Battery pack SOC-ocv data acquisition system, battery pack SOC-ocv data acquisition method, and battery pack charging / discharging method
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- MURATA MFG CO LTD
- Filing Date
- 2026-01-09
- Publication Date
- 2026-07-30
Smart Images
Figure JP2026000417_30072026_PF_FP_ABST
Abstract
Description
Battery Pack SOC-OCV Data Acquisition System, Battery Pack SOC-OCV Data Acquisition Method, and Battery Pack Charging and Discharging Method
[0001] It relates to the SOC-OCV data acquisition technology of battery packs for EVs.
[0002] Patent Document 1 describes a battery state detection device that detects the degradation state of a lithium-ion battery.
[0003] The battery state detection device of Patent Document 1 calculates a fitting coefficient based on battery information including voltage values and current values obtained by charging or discharging the target battery multiple times. The battery state detection device of Patent Document 1 pre-stores SOC-OCV data. The battery state detection device of Patent Document 1 multiplies the calculated fitting coefficient by the SOC-OCV data to detect (estimate) the degradation state of the lithium-ion battery.
[0004] Japanese Patent Application Laid-Open No. 2023-140942
[0005] In-vehicle batteries are often set not to be used in the low SOC region and the high SOC region in order to extend their lifespan. For this reason, in a normal configuration, for example, it is impossible to acquire SOC-OCV data in the range where SOC is from 0% to 100%.
[0006] Therefore, there is a limit to the accuracy of fitting for estimating the degree of degradation, and it has been difficult to accurately estimate the degradation state.
[0007] An object of this invention is to enable the acquisition of SOC-OCV data in the low SOC region and the high SOC region even for batteries that are difficult to utilize the low SOC region and the high SOC region in normal control.
[0008] A battery pack according to an embodiment of this invention includes a cell module with a plurality of battery cells built in, a power management system that controls the charging and discharging of the plurality of cell modules, a first external connection terminal, and a second external connection terminal, and has a configuration in which the plurality of cell modules are connected in series between the first external connection terminal and the second external connection terminal.
[0009] Multiple battery cells each consist of multiple unit cells connected in parallel. One battery cell in a group of multiple battery cells is composed of one evaluation cell and multiple standard specification cells.
[0010] The evaluation cell comprises a voltage-holding capacitor connected in parallel to the evaluation unit cell, and a bidirectional DC-DC converter inserted into the connection line between the evaluation unit cell and the voltage-holding capacitor.
[0011] The evaluation cell / SOC control unit monitors the voltage across the voltage-holding capacitor and the parallel circuit of multiple standard unit cells, and controls the operation of the bidirectional DC-DC converter.
[0012] In this configuration, charge transfer between the evaluation unit cell and multiple standard unit cells is achieved while being controlled by the evaluation cell and SOC control unit, which refer to the voltage across the capacitor. This allows the SOC of the evaluation unit cell to be varied from 0% to 100%.
[0013] A battery pack according to one embodiment of this invention comprises a cell module containing a plurality of battery cells, a power management system for controlling the charging and discharging of the plurality of cell modules, and a first external connection terminal and a second external connection terminal, wherein the plurality of cell modules are connected in series between the first external connection terminal and the second external connection terminal.
[0014] The battery pack comprises a plurality of first relays, a plurality of capacitors, a bidirectional DC-DC converter, and a second relay. The plurality of first relays are each connected between a plurality of cell modules. The plurality of capacitors are connected in parallel to each of the plurality of cell modules, and also in series. The bidirectional DC-DC converter is connected between the evaluation cell module, which is designated as the evaluation cell module, and the capacitor connected in parallel to the evaluation cell module. The second relay is connected between the evaluation cell module and the first external connection terminal. The capacitor connected in parallel to the evaluation cell module and the connection node between the first external connection terminal and the second relay are directly connected. The power management system monitors the voltage across each of the plurality of capacitors and controls the opening and closing of the first relay and the second relay.
[0015] In this configuration, the power management system references the voltages across multiple capacitors to perform charging and discharging within a predetermined range of State of Charge (SOC). Therefore, the SOC of the evaluation cell module can be varied from 0% to 100%.
[0016] A battery pack charging method according to one embodiment of this invention corresponds to a battery pack charging method in which a plurality of unit cells are connected in parallel to form a battery cell, a plurality of battery cells having the same configuration are connected in series to form a cell module, and a plurality of cell modules having the same configuration are further connected in series to form a battery pack.
[0017] The battery pack charging method involves designating one cell module from among multiple cell modules as an evaluation cell module, connecting a voltage-holding capacitor in parallel to the evaluation cell module, inserting a bidirectional DC-DC converter into the connection line between the evaluation cell module and the voltage-holding capacitor, and connecting a relay switch in parallel to the bidirectional DC-DC converter.
[0018] The method for acquiring SOC-OCV data for the evaluation unit cell is performed in the following order: measurement preparation mode, measurement mode, and post-measurement processing mode. In measurement preparation mode, the bidirectional DC-DC converter is driven in boost mode to transfer the charge of the evaluation unit cell to the normal-spec (unit cell and) voltage-holding capacitor. In measurement mode, the bidirectional DC-DC converter is driven in buck mode to intermittently charge the evaluation unit cell with the charge of the normal-spec unit cell and acquire SOC-OCV data for the evaluation unit cell. In post-measurement processing mode, the bidirectional DC-DC converter is driven in boost mode to transfer the charge of the evaluation unit cell to the normal-spec unit cell, making the voltage across the evaluation unit cell the same as the voltage across the normal-spec unit cell. Separately, in normal charging mode where SOC-OCV data is not acquired, the bidirectional DC-DC converter charges all unit cells constituting the battery pack while maintaining equipotential control so that the voltage across the evaluation unit cell and the voltage across the voltage-holding capacitor are equal. Instead of equipotentially controlling the bidirectional DC-DC converter, a relay switch may be provided connecting the input and output terminals of the bidirectional DC-DC converter. In a normal charging mode where SOC-OCV data is not acquired, the relay switch may be controlled to conduct and the bidirectional DC-DC converter may be stopped.
[0019] This method allows the State of Charge (SOC) of an evaluation unit cell to be varied from 0% to 100% by transferring charge between multiple unit cells that make up a single battery cell.
[0020] A battery pack charging method according to one embodiment of this invention comprises a cell module containing a plurality of battery cells, a plurality of capacitors connected in parallel to each of the plurality of cell modules and each connected in series, a cell module among the plurality of series-connected cell modules that is directly connected to a first external connection terminal designated as an evaluation cell module, a bidirectional DC-DC converter connected between the capacitor connected in parallel to the evaluation cell module and the evaluation cell module, a plurality of first relays connected between each of the plurality of cell modules, and a second relay connected between the evaluation cell module and the first external connection terminal, wherein the capacitor connected in parallel to the evaluation cell module is directly connected to the first external connection terminal.
[0021] This charging method includes a first operating mode in which the first relay and the second relay are conductive, a second operating mode in which the first relay and the second relay are open, and a third operating mode in which the first relay is conductive and the second relay is open. This charging method charges the battery pack in the order of the first operating mode, the second operating mode, the third operating mode, the second operating mode, and the first operating mode.
