Battery management device for electric vehicles

Abstract

To provide a battery management device of an electric vehicle which can sufficiently exhibit capability of a battery.SOLUTION: A battery management device of an electric vehicle is mounted on an electric vehicle which includes a driving wheel, a traveling motor for generating power of the driving wheel, and a battery for accumulating power consumed by the traveling motor. The battery management device includes a detection part for detecting the state of the battery, and a controller for calculating a characteristic value indicating the capability of the battery on the basis of output of the detection part, and managing charging / discharging of the battery on the basis of the characteristic value. The controller discriminates whether or not the degradation of the characteristic value is reversible degradation on the basis of the output of the detection part when there is degradation of the characteristic value, and returns the characteristic value to a value before the degradation when discriminating that the degradation is the reversible degradation.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a battery management device for an electric vehicle.

Background Art

[0002] Patent Document 1 describes a battery deterioration determination system that determines that a battery has undergone deterioration other than high-rate deterioration based on a change in a peak position appearing on a dQ / dV characteristic line of the battery.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] In a battery management device, characteristic values representing the performance of a battery (full charge capacity, internal resistance, etc.) are calculated, and when these values are registered as control data for management, charging and discharging of the battery are managed based on the registered values. While the characteristic values of a battery gradually deteriorate over time or with use, a recovered characteristic value may be calculated due to errors. Therefore, conventionally, even if a recovered characteristic value is calculated, the battery management device normally does not register the value as control data for management.

[0005] In recent years, it has been found that the characteristic value of a battery may temporarily deteriorate due to reversible degradation and then recover. If the charging and discharging of the battery are managed using the characteristic value obtained when the battery was deteriorated even after the characteristic value has recovered, a problem arises in that the battery cannot fully exhibit its performance in an electric vehicle.

[0006] An object of the present invention is to provide a battery management device for an electric vehicle that allows the battery to fully exhibit its performance. [Means for solving the problem]

[0007] The present invention relates to a battery management device for an electric vehicle, which is mounted on an electric vehicle comprising a drive wheel, a drive motor that generates power for the drive wheel, and a battery that stores the power consumed by the drive motor. A detection unit for detecting the state of the battery, A controller that calculates a characteristic value representing the capacity of the battery based on the output of the detection unit and manages the charging and discharging of the battery based on the characteristic value, Equipped with, When the characteristic value deteriorates, the controller determines, based on the output of the detection unit, whether the deterioration of the characteristic value is reversible or not, and if it is determined to be reversible deterioration, it restores the characteristic value to its value before deterioration. death, The battery has the characteristic of exhibiting multiple peaks on the dV / dQ characteristic line in the first SOC range. The controller determines, based on the output of the detection unit in the first SOC range, whether the degradation of the characteristic value is reversible or not. The controller determines that the degradation of the characteristic value is reversible based on whether the number of peaks on the dV / dQ characteristic line is lower than the comparison standard, or whether the peaks are less pronounced than the comparison standard. It is characterized by the following: Furthermore, the present invention relates to a battery management device for an electric vehicle, which is mounted on an electric vehicle comprising a drive wheel, a drive motor that generates power for the drive wheel, and a battery that stores the power consumed by the drive motor, A detection unit for detecting the state of the battery, A controller that calculates a characteristic value representing the capacity of the battery based on the output of the detection unit and manages the charging and discharging of the battery based on the characteristic value, Equipped with, The controller, when it detects that the characteristic value has deteriorated, determines whether the deterioration is reversible or not based on the output of the detection unit, and if it determines that the deterioration is reversible, it restores the characteristic value to its value before deterioration. The battery has the characteristic of exhibiting multiple peaks on the dV / dQ characteristic line in the first SOC range. The controller determines, based on the output of the detection unit in the first SOC range, whether the degradation of the characteristic value is reversible or not. The electric vehicle is equipped with a vehicle controller that controls the operation of the electric vehicle. The controller is characterized in that, in accordance with the progression of the deterioration of the characteristic value, it requests the vehicle controller to perform discharge or charge over the first SOC range. [Effects of the Invention]

[0008] According to the present invention, when a characteristic value representing the battery's capacity undergoes reversible degradation and subsequently recovers, the controller can restore the characteristic value to its pre-degradation value. Therefore, the characteristic value is prevented from remaining at its degraded value, and the battery's capacity can be fully utilized. [Brief explanation of the drawing]

