Patent Publication Number: US-2021184271-A1

Title: Battery pack switch

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/845,068, filed Dec. 18, 2017, now U.S. Pat. No. 10,944,131, which claims priority to U.S. Provisional Patent Application No. 62/435,453, filed Dec. 16, 2016, the entire content of each of which is incorporated herein by reference. 
    
    
     FIELD 
     Embodiments relate to battery packs containing two or more battery cells. 
     SUMMARY 
     Electrical devices, such as power tools, outdoor tools, etc., may be configured to electrically connect to, and be powered by, a battery pack. Battery packs typically include one or more battery cells, such as battery cells having a lithium-ion chemistry. The battery cells are electrically connected together in a series-type configuration and/or a parallel-type configuration, such that the electrically-connected battery cells, and thus the battery pack, output a power having predetermined electrical characteristics (for example, a predetermined voltage, a predetermined power capacity, etc.) for powering the device. 
     Battery packs having cells with a lithium-ion chemistry may be subject to shipping regulations. Such shipping regulations may limit the voltage and/or power capacity of the battery pack being shipped. 
     In one independent embodiment, battery pack may generally include a housing defining an aperture, a first battery cell within the housing, a second battery cell within the housing, and a switch. The first battery cell is electrically connected to a first terminal. The second battery cell is electrically connected to a second terminal. The switch is configured to be in a first position and a second position. The switch includes a user-interface, which may extend through the aperture, and a plate, located within the housing. The plate includes a conductive portion and a non-conductive portion. The conductive portion is configured to electrically connect the first terminal to the second terminal when the switch is in the first position. The non-conductive portion is configured to galvanically isolate the first terminal from the second terminal when the switch is in the second position. 
     In another independent embodiment, a battery pack may generally include a housing, a first battery cell within the housing, a second battery cell within the housing, and a switch. The first battery cell may be electrically connected to a first terminal having a first upper foot and a first lower foot biased toward each other. The second battery cell may be electrically connected to a second terminal having a second upper foot and a second lower foot biased toward each other. The switch is configured to be in a first position and a second position. The switch includes a plate located within the housing. The plate includes a conductive portion configured to electrically connect the first terminal to the second terminal when the switch is in the first position, and a non-conductive portion configured to galvanically isolate the first terminal from the second terminal when the switch is in the second position. 
     In another embodiment, a battery pack including a housing, a first battery cell within the housing, a second battery cell within the housing, and a sliding switch. The first battery cell is electrically connected to a first terminal. The second battery cell is electrically connected to a second terminal. The sliding switch is located on an exterior portion of the housing. The sliding switch is configured to be in a first position and a second position. The sliding switch includes a plate having a conductive portion and a non-conductive portion. The conductive portion is configured to electrically connect the first terminal to the second terminal when the switch is in the first position. The non-conductive portion is configured to galvanically isolate the first terminal from the second terminal when the switch is in the second position. 
     In another embodiment, a battery pack including a housing defining an aperture, a first battery cell within the housing, a second battery cell within the housing, and a plate. The first battery cell is electrically connected to a first terminal. The second battery cell is electrically connected to a second terminal. The plate is configured to be in a first position and a second position. The plate includes a plunger extending from the plate into the aperture. The plunger includes a conductive portion and a non-conductive portion. The conductive portion is configured to electrically connect the first terminal to the second terminal when the plunger is in the first position. The non-conductive portion is configured to galvanically isolate the first terminal from the second terminal when the plunger is in the second position. 
     In another independent embodiment, a battery pack may generally include a housing, a first battery cell disposed within the housing, a second battery cell disposed within the housing, and a switch located on an exterior of the housing and configured to be in a first or on position, in which the first battery cell is electrically connected to the second battery cell, or in a second or off position, in which the first battery cell is electrically disconnected from the second battery cell. 
     In another independent embodiment, a battery pack may generally include a housing, a first battery cell within the housing, a second battery cell within the housing, and a switch located on an exterior of the housing and configured to be in a first position and a second position. The switch may include a first terminal electrically connected to the first battery cell, a second terminal electrically connected to the second battery cell, a conductive portion configured to engage the first terminal and the second terminal when the switch is in the first position, and a non-conductive portion configured to engage at least one of the first terminal and the second terminal when the switch is in the second position. 
     In yet another independent embodiment, a battery pack may generally include a housing defining an aperture, a first battery cell within the housing, a second battery cell within the housing, and a switch located on an exterior of the housing and configured to be in a first position, in which the first battery cell is electrically disconnected from the second battery cell, and a second position, in which the first battery cell is electrically connected to the second battery cell. The switch may include a plate, a male member configured to be inserted into the aperture when the switch is in the second position, and a biasing member biasing the plate away from the housing. 