[0022] In this charging method, during the first second operating mode, the evaluation cell SOC control unit drives a bidirectional DC-DC converter to transfer charge from the evaluation cell module to other cell modules. In the third operating mode, this charging method acquires SOC-OCV data of the evaluation cell module while charging all cell modules, including the evaluation cell module. In the second second operating mode, this charging method acquires SOC-OCV data of the evaluation cell module while the evaluation cell SOC control unit drives a bidirectional DC-DC converter to transfer charge from other cell modules to the evaluation cell module.
[0023] This method allows the SOC of the evaluation cell module to be varied without directly measuring the voltage of the evaluation cell module using the power management system described above. This makes it possible to vary the SOC of the evaluation cell module from 0% to 100%.
[0024] According to this invention, even with batteries where it is difficult to utilize the low SOC region and the high SOC region using conventional control methods, SOC-OCV data in the low SOC region and the high SOC region can be acquired.
[0025] Figure 1 is a functional block diagram of a battery pack according to the first embodiment. Figure 2 is a functional block diagram of a normal cell module according to the first embodiment. Figure 3 is a functional block diagram of an evaluation cell module according to the first embodiment. Figure 4 is a functional block diagram showing an example of a battery pack degradation degree estimation system according to the first embodiment. Figure 5 is a diagram showing the schematic configuration of a vehicle equipped with a battery pack according to the first embodiment. Figure 6 is a flowchart showing an example of a method for acquiring SOC-OCV data for a battery pack according to the first embodiment. Figure 7 is a diagram showing an example of the charge state and voltage after each operating mode and a predetermined operating mode in the first embodiment. Figure 8 is a diagram showing an example of the charge state and voltage after each operating mode and a predetermined operating mode in the first embodiment. Figure 9 is a diagram showing an example of the charge state and voltage after each operating mode and a predetermined operating mode in the first embodiment. Figure 10 is a diagram showing an example of the charge state and voltage after each operating mode and a predetermined operating mode in the first embodiment. Figure 11 is a diagram showing an example of the charge state and voltage after each operating mode and a predetermined operating mode in the first embodiment. Figure 12 is a diagram showing an example of the charge state and voltage after each operating mode and a predetermined operating mode in the first embodiment. Figure 13 is a functional block diagram of the battery pack according to the second embodiment. Figure 14 is a flowchart showing an example of a method for acquiring SOC-OCV data for the battery pack according to the second embodiment. Figure 15 is a diagram showing an example of the charge state and voltage after each operating mode and a predetermined operating mode in the second embodiment. Figure 16 is a diagram showing an example of the charge state and voltage after each operating mode and a predetermined operating mode in the second embodiment. Figure 17 is a diagram showing an example of the charge state and voltage after each operating mode and a predetermined operating mode in the second embodiment. Figure 18 is a diagram showing an example of the charge state and voltage after each operating mode and a predetermined operating mode in the second embodiment. Figure 19 is a diagram showing an example of the charge state and voltage after each operating mode and a predetermined operating mode in the second embodiment. Figure 20 is a diagram showing an example of the charge state and voltage after each operating mode and a predetermined operating mode in the second embodiment.Figure 21 shows an example of each operating mode and the charge state and voltage after a predetermined operating mode in the second embodiment. Figure 22 shows an example of each operating mode and the charge state and voltage after a predetermined operating mode in the second embodiment.
[0026] [First Embodiment] A battery pack SOC-OCV acquisition system, a battery pack SOC-OCV acquisition method, and a battery pack charging method according to the first embodiment of the present invention will be described with reference to the figures.
[0027] Figure 1 is a functional block diagram of a battery pack according to the first embodiment.
[0028] As shown in Figure 1, the battery pack 10 includes a plurality of cell modules 201-212, a PMS 100, a first external connection terminal TL11, and a second external connection terminal TL12.
[0029] Multiple cell modules 201-212 are connected in series between the first external connection terminal TL11 and the second external connection terminal TL12.
[0030] Specifically, the positive terminal of cell module 201 is connected to the first external connection terminal TL11. The positive terminal of cell module 202 is connected to the negative terminal of cell module 201. The positive terminal of cell module 203 is connected to the negative terminal of cell module 202. The positive terminal of cell module 204 is connected to the negative terminal of cell module 203.
[0031] The negative terminal of cell module 204 is connected to the positive terminal of cell module 205. The negative terminal of cell module 205 is connected to the positive terminal of cell module 206. The negative terminal of cell module 206 is connected to the positive terminal of cell module 207. The negative terminal of cell module 207 is connected to the positive terminal of cell module 208.
[0032] The negative terminal of cell module 208 is connected to the positive terminal of cell module 209. The negative terminal of cell module 209 is connected to the positive terminal of cell module 210. The negative terminal of cell module 210 is connected to the positive terminal of cell module 211. The negative terminal of cell module 211 is connected to the positive terminal of cell module 212. The negative terminal of cell module 212 is connected to the second external connection terminal TL12.
[0033] Cell module 201 corresponds to the "evaluation cell module" of the present invention, and the multiple cell modules 202-212 correspond to the "other cell modules" of the present invention.
[0034] The PMS100 is connected to the positive and negative terminals of each of the multiple cell modules 201-212.
[0035] The PMS100 is a so-called power management system. The PMS100 integrates multiple cell modules 201-212 and controls the entire battery pack 10.
[0036] Figure 2 is a functional block diagram of a standard cell module according to the first embodiment.
[0037] Multiple cell modules 202-212 have similar configurations and are configured similarly to cell module 200 shown in Figure 2.
[0038] The cell module 200 comprises a plurality of battery cells B1-B8, a BMS290, a positive terminal TLC+, and a negative terminal TLC-.
[0039] Each of the battery cells B1-B8 is composed of a lithium-ion battery and has a similar configuration. Each of the battery cells B1-B8 comprises multiple unit cells connected in parallel.
[0040] Specifically, in the standard cell module 200, battery cell B1 comprises four unit cells B11-B14. These four unit cells B11-B14 are connected in parallel. Battery cell B2 comprises four unit cells B21-B24. These four unit cells B21-B24 are connected in parallel.
[0041] The battery cell B3 includes four unit cells B31 - B34. The four unit cells B31 - B34 are connected in parallel. The battery cell B4 includes four unit cells B41 - B44. The four unit cells B41 - B44 are connected in parallel.
[0042] The battery cell B5 includes four unit cells B51 - B54. The four unit cells B51 - B54 are connected in parallel. The battery cell B6 includes four unit cells B61 - B64. The four unit cells B61 - B64 are connected in parallel.
[0043] The battery cell B7 includes four unit cells B71 - B74. The four unit cells B71 - B74 are connected in parallel. The battery cell B8 includes four unit cells B81 - B84. The four unit cells B81 - B84 are connected in parallel.
[0044] Each of the plurality of unit cells B11 - B14, B21 - B24, B31 - B34, B41 - B44, B51 - B54, B61 - B64, B71 - B74, B81 - B84 that make up the cell module 200 corresponds to the "normal specification cell" of the present invention.
[0045] The plurality of battery cells B1 - B8 are connected in series between the positive terminal TLC+ and the negative terminal TLC-.
[0046] The BMS 290 is a so-called battery management system. The positive and negative electrodes of the plurality of battery cells B1 - B8 are connected to the BMS 290. The BMS 290 refers to the voltages across the plurality of battery cells B1 - B8 and controls the cell module 200 to transfer charges between the plurality of battery cells B1 - B8 so that these voltages across the cells become substantially the same, and also provides protection against overcurrent and overvoltage.
