BATTERY PACK FOR A VEHICLE AND METHODS AND SYSTEMS FOR MAKING THE SAME

Embodiments include a method for creating a battery pack for a vehicle. Aspects include receiving a plurality of battery cells, measuring an internal resistance level for each of the plurality of battery cells, and creating, based at least in part on the internal resistance level for each of the plurality of battery cells, a plurality of groups from the plurality of battery cells. Aspects also include connecting each of the plurality of battery cells in each of the plurality of groups in parallel and connecting each of the plurality of groups in series.

INTRODUCTION

The subject disclosure relates to electric vehicles. In particular, the invention relates to a battery pack of an electric vehicle and methods and systems for making the same.

Electric vehicles include battery packs that include several battery cells that are often connected in a configuration that includes both series and parallel connections. In large-capacity batteries made from a multitude of small cells, it is common for subgroups of cells to be connected in parallel. In general, each battery cell has an internal resistance. The variation of the internal resistances among battery cells that are connected in parallel negatively affects the performance of subgroups and the battery pack by reducing the usable energy.

SUMMARY

In one exemplary embodiment, a method for creating a battery pack for a vehicle is provided. The method includes receiving a plurality of battery cells, measuring an internal resistance level for each of the plurality of battery cells, and creating, based at least in part on the internal resistance level for each of the plurality of battery cells, a plurality of groups from the plurality of battery cells. The method also includes connecting each of the plurality of battery cells in each of the plurality of groups in parallel and connecting each of the plurality of groups in series.

In addition to one or more of the features described herein, creating the plurality of groups from the plurality of battery cells includes ordering the plurality of battery cells by the internal resistance level for each of the plurality of battery cells and selecting a number of adjacently ranked battery cells as a group.

In addition to one or more of the features described herein, at least one of the plurality of battery cells is not included in any of the plurality of groups.

In addition to one or more of the features described herein, the at least one of the plurality of battery cells includes a battery cell of the plurality of battery cells having a highest internal resistance level and a battery cell of the plurality of battery cells having a lowest internal resistance level.

In addition to one or more of the features described herein, the plurality of groups from the plurality of battery cells are created such that a standard deviation of the internal resistance level for each of the plurality of groups is minimized.

In addition to one or more of the features described herein, each of the plurality of groups includes a same number of battery cells.

In addition to one or more of the features described herein, creating a group of the plurality of groups includes placing the plurality of battery cells corresponding to the group adjacent to one another.

In addition to one or more of the features described herein, the method also includes placing a group of the plurality of groups that has a highest internal resistance in a center of the battery pack.

In addition to one or more of the features described herein, the method also includes placing a group of the plurality of groups that has a lowest internal resistance at an edge of the battery pack.

In another exemplary embodiment, system for creating a battery pack for a vehicle is provided. The system includes a first robotic arm configured to obtain a plurality of battery cells and a first tool configured to measure an internal resistance level of each of the plurality of battery cells. The system also includes a second robotic arm configured to control a placement of each of the plurality of battery cells in the battery pack and a controller configured to operate the first robotic arm, the first tool and the second robotic arm. The controller is configured to create a plurality of groups from the plurality of battery cells, based on the internal resistance level for each of the plurality of battery cells. The placement of each of the plurality of battery cells in the battery pack is determined based on the plurality of groups.

In addition to one or more of the features described herein, the plurality of groups are created by ordering the plurality of battery cells by the internal resistance level for each of the plurality of battery cells and selecting a number of adjacently ranked battery cells as a group.

In addition to one or more of the features described herein, at least one of the plurality of battery cells is not included in any of the plurality of groups.

In addition to one or more of the features described herein, the at least one of the plurality of battery cells includes a battery cell of the plurality of battery cells having a highest internal resistance level and a battery cell of the plurality of battery cells having a lowest internal resistance level.

In addition to one or more of the features described herein, the plurality of groups from the plurality of battery cells are created such that a standard deviation of the internal resistance level for each of the plurality of groups is minimized.

In addition to one or more of the features described herein, each of the plurality of groups includes a same number of battery cells.

In addition to one or more of the features described herein, the first robotic arm is configured to obtain the plurality of battery cells from an automated guided vehicle that is controlled by the controller.

In addition to one or more of the features described herein, the placement includes placing a group of the plurality of groups that has a highest internal resistance in a center of the battery pack.

In addition to one or more of the features described herein, the placement includes placing a group of the plurality of groups that has a lowest internal resistance at an edge of the battery pack.

In another exemplary embodiment, a battery pack for an electric vehicle is provided. The battery pack includes a first group of battery cells connected to each other in parallel, a second group of battery cells connected to each other in parallel, and a third group of battery cells connected to each other in parallel. The first group of battery cells, the second group of battery cells and the third group of battery cells are connected to each other in series. The internal resistance level of each battery in the first group of battery cells is lower than a minimum internal resistance level of the second group of battery cells. The internal resistance level of each battery in the third group of battery cells is greater than a maximum internal resistance level of the second group of battery cells.