     In some constructions, the housing may include the switch. In some constructions, the switch may be configured to slide between the first position and the second position. 
     In some embodiments, the battery pack may be configured to output 72V when the switch is in the on position. In some embodiments, the battery pack may be configured to output 120V when the switch is in the on position. In some embodiments, the battery pack may be configured to have a power capacity approximately equal to or less than 100 watt-hours. In some embodiments, the battery pack may be configured to have a power capacity approximately equal to or less than 300 watt-hours. 
     Other independent aspects of the application will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  illustrates a battery pack system. 
         FIG. 1B  illustrates a battery pack system. 
         FIG. 2  is a perspective view of a battery pack of the battery pack systems of  FIG. 1A  and/or  FIG. 1B . 
         FIG. 3  is a perspective view of a plurality of subcores of the battery pack of  FIG. 2 . 
         FIG. 4  is partial cutaway view of a plurality of battery cells within the battery pack of  FIG. 1A  and/or  FIG. 1B . 
         FIG. 5  is a block diagram of the battery pack of  FIG. 2 . 
         FIG. 6  is a perspective view of an alternative construction of a battery pack. 
         FIGS. 7A and 7B  are perspective views a switch of the battery pack of  FIG. 6 , illustrating operation of the switch. 
         FIG. 8  illustrates a terminal of the switch of  FIGS. 7A and 7B . 
         FIGS. 9A and 9B  are block diagrams of the battery pack of  FIG. 6 , illustrating operation of the switch. 
         FIG. 10  is an electrical diagram of a switch. 
         FIG. 11  is a perspective view of another alternative construction of a battery pack. 
         FIGS. 12A and 12B  are block diagrams of the battery pack of  FIG. 11 , illustrating operation of the switch. 
         FIG. 13  is a perspective view of another alternative construction of a battery pack. 
         FIGS. 14A and 14B  are perspective view of a switch of the battery pack of  FIG. 13 . 
         FIGS. 15A and 15B  are perspective views a switch of the battery pack of  FIG. 13 , illustrating operation of the switch. 
         FIG. 15C  is a perspective, partially exposed view of a plate of the switch of  FIGS. 15A and 15B . 
         FIG. 15D  is a perspective view of the plate of the switch of  FIGS. 15A  including a terminal. 
         FIGS. 16A-16D  illustrates views of a stop member of the switch of  FIGS. 15A-15D . 
         FIG. 17  is an enlarged view of the switch of  FIGS. 15A and 15B . 
         FIG. 18  is a block diagram of a battery monitoring circuit. 
         FIG. 19  is a block diagram of an alternative battery monitoring circuit. 
         FIG. 20  is a block diagram of a battery monitoring circuit using shared inter-integrated circuit bus. 
         FIGS. 21A-21B  are block diagrams of a battery monitoring circuit using multiplexors and a shared inter-integrated circuit bus. 
         FIG. 22  is a block diagram of a battery monitoring circuit using multiple inter-integrated circuit buses. 
         FIG. 23  is a block diagram of a battery monitoring circuit using a serial peripheral interface. 
     
    
    
     DETAILED DESCRIPTION 
     Before any independent embodiments of the application are explained in detail, it is to be understood that the application is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The application is capable of other independent embodiments and of being practiced or of being carried out in various ways. 
     The phrase “series-type configuration” as used herein refers to a circuit arrangement in which the described elements are arranged, in general, in a sequential fashion such that the output of one element is coupled to the input of another, though the same current may not pass through each element. For example, in a “series-type configuration,” additional circuit elements may be connected in parallel with one or more of the elements in the “series-type configuration.” Furthermore, additional circuit elements can be connected at nodes in the series-type configuration such that branches in the circuit are present. Therefore, elements in a series-type configuration do not necessarily form a true “series circuit.” 
     Additionally, the phrase “parallel-type configuration” as used herein refers to a circuit arrangement in which the described elements are arranged, in general, in a manner such that one element is connected to another element, such that the circuit forms a parallel branch of the circuit arrangement. In such a configuration, the individual elements of the circuit may not have the same potential difference across them individually. For example, in a parallel-type configuration of the circuit, two circuit elements in parallel with one another may be connected in series with one or more additional elements of the circuit. Therefore, a circuit in a “parallel-type configuration” can include elements that do not necessarily individually form a true “parallel circuit.” 
