Electrical connector

The present disclosure presents an electrical connector comprising a wire coupling portion, the wire coupling portion including a generally flat, plateau portion wherein the plateau portion includes a trough. The electrical connector wherein the trough is generally semi-cylindrical. The electrical connector further comprises an overlap portion that is positioned generally parallel to the plateau portion. The electrical connector wherein the overlap portion is positioned generally adjacent to an open side of the trough. The electrical connector further comprising an electrical device coupling portion at an end of the electrical connector opposite to the wire coupling portion.

TECHNICAL FIELD

This application relates to an electrical connector for a battery pack and a method for assembly a battery pack including an electrical connector. In one implementation, the electrical connector includes a cell coupling portion for coupling the connector to a battery cell and a wire coupling portion for coupling the connector to an electrical wire.

BACKGROUND

Cordless power tools, for example circular saws and drills (such as those manufactured by the DeWalt Power Tool Company) rely on removable, rechargeable battery packs, similar to an exemplary battery pack100illustrated inFIGS. 1 and 2to provide power for operation. The battery pack100comprises a housing102. The housing102includes a mechanical interface104for mating and coupling with the power tool. In this example, the mechanical interface104includes a rail and groove system that slides into engagement with a corresponding rail and groove system in the power tool. The battery pack100also includes a latch106that is received in a tool catch (recess) to fix the battery pack100to the tool. The housing102also includes a plurality of slots that provide access through the housing102to a plurality of terminals108of the battery pack100. In the exemplary battery pack100, the housing102includes a top portion/upper housing110and a bottom portion/lower housing112that are coupled together to create an interior cavity for housing various components of the battery pack100. The top portion110and the bottom portion112are held together by a plurality of fasteners114. The battery pack100also includes a state of charge (SOC) display/indicator116.

The battery pack internal components include a spring118operationally associated with the latch106and what is referred to as a core pack120. The core pack120includes a plurality of battery cells122, a battery cell holder124that maintains the battery cells122in a fixed position relative to each other and the housing102, a terminal block assembly126, a printed circuit board (PCB)128and various components mounted to the PCB128, a plurality of battery straps130, a plurality of lead wires132coupling the battery straps130to the terminals108or the PCB128, and a SOC subassembly134.

The terminal block assembly126includes a plurality of terminals108(including a subset of power terminals108A for providing power from the battery pack100to the power tool or receiving power from a battery charger and a subset of data/signal terminals108B for providing data to and/or receiving data from the power tool or battery charger) and a terminal block136that maintains the terminals108in a fixed position relative to each other and the housing102. The PCB128may include various components for monitoring and controlling the operation and status of the battery pack100and the battery cells122. There are various connections between the PCB128and the terminals108. The battery straps130may couple individual battery cells122to each other (to either connect the cells in a series configuration or in a parallel configuration) or may couple a cell122to a power terminal108A via a lead wire132or may couple a node between individual cells122to the PCB128via a lead wire132. The SOC subassembly134may include a PCB, a plurality of LEDs, an actuator button and a set of lead wires coupled to the PCB128.

In an exemplary embodiment, the core pack120is manufactured on an assembly line. The battery cells122are loaded into the cell holder124, the populated PCB128is attached to the cell holder124, and the terminal block assembly126is attached to the cell holder124. As illustrated inFIG. 2, the exemplary battery pack100includes ten (10) battery cells122. Specifically, the battery pack100includes a first string (set) A of five (5) cells A1, A2, A3, A4, A5and a second string (set) B of five (5) cells B1, B2, B3, B4, B5. Each battery cell122includes an anode (+) terminal and a cathode (−) terminal. The battery cells122of each string are positioned in the same plane with their longitudinal axes parallel. Furthermore, the battery cells122are positioned such that within each string the battery cells122are connected in series and the two strings are connected in parallel. The battery straps130are placed on the cell holder124in an appropriate position to electrically couple the battery cells122to connect them as noted above and/or to couple a battery cell122to a terminal108and/or the PCB128.