[0047] In this embodiment, the case where the number of battery cells provided in the cell module 200 is eight is shown, but the number is not limited to this. Similarly, the number of unit cells constituting one battery cell is not limited to four.
[0048] FIG. 3 is a functional block diagram of the evaluation cell module according to the first embodiment. The cell module 201 has the configuration shown in FIG. 3.
[0049] The cell module 201 includes a plurality of battery cells B1 - B8, a BMS 290, a positive terminal TLC+, a negative terminal TLC-, a bidirectional DC - DC converter 110, a current sensor CS, and a capacitor CM for voltage holding. The configurations of the plurality of battery cells B1 - B8, the BMS 290, the positive terminal TLC+, and the negative terminal TLC- of the cell module 201 are the same as those of the cell module 200, and descriptions of the same parts are omitted.
[0050] The unit cell B11 constituting the cell module 201 corresponds to the "evaluation cell" of the present invention, and each of the plurality of unit cells B12 - B14, B21 - B24, B31 - B34, B41 - B44, B51 - B54, B61 - B64, B71 - B74, B81 - B84 corresponds to the "normal specification cell" of the present invention.
[0051] The capacitor CM is connected in parallel to the plurality of unit cells B12 - B14. The bidirectional DC - DC converter 110 is inserted into the connection line between the unit cell B11 and the capacitor CM, one input / output terminal is connected to the positive terminal of the unit cell B11, and the other input / output terminal is connected to the capacitor CM. The current sensor CS is connected in series between the bidirectional DC - DC converter 110 and the battery cell B1.
[0052] (Normal charging control) In normal charging, the PMS 100 controls each battery cell of the plurality of cell modules 201 - 212 to charge and discharge within a predetermined SOC range. For example, when the battery pack 10 is used as a power source for driving a motor of a vehicle described later, the PMS 100 controls to charge and discharge within the range where the SOC is from 20% to 80%. At this time, the PMS 100 outputs the actual SOC range of 20% to 80% as if the SOC range is from 0% to 100% to the vehicle control system and the like.
[0053] Therefore, with conventional charging and discharging, it was not possible to bring the SOC to near 0% or near 100%, and thus it was not possible to obtain SOC-OCV characteristics from 0% to 100% for accurate estimation of the degradation level of the battery pack 10.
[0054] However, the battery pack 10, having the above configuration, can acquire SOC-OCV characteristics from 0% to 100% by performing the charge and discharge control shown below.
[0055] Figure 4 is a functional block diagram showing an example of a battery pack degradation estimation system according to the first embodiment. As shown in Figure 4, the battery pack 10 degradation estimation system comprises a charging device 80, an SOC-OCV data acquisition device 91, and an analysis device 92.
[0056] The charging device 80 includes a charge / discharge control unit 81 and a power supply circuit 82. The charge / discharge control unit 81 performs specific charge / discharge control on the battery pack 10, which will be described later. The charge / discharge control unit 81 is also capable of data communication with the PMS 100 of the battery pack 10, and can issue charge / discharge control instructions to the PMS 100 and obtain various information about the battery pack 10 from the PMS 100.
[0057] The power supply circuit 82 is connected to the charge / discharge control unit 81 and the power receiving socket PR. The power supply circuit 82 receives power through the power receiving socket PR and supplies power to charge the battery pack 10 through the charge / discharge control unit 81.
[0058] The SOC-OCV data acquisition device 91 includes an evaluation cell, an SOC control unit 911, and a communication interface.
[0059] The evaluation cell / SOC control unit 911 is equipped with multiple terminals for connecting to the current sensor CS, the bidirectional DC-DC converter 110, and the capacitor CM. The communication IF is an interface for communicating with the analysis device 92.
[0060] The evaluation cell / SOC control unit 911 acquires SOC-OCV data from a known method based on the charging and discharging currents from the current sensor CS and the control voltage of the bidirectional DC-DC converter 110.
[0061] The current sensor CS measures the charging and discharging currents exchanged between the unit cell (evaluation cell) B11 and the capacitor CM and unit cells B12-B14, and outputs them to the evaluation cell / SOC control unit 911. Preferably, if another current sensor CS is connected between the bidirectional DC-DC converter 110 and the capacitor CM, the inflow and outflow of charge to and from unit cells B111 and B12-B14 can be accurately measured regardless of the power conversion losses of the bidirectional DC-DC converter 110.
[0062] Figure 5 is a schematic diagram of a vehicle equipped with a battery pack according to the first embodiment. As shown in Figure 5, the vehicle EV is, for example, an electric vehicle, and runs by driving a motor (not shown) with power from the battery pack 10. The vehicle EV is equipped with a power supply circuit 82, a charge / discharge control unit 81, and a power receiving socket PR. The power supply circuit 82 is composed of a PFC converter and a DC-DC converter, for example, as shown in Figure 5.
[0063] By attaching the power transmission socket of the EV charger to the power receiving socket PR, the battery pack 10 can be charged.
[0064] The analysis device 92 includes an SOC-OCV characteristic calculation unit 921 and a degradation degree estimation unit 922. The analysis device 92 is configured, for example, by a separate processing unit (computer) from the vehicle EV.
[0065] The SOC-OCV characteristic calculation unit 921 calculates an SOC-OCV characteristic curve (fitting curve) based on the SOC-OCV data acquired from the SOC-OCV data acquisition device 91. The SOC-OCV characteristic calculation unit 921 outputs the SOC-OCV characteristic curve to the degradation degree estimation unit 922.
[0066] The degradation degree estimation unit 922, for example, pre-stores reference SOC-OCV characteristic curves for each degradation degree. The degradation degree estimation unit 922 compares the SOC-OCV characteristic curve calculated by the SOC-OCV characteristic calculation unit 921 with the reference SOC-OCV characteristic curve to estimate the degradation degree of the battery pack 10. Specifically, the degradation degree estimation unit 922 detects the degradation degree corresponding to the reference SOC-OCV characteristic curve that is closest to the calculated SOC-OCV characteristic curve. The degradation degree estimation unit 922 uses this detected degradation degree as the degradation degree of the battery pack 10.
[0067] (Battery pack charging and discharging method 1) Figure 6 is a flowchart showing an example of a method for acquiring SOC-OCV data for a battery pack according to the first embodiment. Figures 7-12 show examples of each operating mode and the charge state and voltage after each operating mode in the first embodiment.
[0068] The evaluation cell / SOC control unit 911 controls the operation of the bidirectional DC-DC converter 110 of the evaluation cell module 201 according to the flow shown in Figure 6.
[0069] At the start of SOC-OCV data acquisition, the evaluation cell / SOC control unit 911 acquires the voltage across the evaluation unit cell B11 provided in the evaluation cell module 201. The evaluation cell / SOC control unit 911 estimates a provisional SOC. The evaluation cell / SOC control unit 911 determines whether the provisional SOC satisfies the conditions for starting the battery pack degradation diagnosis.
[0070] The evaluation cell / SOC control unit 911 executes a measurement preparation mode for SOC-OCV data if the conditions for starting the degradation diagnosis are met (S11).
[0071] For example, the condition for starting the degradation diagnosis is when the SOC is 40%. If the SOC is less than 40%, the evaluation cell / SOC control unit 911 executes the SOC-OCV data measurement preparation mode. On the other hand, if the SOC is 40% or higher, the evaluation cell / SOC control unit 911 performs normal charging or rapid charging.