       FIGS. 1A and 1B  illustrate a battery pack  100  according to some independent embodiments of the application. The battery pack  100  is configured to couple (e.g., electrically, electronically and physically) to one or more electrical devices  105   a - 105   g,  such as power tools, outdoor tools, etc. In the illustrated embodiment, the devices  105   a - 105   g  include, for example, a miter saw  105   a,  a rotary hammer  105   b,  a table saw  105   c,  a circular saw  105   d,  a cut-off machine  105   e,  a leaf blower  105   f,  and a string trimmer  105   g.  However, the battery pack  100  may be configured to couple to other electrical devices (not shown). 
     As shown in  FIG. 2 , the battery pack  100  includes a housing  200 . The housing  200  may be formed of plastic or a similar material. The housing  200  includes a battery pack interface  210  to electrically and physically connect the battery pack  100  to the one or more devices  105 . In some embodiments, the interface  210  includes a positive terminal, a ground terminal, and a communication terminal. Although illustrated as a rail and groove interface, in other embodiments, the interface  210  may be a receptacle and stem interface. 
       FIG. 3  illustrates individual batteries, or electrical subcores,  300   a,    300   b,    300   c , . . .  300   n  (three illustrated) contained within the housing  200 . Each subcore  300   a - 300   c  is electrically and/or communicatively coupled to a slave controller  310 , or slave printed circuit board assembly (PCBA). Each slave controller  310  is electrically and/or communicatively coupled to a master controller  315 , or a master PCBA. As discussed in further detail below, the electrical subcores  300   a - 300   c  are configured to be selectively electrically connected in a series-type configuration and/or a parallel-type configuration. 
       FIG. 4  illustrates a plurality of cells  400  located within the housing  200 . As illustrated, the cells  400  may be physically and/or electrically grouped into electrical subcores  300 . In the illustrated construction, the cells  400 , and thus the electrical subcores  300 , are electrically connected to each other via a plurality of straps  402 . In some embodiments, the straps  402  are permanently attached (for example, welded) to the cells  400 . Although illustrated as having a layout of four subcores  300  each including five cells  400  (for a total of twenty cells  400 ), in other constructions, there may be more or less cells in varying layouts. 
       FIG. 5  is a block diagram of battery pack  100 . Although illustrated as only having two battery cells  400 , each subcore  300   a - 300   c  includes one or more battery cells  400   a,    400   b ,  400   c,  respectively. In some embodiments, each subcore  300  includes ten battery cells  400 . The battery cells  400   a - 400   c  may have a lithium-ion, or similar chemistry. The battery cells  400   a ,  400   b,    400   c,  contained within their respective subcores  300   a,    300   b,    300   c,  may be electrically connected in a series-type configuration and/or a parallel-type configuration such that each subcore  300   a,    300   b,    300   c  provides a desired voltage, a desired current output, and a desired power capacity. In some embodiments, the subcores  300   a,    300   b,    300   c  have approximately the same voltage, current, and power capacity. In other embodiments, the subcores  300   a,    300   b,    300   c  may have different voltages, currents, or power capacities. 
     As discussed above, the subcores  300   a - 300   c  are selectively electrically connected to each other. In the illustrated embodiment, the subcores  300   a - 300   c  are selectively electrically connected to each other via electric switching devices  405   a  and  405   b.  Although illustrated as being electrically connected in a series-type configuration, in other embodiments, the subcores  300   a - 300   c  may be alternatively, or additionally, in a parallel-type configuration, such that the electrically connected the subcores  300   a - 300   c,  and thus battery pack  100 , provides a desired pack voltage, a desired pack current output, and a desired pack power capacity. 
     The master controller  315  includes a plurality of electrical and electronic components providing power, operational control, protection, etc., to the components and modules within the master controller  315  and/or the battery pack  100 . For example, the master controller  315  includes, among other things, a processing unit  410  (e.g., a microprocessor, a microcontroller, or another suitable programmable device) and a memory  415 . In some embodiments, the master controller  315  is implemented partially or entirely on a printed circuit board or a semiconductor (e.g., a field-programmable gate array (“FPGA”) semiconductor) chip, such as a chip developed through a register transfer level (“RTL”) design process. In some embodiments, the master controller  315  may include further modules, such as, but not limited to a communications module (for example, a WiFi module and/or a Bluetooth module). In some embodiments, the slave controllers  310  include similar components. 