In addition to one or more of the features described herein, the third group of battery cells is disposed between the first group of battery cells and the second group of battery cells.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses.

In accordance with an exemplary embodiment, a battery pack having a plurality of battery cells is provided. The plurality of battery cells of the battery pack are configured in a plurality of groups. Each group includes battery cells connected to each other in parallel and the groups are connected to each other in series. In exemplary embodiments, the groups of battery cells are created, based at least in part on the internal resistance level for each of the plurality of battery cells, such that a variance of the internal resistance of the battery cells for each group is minimized. In exemplary embodiments, by minimizing the variance of the internal resistance of the battery cells for each group the performance of the battery pack is improved.

Referring now toFIG.1, a schematic diagram of a vehicle100for use in conjunction with one or more embodiments of the present disclosure is shown. The vehicle100includes a battery pack200. In one embodiment, the vehicle100is a hybrid vehicle that utilizes both an internal combustion engine and an electric motor. In another embodiment, the vehicle100is an electric vehicle that only utilizes electric motors.

Referring now toFIG.2, a schematic diagram of a battery pack200for use in conjunction with one or more embodiments of the present disclosure is shown. As illustrated, the battery pack200includes a plurality of battery cells202. In one embodiment, the plurality of battery cells202are grouped into eight serially connected groups that each contain ten cells that are connected in a parallel configuration. In one embodiment, each group of battery cells202extends along a row in the x-direction. In exemplary embodiments, the plurality of battery cells202of the battery pack200are connected to each other via one or more collector plates (not shown).

Referring now toFIG.3, a flowchart diagram of a method300for creating a battery pack for a vehicle in accordance with one or more embodiments of the present disclosure is shown. At block302, the method300begins by receiving a plurality of battery cells. Next, at block304, the method300includes measuring an internal resistance level for each of the plurality of battery cells. Once the internal resistance level for each of the plurality of battery cells has been measured, the method300includes creating, based at least in part on the internal resistance level for each of the plurality of battery cells, a plurality of groups from the plurality of battery cells, at block306. In one embodiment, the plurality of groups are created from the plurality of battery cells such that a standard deviation of the internal resistance level for each of the plurality of groups is minimized.

In exemplary embodiments, creating the plurality of groups from the plurality of battery cells includes ordering the plurality of battery cells by the internal resistance level for each of the plurality of battery cells and selecting a number of adjacently ranked battery cells as a group. In one embodiment, at least one of the plurality of battery cells is not included in any of the plurality of groups. For example, the battery cell of the plurality of battery cells having a highest internal resistance level and/or the battery cell of the plurality of battery cells having a lowest internal resistance level may not be included in any of the plurality of groups

In one example, the plurality of battery cells includes one hundred and ten battery cells which are ranked based on their measured internal resistance levels. In this example, the battery cells with the top five and bottom five rankings are not included in any of the groups and ten groups of ten battery cells are created based on the rankings. For example, one group includes battery cells ranked six through fifteen, another group includes battery cells ranked sixteen through twenty-five, and so on. In exemplary embodiments, each of the plurality of groups includes the same number of battery cells.

In exemplary embodiments, creating a group of the plurality of groups includes placing the plurality of battery cells corresponding to the group adjacent to one another. At block308, the method300includes connecting each of the plurality of battery cells in each of the plurality of groups in parallel. The method300concludes at block310by connecting each of the plurality of groups in series.

Referring now toFIG.4a schematic diagram of a system400for creating a battery pack for a vehicle in accordance with one or more embodiments of the present disclosure is shown. The system400includes a first tray402of battery cells404that have not been sorted or tested. The system400also includes a first robotic arm406that is configured to remove one or more battery cells404from the first tray402and place the one or more battery cells404into a second tray408. In exemplary embodiments, the first robotic arm406includes a tool configured to test the internal resistance of the one or more battery cells404. In exemplary embodiments, the first robotic arm406is operated by a controller420. The controller420may be a general-purpose processor, a discrete logic circuit(s) having logic gates for implementing logic functions upon data signals, an application-specific integrated circuit (ASIC) having appropriate combinational logic gates, a programmable gate array(s) (PGA), a field programmable gate array (FPGA), etc. In exemplary embodiments, the controller420is configured to store the measured internal resistance of the battery cells404and the location in the second tray408of each of the battery cells404.

In exemplary embodiments, after all of the battery cells404have been removed from the first tray402, had their internal resistance tested, and placed into the second tray408, the controller420ranks the battery cells404by their internal resistance. The controller420is further configured to divide the battery cells404into a plurality of groups based on their internal resistance and/or their ranking. In exemplary embodiments, the plurality of groups are created such that a variance of the internal resistance among the battery cells of the group is minimized. In some embodiments, not all of the battery cells404in the second tray408are included in the plurality of groups. For example, one or more battery cells404that have either the highest or lowest internal resistance values/ranking may not be included in one of the plurality of groups.