[0009] [Figure 1] It is a block diagram showing an electric vehicle and a battery management device according to an embodiment of the present invention. [Figure 2] It is a time chart explaining changes in characteristic values of a battery. [Figure 3] It is a diagram showing an example of charge-discharge characteristic lines of a battery. [Figure 4] It is a diagram showing an example of charge-discharge characteristic lines of a battery when reversible deterioration occurs. [Figure 5] It is a part of a flowchart showing charge-discharge management processing executed by a controller. [Figure 6] It is another part of the flowchart in FIG. 5. [Figure 7] It is the remaining part of the flowchart in FIG. 5. [Figure 8] It is a flowchart showing control processing performed based on a charge-discharge request for a first SOC range. DESCRIPTION OF EMBODIMENTS

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an electric vehicle and a battery management device according to an embodiment of the present invention.

[0011] The electric vehicle 1 according to the present embodiment includes drive wheels 2, a travel motor 11 that generates power transmitted to the drive wheels 2, an inverter 12 that drives the travel motor 11, a battery 14 that stores electric power, an electric device 16 driven using electric power from the battery 14, an operation unit 18 on which driving operation is performed, a vehicle controller 21 that controls the inverter 12 and the electric device 16, and a battery management device 30 that manages the battery 14.

[0012] The operation unit 18 includes a steering unit 18a, an accelerator operation unit 18b, a brake operation unit 18c, and the like. When the operation unit 18 is operated, an operation signal is sent from the operation unit 18 to the vehicle controller 21.

[0013] The vehicle controller 21 consists of one ECU (Electronic Control Unit) or multiple ECUs that operate in cooperation with each other via communication. The vehicle controller 21 receives operation signals from the operation unit 18. The vehicle controller 21 communicates with the battery management device 30. Based on the operation signals and communication data from the battery management device 30, the vehicle controller 21 controls the inverter 12, and through this control, operates the drive motor 11 in either a powered or regenerative mode. In addition, the vehicle controller 21 can drive and control the electrical equipment 16.

[0014] During powered operation, the traction motor 11 consumes power from the battery 14. During regenerative operation, the regenerative power generated by the traction motor 11 is sent to the battery 14, thereby charging the battery 14.

[0015] Electrical equipment 16 includes heaters, compressors, DC / DC converters that generate power for low-voltage equipment, etc. Electrical equipment 16 may also include any other equipment.

[0016] The battery management device 30 includes a detection unit 32 for detecting the state of the battery 14. Specifically, the detection unit 32 includes a current sensor 32a and a voltage sensor 32b for detecting current and voltage as the state of the battery 14. The detection unit 32 may also include a temperature sensor 32c for detecting temperature as the state of the battery 14. Note that the detection unit 32 is not limited to a configuration that detects the current, voltage, and temperature of the battery 14; any configuration that detects electrical and physical variables is acceptable as long as it can detect a state in which values ​​necessary for charge and discharge management can be calculated.

[0017] The battery management device 30 further includes a controller 34. The controller 34 is a single ECU, but may be composed of multiple ECUs that cooperate with each other via communication. The controller 34 receives the detection results from the detection unit 32 and manages the charging and discharging of the battery 14.

[0018] The characteristic values ​​representing the capacity of battery 14 deteriorate with age and use. This capacity includes full charge capacity, output power, and input power, and the characteristic values ​​representing the capacity include internal resistance. Full charge capacity is both a capacity and a characteristic value. Internal resistance corresponds to the characteristic values ​​representing output power and input power. That is, as internal resistance increases, the amount of heat generated by the battery in relation to the input and output current increases, so the output power and input power decrease. Note that the capacity of battery 14 and the characteristic values ​​representing it are not limited to the above example and may include other quantities or values.