The core pack120is then placed on an assembly line to solder the lead wires132to the battery straps130. As illustrated inFIG. 3, in an exemplary conventional battery pack100, the battery strap130may be manufactured and formed by stamping the appropriately shaped piece of metal and folding the metal into the appropriate configuration. The illustrated battery strap130is a simple piece of metal, generally rectangular, that is bent at approximately ninety degrees at a central location of the part. This provides a battery cell coupling portion for coupling to the battery cell122and a wire coupling portion for coupling to the lead wire132. As noted inFIG. 3andFIG. 4A, the lead wire132is place on or very near the wire coupling portion of the battery strap130. As illustrated inFIG. 4B, when the core pack120is placed on the assembly line it is placed in a fixture or jig138. The fixture138includes a fixing element that presses the lead wire132onto the wire coupling portion of the battery strap130. As illustrated, it is common for the lead wire132to curl away from the coupling portion of the battery strap130when the fixing element engages the lead wire132. Thereafter, a soldering device solders the lead wire to the wire coupling portion of the battery strap. As illustrated inFIG. 4C, due to the curling of the lead wire132, the resulting solder140may leave a less than satisfactory connection between the lead wire132and the battery strap130. This may result in the lead wire132coming loose from the battery strap130at some later point in the assembly process, and/or a less than satisfactory electrical connection between the lead wire132and the battery strap130. Alternatively, it is possible that during operation of the battery pack100when a significant amount of current is drawn through the lead wire132and battery strap130, the solder material140may begin to liquefy. If this occurs and there is not a satisfactory connection between the lead wire132and the battery strap130, the lead wire132may pull away from the battery strap130resulting in an open circuit and faulty battery pack100.

As such, what is needed is a battery strap130that provides a better connection with the lead wire132.

SUMMARY

An aspect of the present invention includes a battery strap for coupling a battery cell to a battery pack terminal wherein the battery strap includes a lead wire connecting portion including plateau portion having a trough formed therein and configured to receive a lead wire and/or an overlap portion (also referred to as an overlap member) adjacent to the plateau portion and forming a space therebetween to receive a lead wire.

Another aspect of the present invention includes a method of assembling a battery pack comprising providing a plurality of battery cells, providing at least one battery pack terminal, providing at least one battery strap, providing at least one lead wire coupling the at least one battery pack terminal and one of the plurality of battery cells, wherein the at least one battery strap includes in lead wire coupling portion having a plateau region, the plateau region including a trough formed therein and configured to receive one end of the lead wire, and placing the one of the lead wire in the trough and soldering the lead wire to the battery strap in the trough.

Implementations of this aspect may include one or more of the following features.

Advantages may include one or more of the following. A lead wire coupling a battery strap to a battery pack terminal or to a printed circuit board location is more easily coupled to the battery strap. The solder connection between the lead wire and the battery strap is more stable and provides a better connection between the lead wire and the battery strap. The better connection provides for improved electrical current flow between the battery strap and the lead wire. Furthermore, during use of the battery pack100if the solder coupling the lead wire to the battery strap heats up to the point of beginning to liquefy, the lead wire is more likely to maintain its position relative to the battery strap.

These and other advantages and features will be apparent from the description and the drawings.