[0072] Furthermore, the evaluation cell / SOC control unit 911 may add the following conditions to the conditions for starting the deterioration degree diagnosis.
[0073] At least one of the following conditions must be met: the charger used to charge the battery pack 10 is a pre-registered charger; there is sufficient time before the battery pack 10 is used to supply power to the vehicle EV again; and a certain amount of time has elapsed since the last degradation analysis was performed. However, it is more preferable that all of these conditions are met.
[0074] When SOC-OCV data is not being measured, that is, during normal charging and discharging, the bidirectional DC-DC converter 110 operates so that the evaluation unit cell B11 and the voltage-holding capacitor CM are at the same potential (the voltage across both ends is the same).
[0075] In measurement preparation mode, the evaluation cell / SOC control unit 911 drives the bidirectional DC-DC converter 110 in boost mode. This transfers the charge from unit cell B11 to multiple unit cells B12, B13, and B14 via the voltage-holding capacitor CM (see Figure 8).
[0076] By continuing the measurement preparation mode, the charge of unit cell B11 becomes 0 and the voltage across its terminals decreases. Meanwhile, the charges and voltages across the terminals of the multiple unit cells B12, B13, and B14 increase in accordance with the charge supplied from unit cell B11.
[0077] At this time, charge is also supplied to capacitor CM. As a result, even if the voltage across unit cell B11 decreases, the voltages across capacitor CM and the multiple unit cells B12, B13, and B14 are maintained according to the charge they each hold (see Figure 9). Therefore, BMS290 does not recognize that the SOC has fallen below the lower limit for normal use. Thus, the degradation estimation system can discharge the evaluation unit cell B11 to SOC 0%.
[0078] When the evaluation cell / SOC control unit 911 detects the end of the measurement preparation mode, it executes the measurement mode (S12). The end of the measurement preparation mode is detected, for example, by the convergence of the voltage changes across the capacitor CM and the multiple unit cells B12, B13, and B14.
[0079] In measurement mode, the evaluation cell / SOC control unit 911 drives the bidirectional DC-DC converter 110 in step-down mode. This transfers the charge from multiple unit cells B12, B13, and B14 to unit cell B11 via the voltage-holding capacitor CM (see Figure 10). During this process, the evaluation cell / SOC control unit 911 operates intermittently. Intermittent operation is a charging method in which, for example, the unit is driven in step-down mode for one minute to transfer charge, and then the charge is not transferred for 10 minutes, during which the open-circuit voltage of unit cell B11 is measured and this process is repeated. The open-circuit voltage is obtained from the voltage across unit cell B11 and is sent from the bidirectional DC-DC converter 110 to the evaluation cell / SOC control unit 911.
[0080] By continuing the measurement mode, the charge and voltage across multiple unit cells B12, B13, and B14 decrease, while the charge and voltage across unit cell B11 increase.
[0081] In this case, even if the voltage across unit cell B11 increases, the voltages across capacitor CM and the multiple unit cells B12, B13, and B14 are maintained according to the charge they each hold (see Figure 11). Therefore, the BMS290 does not recognize that the SOC has exceeded the upper limit under normal use. Thus, the degradation estimation system can charge the evaluation unit cell B11 to 100% SOC.
[0082] When the evaluation cell / SOC control unit 911 detects the end of the measurement mode, it executes a post-processing mode (S13). The end of the measurement mode is detected by the voltage across the unit cell B11.
[0083] In post-processing mode, the evaluation cell / SOC control unit 911 drives the bidirectional DC-DC converter 110 in boost mode. This transfers the charge from unit cell B11 to multiple unit cells B12, B13, and B14 (see Figure 12).
[0084] The evaluation cell / SOC control unit 911 terminates the post-processing mode when the voltages across the capacitor CM and the multiple unit cells B11, B12, B13, and B14 become equipotential (the same voltage).
[0085] The explanation of the measurement preparation mode and measurement mode so far has not mentioned the behavior of the charge / discharge control unit 81. However, depending on the voltage of battery cell B1 when the measurement preparation mode is started, it may not be possible to bring the State of Charge (SOC) of unit cell B11 to 100% by transferring charge from multiple unit cells B12, B13, and B14 to unit cell B11. In that case, the entire battery pack 10 is charged to supply charge to unit cell B11 from an external source. At that time, the charge / discharge control unit 81 performs intermittent charging as appropriate to adjust the amount of charge supplied to unit cell B11.
[0086] In this way, the degradation estimation system can change the SOC-OCV data of one unit cell B11 (evaluation cell) constituting the battery pack 10 from 0% to 100%, acquire SOC-OCV data, and charge the battery pack 10.
[0087] Furthermore, by acquiring SOC-OCV data from 0% to 100% SOC, the degree of degradation of the battery pack 10 can be estimated with high accuracy.
[0088] (Example of specific operating state) Using Figures 7-12, specific examples of changes in SOC and voltage when the above control is performed will be explained. Figures 7-12 show the case where the vehicle EV is stopped when the SOC reaches 40% and charging is started. Furthermore, this charging is set with a timer, and it shows the case where the driver returns home in the evening, connects the receiving socket PR to the charging port socket of the charger, and charges using off-peak electricity. In addition, this example shows the case where the rated voltage of the unit cell is 3.7V and the capacity is 14.075Ah.
[0089] Figure 7 shows the charging start state, where the State of Charge (SOC) of all unit cells B1-B8 is 40%. In this case, the voltage across all unit cells is 3.45V, and the voltage across capacitor CM is also 3.45V. At this time, the bidirectional DC-DC converter 110 is controlled to equipotential.
[0090] When the measurement preparation mode is executed, the state shown in Figure 8 is reached.
[0091] Specifically, the bidirectional DC-DC converter 110 operates in boost mode. This causes the bidirectional DC-DC converter 110 to extract charge from unit cell B11 and supply this charge to multiple unit cells B12, B13, and B14. Unit cell B11 discharges, and the multiple unit cells B12, B13, and B14 are charged. At the same time, charge is also supplied to capacitor CM.
[0092] As a result, the SOC and voltage across unit cell B11 decrease, while the SOC and voltage across multiple unit cells B12, B13, and B14 increase.
[0093] The measurement preparation mode is maintained until all the charge in unit cell B11 is extracted and the true SOC value becomes 0%, at which point the charge transfer operation of the bidirectional DC-DC converter 110 is stopped.
[0094] As a result, as shown in Figure 9, the SOC of unit cell B11 becomes 0%, and the voltage across its terminals becomes 3.00V. On the other hand, the SOC of unit cells B12, B13, and B14 becomes 53.3%, and the voltage across their terminals becomes 3.65V. The voltage across capacitor CM also becomes 3.65V. The voltage across its terminals measured by BMS290 is the voltage across the parallel circuit of unit cells B12, B13, B14 and capacitor CM, which is 3.65V. Therefore, BMS290 does not detect that unit cell B11 has an SOC of 0% and a voltage across its terminals of 3.00V, and determines that the SOC is within the normal range for normal operation. As a result, unit cell B11 can be discharged to its true SOC of 0%.
[0095] Next, when the measurement mode is executed, the state shown in Figure 10 is reached. Specifically, the bidirectional DC-DC converter 110 operates in step-down mode. As a result, the bidirectional DC-DC converter 110 extracts charge from multiple unit cells B12, B13, and B14 and supplies this charge to unit cell B11. Multiple unit cells B12, B13, and B14 discharge, and unit cell B11 is charged. During this process, unit cell B11 is charged by the intermittent operation of the bidirectional DC-DC converter 110.
