METHOD OF MANUFACTURE FOR A HYBRID COOLING BATTERY PACK

Abstract

Electrochemical cell battery system and associated methods of operation are provided based on the incorporation of a thermal suppression construct including a supply of cooling fluid dispensed in intimate contact with the cells disposed within an enveloping sealed enclosure. The electrochemical cells are connected electrically by bus bars to form a battery of cells. The bus bars support cooling by convection methods. The cells are allowed to float mechanically as they are charged and discharged while maintaining intimate thermal contact with the enveloping sealed enclosure through conduction and the bus bars through conduction. The system provides a method of cooling the cells by conduction and convection and that accommodates mechanical changes to both the cells and the enveloping sealed enclosure.

Claims

1. A method of manufacturing a battery pack, the method comprising: inserting a first cell in a first recess in a plurality of recesses of a hollow enclosure and a second cell in a second recess in the plurality of recesses of the hollow enclosure, a first majority of the first cell and a second majority of the second cell extending into the hollow enclosure and substantially below a top surface of the hollow enclosure, the hollow enclosure defining a flow path therethrough, the flow path including a channel between the first recess and the second recess; capacitive discharging welding a first threaded stud to a first terminal of the first cell and a second threaded stud to a second terminal of the second cell; and coupling a flexible bus bar to the first threaded stud and the second threaded stud, the flexible bus bar including a non-linear contour.

2. The method of claim 1, wherein the flexible bus bar comprises a plurality of conductive layers.

3. The method of claim 1, wherein the flexible bus bar is made of copper, and the first terminal of the first cell is made of aluminum.

4. The method of claim 1, further comprising: coupling a first inlet port to the hollow enclosure; coupling a second inlet port to the hollow enclosure; and in response to coupling the first inlet port and the second inlet port to the hollow enclosure, sealing the flow path of the hollow enclosure.

5. The method of claim 1, wherein the flow path is configured for fluid to flow horizontally and vertically through the hollow enclosure.

6. The method of claim 1, further comprising inserting a third cell in a third recess in the plurality of recesses of the hollow enclosure and a fourth cell in a fourth recess in the plurality of recesses of the hollow enclosure.

7. The method of claim 6, further comprising: capacitive discharge welding a third threaded stud to a third terminal of the third cell and a fourth threaded stud to a fourth terminal of the second cell; and coupling a second flexible bus bar to the third threaded stud and the fourth threaded stud, the second flexible bus bar including the non-linear contour.

8. The method of claim 1, wherein the flow path comprises a corrugated indentation in a side of the hollow enclosure configured to provide a serpentine shape to the flow path.

9. The method of claim 1, wherein the flow path comprises an entry channel, an exit channel and the channel disposed between the first cell and the second cell.

10. The method of claim 9, wherein the entry channel and the exit channel are substantially larger than the channel.

11. The method of claim 1, further comprising inserting a first thermally conductive compound in the first recess and a second thermally conductive compound in the second recess prior to inserting the first cell and inserting the second cell.

12. The method of claim 1, wherein the inserting the first cell comprises press fitting the first cell into the first recess, and wherein the inserting the second cell comprises press fitting the second cell into the second recess.

13. The method of claim 1, wherein each recess in the plurality of recesses is spaced apart in a longitudinal direction from an adjacent recess in the plurality of recesses.

14. The method of claim 13, further comprising: coupling an inlet port to a first longitudinal end of the hollow enclosure; and coupling an outlet port to a second longitudinal end of the hollow enclosure.

15. The method of claim 14, wherein the inlet port is disposed at a first height from a bottom surface of the hollow enclosure and the outlet port is at a second height from the hollow enclosure, and wherein the second height is greater than the first height.

16. The method of claim 15, wherein the flow path is a serpentine flow path.

17. The method of claim 15, wherein the flow path comprises an entry channel, an exit channel and the channel disposed between the first cell and the second cell.

18. The method of claim 17, wherein an inter-cell cooling channel is disposed between each recess and the adjacent recess in the plurality of recesses.

19. The method of claim 1, further comprising molding the hollow enclosure prior to the inserting the first cell and the inserting the second cell.

20. The method of claim 19, wherein the molding comprises one of injection molding or blow molding.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The accompanying drawings, which are hereby incorporated into and constitute a part of this specification, illustrate example embodiments and, together with the description, serve to explain the principles set forth in this disclosure. In the drawings, wherein like reference numerals represent like parts:

[0011] FIG. 1 is a side view diagram representing a battery in accordance with an example embodiment.

[0012] FIG. 2 is a top view diagram showing a serpentine flow style coolant path of the hollow enclosure from FIG. 1 in accordance with an example embodiment.

[0013] FIG. 3 is a top view diagram showing the balanced side flow coolant path of the hollow enclosure from FIG. 1 in accordance with an example embodiment.

[0014] FIG. 4 is a method to thermally manage a battery, in accordance with an example embodiment.

DETAILED DESCRIPTION

[0015] The proposed battery solution is an apparatus, comprising a sealed hollow enclosure (1) capable of housing one or more cells (2). The hollow enclosure (1) comprises slots having an internal surface and an external surface that are configured to house the one or more cells (2). The cell (2) may extend partially out of the slot above the top surface of the hollow enclosure (1).