[0019] The battery management device 30 manages the charging and discharging of the battery 14 so as not to exceed the capacity of the battery 14, according to the characteristic values ​​described above. Specifically, the battery management device 30 manages the charging and discharging of the battery 14 so as not to exceed 100% SOC (State of Charge) of the battery 14, and so as not to fall to an extremely low value, based on the full charge capacity of the battery 14. This management is achieved, for example, by having the vehicle controller 21 limit the output power of the drive motor 11 when the SOC of the battery 14 is low, and by having the vehicle controller 21 limit the regenerative braking of the drive motor 11 when the SOC of the battery 14 is high. Furthermore, the battery management device 30 sets the output power and input power of the battery 14 based on the internal resistance of the battery 14, and has the vehicle controller 21 perform the traction and regenerative operation of the drive motor 11 so as not to exceed the set output power and input power. When setting the output power and input power, the battery management device 30 may also set them based on the temperature of the battery 14 in addition to the internal resistance.

[0020] The controller 34 may have memory units 34a and 34b in which characteristic values ​​representing capabilities are registered. The controller 34 may also manage charging and discharging based on the characteristic values ​​registered in the memory units 34a and 34b, rather than the characteristic values ​​calculated at each point in time or the actual characteristic values. In other words, even if there is a change in the characteristic value, the change may not be immediately reflected in the charging and discharging management, and the change in the characteristic value may be reflected in the charging and discharging management only when the characteristic values ​​in the memory units 34a and 34b are updated.

[0021] The characteristic values ​​registered in memory units 34a and 34b, or the capacity of the battery 14 determined from these characteristic values, may be values ​​transmitted to the vehicle controller 21 via communication. Furthermore, the full charge capacity registered in memory unit 34a may be a value displayed on the driver's seat display panel, the user's portable device, etc., or a value applied when calculating the State of Charge (SOC) displayed on these devices. Similarly, the internal resistance value registered in memory unit 34b, or the output power and input power determined from this value, may be values ​​displayed on the driver's seat display panel, the user's portable device, etc.

[0022] The controller 34 may update the values ​​in the memory units 34a and 34b each time a characteristic value is calculated, or it may update them according to predetermined conditions. For example, the internal resistance of the battery 14 fluctuates relatively large when the battery 14 is in use and can be calculated frequently when the battery 14 is in use. On the other hand, the value of the internal resistance registered in the memory unit 34b is used to determine the output power and input power, so it is desirable that the value reflects the averaged fluctuation over the medium to long term, excluding fluctuations that occur within a short period. Therefore, the controller 34 may collect the internal resistance of the battery 14, which is calculated frequently, for a predetermined number of cycles (such as a predetermined period or predetermined number of operations), statistically process these values ​​to obtain the averaged internal resistance, and register this value in the memory unit 34b.

[0023] <Battery Characteristics> Figure 2 is a time chart illustrating the changes in the characteristic values ​​of the battery. As shown in Figure 2, the characteristic values ​​(full charge capacity and internal resistance) and capabilities (full charge capacity, output power, and maximum input power) of the battery 14 deteriorate over time or with use. On the other hand, as shown in period T1, the characteristic values ​​and capabilities of the battery 14 may temporarily deteriorate and then recover over several hours or days. This type of deterioration that recovers afterward is called reversible deterioration. On the other hand, if the controller 34 calculates the characteristic values ​​and capabilities at any timing t1, an error may result in a value a1 that is better than the previous value.

[0024] Here, we consider a scenario where the comparative example's controller cannot determine whether the fluctuation is due to recovery after reversible degradation or simply an error. In this case, even if the calculated characteristic values ​​and capacity of battery 14 are recovered compared to before, the comparative example's controller would find it difficult to use the recovered values ​​for charge and discharge management because they could be due to errors. This is because if the recovered values ​​are used for management when the capacity of battery 14 has not actually recovered, there is a possibility that charge and discharge operations will exceed the capacity of battery 14. Therefore, even if the comparative example's controller calculates recovered characteristic values, it will continue to manage charge and discharge using the characteristic values ​​from before the recovery, without updating the management characteristic values.

[0025] Figure 2 shows an example of registered values ​​for the characteristics and capacity of the comparative example battery management device, labeled "Registered Values ​​of Comparative Example." "Registered Values ​​of Embodiment" shows an example of registered values ​​for the characteristics and capacity of the embodiment battery management device 30. "Registered values" refer to values ​​registered in the memory units 34a and 34b and used by the controller 34 for charge and discharge management, as well as the capacity values ​​converted from these values. "Registered values" may differ from the true values ​​of the characteristics and capacity at each point in time.

