Battery pack management method

Abstract

This ensures the long-term reliability of battery stacks housed in battery cases under pressurized conditions. [Solution] The battery stack is housed in a battery case with a restraining load applied to both sides in the longitudinal direction of the battery stack. The battery stack also includes adjacent first and second cells and a contact pressure sensor. The contact pressure sensor is provided between the first and second battery cells and at a location that receives the restraining load applied to the battery stack. When charging or discharging the battery stack, the value detected by the contact pressure sensor is acquired. Based on this detected value, the current value of the restraining load applied to the battery stack is calculated. Then, the target charge level of the battery stack at which charging to the battery stack is stopped during charging control, or discharging from the battery stack is stopped during discharging control, is set according to this current value of the restraining load.

Description

Technical Field

[0001] This disclosure relates to a method for managing a battery pack mounted on a vehicle.

Background Art

[0002] Patent Document 1 discloses a method for manufacturing a battery module in which a battery stack is housed in a battery case. In this conventional method, a shim is disposed between the battery case and the battery stack so that the pressurized state of the battery stack is maintained by the inner surfaces of the battery case located at both ends in the longitudinal direction of the battery stack. The purpose of disposing this shim is to absorb variations in dimensions in the longitudinal direction of the battery stack and to ensure pressurization of the battery stack by the inner surface of the battery case.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The battery module of Patent Document 1 is mounted on a vehicle. When mounted on a vehicle, the battery stack housed in the battery case supplies power to a motor as a drive source of the vehicle and receives power from an external power source according to the remaining amount. The battery stack is exposed to various stresses (e.g., temperature stress, charge-discharge stress) during a series of operations. Then, the dimensions in the longitudinal direction of the battery stack change, and the pressurized state of the battery stack also changes. Therefore, there is a problem that it is difficult to guarantee the reliability of the battery stack housed in the battery case over a long period.

[0005] One objective of this disclosure is to provide a technology that can ensure the long-term reliability of a battery stack housed in a battery case under pressurized conditions. [Means for solving the problem]

[0006] This disclosure relates to a method for managing a battery pack installed in a vehicle, and has the following features: A battery pack applicable to the method of this disclosure includes a battery stack housed in a battery case. The battery stack is housed in the battery case with a restraining load applied to both sides of the battery stack in the longitudinal direction. The battery stack also includes adjacent first and second cells and a contact pressure sensor. The contact pressure sensor is located between the first and second battery cells and at a location that receives the restraining load applied to the battery stack. The method of this disclosure includes the steps of: acquiring a value detected by a contact pressure sensor when controlling the charging or discharging of a battery stack; calculating the current value of the restraining load applied to the battery stack based on the detected value; and setting a target charge rate of the battery stack in accordance with the current value of the restraining load, which is used to stop charging the battery stack during charging control or to stop discharging from the battery stack during discharging control.

[0007] In the method disclosed herein, in the step of setting the target charge rate, the target charge rate during charge control may be set to a lower value as the current value of the constraint load increases.

[0008] In the method disclosed herein, in the step of setting the target charge level, the target charge level during discharge control may be set to a higher value as the current value of the constraint load increases.

[0009] In this disclosure, the battery stack may include a plate member provided between the end face of a first battery cell and the end face of a second battery cell. In this case, a contact pressure sensor may be provided between the end face of the first battery cell and the end face of the second battery cell, and in a location that does not interfere with the plate member.

[0010] In this disclosure, a first terminal indicating the external terminal of the positive or negative electrode of the first battery cell may be provided on the end face of the first battery cell, and a second terminal indicating the external terminal of the positive or negative electrode of the second battery cell, which is paired with the first terminal, may be provided on the end face of the second battery cell facing the end face of the first battery cell. In this case, the first terminal may have a terminal surface parallel to the end face of the first battery cell, and the second terminal may have a terminal surface parallel to the end face of the second battery cell. In this case, a contact pressure sensor may be provided between the terminal surface of the first terminal and the terminal surface of the second terminal. [Effects of the Invention]

[0011] According to this disclosure, the detection value of a contact pressure sensor, which is provided between the first and second battery cells and at a location that receives a restraining load applied to the battery stack, is acquired during charging or discharging control of the battery stack. The current value of the restraining load applied to the battery stack is calculated based on this detection value. Then, the target charge level of the battery stack at which charging to the battery stack is stopped during charging control, or discharging from the battery stack is stopped during discharging control, is set according to this current value of the restraining load.