     The master controller  315  receives power from, and monitors, the electrically-connected subcores  300 . For example, in some embodiments, the master controller  315  monitors characteristics of the pack  100 , such as a pack voltage, a pack current, one or more pack temperatures, and a pack power capacity. The slave controllers  310  receive power from, and monitor, the individual subcores  300   a - 300   c.  For example, in some embodiments, the slave controllers  310  monitor characteristics of the respective subcore  300 , such as a subcore voltage, a subcore current, a subcore temperature, and a subcore power capacity. The slave controllers  310  may further be communicatively coupled to the master controller  315  and communicate characteristics of the respective subcore  300 , such as subcore voltages, subcore currents, subcore temperatures, and subcore power capacities, to the master controller  315 . 
       FIG. 6  illustrates an alternative battery pack  500 . The battery pack  500  may include substantially similar components as discussed above in relation to the battery pack  100 . 
     The battery pack  500  includes a battery pack housing  505  which may be substantially similar to battery pack housing  200  discussed above. The housing  505  has a battery pack interface  510  and a switch or cap  515 . As discussed in more detail below, the switch  515  is configured to be in a first position and a second position. When in the first (e.g., “OFF”) position, electrical components (for example, the subcores  300 ) of the battery pack  500  contained within the housing  505  are electrically disconnected from each other. When in the second (e.g., “ON”) position, electrical components (for example, the subcores  300 ) are electrically connected to each other. The switch  515  may be manipulated by a user from the first position to the second position. For example, in the illustrated embodiment, the switch  515  is slid in a first direction  520  to electrically connect the electrical components. 
       FIGS. 7A and 7B  illustrate the switch  515  of the battery pack  500 . The switch  515  includes a shell  600 , terminals  605   a,    605   b,    605   c , . . .  605   n,  a conductive bus  610 , and a non-conductive layer  615 . Similar to the housings  200  ( FIGS. 2 ) and  505  ( FIG. 6 ), the shell  600  may be formed of plastic or a similar material. The shell  600  is slidingly coupled to the housing  505  ( FIG. 6 ), while the conductive bus  610  and non-conductive layer  615  are coupled, or integral to, the housing  505  ( FIG. 6 ), such that the shell  600  are slidingly coupled to the conductive bus  610  and non-conductive layer  615 . 
     Although illustrated as having six terminals  605   a - 605   f,  in other embodiments (not shown), the battery pack  500  may have fewer or more terminals  605 . Each terminals  605  has a first end  630  coupled to the shell  600  and electrically coupled to the subcores  300  (for example, via subcore terminals). Each terminal  605  has a second end  635  configured to slidingly contact, when the switch is in the off position, the non-conductive layer  615  and, when the switch  515  is in the on position, the conductive bus  610 . As illustrated in  FIG. 8 , the second end  625  includes an upper foot  640  and a lower foot  645 . In such an embodiment, the upper foot  640  and the lower foot  645  are biased toward each other and configured to grasp the conductive bus  610  or the non-conductive layer  615  in order to make physical contact. 
     Returning to  FIGS. 7A and 7B , the conductive bus  610  is composed of a conductive material, such as but not limited to, a substantially copper material. In the illustrated embodiment, the conductive bus  610  includes a number conductive buses  610   a,    610   b ,  610   c , . . .  610   n  corresponding to the terminals  605 . As illustrated in  FIG. 7A , when the switch  515  is in the on position, the first conductive bus  610   a  provides an electrical connection between the terminals  605   a  and  605   f  , the second conductive bus  610   b  provides an electrical connection between the terminals  605   b  and  605   c,  and the third conductive bus  610   c  provides an electrical connection between the terminals  605   d  and  605   e.    
     The non-conductive layer  615  is composed of a non-conductive material, such as but not limited to, a substantially plastic or silicon material. As illustrated in  FIG. 7B , when the switch  515  is in the off position, the non-conductive layer  615  prevents an electrical connection between the terminals  605   a - 605   f.    
       FIGS. 9A and 9B  are block diagrams of the battery pack  500  and switch  515 .  FIG. 9A  illustrates the battery pack  500  in the first (e.g., “OFF”) state. As illustrated, when in the off state, the subcore  300   a  is electrically disconnected from the subcore  300   b,  the subcore  300   b  is electrically disconnected from the subcore  300   c,  and the subcore  300   c  is electrically disconnected from the subcore  300   d.    
       FIG. 9B  illustrates the battery pack  500  in the second (e.g., “ON”) state. As illustrated, when in the on state, the subcore  300   a  is electrically connected to the subcore  300   b  via the first conductive bus  610   a,  the subcore  300   b  is electrically connected to the subcore  300   c  via the second conductive bus  610   b,  and the subcore  300   c  is electrically connected to the subcore  300   d  via the third conductive bus  610   c.    