[0026] As shown in period T1, in the comparative example, even if the battery 14 recovers after reversible degradation, the characteristic value at the time of reversible degradation is used for charge and discharge management, which can result in the battery 14 not being able to perform at its maximum capacity. On the other hand, the controller 34 of the embodiment performs a process to determine whether or not the degradation is reversible, and if the characteristic value recovers after reversible degradation, it can perform charge and discharge management reflecting the recovered characteristic value. Therefore, the battery 14 can perform at its full capacity.

[0027] <Characteristics of reversible degradation> Figure 3 shows an example of a battery charge / discharge characteristic curve. Figure 4 shows an example of a battery charge / discharge characteristic curve when reversible degradation occurs. Figures 3 and 4 show characteristic curves when stable charging (e.g., constant current charging) is performed from a low SOC value to a high SOC value, or when stable discharging (e.g., constant current discharging) is performed from a high SOC value to a low SOC value. "V" is voltage (e.g., CCV: Closed circuit voltage), "Q" is the amount of stored energy, and "dV / dQ" represents the derivative of voltage V with respect to the amount of stored energy Q.

[0028] Battery 14 has the characteristic of exhibiting multiple peaks b on the dV / dQ characteristic line in the first SOC range D1. As a battery 14 having this characteristic, for example, a lithium-ion secondary battery having a graphite-based negative electrode can be applied.

[0029] The first SOC range D1 in which multiple peaks b appear is a predetermined range that does not change significantly with age or use, for example, around 20% SOC. Depending on the structure of the battery cell, the first SOC range D1 may be a different range, for example, around 50% SOC. Furthermore, the first SOC range D1 may shift predictably with age or use.

[0030] As shown in Figure 4, when reversible degradation occurs in the battery 14, a change occurs in the peak b of the dV / dQ characteristic curve. More specifically, the number of peak b decreases, the degree of variation of peak b becomes gentler, and if there are multiple peak b, the deviation in the positions of the multiple peak b decreases. Then, when the reversible degradation is reversed, the dV / dQ characteristic curve returns to the original number and shape of peak b as shown in Figure 3.

[0031] <Process for determining reversible degradation> The controller 34, as part of its discrimination process, determines whether or not the degradation of characteristic values ​​and capabilities is reversible by determining whether or not there is a change in peak b of the dV / dQ characteristic line.

[0032] Specifically, in the discrimination process, the controller 34 determines whether the number of peaks has decreased to below a threshold, whether the degree of variation in the peaks is below a threshold, or whether the deviation of multiple peak positions is below a threshold. Alternatively, the controller 34 may determine whether two or three of the above conditions are met. Then, if the result of the discrimination is YES, the controller 34 determines that it is a reversible degradation.

[0033] Here, the change in peak b refers to the change from the reference peak b to the observed peak b. The reference peak b is the peak b of the battery 14 in its initial state, which may be determined by testing or simulation, and its number and shape may be provided to the controller 34 in advance. Alternatively, the reference peak b may be the peak b of the previous dV / dQ characteristic line observed by the controller 34 when the battery 14 is stably discharged or charged.

[0034] According to the above determination process, when a recovered characteristic value is obtained, the controller 34 can determine whether it is a recovery after reversible degradation or a fluctuation in the value due to error. If the controller 34 determines that it is a recovery after reversible degradation, it can return the management characteristic value (the characteristic value registered in memory units 34a and 34b) to the value before degradation, i.e., the recovered characteristic value. Therefore, the battery 14 can then fully utilize its capabilities.

[0035] The controller 34 needs to acquire the dV / dQ characteristic curve of the first SOC range D1 in order to perform the above determination process. Therefore, the controller 34 may perform the above determination process only when there is a high possibility of reversible degradation, such as when rapid degradation occurs, depending on the progression of degradation of the characteristic value of the battery 14. Furthermore, when performing the determination process, the controller 34 may send a request to the vehicle controller 21 to perform charging or discharging in the first SOC range D1 so that the dV / dQ characteristic curve of the first SOC range D1 can be acquired quickly.