[0012] A contact pressure sensor can detect the pressure (i.e., the restraining load) applied to the sensor's installation location. Therefore, the current value of the restraining load calculated from the sensor's detection value indicates the current pressurized state of the battery stack, which changes over time. Consequently, by setting the target charge rate of the battery stack during charge or discharge control according to the current value of the restraining load, it becomes possible to guarantee the reliability of the battery stack over the long term. [Brief explanation of the drawing]

[0013] [Figure 1] This figure illustrates an example of the configuration and manufacturing method of a battery pack applied to the method according to the embodiment. [Figure 2] This figure shows a first configuration example of a battery cell with a contact pressure sensor applied to the method according to the embodiment. [Figure 3]This figure illustrates an example of applying the method according to the embodiment to a battery stack including the battery cells described with reference to Figure 2. [Figure 4] This diagram illustrates an example of setting a target charge level (target SOC). [Figure 5] This figure shows a second example configuration of a battery cell with a contact pressure sensor applied to the method according to the embodiment. [Figure 6] This figure illustrates an example of applying the method according to the embodiment to a battery stack including the battery cells described with reference to Figure 5. [Modes for carrying out the invention]

[0014] Embodiments of this disclosure will be described below with reference to the drawings. However, structures and the like described in the embodiments below are not necessarily essential to the present invention unless specifically stated or clearly defined in principle.

[0015] The battery pack used in the method according to the embodiments of this disclosure is mounted on a vehicle. Examples of such vehicles include battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs) that run using electricity supplied from the battery pack. The battery pack is mounted, for example, on the underbody of the vehicle.

[0016] Figure 1 illustrates an example of the configuration and manufacturing method of a battery pack applied to the method according to the embodiment. Figure 1 shows the lower case 11 of the battery pack 1. The lower case 11 is combined with an upper cover (not shown) to constitute the battery pack 1. The X-axis shown in Figure 1 corresponds to, for example, the front-rear direction of the vehicle, and the Y-axis, which is perpendicular to the X-axis, corresponds to, for example, the left-right direction of the vehicle. More specifically, the positive direction of the X-axis corresponds to the front direction of the vehicle, and the positive direction of the Y-axis corresponds to the left direction of the vehicle.

[0017] In the example shown in FIG. 1, the lower case 11 has four spaces 12 formed in the X-axis direction. Three of these spaces 12 each house three battery stacks 2. These battery stacks 2 are formed by stacking a plurality of battery cells. The total number NC of battery cells constituting one battery stack 2 is set in advance. The total number NC is, for example, 20 to 50 cells.

[0018] FIG. 1 also depicts one battery stack 2 outside the lower case 11. In the example shown in FIG. 1, first, outside the lower case 11, a plurality of battery cells are arranged in a certain direction. During this arrangement, plate materials are appropriately placed on the side surfaces of the battery cells. As the plate member, a cooling plate having a function of cooling the battery cells is exemplified. An aggregate of these cells in a state where a predetermined number (total number NC) of battery cells are arranged corresponds to the battery stack 2 shown in FIG. 1.

[0019] In the example shown in FIG. 1, subsequently, a restraining load is applied to these battery cells from both side surfaces in the arrangement direction of the plurality of battery cells. Then, the stack of a plurality of battery cells (that is, the battery stack 2) is subjected to a restraining load from both side surfaces in the stacking direction of these cells (that is, the longitudinal direction of the battery stack 2). Subsequently, while maintaining the state where the restraining load is applied to the battery stack 2, the battery stack 2 is inserted into the space 12. Thereby, the battery stack 2 is housed in the lower case 11. After all the spaces 12 are filled with the battery stacks 2, the battery pack 1 is manufactured by combining with an upper cover.

[0020] The manufacturing example described with reference to FIG. 1 is also called the CTP (Cell To Package) method. The following description is based on the battery pack 1 manufactured by the CTP method, but battery packs manufactured by methods other than the CTP method can also be applied to the method according to the embodiment. As a method other than the CTP method, an MTP (Module To Pack) method in which a plurality of battery cells are grouped into modules and then a battery pack is manufactured through a restraining member is exemplified.