     In the illustrated embodiment, each subcore  300   a - 300   d  has a nominal voltage of approximately 21V. Thus, battery pack  500  has a nominal pack voltage of approximately 72V. In other embodiments, the battery pack  500  may have a nominal voltage of approximately 70V to approximately 80V. In yet another embodiment, the battery pack  500  may have a nominal voltage of approximately 100V to approximately 130V (for example, approximately 108V). In yet another embodiment, the battery pack  500  may have a nominal voltage of approximately 30V to approximately 40V (for example, approximately 36V). In some embodiments, each subcore  300   a - 300   d  has a power capacity approximately equal or less than 100 Wh. In some embodiments, each subcore  300   a - 300   d  has a power capacity approximately equal or less than 300 Wh. In some embodiments, battery pack  500  may have a power capacity approximately equal to or greater than 300 Wh. In some embodiments, the battery pack  500  may have a power capability of approximately 3000 Watts to approximately 5500 Watts. 
     In the illustrated embodiment, the battery pack  500  further includes a plurality of fuses  525 . The fuses  525  provide overcurrent protection between the subcores  300   a - 300   d.    
       FIG. 10  is an electrical diagram of a switch  800  configured to selectively electrically connect a plurality of subcores  300  in a series-type configuration and a parallel-type configuration. As illustrated, the switch  800  electrically connects a plurality of subcores  300  in a series-type configuration such that the subcores  300  have a nominal voltage of approximately 70V to approximately 90V (for example, 72V, 84V, etc.). The switch  800  also electrically connects the subcores  300  in a parallel-type configuration such that the battery pack has a power capacity approximately equal to or greater than 300 Wh. Thus, in such an embodiment, the battery pack will have a nominal voltage of approximately 70V to approximately 90V (for example, 72V, 84V, etc.) and a power capacity approximately equal to or greater than 300 Wh. In such an embodiment, each subcore has a power capacity of approximately equal or less than 100 Wh. In other embodiments, the battery pack may have a nominal voltage of approximately 70V to approximately 80V (for example, approximately 72V). In yet another embodiment, the battery pack may have a nominal voltage of approximately 100V to approximately 130V (for example, approximately 108V). In yet another embodiment, the battery pack may have a nominal voltage of approximately 30V to approximately 40V (for example, approximately 36V). In some embodiments, the battery pack 500 may have a power capability of approximately 3000 Watts to approximately 5500 Watts. 
       FIG. 11  illustrates another alternative battery pack  900 . The battery pack  900  may include substantially similar components as discussed above in relation to the battery pack  100 ,  500 . 
     The battery pack  900  includes a housing  905  having an interface  910  and a switch  915 . The switch  915  includes at least one plate  920  located on a first side  925  of the battery pack  900 . In the illustrated embodiment, the switch  915  includes a second plate  930  located on a second side  935 , opposite the first side  925 . In such an embodiment, the second plate  927  is substantially similar to plate  920 . 
     As further illustrated in  FIGS. 12A and 12B , the plate  920  includes at least one male member or plunger  930  extending from the plate  920  (e.g., in a substantially perpendicular direction). The male member  930  is configured to be inserted into an aperture  935  defined by the housing  905 . The male member  930  includes a conductive bus  1000  and a non-conductive portion  1005 . The conductive bus  1000  is configured to electrically connect the subcores  300  in a series-type and/or a parallel-type configuration. 
       FIG. 12A  illustrates the switch  915  in a first (e.g., “OFF”) position. In the first position, the terminals of the subcores  300   a - 300   d  are in contact with the non-conductive portions  1005  of the male member  930  and, thus, are electrically disconnected from each other. In some embodiments, the plate  920  and, thereby, the male members  930  are biased in a first direction  1015 . In such an embodiment, the plate  920  may be biased via a biasing member  1020 , such as, but not limited to a spring. 
       FIG. 12B  illustrates the switch  915  in a second (e.g., “ON”) position. The plate  920  is manipulated by the user in a second direction  1025 , opposite the first direction  1015 , into the second position. In the second position, the terminals of the subcores  300   a - 300   d  are in contact with the conductive busses  1000  and, thus, electrically connected to each other. 
     Although illustrated as being in a series-type electrical connection, the subcores  300   a - 300   d  may be connected alternatively, or additionally, in a parallel-type configuration, such that the electrically connected the subcores  300   a - 300   d  and, thus, the battery pack  900 , provide desired characteristics, such as a desired pack voltage, a desired pack current output, and a desired pack power capacity. 
