Battery control method and battery control device

Abstract

In the present invention, a control method for a battery 3 including a plurality of cells 1 is executed by a processor. The processor: detects voltages of the respective plurality of cells 1; calculates the voltage difference between the highest voltage and the lowest voltage of the plurality of cells 1 on the basis of the detected voltages; and executes output limitation of the battery 3 when the voltage difference is equal to or higher than a predetermined first voltage difference threshold value.

Description

[Technical Field]

[0001] The present invention relates to a battery control method and a battery control device. [Background technology]

[0002] Conventionally, a battery pack control device is known that includes a plurality of first voltage detection means connected to the individual cells constituting the battery pack and detecting the voltage of the individual cells, a second voltage detection means for detecting the total voltage of the battery pack, and a control means that selects either the voltage of an individual cell or the total voltage of the battery pack and controls the power of the battery pack according to the selected voltage (for example, Patent Document 1). The battery pack control device described in Patent Document 1 calculates the voltage difference between the average voltage (V1) calculated from the total voltage of the battery 3 and the minimum voltage (V2) of each individual cell, and if the voltage difference is greater than a threshold (C1), it selects the minimum voltage (V2) and performs output limiting to prevent over-discharge according to the selected minimum voltage (V2). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2010-226792 [Overview of the project] [Problems that the invention aims to solve]

[0004] In batteries with multiple cells, the temperature may differ depending on the cell's location. For example, if the temperature of a particular cell is lower than that of other cells, the voltage of the low-temperature cell will drop even if it is not a faulty cell. When the conventional battery pack control device described above is applied under such battery conditions, the lowest voltage of the low-temperature cell will result in a large output limit being imposed to prevent over-discharge. In other words, there is a problem in that an unnecessarily large output limit is imposed on normal cells.

[0005] The problem to be solved by the present invention is to provide a battery control method and a battery control device that can prevent an unnecessarily large output limit from being applied to normal cells.

Means for Solving the Problem

[0006] The present invention detects the voltages of a plurality of cells respectively, Multiple calculates the voltage difference between the highest voltage and the lowest voltage of several cells, and when the voltage difference is greater than or equal to a predetermined first voltage difference threshold value, executes the output limit of the battery to solve the above problem.

Effect of the Invention

[0007] According to the present invention, it is possible to prevent an unnecessarily large output limit from being applied to normal cells.

Brief Description of the Drawings

[0008] [Figure 1] FIG. 1 is a block diagram of a battery control system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a side view of a vehicle. [Figure 3] FIG. 3 is a flowchart showing the control flow of the LBC and the vehicle controller. [Figure 4] FIG. 4 is a graph showing the voltage characteristics (a) and SOC characteristics (b) of a battery. [Figure 5] FIG. 5 is a graph showing the relationship between the output limit threshold value and the limit value in another embodiment of the present invention. [Figure 6] FIG. 6 is a flowchart showing the control flow of the LBC and the vehicle controller.

Mode for Carrying Out the Invention

[0009] ≪First Embodiment≫ Hereinafter, an embodiment of the battery control method and battery control device according to the present invention will be described with reference to the drawings. Figure 1 is a block diagram of a battery control system according to an embodiment of the present invention. The battery control system comprises a battery 3 including a plurality of cells (batteries) 1, an inverter 2, a relay switch 4, a motor 5, a total voltage sensor 6, a current sensor 7, a temperature sensor 8, a lithium-ion battery controller (LBC) 100, and a vehicle controller 200. At least the device including the battery controller 100 and the vehicle controller 200 corresponds to the "battery control device" of the present invention, and the control processing performed by the battery controller 100 and the vehicle controller 200 corresponds to the "battery control method" of the present invention.

[0010] Battery 3 has battery modules M1, M2, and M3, each consisting of n cells (batteries) 1 connected in series (n is any positive integer; in the example shown in Figure 1, n=4). For example, lithium-ion batteries are used for cell 1. Battery 3 is a rechargeable secondary battery that can be charged by an external charging device. When a charging cable is connected to the vehicle, battery 3 is electrically connected to the external charging device in a rechargeable state. Battery 3 is also connected to motor 5 via inverter 2. Battery 3 discharges when motor 5 is operating and charges when motor 5 is regenerating. The number of battery modules is not limited to three; it may be one, two, or four or more.

[0011] Three battery modules M1 to M3 are connected in series, and motors 5 for electric vehicles, etc., are connected to both ends of them via inverters 2. Inverter 2 is a power conversion circuit that converts power between the battery 3 and the motor 5.

[0012] The relay switch 4 controls the main power supply by switching it ON or OFF, and is connected between the battery 3, the motor 5, and the inverter 2.

[0013] The total voltage sensor 6 is connected between the terminals of both poles of the battery 3 and detects the voltage of the battery 3. The current sensor 7 is connected between the battery 3 and the inverter 2 and detects the current output from the battery 3. The temperature sensor 8 is installed on the battery 3 and detects the temperature of the battery 3. The temperature sensor 8 is installed at multiple locations on the battery 3, and the average temperature of the detected values ​​from the multiple temperature sensors is used as the detected temperature of the battery 3. The total voltage sensor 6, current sensor 7, and temperature sensor 8 detect the total voltage, current, and temperature of the battery 3 in response to commands from the battery controller 100 and / or vehicle controller 200, and transmit the detection results to the battery controller 100 and / or vehicle controller 200.