Once the controller420has created the plurality of groups of battery cells404, the controller420instructs a second robotic arm410to pick and place the battery cells404into a third tray412, which is used to form the battery pack. In one embodiment, the battery cells of each group are placed into a single row or column in the third tray412. Once all of the battery cells404of the plurality of groups have been placed in the third tray412each of the plurality of battery cells in each of the plurality of groups are connected in parallel and the plurality of groups are connected in series.

Referring now toFIG.5, a schematic diagram of a system500for creating a battery pack for a vehicle in accordance with one or more embodiments of the present disclosure is shown. As illustrated, the system includes an automated guided vehicle (AGV)502that is configured to bring a first tray504of battery cells to a first location adjacent a table512. Once the AGV502is in place, a first robotic arm508is configured to use tool506to remove the battery cells from the first tray504and place the battery cells onto a second tray510located on the table512. In exemplary embodiments, the tool506is further configured to measure the internal resistance of each of the battery cells before placing the battery cells into the second tray510. In one embodiment, each battery cell includes a unique bar code that the tool506scans and the tool transmits the bar code, a measured internal resistance, and a location where each battery cell is placed in the second tray510to a controller (not shown). Once the second tray510is full, the table512rotates and the process of picking, testing, and placing the battery cells restarts.

The system500also includes a second robotic arm520that includes a second tool518that is configured to pick battery cells from tray516and place them in tray522. In exemplary embodiments, the second robotic arm520is operated by a controller, which controls the location where the battery cells are placed in the tray522. In one embodiment, the battery cells are divided into groups based on their internal resistance, and the second robotic arm520and second tool518place the battery cells into locations on the second tray based on their assigned group. Once all of the battery cells have been placed into the tray522, the table524rotates and the battery pack is prepared for assembly. In exemplary embodiments, one or more controllers are configured to operate and coordinate the operation of, the AGV502, the tool506, the first robotic arm, the table512, the second robotic arm520, the second tool, and the table524.

Referring now toFIG.6a graph600illustrating the variance of internal resistance of the cells of a traditional battery pack of a vehicle is shown. Traditional battery packs are assembled by grouping random battery cells from a lot of battery cells. As a result, as shown in the graph600, the variance of internal resistance of the battery cells each group is representative of the overall variance of the lot of battery cells. In contrast, by assembling a battery pack using the methods and systems disclosed herein the variance of internal resistance of the battery cells of group of a battery pack can be significantly reduced as shown inFIG.7.

FIG.7is a graph700illustrating the variance of internal resistance of the cells of a battery pack of a vehicle in accordance with one or more embodiments of the present disclosure. As shown in the graph700, the battery pack includes twelve groups of twenty battery cells. Each of the battery cells has an internal resistance level and the battery cells are separated into groups based on their internal resistance level. For example, a maximum internal resistance level of the battery cells for group 1 is less than the minimum internal resistance level of the battery cells for group 2. Likewise, the maximum internal resistance level of the battery cells for group 2 is less than the minimum internal resistance level of the battery cells for group 3. In exemplary embodiments, each group of battery cells are connected to each other in parallel and the groups of battery cells are connected to each other in series.

In exemplary embodiments, once the internal resistance of the battery cells have been measured, the battery cells have been ranked and sorted into groups, the battery module can be built using multiple cell arrangements. One such arrangement is a rank-ordered configuration where each of the cell groups is placed into the battery pack in order of increasing internal resistance, as shown inFIG.8.

Another arrangement is a temperature-ordered configuration where the cell group with the highest internal resistance is placed in the center of the battery pack, as shown inFIG.9

FIG.8is three-dimensional graph800illustrating the internal resistance of the cells of a battery pack of a vehicle in accordance with one or more embodiments of the present disclosure. As shown in the graph800, each of the groups of cells includes twenty battery cells and the groups were formed and placed in the battery pack in increasing order of internal resistance. In this configuration, the internal resistance of the battery cells increases from one side of the battery pack to the other.

FIG.9is three-dimensional graph900illustrating the internal resistance of the cells of a battery pack of a vehicle in accordance with one or more embodiments of the present disclosure. As shown in the graph900, the cell group with the highest internal resistance is placed in the center of the battery pack and the cell group with the lowest internal resistance is placed at an edge of the battery pack. The remaining cell groups are placed in order of decreasing internal resistance from the center of the battery pack to the edges of the battery pack. In exemplary embodiments, during use of the battery pack, as the battery charges and discharges, the battery pack heats up with the battery cells in the middle of the battery pack rising to higher temperatures compared to the cells around the boundaries. In general, when the temperature of a battery cell increases the internal resistance of the battery cell is reduced. Accordingly, during the use of the battery pack, the graph900will flatten out during operation, as the internal resistance of the centrally located battery cells decreases due to their increased temperature.