[0036] Based on the request, the vehicle controller 21 controls the drive motor 11 and electrical equipment 16 in parallel with vehicle control according to the driving operation so that charging or discharging occurs over the first SOC range D1. For example, if the SOC of the battery 14 is higher than the first SOC range D1, the vehicle controller 21 controls the drive motor 11 or electrical equipment 16 so that the SOC becomes below the first SOC range D1 by consuming power. This control enables discharging over the first SOC range D1. Also, if charging such as external charging is performed when the SOC is higher than the lower limit of the first SOC range D1, the vehicle controller 21 or controller 34 first releases the power of the battery 14 to the outside (or uses it with electrical equipment 16, etc.). Then, the vehicle controller 21 or controller 34 lowers the SOC to the lower limit of the first SOC range D1 and then charges the battery 14. This control enables charging over the first SOC range D1. Through the above processing, the controller 34 can quickly acquire the dV / dQ characteristic curve of the first SOC range D1 and determine whether or not it is a reversible change.

[0037] If the result of the above determination process is reversible degradation, the controller 34 may recalculate the characteristic value again and, provided that the characteristic value has recovered, return the management characteristic value (the characteristic value registered in memory units 34a and 34b) to the value before degradation, i.e., the recovered value. Alternatively, in addition to the above conditions, the controller 34 may then acquire the dV / dQ characteristic line again and, provided that the peak has returned to its original value, return the management characteristic value to the recovered value before degradation. This process prevents the management characteristic value from being returned to the recovered value before the battery 14 has actually recovered.

[0038] <Charge / Discharge Management Process> Next, we will explain a detailed example of the charge and discharge management process performed by the controller. Figures 5 to 7 are flowcharts of the charge and discharge management process.

[0039] In the charge / discharge management process, the controller 34 repeatedly executes steps S1 and S2 in the loop processing of steps S1 to S3, S11, and S19. That is, the controller 34 obtains the current, temperature, and voltage values ​​of the battery 14 from the output of the detection unit 32 (step S1), and manages charge / discharge based on the characteristic values ​​of the storage units 34a and 34b (step S2). In the management of step S2, when the controller 34 receives a discharge request or charge request from the vehicle controller 21, it decides whether to permit or deny discharge or charge to prevent discharge or charge exceeding the capacity, and sends the decision back to the vehicle controller 21.

[0040] The controller 34 further determines in the above loop processing whether the calculation conditions for characteristic values ​​(full charge capacity and internal resistance) are met (step S3). If the result is NO, the controller 34 determines whether the charge / discharge request flag for the first SOC range D1 is valid (step S11) and whether the reversible degradation flag is valid (step S19). If the results of both steps S11 and S19 are NO, the controller 34 returns to step S1.

[0041] The calculation conditions for the characteristic values ​​described above include collecting enough detected values ​​to determine the full charge capacity by repeatedly acquiring the detected values ​​in step S1, or collecting enough detected values ​​to determine the average value of the internal resistance through statistical processing. Furthermore, other conditions may be added to the calculation conditions above, such as whether a predetermined period (usage period of the battery 14) or a predetermined amount of discharge or charge has occurred since the previous calculation of the characteristic values.

[0042] In the loop processing described above, if the result of step S3 is YES, the controller 34 calculates characteristic values ​​(full charge capacity and internal resistance) based on the collected current, temperature, and voltage detection values ​​(step S4). The controller 34 then determines whether the characteristic values ​​have deteriorated from the previous values ​​(step S5), and if YES, registers the deteriorated characteristic values ​​in the storage units 34a and 34b (step S6). With this update of registered values, charging and discharging will be managed using the updated characteristic values ​​in the subsequent step S2.

[0043] Next, the controller 34 determines whether the degradation level of the characteristic value is equal to or greater than the first threshold (step S7). If the degradation level is high, there is a possibility of reversible degradation, and in this step, the controller 34 confirms this possibility. Furthermore, the controller 34 determines whether there was charging or discharging (or a charge amount or discharge amount equal to or greater than the threshold) of a second threshold or greater during the period of degradation (step S8). If there was excessive charging or discharging, or an excessive charge amount or discharge amount, the battery 14 may undergo reversible degradation, and in this step, the controller 34 confirms this possibility. The first and second thresholds are set to values ​​that identify the presence or absence of the possibility of reversible degradation.