DETAILED DESCRIPTION

Referring toFIGS. 5A, 5B, 5C, and 5D(generally referred to collectively asFIG. 5), there is illustrated a first exemplary embodiment of a battery strap200BS1of the present disclosure. This battery strap200BS1is made of an electrically conductive material. The battery strap200BS1may be formed by stamping the material into a predetermined shape and then bending the stamped material in to the shape illustrated inFIG. 5. The battery strap200BS1includes a lead wire coupling portion202, two cell (terminal) coupling portions204and an inter-terminal coupling portion206. The cell coupling portion204electrically couples to a terminal (either positive or negative) of a battery cell122, as described and illustrated in more detail below. The inter-terminal coupling portion206electrically couples the two cell coupling portions204and effectively electrically couples the terminals of two discrete battery cells122. For example, the first cell coupling portion204A may couple to a cathode (−) terminal A5− of a first battery cell122A5and the second cell coupling portion204B may couple to a cathode (−) terminal B5− of a second battery cell122B5thereby effectively forming part of a parallel connection between the first and second battery cells122A5,122B5—the anode (+) terminals of the first and second battery cells122A5,122B5would need to be electrically coupled by another battery strap200BS3B to complete the parallel connection, as described below. The cell coupling portions204A,204B may be soldered or welded or otherwise fixedly coupled to the appropriate terminal.

The lead wire coupling portion202is configured to attach to the lead wire208. As such, the battery strap200BS1serves to electrically connect the battery cells122A5,122B5to the lead wire208(which is coupled to a battery pack terminal, for example BATT− terminal216). The lead wire coupling portion202includes a plateau portion210which generally receives the lead wire208. The plateau portion210may include a trough212. The trough212(also considered a receptacle or valley) is generally a semi-circular cylindrical of a diameter approximately matching the gauge of the lead wire208. The lead wire coupling portion202may also include a folded back portion214(also considered an overlap portion). The folded back portion214extends over at least part of the trough212providing a space between the folded back portion214and the trough212to place the lead wire208. As such, when the lead wire208is placed in the trough212the lead wire208is between the folded back portion214and the trough212or plateau portion210. The trough212allows the lead wire208to be seated therein. As such, when the lead wire208is soldered to the battery strap200BS1the lead wire208does not curl up, as in the conventional systems and may be fully covered by solder material and fixed to the battery strap200BS1. The folded back portion214also assists to maintain the lead wire208in a seated position during soldering of the lead wire208to the battery strap200BS1and during operation of the battery pack100. The folded back portion214may also provide additional electrically conductive material to solder to the lead wire208. The battery strap200BS1may include the trough212and/or the folded back portion214.

Referring toFIGS. 6A, 6B, 6C, and 6D(generally referred to collectively asFIG. 6), there is illustrated a second exemplary embodiment of a battery strap300BS2of the present disclosure. The battery strap300BS2illustrated inFIG. 6is generally the same as the battery strap200BS1illustrated inFIG. 5except for the general configuration. More specifically, this battery strap300BS2includes a lead wire coupling portion302, a cell coupling portion304and an inter-terminal coupling portion306. Furthermore, the lead wire coupling portion302includes a plateau portion310including a trough312and a folded back portion314. This battery strap300BS2is shaped differently than the battery strap200BS1ofFIG. 5in part due to the configuration of the battery cells122in the core pack120and positioning of the lead wire308relative to the battery strap300BS2. In other respects, particularly the manner in which the lead wire308couples to the battery strap300BS2, the battery straps serve the same purpose and operate in the same manner.

Referring toFIGS. 7A, 7B, 7C, and 7D(generally referred to collectively asFIG. 7), there is illustrated a third exemplary embodiment of a battery strap400BS3of the present disclosure. The battery strap400BS3illustrated inFIG. 7is generally the same as the battery straps200BS1,300BS2illustrated inFIGS. 5 and 6except for the general configuration. More specifically, this battery strap400BS3includes a lead wire coupling portion402, a cell coupling portion404and an inter-terminal coupling portion406. However, the lead wire coupling portion402of this battery strap400BS3is somewhat different than the lead wire coupling portion202,302of the battery straps200BS1,300BS2ofFIGS. 5 and 6. As the lead wire408that connects to this type of battery strap400BS3is somewhat different so it requires a different connection. For example, the lead wire408that will connect to this battery strap400BS3is typically of a higher gauge wire and will connect the battery strap400BS3to the printed circuit board128. In this example, these battery straps400BS3are used to connect nodes between cells122of a string of cells (intra-cell) to the PCB128to determine voltage levels of cells122within the string of cells. Again, in this example, the battery straps200BS1,200BS2illustrated inFIGS. 5 and 6are used to connect the ends of the strings of cells (the most positive or the most negative cell of the string of cells) to the battery pack terminals216,316and/or to the PCB128.