[0096] As a result, the SOC and terminal voltage of multiple unit cells B12, B13, and B14 decrease, while the SOC and terminal voltage of unit cell B11 increase.
[0097] The measurement mode is continued, and when unit cell B11 reaches a truly fully charged state, the bidirectional DC-DC converter 110 stops transferring charge.
[0098] As a result, as shown in Figure 11, the SOC of unit cell B11 becomes 100%, and the voltage across its terminals becomes 4.2V. On the other hand, the SOC of unit cells B12, B13, and B14 becomes 20%, and the voltage across their terminals becomes 3.25V. The voltage across capacitor CM also becomes 3.25V. The voltage across which the BMS290 measures is the voltage across the parallel circuit of unit cells B12, B13, B14 and capacitor CM, which is 3.25V. Therefore, the BMS290 does not detect that unit cell B11 has an SOC of 100% and a voltage across its terminals of 4.2V, and determines that the SOC is within the normal range for normal operation. As a result, unit cell B11 can be charged to its true SOC of 100%.
[0099] This allows the degradation estimation system to intermittently charge the evaluation unit cell B11 from true SOC 0% to 100%. Therefore, the degradation estimation system can obtain SOC-OCV data for unit cell B11 from true SOC 0% to 100%.
[0100] Next, when the post-processing mode is executed, the state shown in Figure 12 is reached. Specifically, the bidirectional DC-DC converter 110 operates in boost mode. As a result, the bidirectional DC-DC converter 110 extracts charge from unit cell B11 and supplies this charge to multiple unit cells B12, B13, and B14. Unit cell B11 is discharged, and the multiple unit cells B12, B13, and B14 are charged.
[0101] As a result, the SOC and voltage across unit cell B11 decrease, while the SOC and voltage across multiple unit cells B12, B13, and B14 increase.
[0102] The post-processing mode continues until the voltages across all unit cells B11, B12, B13, and B14 and the SOC become the same, at which point the bidirectional DC-DC converter 110 stops operating.
[0103] As a result, as shown in Figure 7, the State of Charge (SOC) of all unit cells B11, B12, B13, and B14 becomes 40%, and the voltage across them becomes 3.45V. In other words, the battery pack 10 returns to the state it was in when charging started.
[0104] Subsequently, through normal charging, all unit cells constituting the battery pack 10 are charged to the maximum SOC value under normal use (for example, true SOC of 80%).
[0105] This type of control makes it possible to acquire SOC-OCV data in both the low SOC and high SOC regions, even for batteries where it is difficult to utilize the low SOC and high SOC regions with conventional control methods.
[0106] Furthermore, the above control, by appropriately setting the power capacity of the bidirectional DC-DC converter 110 and the ratio of the charging time to the discharging time of intermittent charging, is possible, depending on the State of Charge (SOC), to start charging the night before, finish charging the next day, and then operate the EV vehicle the following day.
[0107] [Second Embodiment] A second embodiment of the present invention will describe, with reference to the figures, a system for acquiring SOC-OCV data for a battery pack, a method for acquiring SOC-OCV data for a battery pack, and a method for charging a battery pack. Below, the differences between the configuration and method of the second embodiment and the configuration and method of the first embodiment will be described. For parts of the configuration and method of the second embodiment that are the same as those of the first embodiment, the contents of the first embodiment will be described as appropriate.
[0108] Figure 13 is a functional block diagram of a battery pack according to the second embodiment. As shown in Figure 13, the battery pack 10A includes a plurality of cell modules 201-212, a plurality of relay switches S1-S12, a plurality of capacitors C1-C12, a PMS 100, a bidirectional DC-DC converter 110, a first external connection terminal TL11, a second external connection terminal TL12, and a current sensor CS.
[0109] Multiple cell modules 201-212 have a similar configuration and are configured as cell module 200 in Figure 2. Multiple cell modules 201-212 are connected in series between a first external connection terminal TL11 and a second external connection terminal TL12 via multiple relay switches S1-S12.
[0110] Specifically, the positive terminal of cell module 201 is connected to the first external connection terminal TL11 via relay switch S1. The positive terminal of cell module 202 is connected to the negative terminal of cell module 201 via relay switch S2.
[0111] The negative terminal of cell module 202 is connected to the positive terminal of cell module 203 via relay switch S3. The negative terminal of cell module 203 is connected to the positive terminal of cell module 204 via relay switch S4.
[0112] The negative terminal of cell module 204 is connected to the positive terminal of cell module 205 via relay switch S5. The negative terminal of cell module 205 is connected to the positive terminal of cell module 206 via relay switch S6.
[0113] The negative terminal of cell module 206 is connected to the positive terminal of cell module 207 via relay switch S7. The negative terminal of cell module 207 is connected to the positive terminal of cell module 208 via relay switch S8.
[0114] The negative terminal of cell module 208 is connected to the positive terminal of cell module 209 via relay switch S9. The negative terminal of cell module 209 is connected to the positive terminal of cell module 210 via relay switch S10.
[0115] The negative terminal of cell module 210 is connected to the positive terminal of cell module 211 via relay switch S11. The negative terminal of cell module 211 is connected to the positive terminal of cell module 212 via relay switch S12. The negative terminal of cell module 212 is connected to the second external connection terminal TL12.
[0116] Cell module 201 corresponds to the "evaluation cell module" of the present invention, and the multiple cell modules 202-212 correspond to the "other cell modules" of the present invention. The multiple relay switches S2-S12 correspond to the "first relay" of the present invention, and relay switch S1 corresponds to the "second relay" of the present invention.
[0117] Furthermore, a bidirectional DC-DC converter 110 is connected to the positive and negative terminals of the cell module 201.
[0118] Multiple capacitors C1-C12 are connected in parallel to each of the multiple cell modules 201-212. Furthermore, multiple capacitors C1-C12 are connected in series between the first external connection terminal TL11 and the second external connection terminal TL12.
[0119] Specifically, capacitor C1 is connected in parallel to cell module 201, capacitor C2 is connected in parallel to cell module 202, and capacitor C3 is connected in parallel to cell module 203.
[0120] Capacitor C4 is connected in parallel to cell module 204, capacitor C5 is connected in parallel to cell module 205, and capacitor C6 is connected in parallel to cell module 206.
[0121] Capacitor C7 is connected in parallel to cell module 207, capacitor C8 is connected in parallel to cell module 208, and capacitor C9 is connected in parallel to cell module 209.
[0122] Capacitor C10 is connected in parallel to cell module 210, capacitor C11 is connected in parallel to cell module 211, and capacitor C12 is connected in parallel to cell module 212.
[0123] One terminal of capacitor C1 is connected to the bidirectional DC-DC converter 110. The other terminal of capacitor C1 is connected to one terminal of capacitor C2, and the other terminal of capacitor C2 is connected to one terminal of capacitor C3.
[0124] The other terminal of capacitor C3 is connected to one terminal of capacitor C4, and the other terminal of capacitor C4 is connected to one terminal of capacitor C5.
[0125] The other terminal of capacitor C5 is connected to one terminal of capacitor C6, and the other terminal of capacitor C6 is connected to one terminal of capacitor C7.