[0044] Then, if the result of either step S7 or S8 is NO, the controller 34 returns to the loop processing from step S1. On the other hand, if the results of both steps S7 and S8 are YES, the controller 34 sends a request for charging and discharging across the first SOC range to the vehicle controller 21 (step S9). The controller 34 then activates the charge / discharge request flag indicating that the request is in progress (step S10).

[0045] If the charge / discharge request flag is determined to be valid in step S11 of the loop processing, the controller 34 determines whether the detected values ​​(current, temperature, and voltage) of the first SOC range D1 have been acquired (step S12). If the result of the determination is NO, the controller 34 returns to the loop processing from step S1.

[0046] On the other hand, if charging or discharging is performed over the first SOC range D1 as requested in step S9, and the result of the determination in step S12 is YES, the controller 34 resets the charge / discharge request flag to invalid (step S13). The controller 34 then maps the characteristic curve of the SOC-voltage during charging or discharging in the first SOC range D1 (step S14). Furthermore, the controller 34 differentiates the mapped characteristic curve to generate a dV / dQ characteristic line (step S15). The controller 34 then calculates the position, number, and intensity of peak b appearing on the dV / dQ characteristic line (step S16) and determines whether the conditions for reversible degradation are met (step S17). These conditions include, for example, whether the number of peak b has decreased to below a threshold, whether the variance value of the positions of multiple peak b has decreased to below a threshold, or whether the intensity of peak b has become less than or equal to a threshold.

[0047] If the result of the determination in step S17 is YES, the controller 34 activates the reversible degradation flag indicating that the degradation is reversible (step S18). If the result is NO, the controller 34 returns to the loop processing from step S1.

[0048] In the loop processing, if the reversible degradation flag is determined to be valid in step S19, the controller 34 determines whether the recovery period for reversible degradation (for example, a predetermined period) has elapsed (step S20). If the result is NO, the controller 34 returns to the loop processing from step S1. On the other hand, if it is YES, the controller 34 determines whether detection (detected values ​​of current, temperature, and voltage) across the first SOC range D1 was performed after the recovery period (step S21). If it is NO, the controller 34 returns to the loop processing from step S1. On the other hand, if it is YES, the controller 34 calculates the position, number, and intensity of peak b appearing on the dV / dQ characteristic line by processing similarly to steps S14 to S16 (step S22). Then, the controller 34 determines whether the number and shape of peak b have returned to those before the reversible degradation (step S22). If it is NO, the processing returns to the loop processing from step S1, but if it is YES, the peak recovery flag is enabled (step S24).

[0049] Then, if the characteristic value is calculated in step S4 as described above, and it is determined to be NO (characteristic value recovered) in step S5, the controller 34 determines whether the reversible degradation flag and the peak recovery flag are enabled. If it is YES, the controller 34 deactivates the reversible degradation flag and the peak recovery flag (step S26) and registers the characteristic value before degradation (i.e., the recovered characteristic value) in the memory units 34a and 34b (step S27). The characteristic value before degradation in step S27 may be the characteristic value calculated before it was determined to be reversible degradation, or it may be a newly calculated characteristic value that has recovered more than the previous characteristic value. If the determination result in step S25 is NO, or if the registration in step S27 is performed, the controller 34 returns to the loop processing from step S1. Due to the update of the registered value in step S27, in the subsequent step S2, charging and discharging will be managed with the recovered characteristic value. In other words, the capacity of the battery 14 can be fully utilized.

[0050] The charge / discharge management process program described above is stored in a non-transient storage medium (non-transient computer-readable medium), such as the storage unit 34e of the controller 34. The controller 34 may be configured to read a program stored in a portable non-transient recording medium and execute the program. The portable non-transient storage medium described above may store the charge / discharge management process program described above.

[0051] <Charge / Discharge Control> Figure 8 is a flowchart showing the control process performed based on the charge / discharge request for the first SOC range. This control process is performed by the vehicle controller 21 based on the request in step S9 of Figure 5. Alternatively, the control process in Figure 8 may be performed by the controller 34 of the battery management device 30 based on the above request.