[0014] The battery controller 100 is a controller (processor) that manages the state of the battery 3 and controls the charging and discharging of the battery 3, and comprises cell controllers CC1, CC2, and CC3, photocouplers PC1 and PC2, and a battery controller (CPU) 10. The three cell controllers CC1, CC2, and CC3 monitor the battery capacity (specifically, the voltage VC1 to VC4 of each individual cell) of the corresponding battery modules M1, M2, and M3. The input terminals VC1 to VC4 of each cell controller CC1 to CC3 are connected to each cell 1 of the battery modules M1 to M3, and the cell controllers CC1 to CC3 are cascaded together.

[0015] The CPU 10 sends a command to cell controllers CC1 to CC3 to detect the voltage of each cell 1 at a predetermined timing. Upon receiving this command, cell controllers CC1 to CC3 detect the voltage of each cell 1. The detected voltages are stored in memory (not shown) or the like, which are located in each cell controller CC1 to CC3.

[0016] The CPU 10 also sends commands to cell controllers CC1 to CC3 at predetermined timings to read the voltage of each cell 1. Upon receiving these commands, cell controllers CC1 to CC3 read the detected voltages stored in their respective memories and send them to the CPU 10.

[0017] Electrically insulating photocouplers PC1 and PC2 are used for communication between the CPU 10 and the cell controllers CC1 to CC3. Each photocoupler PC1 and PC2 has photodiodes PD1 and PD2, which are light-emitting elements, and phototransistors PT1 and PT2, which are light-receiving elements.

[0018] Communication between cell controller CC2 and CPU 10 does not use a photocoupler. Instead, a so-called cascade communication method is employed, in which data sent from CPU 10 to cell controller CC3 is sent from cell controller CC3 to cell controller CC2, then from cell controller CC2 to cell controller CC1, and finally this data is sent from cell controller CC1 to CPU 10 via photocoupler PC2.

[0019] The vehicle controller 200 is a controller (processor) that controls the entire vehicle, including the drive system including the motor 5 and the auxiliary systems such as lights. The vehicle controller 200 also controls the battery 3 together with the battery controller 100. For example, the vehicle controller 200 limits the output torque of the motor by controlling the inverter 2 to prevent over-discharge or over-discharge of the battery 3, according to the State of Charge (SOC) of the battery 3. In the example in Figure 1, the LBC 100 and the vehicle controller 200 are separate, but the LBC 100 and the vehicle controller 200 may be combined into a single controller. Also, the detected values ​​of the total voltage sensor 6, current sensor 7, and temperature sensor 8 may be output directly to the battery controller 100.

[0020] Next, with reference to Figure 2, the installation location of the battery 3 in the vehicle and the temperature of the battery 3 will be explained. Figure 2 is a diagram illustrating the installation location of the battery 3 and is a side view of the vehicle. As shown in Figure 2, the battery 3 is installed on the chassis along the bottom surface of the vehicle. In order to secure space inside the passenger compartment, the battery 3 consists of multiple flat-shaped battery modules arranged parallel to each other along the bottom surface (driving surface). When the vehicle is in motion, airflow hits the vehicle. As shown in Figure 2, since the airflow blows from left to right on the plane of Figure 2, the airflow is more likely to hit the battery module M located at the front of the vehicle (the area indicated by the dotted line in Figure 2) and less likely to hit the battery module M located at the rear of the vehicle. When the vehicle is operating under high load, such as at high speed (for example, around 100 km / h), the airflow becomes stronger, and the temperature of the cells 1 in the battery modules at the front of the vehicle may become extremely low compared to the temperature of the cells 1 in the other battery modules.

[0021] As a characteristic of secondary batteries, when the temperature of cell 1 is low, the internal resistance of cell 1 increases, causing the voltage of cell 1 (the voltage across the terminals of cell 1) to decrease. In other words, in a battery 3 installed outside the vehicle, some battery modules are cooled by the airflow while driving, etc., so even if there is no abnormality in the cooled cell 1, its voltage will be lower than that of other cells.

[0022] By the way, the State of Charge (SOC) of battery 3 is calculated based on the average voltage and minimum voltage of battery 3. The average voltage of battery 3 is the average value of the voltages of multiple cells 1, and the minimum voltage of battery 3 is the lowest voltage among the voltages of multiple cells 1 (in the following explanation, the lowest voltage among the voltages of multiple cells 1 will also be referred to as the "minimum voltage of battery 3"). The following method is an example of how to calculate the SOC of battery 3. The SOC of cell 1 or battery 3 is correlated with voltage, and the correlation between SOC and voltage is experimentally determined according to the battery performance, the degree of battery degradation, etc. b If the above conditions are met, the SOC corresponding to the average voltage of battery 3 is calculated as the SOC of battery 3.C а Below It is above and SOC b If the value is within the range of less than , the State of Charge (SOC) of battery 3 is calculated from a predetermined formula that includes the SOC corresponding to the average voltage of battery 3 and the SOC corresponding to the lowest voltage of battery 3. а If the value is less than the minimum voltage of battery 3, the SOC corresponding to the lowest voltage of battery 3 will be calculated as the SOC of battery 3.