[0126] The other terminal of capacitor C7 is connected to one terminal of capacitor C8, and the other terminal of capacitor C8 is connected to one terminal of capacitor C9.
[0127] The other terminal of capacitor C9 is connected to one terminal of capacitor C10, and the other terminal of capacitor C10 is connected to one terminal of capacitor C11.
[0128] The other terminal of capacitor C11 is connected to one terminal of capacitor C12, and the other terminal of capacitor C12 is connected to the second external connection terminal TL12.
[0129] The bidirectional DC-DC converter 110 is connected between the positive terminal of the cell module 201 and one terminal of the capacitor C1.
[0130] The current sensor CS is connected between the bidirectional DC-DC converter 110 and the positive terminal of the cell module 201.
[0131] The PMS 100 is connected to both terminals (one terminal and the other terminal) of multiple capacitors C1-C12. With this configuration, the PMS 100 monitors the voltage across the multiple capacitors C1-C12.
[0132] The PMS100 references the voltages across multiple capacitors C1-C12 and controls the exchange of charge between multiple cell modules 201-212 so that these voltages are approximately the same.
[0133] (Battery pack charging and discharging method 2) Figure 14 is a flowchart showing an example of a method for acquiring SOC-OCV data for a battery pack according to the second embodiment. The same system as in Figure 4 can be used for the battery pack according to the second embodiment.
[0134] The evaluation cell / SOC control unit 911 outputs control commands to the charge / discharge control unit 81 and the PMS 100 of the battery pack 10 according to the flow shown in Figure 14. The PMS 100 controls the operation of the bidirectional DC-DC converter 110 and the multiple relay switches S1-S12 of the battery pack 10 according to these control commands. At this time, the evaluation cell / SOC control unit 911 may directly control the operation of the relay switches S1-S12 without going through the PMS 100.
[0135] The first, second, and third operating modes shown in each step of the flowchart in Figure 14 are as follows:
[0136] In the first operating mode, all of the relay switches S1-S12 are made conductive, and the bidirectional DC-DC converter 110 is stopped.
[0137] In the second operating mode, all of the relay switches S1-S12 are opened, and the bidirectional DC-DC converter 110 is operated.
[0138] In the third operating mode, relay switch S1 is opened, multiple relay switches S2-S12 are made conductive, and the bidirectional DC-DC converter 110 is operated.
[0139] Figures 15-22 show examples of each operating mode and the charge state and voltage after a predetermined operating mode in the second embodiment.
[0140] At the start of charging and discharging, the evaluation cell SOC control unit 911 executes the first operating mode via the PMS 100 (S21). Specifically, the evaluation cell SOC control unit 911 turns on all of the relay switches S1-S12 and stops the bidirectional DC-DC converter 110 to perform normal charging without acquiring SOC-OCV data.
[0141] In this case, the voltage across the multiple capacitors C1-C12 is the same as the voltage across the multiple cell modules 201-212.
[0142] The evaluation cell / SOC control unit 911, upon confirming that the execution conditions for the SOC-OCV data acquisition mode are met, instructs the PMS 100 to transition to the second operation mode, and the PMS 100 executes the second operation mode (the first second operation mode) (S22).
[0143] The execution conditions for the SOC-OCV data acquisition mode are that at least one of the following conditions is met: • The SOC of multiple cell modules 201-212 of the battery pack 10 is above a predetermined value; • The charger used to charge the battery pack 10 is a pre-registered charger; • There is sufficient time before the battery pack 10 is used again to supply power to the vehicle EV; • A certain amount of time has elapsed since the last degradation analysis was performed. However, it is more preferable that all of the above conditions are met. The SOC for determining these execution conditions can be obtained from the PMS 100.
[0144] When the first second operating mode is executed, the bidirectional DC-DC converter 110 is driven in boost mode, transferring the charge stored in cell module 201 from cell module 201 to multiple cell modules 202-212.
[0145] In this process, the charge stored in the cell module 201 is supplied through multiple capacitors C1-C12. As a result, the voltage across the multiple capacitors C1-C12 remains approximately the same.
[0146] Furthermore, since the PMS 100 references these multiple capacitors C1-C12, even if the SOC of cell module 201 becomes smaller than the SOC of the other cell modules 202-212, it does not perform charge exchange control between the multiple cell modules 201-212 based on the fact that the multiple capacitors C1-C12 have approximately the same voltage.
[0147] As a result, even with the PMS100, the charge stored in cell module 201 is transferred to cell modules 202-212. This allows cell module 201 to be discharged to SOC 0%.
[0148] The evaluation cell SOC control unit 911, based on the voltage of the cell module 201 obtained from the DC-DC converter, executes a third operating mode when it detects that the SOC of the cell module 201 has become 0% (S23).
[0149] When the third operating mode is executed, the multiple cell modules 201-212 of the battery pack 10 are intermittently charged by the current supplied from the charge / discharge control unit 81. The open-circuit voltage is obtained from the voltage across the cell module 201, which is obtained from the bidirectional DC-DC converter 110.
[0150] The evaluation cell / SOC control unit 911 acquires the SOC-OCV data of the cell module 201 by sequentially acquiring this open-circuit voltage.
[0151] This intermittent charging is carried out until the maximum SOC in normal charging is reached, i.e., the maximum SOC defined by the PMS 100, and then stopped by the PMS 100. The PMS 100 then notifies the evaluation cell / SOC control unit 911 of the stoppage of intermittent charging.
[0152] When the evaluation cell / SOC control unit 911 acquires information that intermittent charging has stopped, it instructs the PMS 100 and the charge / discharge control unit 81 to switch to the second operating mode. The PMS 100 and the charge / discharge control unit 81 receive this instruction and execute the second operating mode (S24).
[0153] When the second operation mode is executed for the second time, the bidirectional DC-DC converter 110 is driven in step-down mode, transferring the charge stored in the multiple cell modules 202-212 from the multiple cell modules 202-212 to the cell module 201, thereby charging the cell module 201.
[0154] In this case, the PMS 100 performs intermittent charging of the cell module 201 in the second operating mode, similar to the third operating mode described above.
[0155] The evaluation cell / SOC control unit 911 acquires SOC-OCV data for the cell module 201 by sequentially acquiring the open-circuit voltage of the cell module 201 during intermittent charging.
[0156] In this process, the charge used to charge the cell module 201 is supplied through multiple capacitors C1-C12. As a result, the voltage across the multiple capacitors C1-C12 remains approximately the same.
[0157] Furthermore, since the PMS 100 references these multiple capacitors C1-C12, even if the SOC of cell module 201 becomes larger than the SOC of the other cell modules 202-212, it does not perform control to return the charge of cell module 201 to the other cell modules 201-212, based on the fact that the multiple capacitors C1-C12 have approximately the same voltage.
[0158] As a result, even with the PMS100 present, the charge from multiple cell modules 202-212 can charge cell module 201 to 100% of its State of Charge (SOC).
[0159] As a result, the evaluation cell / SOC control unit 911 can acquire SOC-OCV data from 0% to 100% for the battery pack 10 equipped with the PMS 100.
[0160] The evaluation cell SOC control unit 911 detects that the SOC of the cell module 201 has reached 100% based on the voltage across the cell module 201 measured by the bidirectional DC-DC converter 110, and then executes the second operation mode for the second time (S24).
[0161] When the second operation mode is executed for the second time, the bidirectional DC-DC converter 110 is driven in boost mode, and the charge stored in the cell module 201 is transferred from the cell module 201 to the multiple cell modules 202-212.
