battery cells  78 . The battery cells  78  are housed in the plastic cell holder  30  and end caps  80 . The end caps  80  include recesses/cutouts  82  which expose the positive or negative poles of the battery cells  78 . The core pack  14  also includes metal conductors  42  (also referred to as power straps or battery straps) positioned in the recesses  82  that electrically couple a negative pole of a first battery cell to a positive pole of a second battery cell to connect the cells in series or connect a battery cell pole to a circuit board which provides current from the cells to a connected device. 
     In order to protect or insulate the power straps  42  from water or other particulates, an amount of room temperature vulcanized (RTV) silicone  84  or a similar encapsulate coating is applied in the recess  82  to fully or partially cover the power strap  42 .  FIG. 12  illustrates a single power strap  42   a  having the RTV silicone  84  applied thereto, however some or all of the power straps  42  may have RTV silicone  84  applied thereto. The RTV silicone prevents water or other particulates from the power traps  42 . 
     Referring to  FIGS. 12, 13 and 14 , in certain instances a first power strap  42   a —which in conventional battery packs is not insulated—is overlapped by a portion of a second power strap  42   b —which is also not insulated. If a short, caused for example by water or metal particulates, bridges between the two power straps  42   a ,  42   b , undesired heating may occur. 
     In order to address this issue, the first power strap  42   a  housed in one of the recesses  82  in the end cap  80 . An amount of the RTV silicone  84  or similar encapsulate coating is applied in the recess  82  to fully or partially cover the power strap  18   a . In another exemplary embodiment of the core pack  14 , a dielectric, high temperature insulator  86  is placed over the RTV silicone  22 . The insulator  86  is pressed into the recess  82  thereby compressing the RTV silicone  84  until the RTV silicone  84  expresses around the insulator  86  and effectively creates a seal to prevent liquid or fine particulate contaminants from contacting the first battery cell  78  or the first battery strap  42   a . Referring to  FIG. 14 , the second power strap  42   b  is placed on the battery core pack  14  overlapping a portion of the first power strap  42   a . The RTV silicone  84  and the insulator  86  provide an insulating layer between the first power strap  42   a  and the second power strap  42   b . This effectively prevents a short from occurring between the first and the second power straps  42   a ,  42   b . In an alternate exemplary embodiment of the core pack  14 , the insulator  86  may be omitted such that only the RTV silicone  22  is positioned between the two battery straps  42   a ,  42   b . In another alternate exemplary embodiment of the core pack  14 , the RTV silicone  84  may be omitted such that only the insulator is positioned between the two battery straps  42   a ,  42   b.    
     Referring to  FIG. 14 , RTV silicone adhesive coatings  84  and/or insulator pads  86 , in either custom or generic shapes, may be applied to some or all of the recesses  82  of the battery core pack  14  to seal all of the positive poles of the battery cells  78  and the associated battery straps  42  or all of both the positive and the negative poles of the battery cells and the associated battery straps. The battery core pack  14  illustrates the RTV adhesive coating  84  applied to several of the battery straps  42  or having the adhesive coating  84  and the insulating pad  86  applied to the battery straps  42 . The adhesive coating  84  and/or the insulating pad  86  may be applied to all of or less than all of the battery straps  42 , depending upon the cell layout and the voltage differentials between adjacent cells and associated power straps. 
     The RTV adhesive  84  may also be applied to the lead wires  40  at the connection to the battery straps  42 , as illustrated in  FIG. 14 . 
       FIG. 15  illustrates a cross section view of the core pack  14  along line  15 - 15  of  FIG. 14 . As illustrated in  FIG. 15 , three battery cells  78   a ,  78   b ,  78   c  are held in fixed relation to each other by the cell holder  30  and the end caps  80   a ,  80   b . The first battery strap  42   a  connects the first battery cell  78   a  to the second battery cell  78   b . The RTV silicone (encapsulating material)  84  is applied and positioned in the recess  82   a  exposing the first battery strap  42   a  to cover the first battery strap  42   a . The insulating pad  86  is applied to and positioned in the recess  82   a  to cover the RTV silicone  84 . The second power strap  42   b  connects the third battery cell  78   c  and a printed circuit board  34  (as illustrated in  FIG. 2 ). The RTV silicone  84  and the insulating pad  86  insulate the first battery strap  42   a  and the second battery strap from each other. 
     Referring to  FIG. 16 , another exemplary embodiment of a core pack  14  is illustrated. In this embodiment, one or more gaskets  90  may be placed over the positive poles of the battery cell  78  to keep fine dust particulate out. In a first embodiment, the gaskets  90  are placed over only the positive battery cell poles. In a second embodiment, the gaskets  90   b  are placed over both the positive battery cell poles and the negative battery cell poles to give further protection against liquid contamination. The silicone gasket pads  90  are sized such that they can fit many different cell/strap shapes and such that they are oversized to the recess  82  such that the gasket pads  90  wrap up and over the walls of the recess  82  of the end cap  80  to provide a seal for the recess  82  and enclose the battery strap  42 . The RTV silicone  84  may also be applied to the battery straps  42  without a gasket  90 . The RTV silicone  84  may also be applied to the lead wires  40  to provide additional protection. 
     Referring to  FIG. 17 , another exemplary embodiment of the core pack  14  is illustrated. In this embodiment, the RTV silicone material  84  is applied to the end caps  80  between battery straps  42   c ,  42   d  having a high voltage differential. For example, the voltage differential between the third battery strap  42   c  and the fourth battery strap  42   d  could be 20V. The side portions  28   a ,  28   b  are then assembled to the battery core pack and pressed against the RTV silicone  84 —effectively forming a seal. A gasket could be used as an alternate to the RTV silicone. 