[0016] The hollow enclosure may be made from a wide variety of electrically non-conductive materials capable of be providing the mechanical support for the cells and having the ability to be completely sealed to prevent leakage or ingress of contaminants. Various plastics, including Acrylonitrile butadiene styrene (ABS) and high-density polyethylene (HDE), and the like are suitable materials. Such materials can be recycled in order to increase their environmental friendliness and reduce cost.

[0017] Cells are disposed within slots in the hollow enclosure (1) having an internal surface, which is internal to the hollow enclosure and an external surface, which is external to the hollow enclosure. Substantially the entire cell (2) surface is in intimate contact with the external surface of the slot. The outer cell (2) surface to external surface interface may be facilitated by use of a thin layer of thermally conductive compound to fill in the air gaps. This material may be applied to the surface of the cell (2) before it is inserted into the hollow enclosure (1).

[0018] The hollow enclosure (1) design is sealed, with one or more inlet ports (4) and one or more outlet ports (5) for a thermally conductive fluid (6) to pass through. The inlet ports (4) and outlet ports (5) are disposed on the exterior of the hollow enclosure, and their locations can vary based on the interfacing components. A flow path is created through the hollow enclosure (1) and the flow path is configured to connect the inlet port (4) to the outlet port (5) and creates a cooling channel through the enclosure. The design is such that the fluid (6) passing through is forced to come into intimate contact with the internal surface of the slots as it snakes its way through the hollow enclosure and around all of the slots. Thus, the external temperature of the cell (2) is thermally managed through conduction by the thermally conductive fluid (6) as heat is transferred through the slots to the cell (2). Furthermore, through the flow path, turbulence creators can be added to create a more desirable heating coefficient and allowing better thermal management of the cells (2).

[0019] Depending on the application, different flow paths may be utilized in the design. FIG. 2 shows a serpentine shape for the flow path. In accordance with the arrows shown in FIG. 2, the flow is directed at least one corrugated indentation (7) in the sides of the hollow enclosure (1) that forces the fluid to flow around the slots housing each cell (2) disposed therein and also serve to strengthen the hollow enclosure (1) mechanically. Additionally, the fluid may constantly flow under the cells as well, as illustrated in FIG. 1. FIG. 3 shows a balanced flow path. In accordance with the arrows shown in FIG. 3, the flow is inserted into one corner of the hollow enclosure (1) at inlet port (4) and flows across the four sides of each cell (2), as well as the bottom of each cell (2) disposed therein. The entry channel and exit channel, indicated by the rightward pointing arrows, are substantially larger than the at least one inter-cell cooling channel, indicated by the downward pointing arrows. This allows for a more equalized flow rate and pressure across the surfaces of each cell (2). By having the outlet port (5) on the opposing corner of the hollow enclosure (1), the pressure is balanced across all of the cells (2) disposed in the hollow enclosure (1) so that each gets the same amount of coolant and flow rate.

[0020] The fluid (6) is pumped, cooled or heated externally using conventional fluid moving equipment, thereby cooling or heating the cells (2) as desired. The depicted fluid (6) path and hollow enclosure (1) indentations (7) are representational, and it is noted that a wide variety of variation is available to the designer to optimize for various characteristics in the design without departing from the spirit of the present disclosure.

[0021] The hollow enclosure (1) is preferably made of thin material to enhance the thermal conduction between the fluid (6) and the cells (2). The process of manufacture may use injection molding, blow molding or similar processes. Blow molding, such as is used to make dairy milk one gallon containers, is preferred as it is a very low cost high volume process for consumer goods using very low cost and simple machinery. However, other low cost methods, such as injection molding, can be used without departing from the spirit of the disclosure. The solution of the present disclosure uses a single low cost part, the hollow enclosure (1), in order to contain and cool a plurality of cells (2). Further, the hollow enclosure (1) may be ribbed for improved structural integrity.

[0022] Such low cost hollow enclosures (1) will not have very tight physical accuracy over the final product. This is a limitation of such low cost manufacturing processes. Once the cells (2) are inserted into the slots (3) of the hollow enclosure (1), the position of their tops and cell terminals (8) will vary substantially. In addition, the thin walls of the hollow enclosure (1) will move when the flow rate varies, when the temperature fluctuates, and as the cells (2) themselves swell and decay over time and as they cycle. Therefore, a low-cost approach to managing the terminals (8) and bus bar interconnects is needed.

[0023] To overcome this, the present disclosure employs use of a stud welding process to attach a threaded stud (9) to the top of each cell rather than welding a bus bar directly to the top of the cell (2). The latter may be problematic with the substantial first cell to second cell variance that happens as a result of the low cost hollow enclosure production method. The stud welding process uses a form of capacitive discharge welding to attach threaded studs to a surface. This process is low cost, fast, and uses parts that are mass produced for the fastener industry. The speed of this process keeps it from overheating and thereby damaging the cells (2). The process provides a broad area of connection between the stud (9) and the terminals (8) of the cell (2), as opposed to the conventional process of spot welding a battery strap directly to the cell terminal that requires repeated welds of small conduction area that may heat up the cell (2) in the process. This process is also faster than the more expensive laser welding processes, and requires much less investment in machinery. It has also been shown to be more repeatable under less controlled conditions, further reducing cost and improving quality.