       FIG. 13  illustrates a battery pack  1300  according to some embodiments of the application. The battery pack  1300  includes a housing  1305  having a battery pack interface  1310  and a switch  1315 . The housing  1305  may be formed of similar materials as housing  200 , discussed above. Additionally, the housing  1305  may contain battery modules  300  and battery cells  400 , as discussed above. The battery pack interface  1310  is configured to electrically, via electrical interface  1320 , and physically, via physical interface  1325 , connect the battery pack  1300  to one or more devices  105 . The electrical interface  1320  may include one or more positive terminals, one or more ground terminals, and one or communication terminals. Although illustrated as a rail and groove interface, in other embodiments, the physical interface  1325  may be a receptacle and stem interface. 
     The switch  1315  includes a user-interface  1330  and is configured to be in a first position ( FIG. 14A ) and a second position ( FIG. 14B ). When in the first (e.g., “OFF”) position, electrical components (for example, the subcores  300 ) of the battery pack  1300  contained within the housing  1305  are electrically disconnected from each other. When in the second (e.g., “ON”) position, electrical components (for example, the subcores  300 ) are electrically connected to each other. The switch  1315  may be manipulated by a user from the first position to the second position by pressing the switch  1315 . Additionally, the switch  1315  may be manipulated by an electrical device (e.g., a power tool and/or charger) when the battery pack is physically coupled to the electrical device. 
     As illustrated, in some embodiments the user-interface  1330  includes a slot, or aperture,  1335  formed by the switch  1315 . In such an embodiment, the user may manipulate the switch  1315  from the second position to the first position by placing a variety of tools (for example, a flat head screw driver) into the slot  1335 . In some embodiments, a stopper (for example, a zip-tie or other molded piece) may be placed, or positioned, within the slot  1335  to prevent the switch  1315  from moving from the first position to the second position. 
     In some embodiments, the battery pack  1300  further includes a latch configured to prevent accidental operation of the switch  1315 . For example, in some embodiments, a user activates the latch before manipulating the switch  1315  from the first (e.g., “OFF”) position to the second (e.g., “ON”) position and/or from the second (e.g., “ON”) position to the first (e.g., “OFF”) position. 
       FIGS. 15A and 15B  illustrates the switch  1315  according to another embodiment of the application. As discussed above, the switch  1315  is configured to be in the first position ( FIGS. 14A &amp; 15A ) and the second position ( FIGS. 14B &amp; 15B ). Switch  1315  includes a shell  1500 , terminals  605   a,    605   b,    605   c , . . .  605   n,  a conductive bus  1505 , and a non-conductive layer  1510 . Shell  1500  may be substantially similar to shell  600 , the conductive bus  1505  may be substantially similar to conductive bus  610 , and the non-conductive layer  1510  may be substantially similar to non-conductive layer  615 . Shell  1500  may include one or more recesses  1515 , a front stop member  1520 , and a rear stop member  1525 . 
     As illustrated in  FIGS. 15A and 15B , in some embodiments, the conductive bus  1505  and non-conductive layer  1510  are coupled to the user-interface  1330  via a protective member  1530  having one or more projections  1535  and forming an aperture  1540 . The projections  1535  engage with the one or more recesses  1515  of the shell  1500  to prevent unwanted movement between the first position and the second position. As illustrated in  FIG. 15C  the conductive bus  1505  and the non-conductive layer  1510  may form a plate  1542 . As illustrated, in some embodiments, plate  1542  has a rectangular shape. However, in other embodiments, the plate  1542  may be formed into other shapes (for example, a square). Although illustrated as the conductive bus  1505  having four conductive members  1544 , in other embodiments, the conductive bus  1505  may have more or less conductive member  1544 . 
     In the illustrated embodiment of  FIG. 15C , the conductive members  1544  are approximately flush, or continuous, with the non-conductive layer  1510 . Such an embodiment promotes movement of the terminals  605  between connection to the non-conductive layer  1510  and connection to the conductive members  1544  of the conductive bus  1505 . In some embodiments, as illustrated in  FIG. 15C , the conductive bus  1505  is formed of a continuous conductive material (for example, copper). 