[0052] When the above request is received, the vehicle controller 21 determines whether the State of Charge (SOC) of the battery 14 is above the upper limit of the first SOC range D1 (see Figures 3 and 4) (step S31). If the result is YES, the vehicle controller 21 drives the drive motor 11 or electrical equipment 16 so that constant current discharge is performed until the battery is below the lower limit of the first SOC range D1 (step S32). As a result of the process in step S32, a stable discharge process is performed in the battery 14 across the first SOC range D1, and the controller 34 of the battery management device 30 can obtain a discharge characteristic line across the first SOC range D1. Note that the above constant current discharge does not have to be a strictly constant current; it is sufficient if the discharge is stable enough that the peak b of the dV / dQ characteristic line can be detected normally.

[0053] On the other hand, if the determination result in step S31 is NO, the vehicle controller 21 determines whether plug charging has started (step S33), and if NO, returns to step S31. Plug charging means charging the battery 14 by taking power from outside the electric vehicle 1 via a power cable. Note that instead of plug charging in step S33, charging of the battery 14 by stable power generation by an internal combustion engine may be applied, or contactless charging from a power transmission coil of a ground facility to a power receiving coil mounted on the electric vehicle 1 may be applied.

[0054] Then, if the determination result in step S33 is YES, the vehicle controller 21 determines whether the State of Charge (SOC) of the battery 14 is less than the lower limit of the first SOC range D1 (step S34). If the result is YES, the vehicle controller 21 causes constant current charging up to the upper limit of the first SOC range D1 (step S36). This charging process ensures that the battery 14 undergoes stable charging across the first SOC range D1, and the controller 34 of the battery management device 30 can obtain a charging characteristic curve across the first SOC range D1.

[0055] On the other hand, if the result of step S34 is NO, the vehicle controller 21 first discharges the battery 14 until its SOC falls below the lower limit of the first SOC range, and then performs constant current charging until it exceeds the upper limit of the first SOC range (step S35). This charging process ensures that the battery 14 undergoes stable charging across the first SOC range D1, and the controller 34 of the battery management device 30 can obtain a charging characteristic line across the first SOC range D1. The discharge in step S35 may be discharge to an external charging facility (power system), discharge to the electrical equipment 16 of the electric vehicle 1, or discharge to external electrical equipment connected to the electric vehicle 1. Note that the constant current charging in steps S35 and S36 does not need to be strictly constant current; it is sufficient if the charging is stable enough that the peak b of the dV / dQ characteristic line can be detected normally.

[0056] This charge / discharge control process allows for the rapid and stable charging or discharging of the first SOC range D1 when the battery 14 may experience reversible degradation and the controller 34 of the battery management device 30 requests charging or discharging within the first SOC range D1.

[0057] The charge / discharge control process program described above is stored in a non-transient storage medium, such as the storage unit 21a of the vehicle controller 21. The vehicle controller 21 may be configured to read a program stored in a portable non-transient recording medium and execute the program. The portable non-transient storage medium may store the charge / discharge management process program described above. If the charge / discharge control process is executed by the controller 34 of the battery management device 30, then in the above description, the vehicle controller 21 should be read as controller 34.

[0058] As described above, according to the battery management device 30 of this embodiment, when the characteristic value of the battery 14 deteriorates, the controller 34 determines whether the deterioration is reversible or not based on the output of the detection unit 32. If the controller 34 determines that the deterioration is reversible, it restores the characteristic value to its pre-deterioration value. Therefore, when the characteristic value of the battery 14 recovers after reversible deterioration, charging and discharging are managed according to the recovered characteristic value, allowing the battery 14 to fully utilize its capacity. Furthermore, by determining whether the deterioration is reversible or not, the characteristic value is restored to its pre-deterioration value (recovered value) in distinction from cases where it appears to have recovered due to a simple error, thus preventing charging and discharging that exceeds the capacity of the battery 14.

[0059] Furthermore, according to the battery management device 30 of this embodiment, the battery 14 to be managed has the characteristic that multiple peaks b appear on the dV / dQ characteristic line in the first SOC range D1. The controller 34 then determines whether the degradation of the characteristic value is reversible or not based on the output of the detection unit 32 in the first SOC range D1. More specifically, the controller 34 determines that the degradation of the characteristic value is reversible based on whether the number of peaks on the dV / dQ characteristic line is lower than the comparison standard, or whether the peaks are gentler than the comparison standard. With this determination method, the controller 34 can determine whether or not the degradation is reversible more accurately. Note that other means depending on the characteristics of the battery 14 may be applied as means for determining whether or not the degradation is reversible or not.