[0021] When battery pack 1 is installed in a vehicle, the battery stack 2 housed in the lower case 11 will undergo repeated charging and discharging. For example, during discharge control, the battery stack 2 supplies power to the vehicle's motor. Conversely, during charge control, the battery stack 2 receives power from an external power source. If a regenerative energy recovery system is installed in the vehicle, the battery stack 2 receives power from the regenerative system during charge control. The main component of charge and discharge control is the processing unit installed in the vehicle.

[0022] During charge and discharge control, the battery stack 2 is exposed to various stresses (e.g., temperature stress, charge / discharge stress). This causes changes in the longitudinal dimensions of the battery stack 2 and also changes in its pressurized state. For example, if a battery cell expands, the longitudinal dimensions of the battery stack 2 increase. This results in high pressure being applied to the multiple battery cells that make up the battery stack 2. In other words, a change in the pressurized state of the battery stack 2 means a change in the constraining load. Therefore, it is desirable to ensure the reliability of the battery stack 2 from a long-term perspective.

[0023] Therefore, in the method according to the embodiment, at least one contact pressure sensor is provided between two adjacent battery cells and at a location that receives a restraining load applied to the battery stack 2. Figure 2 is a diagram showing an example of the configuration of an electrical cell with a contact pressure sensor applied to the method according to the embodiment. In the example shown in Figure 2, a contact pressure sensor 22 is provided on the end face 211 of the battery cell 21. Examples of contact pressure sensors 22 include load cell sensors and tactile sensors. However, single-point measuring sensors such as strain gauges, piezoresistive sensors, and force sensors, or surface measuring sensors such as force sensing mats, microfluidic pressure sensors, and flexible dielectric sensors may also be used as contact pressure sensors 22. Note that the Z-axis shown in Figure 2 corresponds, for example, to the vertical direction of the vehicle. More specifically, the positive direction of the Z-axis corresponds to the upward direction of the vehicle.

[0024] Figure 2 shows a view of the end face 211 along line AA. As can be seen from this view, the end face of the contact pressure sensor 22 has a square shape (hollow rectangle). The contact pressure sensor 22 has a size approximately equal to the size of the end face 211. The reason the contact pressure sensor 22 has a square shape is that a plate member 23 (for example, a cooling plate) is provided in the opening. The end face 211 on which the plate member 23 is provided is the same as the end face on which the contact pressure sensor 22 is provided. The thickness of the contact pressure sensor 22 in the direction of arrangement of the battery cells 21 is less than or equal to the thickness of the plate member 23, and is greater than or equal to the distance (design value) between the end face 211 when the battery stack 2 is housed in the lower case 11 and the end face of another battery cell 21 facing this end face 211.

[0025] The shape of the end face of the contact pressure sensor 22 shown in Figure 2 is just one example, and the shape of the end face of the contact pressure sensor 22 can be arbitrarily changed as long as it does not interfere with the plate member 23. For example, the shape of the end face of the contact pressure sensor 22 may be U-shaped, L-shaped, or straight. Also, the installation position of the contact pressure sensor 22 shown in Figure 2 is just one example, and the installation position can be arbitrarily changed as long as it does not interfere with the plate member 23 on the end face 211.

[0026] In the method according to the embodiment, the detected value of the contact pressure sensor 22 is acquired during charging or discharging control of the battery stack 2, and the current value LC of the constrained load is calculated. Figure 3 is a diagram illustrating an example in which the method according to the embodiment is applied to a battery stack 2 including the battery cells described with reference to Figure 2. In the example shown in Figure 3, the contact pressure sensor 22 shown in Figure 2 is incorporated into the battery stack 2. The contact pressure sensor 22 is connected to a control device 3 (for example, a vehicle processing device) of the battery pack 1 (battery stack 2). The contact pressure sensor 22 can measure the pressure (i.e., constrained load) applied to the installation location of the contact pressure sensor 22. Therefore, the current value LC calculated from the measured value of the contact pressure sensor 22 indicates the current pressurized state of the battery stack 2, which changes over time.

[0027] In the method according to the embodiment, the target charge rate of the battery stack 2 is set based on the current value LC, which stops charging the battery stack 2 during charge control or stops discharging from the battery stack 2 during discharge control. Figure 4 is a diagram illustrating an example of setting the target charge rate (target SOC). The upper part of Figure 4 shows an example of the setting during charge control, and the lower part of Figure 4 shows an example of the setting during discharge control. The upper and lower parts of Figure 4 show the reference value L0 of the constraint load of the battery stack 2. The reference value L0 is, for example, the constraint load of the battery pack 1 at the time of shipment. The reference value L0 may be set based on the specification information of the battery pack 1, or it may be set based on the detected value of the contact pressure sensor 22.