       FIG. 15D  illustrates the conductive bus  1505  and non-conductive layer  1510  electrically and/or physically connected to terminals  1546   a,    1546   b  according to another embodiment. Each illustrated terminal  1546  includes a first terminal portion  1548   a  and a second terminal portion  1548   b  connected via a bus bar  1549 . In some embodiments, the bus bar  1549  provides a parallel connection between the terminal portions  1548   a,    1548   b,  while reducing electrical resistance and heat generated via the connection of subcores. As illustrated, each terminal portion  1548  includes an upper foot  640  and a lower foot  645 , which are substantially similar to the upper and lower feet  640 ,  645  of terminal  605 . Terminals  1546 , including bus bar  1549 , allow for a single electrical connection between a first plurality of subcores (for example, subcores  300   a,    300   b ) and a second plurality of subcores (for example, subcores  300   c,    300   d ). In other embodiments, the terminal  1546  may include more than two terminal portions  1548 . 
     As further illustrated in  FIG. 16A , the front stop member  1520  is positioned within the aperture  1540  and engages the protective member  1530  to prevent the conductive bus  1505  and non-conductive layer  1510  from surpassing the first position, when moving from the second position to the first position. 
     In another embodiment, as illustrated in  FIGS. 16B-16D , the plate  1542  may include, in addition to or in lieu of front stop member  1520 , a rear stop member  1522 . Similar to front stop member  1520 , the rear stop member  1522  may prevent the conductive bus  1505  and non-conductive layer  1510  from moving beyond the first position, when moving from the second position to the first position. In some embodiments, the rear stop member  1522  is formed of steel or a similar material. As illustrated in  FIG. 16C , the rear stop member  1522  engages a first rear aperture  1524   a,  when in the first (e.g., “OFF”) position, and a second rear aperture  1524   b , when in the second (e.g., “ON”) position. As illustrated in  FIG. 16D , in some embodiments, the rear stop member  1522  may include a spring heat staked to the plate  1542 . 
     As further illustrated in  FIG. 17 , the rear stop member  1525  prevents the conductive bus  1505  and non-conductive layer  1510  from surpassing the second position, when moving from the first position to the second position. 
       FIG. 18  illustrates an exemplary battery monitoring circuit  2248  of the battery pack  100 . As illustrated, the battery monitoring circuit  2248  includes two 5S1P cell blocks  2000 A and  2000 B. Cell blocks  2000  may be substantially similar to subcores  300 , discussed above. The cell block  2000 A is monitored by an electronic processor  2252 A using an analog front end (AFE)  2256 A. The cell block  2000 B is monitored by an electronic processor  2252 B using an AFE  2256 B. 
     The AFEs  2256 A-B are capable of monitoring individual cells in the cell blocks  2000 A-B. The AFEs  2256 A-B may be implemented using, for example, BQ76925 host-controlled analog front end designed by Texas Instruments. The AFEs  2256 A-B may be referred to singularly as the AFE  2256 , and the processors  2252 A-B may be referred to singularly as the processor  2252 . In other embodiments, the battery monitoring circuit  2248  may include more or fewer cell blocks  2000  monitored by more or fewer processors  2252  and AFEs  2256 . 
     The AFE  2256  provides operating power to the processor  2252  over the V3P3 line. The processor  2252  provides serial clock (SCL) to the AFE  2256  over the SCL line. The processor  2252  and the AFE  2256  exchange serial data over the SDA line. For example, the processor  2252  may write an address of an individual cell to be monitored at a given time to a register of the AFE  2256  over the SDA line. The AFE  2256  provides a reference voltage used to measure individual voltages of the cells  400  over the VREF+ line to the processor  2252 . The AFE  2256  provides individual states (for example, voltages of individual cells  400 ) over the VCOUT line to the processor  2252 . The AFE  2256  may provide a voltage of a particular cell  400  at the VCOUT line based on request written to the AFE  2256  over the SDA line. The battery monitoring circuit  2248  may additionally include a coupling circuit, for example, an opto-coupling circuit  2258  that facilitates communication between the processors  2252 A-B and an electronic processor of a tool. 
       FIG. 19  illustrates a further alternative battery monitoring circuit  2260 . As illustrated, the battery monitoring circuit  2260  includes three 5S1P cell blocks  2000 A-C. Each cell block  2000 A-C is monitored by a single electronic processor  2264  using AFEs  2268 A-C, respectively. As described above, the AFEs  2268 A-C are capable of monitoring individual cells  400  in the cell blocks  2000 A-C. The AFEs  2268 A-C may be referred to singularly as the AFE  2268 . In other embodiments, the battery monitoring circuit  2248  may include more or fewer cell blocks  2000  monitored by the processor  2264  using more or fewer AFEs  2268 . 