[0024] Connection of the cells is done with a flexible copper bus bar (10) that comprises a plurality of layers of thin copper. Copper is the preferred bus bar material as it has the lowest resistance for the cost of any suitable conductor and therefore results in less energy loss and less heat generation when current flows through it. The bus bars (10) have a non-linear contour to improve flexibility, and are punched with a first hole and a second hole, so the first threaded stud is configured to receive the first hole and the second threaded stud is configured to receive the second hole. The bus bars can be screwed or bolted on to a first threaded stud and a second threaded stud on the cell (2). The flexibility allows the installer to move the bus bar (10) and position it over the stud (9) during installation. It also takes up the mechanical changes in the cells (2) and the hollow enclosure (1) both as they are cycled and as they age. The bus bars (10) are secured to the studs (9) using conventional nuts and washers.

[0025] Copper cannot be welded by any conventional techniques directly to cells that have aluminum terminals, so this process allows copper bus bars to be attached directly to lithium ion cells that have aluminum terminals. The copper bus bars (10) have a fanned out lamination structure as shown in FIG. 1 that allows airflow to pass over and under each layer of the lamination. This provides access to a great deal of exposed surface area for thermal transfer. Copper is highly thermally conductive, and since the bus bars (10) are conductive bolted to the cell terminals (8), they can be used to pull heat from or put heat into the internals of the cell (2) directly from the current collectors and the electrodes by forcing hot or cold air through and around them. This results in a greater ability to thermally manage the internal temperature of the cell (2). Thus, the present disclosure supports hybrid cooling and heating of the cells (2), from the inside through the bus bars (10) as well as simultaneously outside through the hollow enclosure (1). Thus, in an example embodiment, the system further comprises a fan, blower, suction fan, pump, or other device for causing movement of the convection fluid.

[0026] In a novel manner, the present disclosure enables a tremendous hybrid cooling and heating advantage, including external conduction through moving fluid and internal convection by cooling or heating the cell (2) internals through the terminal by airflow over a high surface area copper bus bar (10). Although airflow is mentioned, other fluids could be utilized to heat or cool the cell (2) through convection. It also provides for a very low cost mechanical hollow enclosure (1) produced on low cost machinery for the cells (2) to reside that is flexible and accommodating as the fluid (6) moves through said hollow enclosure (1) and the cells (2) are cycled through use of highly flexible bus bars (10). Further, the terminals (8) on the cells are attached to by way of a low cost stud (9) and associated welding fabrication techniques that allows copper connection directly to the cell terminals (8). Another benefit set forth by the present disclosure over the prior art concerns shipping costs. As lithium ion batteries are considered hazardous materials, they are expensive to ship. Product weight is a significant cost driver in shipping costs. The hollow enclosure (1) set forth in the present disclosure may be shipped empty, the thermally conductive fluid (6) may be shipped separately non-hazmat which saves on cost, or separately acquired at the destination. Since the hollow enclosure (1) is made from thin wall light-weight plastic, it is extremely light-weight when not filled with thermally conductive fluid (6) and therefore not a significant contributor to the overall battery weight.

[0027] Referring now to FIG. 4, a method (400) for thermally managing a battery, in accordance with an example embodiment, is illustrated. The method comprises managing an external temperature of a first cell and a second cell by conduction (step 402). Managing the external temperature may occur by flowing a thermally conductive fluid around an external surface of the first cell and an external surface of the second cell. The fluid may flow through channels of a hollow enclosure. The channels may maximize the surface area that the fluid contacts when flowing through the channels. The method (400) may further comprise managing an internal temperature of the first cell and the second cell by convection (step 404). Managing the internal temperature may occur by flowing an airflow around a bus coupling the first cell to the second cell. The bus may be disposed external to the hollow enclosure.

[0028] While the principles of this disclosure have been shown in various embodiments, many modifications of structure, arrangements, proportions, elements, materials and components (which are particularly adapted for a specific environment and operating requirements) may be used without departing from the principles and scope of this disclosure. These and other changes or modifications are intended to be included within the scope of the present disclosure and may be expressed in the following claims.

[0029] The present disclosure has been described with reference to various embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present disclosure. Accordingly, the specification is to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present disclosure. Likewise, benefits, other advantages, and solutions to problems have been described above with regard to various embodiments.

[0030] However, benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature or element of any or all the claims. As used herein, the terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0031] When language similar to “at least one of A, B, or C” or “at least one of A, B, and C” is used in the claims or specification, the phrase is intended to mean any of the following: (1) at least one of A; (2) at least one of B; (3) at least one of C; (4) at least one of A and at least one of B; (5) at least one of B and at least one of C; (6) at least one of A and at least one of C; or (7) at least one of A, at least one of B, and at least one of C.