[0060] Furthermore, according to the battery management device 30 of this embodiment, the controller 34 requests the vehicle controller 21 to discharge or charge over the first SOC range D1 in accordance with the progression of characteristic value degradation. Therefore, if there is a possibility of reversible degradation, the controller 34 can quickly obtain a discharge characteristic line or a charge characteristic line over the first SOC range D1, enabling more accurate determination of reversible degradation.

[0061] Furthermore, according to the battery management device 30 of this embodiment, when the controller 34 determines that the degradation of the characteristic value is reversible, it recalculates the characteristic value and, on the condition that the characteristic value has recovered, returns the characteristic value to its value before degradation. This re-verification process reduces the inconvenience of returning the characteristic value to a recovered value even though it has not actually recovered.

[0062] Embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. For example, in the charge and discharge management process shown in Figures 5 to 7, the controller 34 returns the characteristic value to the recovered value, provided that the peak b of the dV / dQ characteristic line has recovered through the processing in steps S21 to S25. However, the controller 34 may return the characteristic value to the recovered value without confirming the recovery of peak b. Alternatively, the controller 34 may, without confirming the recovery of the characteristic value, wait for a recovery period and return the characteristic value to the value before degradation if it determines that reversible degradation has occurred. Furthermore, in the above embodiments, an example was shown in which the battery management device 30 manages charge and discharge based on the overall characteristic value of one battery 14. However, the battery management device according to the present invention may manage the charge and discharge of the entire battery or individual battery cells based on the individual characteristic values ​​of multiple battery cells contained in one battery. Other details shown in the embodiments can be modified as appropriate without departing from the spirit of the invention. [Explanation of Symbols]

[0063] 1. Electric Vehicle 2 drive wheels 11. Driving motor 12 Inverters 14 batteries 16 Electrical equipment 18 Control section 21 Vehicle Controller 21a Storage section 30 Battery management device 32 Detection unit 32a Current Sensor 32b Voltage Sensor 32°C temperature sensor 34 controllers 34a, 34b storage section 34e Storage section D1 First SOC range b peak

Claims

1. A battery management device for an electric vehicle, which is mounted on an electric vehicle comprising drive wheels, a drive motor that generates power for the drive wheels, and a battery that stores the power consumed by the drive motor, A detection unit for detecting the state of the battery, A controller that calculates a characteristic value representing the capacity of the battery based on the output of the detection unit and manages the charging and discharging of the battery based on the characteristic value, Equipped with, The controller, when it detects that the characteristic value has deteriorated, determines whether the deterioration is reversible or not based on the output of the detection unit, and if it determines that the deterioration is reversible, it restores the characteristic value to its value before deterioration. The battery has the characteristic of exhibiting multiple peaks on the dV / dQ characteristic line in the first SOC range. The controller determines, based on the output of the detection unit in the first SOC range, whether the degradation of the characteristic value is reversible or not. The battery management device for an electric vehicle is characterized in that the controller determines that the degradation of the characteristic value is reversible based on the fact that the number of peaks on the dV / dQ characteristic line is lower than a comparison standard, or that the peaks are less pronounced than a comparison standard.

2. A battery management device for an electric vehicle, which is mounted on an electric vehicle comprising drive wheels, a drive motor that generates power for the drive wheels, and a battery that stores the power consumed by the drive motor, A detection unit for detecting the state of the battery, A controller that calculates a characteristic value representing the capacity of the battery based on the output of the detection unit and manages the charging and discharging of the battery based on the characteristic value, Equipped with, The controller, when it detects that the characteristic value has deteriorated, determines whether the deterioration is reversible or not based on the output of the detection unit, and if it determines that the deterioration is reversible, it restores the characteristic value to its value before deterioration. The battery has the characteristic of exhibiting multiple peaks on the dV / dQ characteristic line in the first SOC range. The controller determines, based on the output of the detection unit in the first SOC range, whether the degradation of the characteristic value is reversible or not. The electric vehicle is equipped with a vehicle controller that controls the operation of the electric vehicle. The battery management device for an electric vehicle is characterized in that the controller requests the vehicle controller to discharge or charge over the first SOC range in accordance with the progression of deterioration of the characteristic value.

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