[0162] This second operating mode controls the SOCs of multiple cell modules 201-212 to be the same.
[0163] After this, the evaluation cell / SOC control unit 911 executes the second operation mode for the third time to make the SOCs of the multiple cell modules 201-212 the same (S25), then transitions to the first operation mode for the second time (S26) to charge the multiple cell modules 201-212.
[0164] In this way, by performing the above-described charge control using the battery pack 10A, the SOC of one cell module 201 (evaluation cell module) representing the battery pack 10A can be changed from 0% to 100%, and SOC-OCV data can be acquired.
[0165] Furthermore, by acquiring SOC-OCV data from 0% to 100% SOC, the degree of degradation of the battery pack 10A can be estimated with high accuracy.
[0166] (Example of a specific operating state) Figures 15-22 illustrate specific examples of the changes in SOC and voltage when the above control is performed. Figures 15-22 show the case where the vehicle EV is stopped when the SOC reaches 40% and charging is started. This charging is set up with a timer, and it shows the case where the driver returns home in the evening, connects the receiving socket PR to the charging socket of the charger, and charges using off-peak electricity. Furthermore, in this example, the rated voltage of battery cells B1-B8 is 3.65V and the capacity is 112.6Ah, and the terminal voltage of battery pack 10 is 3.65 × 96 = 350.4V and the capacity is 350.4 × 0.1126 ≈ 40kWh.
[0167] Figure 15 shows the charging start state (the state of the first operating mode), where the SOC of all cell modules 201-212 is 40%. In this case, the voltage across all cell modules 201-212 is 27.6V, and the voltage across all capacitors C1-C12 is also 27.6V.
[0168] When the system transitions from the first operating mode to the second operating mode, the state shown in Figure 16 occurs. Specifically, relay switches S1-S12 are opened, and the bidirectional DC-DC converter 110 is operated in boost mode for cell module 201, which is the evaluation cell module among the multiple cell modules 201-212. As a result, the bidirectional DC-DC converter 110 extracts charge from cell module 201 and charges capacitor C1 with this charge.
[0169] As a result, the PMS100's cell balancing function works to bring the voltage of multiple capacitors C2-C12 to the same level as capacitor C1. Therefore, the energy output from cell module 201 is shared and received by multiple cell modules 202-212.
[0170] As a result of this first second operating mode, the operation of the bidirectional DC-DC converter 110 is stopped when the true SOC value of the cell module 201 becomes 0%, as shown in Figure 17.
[0171] At this time, only relay switch S1 is open, while the other relay switches S2-S12 are conductive. As a result, the true SOC of cell module 201 becomes 0%, and the PMS 100 evenly charges the multiple cell modules 202-212 with the 40% SOC charge stored in cell module 201, resulting in a true SOC value of 43.7% for the multiple cell modules 202-212. At this point, the voltage across the multiple cell modules 201-212 becomes 27.64V.
[0172] Therefore, the PMS 100 does not determine that cell module 201 has a SOC of 0%, but rather determines that it has the same SOC as the other multiple cell modules 202-212.
[0173] Next, when the timer charging start time for the charger is reached, the third operating mode is executed, relay switch S1 is opened, and the multiple relay switches S2-S12 become conductive. After this, normal charging starts, and the bidirectional DC-DC converter 110 operates in step-down mode. Since the SOC = 100% on the vehicle meter is equivalent to a true SOC value of 80%, normal charging continues until the true SOC value of cell modules 202-212 reaches 80%, as shown in Figure 18. At the completion of this charging, the true SOC value of cell module 201 is 36.3%.
[0174] During this process, the intermittent charging described above is performed. This allows for the acquisition of SOC-OCV data for the evaluation cell module 201 in the range of SOC = 0% to 36.3%.
[0175] Next, after normal charging is complete, a second operating mode is executed, and the bidirectional DC-DC converter 110 operates in step-down mode. As multiple capacitors C1-C12 are charged and the bidirectional DC-DC converter 110 operates in step-down mode, the energy stored in the multiple cell modules 202-212 is supplied to cell module 201, as shown in Figure 19, and cell module 201 is charged.
[0176] As a result of executing this second operating mode, as shown in Figure 20, cell module 201 is charged until its true SOC value reaches 100%. At this point, the operation of the bidirectional DC-DC converter 110 stops. At this time, only relay switch S1 is open, while the other relay switches S2-S12 are conductive. As a result, the multiple cell modules 202-212 evenly discharge the charge necessary to charge cell module 201 from 36.3% to 100%, and each cell module 202-212 reaches a true SOC value of 74.2%. Then, the voltage across the multiple capacitors C1-C12 becomes 30.64V due to the cell balancing function.
[0177] In this case, since there is no closed circuit in the cell module 201, it is neither charged nor discharged, and its true SOC value remains at 100%. However, the voltage across capacitor C1 is 30.64V, just like the multiple capacitors C2-C12, so the PMS100 does not determine that the cell module 201 has an SOC of 100%.
[0178] During this process, the intermittent charging described above is performed. This allows for the acquisition of SOC-OCV data for the evaluation cell module 201 in the range of SOC = 36.3% to 100%.
[0179] After this, the third second operating mode is executed. In the third second operating mode, the bidirectional DC-DC converter 110 operates in boost mode. As a result, as shown in Figure 21, the bidirectional DC-DC converter 110 extracts charge from the cell module 201 and charges the capacitor C1 with this charge.
[0180] As a result, the PMS100's cell balancing function works to bring the voltage of multiple capacitors C2-C12 to the same level as capacitor C1. Therefore, the energy output from cell module 201 is shared and absorbed by multiple cell modules 202-212. As a result, as shown in Figure 22, multiple cell modules 201-212 all have the same SOC of 76.3%.
[0181] After this, the second run of the first operating mode is performed, and all cell modules 201-212 are charged to 80% of the State of Charge (SOC).
[0182] This type of control makes it possible to acquire SOC-OCV data in both the low SOC and high SOC regions, even for batteries where it is difficult to utilize the low SOC and high SOC regions with conventional control methods.
[0183] Furthermore, the above-described control, similar to the first embodiment, allows for the vehicle EV to be driven by starting charging the night before and finishing charging the next day, although this depends on the initial state of charge (SOC), by appropriately setting the power capacity of the bidirectional DC-DC converter 110 and the ratio of the charging time to the discharging time of intermittent charging.
[0184] In this case, for example, if you have a plan to not move the EV vehicle for two or three days, you can specify that date and time. In this case, by performing charging while acquiring the aforementioned SOC-OCV data according to the specified date and time, the acquisition of SOC-OCV data and charging can be performed more reliably.
[0185] Furthermore, the above description shows a configuration in which the bidirectional DC-DC converter 110 is connected to the cell module 201 on the first external connection terminal TL11 side. However, a configuration in which the bidirectional DC-DC converter is connected to the cell module 212 on the second external connection terminal TL12 side is also possible.
[0186] The first and second embodiments are the same in that they acquire SOC-OCV data by transferring the charge of an evaluation cell or evaluation cell module to another cell or other cell module to adjust it to the desired SOC.