The lead wire coupling portion402of the battery strap400BS3ofFIG. 7includes an eyelet416or cutout to receive and hold the lead wire408. This allows the jig138of the assembly process to not include a feature to hold the lead wire408to the wire coupling portion402and results in a better solder connection between the lead wire408and the battery strap200BS3.

Referring toFIGS. 8A, 8B, 9A, 9B, 10A and 10B, there is illustrated an exemplary core pack120incorporating the exemplary battery straps200BS1,300BS2,400BS3ofFIGS. 5, 6, and7. This exemplary core pack120includes a cell holder124, a terminal block assembly126, a PCB128, a state of charge assembly134, lead wires208,308,408, and a ten (10) battery cells122. The battery cells122are configured into two strings (A, B) of five cells. Each string of cells includes five (5) battery cells122. Using the various battery straps, the battery cells within a string of cells are connected in series and the two strings of battery cells are connected in parallel. Furthermore, the strings of cells are connected such that there are inter-string connections between corresponding battery cells. In other words, for example, the anode (+) terminal of the A2battery cell in the A string of cells is coupled to the anode (+) terminal of the B2battery cell in the B string of cells. Furthermore, the anode (+) terminal of the A2battery cell in the A string of cells is coupled to the cathode (−) terminal of the A1battery cell in the A string of cells.

FIG. 8Aillustrates the core pack120and the first exemplary battery strap200BS1and two of the third exemplary battery straps400BS3C,400BS3D. In this example, the first exemplary battery strap200BS1is attached to the cathode (−) terminal of the most negative battery cell A5, B5in each string of cells A and B, one of the third exemplary battery straps400BS3C is attached to the anode (+) terminal of the A4and B4battery cells and the cathode (−) terminal of the A3and B3battery cells, and one of the third exemplary battery straps400BS3D is attached to the anode (+) terminal of the A2and B2battery cells and the cathode (−) terminal of the A1and B1battery cells (the most positive battery cells in each string).FIG. 8Aalso illustrates a lead wire208coupled to the first battery strap200BS1and to the battery pack negative terminal BATT−216of the terminal block assembly126.

FIG. 8Billustrates the core pack120and the second exemplary battery strap300BS2and two of the third exemplary battery straps400BS3A,400BS3B. In this example, the second exemplary battery strap300BS2is attached to the anode (+) terminal of the most positive battery cell A1, B1in each string of cells A and B, one of the third exemplary battery straps400BS3A is attached to the cathode (−) terminal of the A2and B2battery cells and the anode (+) terminal of the A3and B3battery cells, and one of the third exemplary battery straps400BS3B is attached to the cathode (−) terminal of the A4and B4battery cells and the anode (+) terminal of the A5and B5battery cells (the most negative battery cells in each string).FIG. 8Balso illustrates a lead wire308coupled to the second battery strap300BS2and to the battery pack positive terminal BATT+316of the terminal block assembly126.

FIGS. 9A and 9Billustrate different views of the core pack120and the battery straps200BS1,300BS2,400BS3of the present disclosure.FIGS. 10A and 10Billustrate enlarged views of portions ofFIGS. 8A and 8B, respectively. As is illustrated inFIGS. 8-10, a lead wire208/308is placed in the trough212/312(also referred to as a valley) formed in the respective battery strap200BS1,300BS2. Furthermore, the lead wire208/308is sandwiched between the overlap portion214/314and the plateau portion210/310to hold the lead wire208/308in place during the soldering process.