[0028] The upper part of Figure 4 shows the reference value R1 and upper limit value RH for the target SOC. The reference value R1 is set based on the reference value L0. The upper limit value RH (≧R1) is the maximum allowable value of the target SOC, and this is also set based on the reference value L0. As can be seen from the upper part of Figure 4, the target SOC during charge control is set to a lower value as the constraint load increases. This is because if the constraint load is higher than the reference value L0, the battery cells constituting the battery stack 2 may be expanding due to degradation. Therefore, during charge control, based on this relationship in the upper part of Figure 4, the target SOC is set to a lower value as the current value LC increases. This suppresses overcharging.

[0029] The lower part of Figure 4 shows the reference value R2 and the lower limit RL of the target SOC. The reference value R2 is set based on the reference value L0. The lower limit RL (≤ R2) is the minimum allowable value of the target SOC, and this is also set based on the reference value L0. As can be seen from the lower part of Figure 4, the target SOC during discharge control is set to a higher value as the constraint load increases. The reason for this is the same as the reason for charge control. Therefore, during discharge control, based on this relationship in the lower part, the target SOC is set to a higher value as the current value LC increases. This suppresses over-discharge.

[0030] The stopping of charge or discharge control is performed, for example, by calculating the actual charge level of the battery stack 2 based on the detection value of a current sensor connected to the battery stack 2 (see Figure 3). Then, for example, the actual charge level is compared with a target charge level set according to the current LC value, and if the former matches the latter, the ongoing charge or discharge control is stopped. Note that the series of processes from acquiring the current LC value during charge or discharge control to stopping the charge or discharge control are performed, for example, by the management device 3 shown in Figure 2.

[0031] Thus, according to the method of the embodiment, the target charge rate of the battery stack 2 during charging or discharging control is set according to the current value LC of the constraint load. Therefore, it is possible to guarantee the reliability of the battery stack 2 over the long term.

[0032] Figure 5 shows a second example configuration of a battery cell with a contact pressure sensor applied to the method according to the embodiment. In the example shown in Figure 5, an external terminal (e.g., a positive terminal) 24 is provided on the end face 211 of the battery cell 21, and an external terminal (e.g., a negative terminal) 25 is provided on the end face 212 of the battery cell 21.

[0033] Both external terminals 24 and 25 have a plate shape. External terminals 24 and 25 are the same size. The thickness of each external terminal 24 and 25 in the arrangement direction of the battery cells 21 is less than or equal to half the thickness of each plate member 23 (e.g., cooling plate) provided adjacent to the end faces 211 and 212. Also, the thickness of each external terminal 24 and 25 is more than half the distance (design value) between end faces 211 and 212 when the battery stack 2 is housed in the lower case 11. In other words, the sum of the thicknesses of external terminals 24 and 24 is greater than or equal to the distance between end faces 211 and 212 when the battery stack 2 is housed in the lower case 11, and less than or equal to the thickness of the plate member 23.

[0034] Figure 5 also shows arrow views of end face 211 along line BB and end face 212 along line CC. As can be seen from the arrow view along line BB, both end face 211 and the end face of the adjacent plate member 23 are square in shape, but the area of ​​the latter is smaller than that of the former. The external terminal 24 is located outside the area of ​​end face 211 that faces the end face of the plate member 23. Therefore, it can be said that an area for providing the external terminal 24 is secured on end face 211. The same can be seen from the arrow view of end face 212 along line CC. That is, an area for providing the external terminal 25 is secured on end face 212.

[0035] In the example shown in Figure 5, the external terminals 24 and 25 are located at the center of the ends of the end faces 211 and 212 in the Z-axis direction, respectively. In the Y-axis and Z-axis directions, the position of external terminal 24 coincides with the position of external terminal 25. Therefore, when multiple battery cells 21 are arranged, the external terminals 24 (e.g., positive terminal) and the corresponding external terminals 25 (e.g., negative terminal) will face each other between two adjacent battery cells 21 (first and second battery cells). Note that the positions of external terminals 24 and 25 can be changed to any position as long as their positions coincide in the YZ plane (i.e., the plane perpendicular to the direction of arrangement of the battery cells).