[0187] The first embodiment differs in that the BMS within the cell module performs balance control, while the second embodiment uses a PMS. To enable balance control by the PMS, each cell module is configured with an additional capacitor connected in parallel and relays between the cell modules. Therefore, while the first embodiment requires significant design changes due to the addition of components compared to conventional battery packs, the first embodiment allows for the addition of SOC-OCV acquisition functionality to existing battery packs with only minor modifications, such as rerouting the wiring path from the evaluation cell module to the evaluation single cell to a bidirectional DC-DC converter outside the evaluation cell module and wiring to the current sensor and capacitor.
[0188] 10, 10A: Battery pack 91: SOC-OCV data acquisition device 92: Analysis device 100: PMS 110: Bidirectional DC-DC converter 200, 201-212: Cell module 911: Evaluation cell / SOC control unit CS: Current sensor 81: Charge / discharge control unit 82: Power supply circuit 921: SOC-OCV characteristic calculation unit 922: Degradation degree estimation unit B1-B8: Battery cell B11-B14, B21-B24, B31-B34, B41-B44, B51-B54, B61-B64, B71-B74, B81-B84: Unit cell C1-C12, CM: Capacitor EV: Vehicle PR: Power receiving socket S1-S12: Relay switch TL11: First external connection terminal TL12: Second external connection terminal
Claims
1. A SOC-OCV data acquisition system for a battery pack comprising: a cell module containing multiple battery cells; a power management system for controlling the charging and discharging of the multiple cell modules; a first external connection terminal and a second external connection terminal, wherein the multiple cell modules are connected in series between the first external connection terminal and the second external connection terminal, wherein the first battery cell in the multiple battery cells consists of one evaluation cell and multiple normal specification cells connected in parallel to each of the multiple battery cells; the second battery cells other than the first battery cell in the multiple battery cells each comprises multiple unit cells connected in parallel to each of the multiple battery cells; a voltage-holding capacitor connected in parallel to the evaluation cell; a bidirectional DC-DC converter inserted in the connection line between the evaluation cell and the voltage-holding capacitor; and a current sensor connected in series between the evaluation cell and the bidirectional DC-DC converter, or between the bidirectional DC-DC converter and the voltage-holding capacitor. A battery pack SOC-OCV data acquisition system comprising: an evaluation cell / SOC control unit that monitors the voltage across the voltage-holding capacitor and the parallel circuit of the plurality of normally used unit cells, and controls the operation of the bidirectional DC-DC converter.
2. A SOC-OCV data acquisition system for a battery pack comprising: a cell module containing a plurality of battery cells; a power management system for controlling the charging and discharging of the plurality of cell modules; a first external connection terminal and a second external connection terminal, wherein the plurality of cell modules are connected in series between the first external connection terminal and the second external connection terminal, comprising: a plurality of first relays connected between each of the plurality of cell modules; a plurality of capacitors connected in parallel to each of the plurality of cell modules and each connected in series; a cell module among the plurality of series-connected cell modules that is directly connected to the first external connection terminal is designated as an evaluation cell module, a bidirectional DC-DC converter connected between the capacitor connected in parallel to the evaluation cell module and the evaluation cell module; and a second relay connected between the evaluation cell module and the first external connection terminal, wherein the capacitor connected in parallel to the evaluation cell module and the connection node between the first external connection terminal and the second relay are directly connected, and the power management system monitors the voltage across each of the plurality of capacitors. A battery pack SOC-OCV data acquisition system comprising an evaluation cell / SOC control unit that controls the charging and discharging of the evaluation cell module by controlling the conduction and opening of the first relay and the second relay, thereby controlling the exchange of charge between the evaluation cell module and other cell modules.
3. A method for charging a battery pack, wherein a battery cell is constructed by connecting multiple unit cells in parallel, a cell module is constructed by connecting multiple such battery cells, each having the same configuration, and a battery pack is constructed by connecting multiple such cell modules, each having the same configuration, in series, wherein one cell module in the multiple cell modules is designated as an evaluation cell module, one battery cell in the evaluation cell module is designated as an evaluation battery cell, one unit cell in the evaluation battery cell is designated as an evaluation cell, and the other unit cells are designated as standard specification cells, a voltage-holding capacitor is connected in parallel to the evaluation cell, a bidirectional DC-DC converter is inserted in the connection line between the evaluation cell and the voltage-holding capacitor, a current sensor is inserted between the evaluation cell and the bidirectional DC-DC converter, and the following modes are executed in this order: a measurement preparation mode, a measurement mode, and a measurement post-processing mode, in the measurement preparation mode, the bidirectional DC-DC converter is driven in boost mode, and the charge of the evaluation cell is transferred to the standard specification cell via the voltage-holding capacitor. A method for acquiring SOC-OCV data of a battery pack, wherein in the measurement mode, the bidirectional DC-DC converter is driven in step-down mode, the evaluation cell is intermittently charged with the charge of the normal-use cell, and SOC-OCV data of the evaluation cell is acquired; and in the post-measurement processing mode, the bidirectional DC-DC converter is driven in step-up mode, the charge of the evaluation cell is transferred to the normal-use cell, and the voltage across the evaluation cell and the voltage across the normal-use cell are made the same.
4. A method for acquiring SOC-OCV data from a battery pack according to claim 3, comprising a relay switch that bypasses the input and output terminals of the bidirectional DC-DC converter, wherein the relay switch is controlled to conduct and the bidirectional DC-DC converter is stopped before the measurement preparation mode and after the measurement post-processing mode.
5. A battery pack charging method comprising: a cell module containing multiple battery cells; a plurality of capacitors connected in parallel to each of the plurality of cell modules and each connected in series; a cell module among the plurality of series-connected cell modules that is directly connected to a first external connection terminal designated as an evaluation cell module, a bidirectional DC-DC converter connected between the capacitor connected in parallel to the evaluation cell module and the evaluation cell module; a plurality of first relays connected between each of the plurality of cell modules; and a second relay connected between the evaluation cell module and the first external connection terminal, wherein a capacitor connected in parallel to the evaluation cell module and the connection node of the first external connection terminal and the second relay are directly connected, comprising: a first operating mode in which the first relay and the second relay are in a conductive state; a second operating mode in which the first relay and the second relay are in an open state; and a third operating mode in which the first relay is in a conductive state and the second relay is in an open state. A method for acquiring SOC-OCV data for a battery pack, comprising: charging the battery pack in the order of the first operating mode, the second operating mode, the third operating mode, the second operating mode, and the first operating mode; driving the bidirectional DC-DC converter to transfer charge from the evaluation cell module to other cell modules during the first second operating mode; acquiring SOC-OCV data of the evaluation cell module while charging all cell modules, including the evaluation cell module, during the third operating mode; and acquiring SOC-OCV data of the evaluation cell module while driving the bidirectional DC-DC converter to transfer charge from other cell modules to the evaluation cell module during the second second operating mode.
6. A method for controlling the charging and discharging of a battery pack, comprising a method for acquiring SOC-OCV data of a battery pack according to any one of claims 3 to 5, wherein the battery pack is used as an on-board drive battery for an electric vehicle, and the plurality of cell modules in the battery pack are controlled to remain within a predetermined SOC range that does not reach 0% or 100% when the electric vehicle is running.
7. A battery pack charge / discharge control method according to claim 6, wherein the degradation level of the battery pack is analyzed when all of the following conditions are met: the SOC is above a predetermined value; the charger used to charge the battery pack is a pre-registered charger; there is sufficient time before the battery pack is used again to supply power to the electric vehicle; and a certain amount of time has elapsed since the last degradation level analysis was performed.