During the core pack construction process, the various battery straps are temporarily attached to appropriate battery cells of the core pack. Then the various lead wires are temporarily placed in the appropriate position relative to the corresponding battery strap. With regard to the first and second battery straps200BS1,300BS2the lead wires208/308are placed in the trough212/312between the overlap portion214/314and the plateau portion210/310. With regard to the third battery straps400BS3A,400BS3B,400BS3C,400BS3D the lead wires408are placed in the eyelet416of the battery strap400BS3. Thereafter the core pack120is placed in a fixture for the soldering process. The solder guns (typically automated) solder the lead wires208/308/408to the battery straps200BS1/300BS2/400BS3. With regard to the first and second battery straps200BS1,300BS2the solder forms over the overlap portion214/314and the lead wire208/308and preferably into at least a portion of the trough212/312and onto the plateau portion210/310. This will provide a full and secure connection between the lead wire208/308and the battery strap200BS1/300BS2. With regard to the third battery straps400BS3A,400BS3B,400BS3C,400BS3D the solder forms over the lead wire408and the eyelet416.

FIGS. 11-15illustrate additional exemplary embodiments of battery straps200BS1′,300BS2′,400BS3′ and an additional exemplary core pack120′ incorporating the additional battery straps. The difference between the exemplary battery straps of theFIGS. 11-15andFIGS. 5-10is that the battery straps ofFIGS. 11-15are for a battery pack100′ having a single string of battery cells—five (5) battery cells in this example—while the battery straps ofFIGS. 5-10are for a battery pack100having two strings of battery cells—five (5) cells in this example. The lead wire connection features described above with respect toFIGS. 5-10are also found in the battery straps illustrated inFIGS. 11-15.

FIG. 16illustrates a simplified circuit diagram of the battery cells of the exemplary core pack120ofFIGS. 8-10. This exemplary set of battery cells includes a first subset A of battery cells122and a second subset B of battery cells122. The first subset A includes five (5) battery cells A1, A2, A3, A4, A5connected in series presenting a positive node A+ and a negative node A− and the second subset B includes five (5) battery cells B1, B2, B3, B4, B5connected in series presenting a positive node B+ and a negative node B−. The first subset A and the second subset B are connected in parallel. More particularly, the subset A positive node A+ is connected to the subset B positive node B+ and the subset A negative node A− is connected to the subset B negative node B−. Furthermore, there are inter-set connections between nodes found between cells connected within a subset of cells. For example, a node between the A1battery cell and the A2battery cell is connected to a node between the B1battery cell and the B2battery cell. All of these connections are made using the battery straps, as described above.

Numerous modifications may be made to the exemplary implementations described above. These and other implementations are within the scope of this application.

The present disclosure presents an electrical connector comprising a wire coupling portion, the wire coupling portion including a generally flat, plateau portion wherein the plateau portion includes a trough. The electrical connector wherein the trough is generally semi-cylindrical. The electrical connector further comprises an overlap portion that is positioned generally parallel to the plateau portion. The electrical connector wherein the overlap portion is positioned generally adjacent to an open side of the trough. The electrical connector further comprising an electrical device coupling portion at an end of the electrical connector opposite to the wire coupling portion.

The present disclosure presents a method for assembling a battery pack comprising providing a plurality of battery cells in a cell holder, mounting a terminal block and printed circuit board on the cell holder, coupling at least one battery strap to the plurality of battery cells wherein the at least one battery strap includes a trough at a lead wire coupling portion of the battery strap, positioning a lead wire in the trough, and soldering the lead wire in the trough to the battery strap. The method for assembling a battery pack further comprising providing an overlap member at the lead wire coupling portion of the battery strap and positioning the overlap portion adjacent to the trough in a manner such that the lead wire is positioned between the trough and the overlap portion. The method of assembling a battery pack wherein the solder connection couples the overlap portion to the lead wire.

Numerous modifications may be made to the exemplary implementations described above. These and other implementations are within the scope of this application.