[0036] Furthermore, the shape of the end face of the plate member 23 shown in Figure 5 is just one example, and its shape can be arbitrarily modified as long as the external terminals 24 and 25 do not interfere with the plate member 23. For example, the shape of the end face of the plate member 23 may be such that two of the four sides constituting the end face of the plate member 23 are equal in length to those of the end face 211 (or end face 212), and the area corresponding to where the external terminals 24 and 25 are provided is narrow (rectangular). Alternatively, the length of all four sides constituting the end face of the plate member 23 may be equal to those of the end face 211 (or end face 212), and only the area where the external terminals 24 and 25 are provided may be cut out (perforated shape).

[0037] In the example shown in Figure 5, the contact pressure sensor 22 is also installed on the terminal surface of the external terminal 24. Examples of the contact pressure sensor 22 include the various sensors described in the explanation of Figure 2. The end face of the contact pressure sensor 22 shown in Figure 5 is rectangular. However, the shape of the contact pressure sensor 22 shown in Figure 5 is just one example, and its shape can be arbitrarily changed as long as it can be installed on the terminal surface of the external terminal 24.

[0038] Figure 6 illustrates an example of applying the method according to the embodiment to a battery stack 2 including the battery cells described with reference to Figure 5. The explanation of the example shown in Figure 6 is basically the same as the explanations in Figures 3 and 4. The difference between the two is the mounting position of the contact pressure sensor 22 shown in Figure 5. That is, the mounting position of the contact pressure sensor 22 shown in Figure 3 is between two adjacent battery cells 21. In contrast, the mounting position of the contact pressure sensor 22 shown in Figure 6 is between two adjacent external terminals 24 and 25. Therefore, for the explanation of the example shown in Figure 6, please refer to the explanations in Figure 3 and the upper and lower sections of Figure 4 as appropriate. [Explanation of symbols]

[0039] 1...Battery pack, 2...Battery stack, 11...Lower case, 12...Space, 21...Battery cell, 22...Contact pressure sensor, 23...Plate member, 24,25...External terminals, 26...End plate, 211,212...End face, 3...Management device, L0,R1,R2...Reference value, RH...Upper limit, RL...Lower limit

Claims

1. A method for managing battery packs installed in a vehicle, The battery pack includes a battery stack housed in a battery case, The battery stack is housed in the battery case with a restraining load applied to both sides in the longitudinal direction of the battery stack. The battery stack includes adjacent first and second battery cells, and a contact pressure sensor provided between the first and second battery cells and at a location that receives a restraining load applied to the battery stack. A step of acquiring the detected value of the contact pressure sensor when controlling the charging or discharging of the battery stack, A step of calculating the current value of the restraining load applied to the battery stack based on the detected value, The process includes setting a target charge level for the battery stack, in accordance with the current value of the constraint load, which is used to stop charging the battery stack during the charge control or to stop discharging from the battery stack during the discharge control; A method for managing battery packs, characterized by including the following:

2. The method according to claim 1, In the step of setting the target charge rate, the target charge rate during charge control is set to a lower value as the current value of the restraining load increases. A method for managing battery packs characterized by the following features.

3. The method according to claim 1, In the step of setting the target charge rate, the target charge rate during discharge control is set to a higher value as the current value of the restraining load increases. A method for managing battery packs characterized by the following features.

4. A method according to any one of claims 1 to 3, The battery stack includes a plate member provided between the end face of the first battery cell and the end face of the second battery cell, The contact pressure sensor is provided between the end face of the first battery cell and the end face of the second battery cell, and in a location that does not interfere with the plate member. A method for managing battery packs characterized by the following features.

5. A method according to any one of claims 1 to 3, A first terminal is provided on the end face of the first battery cell to indicate the external terminal of the positive or negative electrode of the first battery cell, and a second terminal is provided on the end face of the second battery cell facing the end face of the first battery cell to indicate the external terminal of the positive or negative electrode of the second battery cell, which is paired with the first terminal. The first terminal has a terminal surface parallel to the end face of the first battery cell, and the second terminal has a terminal surface parallel to the end face of the second battery cell. The contact pressure sensor is provided between the terminal surface of the first terminal and the terminal surface of the second terminal. A method for managing battery packs characterized by the following features.

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