     The processor  2264  may receive operating power from one of the AFEs  2268 . The processor  2264  provides a serial clock over the SCL lines to the AFEs  2268 A-C. In addition, the processor  2264  and the AFEs  2268 A-C exchange serial data over the SDA lines. The processor  2264  may receive reference voltages (VREF+) and individual cell states (VCOUT) at analog inputs ANI 0 - 5 . In the illustrated example, analog inputs ANI 0 - 1  are connected to AFE  2268 A, analog inputs ANI 2 - 3  are connected to AFE  2268 B, and analog inputs ANI 4 - 5  are connected to AFE  2268 C. 
       FIG. 20  illustrates another alternative battery monitoring circuit  2272  using shared inter-integrated circuit (I2C) bus. As illustrated, the battery monitoring circuit  2272  includes three 5S1P cell blocks  2000 A-C monitored by a single electronic processor  2276  using AFEs  2280 A-C, respectively. The battery monitoring circuit  2272  operates in a similar manner to the battery monitoring circuit  2260  of  FIG. 19 . 
     The AFEs  2280 A-C communicate with the processor  2276  over a shared I2C channel. Outputs of the AFEs  2280 A-C are provided at analog inputs ANI 0 - 3  of the processor  2276 . Because all cells  400  in the cell blocks  2000 A-C operate at similar voltage levels, the processor  2276  may be provided with a single reference voltage (VREF+) from the AFE  2280 A. The reference voltage VREF+ is provided at the analog input ANIO. States of individual cells (VCOUT) are provided at analog inputs ANI 1 - 3  from the AFEs  2280 A-C, respectively. The battery monitoring circuit  2272  may include more or fewer cell blocks  2000  monitored by the processor  2276  using more of fewer AFEs  2280  over the shared I2C channel. The battery monitoring circuit  2272  may also include an opto-coupling circuit  2284 . 
       FIG. 21A-B  illustrate yet another alternative battery monitoring circuit  2288  using multiplexors. As illustrated, the battery monitoring circuit  2288  includes four 5S1P cell blocks  2000 A-D monitored by a single electronic processor  2292  using AFEs  2296 A-D. The battery monitoring circuit  2288  operates in a manner similar to the battery monitoring circuit  2272  of  FIG. 20 . 
     The AFEs  2296 A-D communicate with the processor  2292  over a shared I2C channel. As shown in  FIG. 21A , a multiplexor  2300  is connected between the processor  2292  and the AFEs  2296 A-D on the shared I2C channel. The processor  2292  provides selection inputs to the multiplexor  2300  in order to select an AFE  2296  between the  2296 A-D with which the processor  2292  exchanges communications at a particular time. As shown in  FIG. 21B , multiple multiplexors  2300 A-B may also be used over multiple I2C channels to facilitate communications between the processor  2292  and the AFEs  2296 A-D. The battery monitoring circuit  2288  may also include an opto-coupling circuit  2302 . 
       FIG. 22  illustrates a further alternative battery monitoring circuit  2304  using multiple inter-integrated circuit (I2C) buses. As illustrated, the battery monitoring circuit  2304  includes three 5S1P cell blocks  2000 A-C monitored by a single electronic processor  308  using AFEs  2312 A-C respectively. The battery monitoring circuit  2304  operates in a manner similar to the battery monitoring circuit  2272  of  FIG. 20 . However, the AFEs  2312 A-C communicate with the processor  2308  over multiple I2C channels. 
     For example, the AFE  2312 A communicates with the processor  2308  over I2C channel I2C  1 , the AFE  2312 B communicates with the processor  2308  over I2C channel I2C  2 , and so on. Outputs of the AFEs  2312 A-C are provided at analog inputs ANIO- 3  of the processor  2308  similar to the battery monitoring circuit  2272  of  FIG. 20 . The battery monitoring circuit  2304  may include more or fewer cell blocks  2000  monitored by the processor  2308  using more or fewer AFEs  2312  over multiple I2C channels. The battery monitoring circuit  2304  may also include an opto-coupling circuit  2316 . 
       FIG. 23  illustrates another alternative battery monitoring circuit  2320  using serial peripheral interface. As illustrated, several 5S1P block  2000  are monitored by a single electronic processor  2324  using several AFEs  2328 . The AFEs  2328  communicate with the processor  2324  using serial peripheral interface bus. The battery monitoring circuit  2320  may also include several switches  2332  with resistors connected across each cell block  2000  to discharge the cell blocks  2000  during cell balancing. 
     Thus, the application may provide, among other things, a system and method for electrically connecting and disconnecting a plurality of battery cells in a battery pack.