       FIG. 18 a    illustrates an exemplary embodiment of terminal block assembly  32 . In order to prevent water, dust, metal shavings or other particulates from connecting adjacent battery terminals  46 , a high temperature, high dielectric tape  94  such as Kapton are placed over the battery pack positive power terminal (B+)  46   a  and the battery pack negative power terminal (B- 46   b . The tape  31  blocks any possible creepage path to nearby terminals of high voltage differential, for example signal terminal  46   c.    
     In one exemplary embodiment, clear RTV silicone  96  is applied along certain exposed metal edges of power terminals  46   a ,  46   b  and/or signal terminals  46 , to provide redundancy to the tape  94 . 
     In addition or alternatively, white RTV silicone  98  is applied vertically between terminals  46  of high voltage differential, for example power terminals  46   a  and signal terminals  46   c  and/or power terminal  46   b  and signal terminal  46   d . Referring to  FIG. 18 b   , there is illustrated an exemplary embodiment of an interior surface of the top portion  16  of the battery pack  10 . The top portion  16  includes ribs  100  extending from the interior surface of the top portion  16 . When the top portion  26  is mated with the core pack  14 , the ribs  100  make contact with the white RTV silicone  98  while still wet to seal the terminals  46   a ,  46   c  and  46   b ,  46   d  from bridging when exposed to liquid or particulate contamination. 
     Referring to  FIG. 19 a   , another exemplary embodiment of the top portion  10  is illustrated. As illustrated a flowable glue  110 , such as RTV is applied onto the interior surface of the battery top housing. As such, when the battery top housing  26  is assembled onto the battery core pack  14  the glue  110  will cover areas of high voltage differential, for example between adjacent battery straps  42 . 
     Referring to  FIG. 19 b   , a “texture mark”  114  may be added to the top housing  26  to aid operators in applying the glue  110  to proper location. 
     Referring to  FIGS. 20 a  and 20 b   , in order to manufacture a battery pack  10  including a converter element (internal switching network) utilizing a plastic board  116  incorporating various metal traces in a cost effective manner, a plurality of holes  118  with exposed metal are created on the board  116 . The exposed metal presents a risk for potential contamination bridging. 
     This risk could be addressed by secondary overmolding, which is costly and adds no value to the part or user beyond contamination protection. Alternatively, a lower cost, more simple option is to use simple pieces of tape  120 , for example, die-cut tape to cover exposed metal that are present in areas of relatively high voltage differential. 
     Referring to  FIGS. 20 b    and  21 , a metal conductor  122  is used to connect a first terminal on the converter element to the battery cells  78 . A metal jumper link  122  was chosen for this purpose due to its ability to conduct high currents in a low profile shape. 
     In order to prevent contamination from bridging the jumper link  122  (which is at 0V potential) to all other high potentials (wire connectors, exposed metal of the board or core pack, etc.), a high temp, high dielectric material  124 , such as Kapton tape, is applied to the jumper link  122 . 
     Referring to  FIG. 22 , another exemplary embodiment of the terminal block assembly  32  is illustrated. In this embodiment, a dielectric grease is applied to the battery terminals/contacts  46  to prevent arcing between adjacent terminals due to contaminants. 
     Referring to  FIGS. 23A, 23B, 24A and 24B , there is illustrated a set of conventional battery pack power terminals  130   a ,  130   b  electrically connected to wires  132   a ,  132   b . The wires  132  are coupled to the battery cells  78  (not shown) to provide power from the battery cells  78  to the power terminals  130   a ,  130   b  for providing power from the battery pack  10  to a connected/mated power tool to power the power tool motor. The conventional power terminals  130  includes a forward end  134  presenting two contact portions  136   a ,  136   b  configured in a tulip-like shape to mate with a corresponding power terminal of the connected power tool and a rearward end  138  presenting a single contact portion  140  configured coupled to the battery cell wire  132 . 
     In this configuration, any current flowing from the battery cells  78  through the cell wires  132  and the power terminals  130  will converge at coupling point  142  where the single contact portion  140  meets the two contact portions  136   a ,  136   b . This will increase resistance and corresponding heat. 
     Referring to  FIGS. 25A, 25B, 26A, and 26B , there is illustrated an exemplary embodiment of a set of battery pack power terminals  150   c ,  150   d  of the present invention (The power terminals  150   c ,  150   d  are also illustrated as terminals  46   c ,  46   d  in  FIGS. 3A, 3B and 22 ) electrically connected to wires  152   a ,  152   b . The wires  152   a ,  152   b  are coupled to the battery cells  78  to provide power from the cells to the power terminals  150   c ,  150   d  for providing power from the battery pack  10  to a connected/mated power tool to power the power tool motor. The presently presented power terminals  150   c ,  150   d  includes a forward end  154  presenting two contact portions  156   a ,  156   b  configured in a tulip-like shape to mate with a corresponding power terminal of the connected power tool and a rearward end  158  presenting two contact portions  160   a ,  160   b  configured to couple to the battery cell wire  152 . 
     In this configuration, any current flowing from the battery cells  78  through the cell wires  152   a ,  152   b  and the presently presented power terminals  150   c ,  150   d  will flow more evenly where the two contact portions  160   a ,  160   b  meet the two contact portions  156   a ,  156   b . This will increase reduce resistance and corresponding heat as compared to the conventional power terminal. 
     Referring to  FIG. 27 , the wire  152   a  is first pre-welded to give it a prismatic shape. After the wire  152   a  has been pre-welded, the two contact portions  160   a ,  160   b  of the terminal  150  and the wire  152  are placed into a fixture and resistance welded. 
     Numerous modifications may be made to the exemplary implementations described above. These and other implementations are within the scope of this application.