[0023] Under the SOC calculation method described above, let's assume, for example, that when the vehicle is traveling at high speed, some cells are cooled by the airflow, causing a phenomenon where the cell temperature drops (hereinafter also referred to as the cell low-temperature phenomenon). In such a situation, if the SOC of battery 3 is high (SOC b In the above cases, the State of Charge (SOC) of battery 3 is calculated from the average voltage of battery 3, so even if the temperature of some cells drops, it has little effect on the calculated SOC value. However, when the vehicle is driving at high speeds, the load on battery 3 is large, so the SOC will decrease if driving at high speeds continues. In addition, the temperature of the cells will drop further due to the airflow while driving, and the minimum voltage of battery 3 will drop even lower. а When the voltage drops below a certain level, the State of Charge (SOC) of Battery 3 is calculated from the lowest voltage of Battery 3, which can result in an extremely low SOC value. In other words, even though the overall battery capacity of Battery 3 is sufficient, the low temperature of some cells causes the low-temperature cell voltage to drop, even though these cells are not abnormal. Since the SOC of Battery 3 is calculated from the voltage of these low-temperature cells, the calculated SOC value for Battery 3 will be low. If the calculated SOC is displayed on the screen, the SOC value will drop extremely low in a short time during high-speed driving, causing the displayed SOC to change rapidly. This can make the occupants feel uneasy about the rapidly decreasing SOC display.

[0024] Furthermore, if the calculated SOC is extremely low, the vehicle controller 200 implements a significant output limit to prevent over-discharge of the battery 3. Therefore, when the SOC decreases due to the cell low-temperature phenomenon during high-speed driving as described above, a significant output limit is imposed. In this way, when the cell low-temperature phenomenon occurs, the temperature of a particular cell becomes lower than the temperature of other cells, and a significant limit is imposed on the battery 3 even though there is no abnormality in the cell. In other words, an unnecessarily large output limit is imposed on a normal cell.

[0025] In particular, as shown in Figure 1, when multiple cells 1 in the battery 3 are connected in series, the output current is larger compared to when two cells 1 are connected in parallel without changing the total number of cells 1. Therefore, if a sudden voltage drop occurs in a low-temperature cell due to the low-temperature phenomenon, there is a risk that output limiting to prevent over-discharge may be applied unnecessarily.

[0026] The battery control method and battery control device according to this embodiment perform output limiting of the battery 3 according to the voltage difference between the highest and lowest voltages of multiple cells, in order to avoid large output limitations to the battery 3 and sudden changes in the SOC display caused by a decrease in the temperature of some cells, as described above.

[0027] The control methods for the battery controller 100 and the vehicle controller 200 will be explained below with reference to Figure 3. Figure 3 is a flowchart of the control flow for the battery controller 100 and the vehicle controller 200. The control flow shown in Figure 3 is repeatedly executed while the battery 3 is discharging (while the vehicle is running). Also, when the vehicle's main switch (the switch that puts the vehicle into a running state) is turned on, the battery controller 100 and the vehicle controller 200 start the control flow shown in Figure 3.

[0028] In step S1, the battery controller 100 detects each voltage (cell voltage) of a plurality of cells 1 included in the battery 3. In step S2, the battery controller 100 calculates a voltage difference (ΔV) between the highest voltage and the lowest voltage of the plurality of cells. The battery controller 100 identifies the highest voltage (V H ) and the lowest voltage (V L ) among the voltages of the plurality of cells 1, and calculates the voltage difference (ΔV) by calculating the difference (V H - V L ) between the highest voltage (V H ) and the lowest voltage (V L ).

[0029] In step S3, the battery controller 100 compares the calculated voltage difference (ΔV) with a voltage difference threshold (V1), and determines whether the voltage difference (ΔV) is equal to or greater than the voltage difference threshold (V1). The voltage difference threshold includes a threshold (limitation execution threshold: V1) for executing output limitation and a threshold (limitation release threshold: V2) for releasing output limitation, and the limitation execution threshold (V1) is greater than the limitation release threshold (V2). When the voltage difference (ΔV) is equal to or greater than the limitation execution threshold (V1), in step S4, the battery controller 100 outputs a limitation execution command for executing output limitation to the vehicle controller 200. When receiving the limitation execution command, the vehicle controller 200 executes output limitation by making the discharge current from the battery 3 lower than the current at present. Thereby, when the voltage difference (ΔV) is equal to or greater than the limitation execution threshold (V1), the battery controller 100 and the vehicle controller 200 execute output limitation of the battery 3.

[0030] Here, the battery controller 100 executes the control flow shown in Figure 3 and calculates the State of Charge (SOC) of battery 3 from the voltage of battery 3. The SOC of battery 3 is calculated from the correlation between the voltage and SOC of battery 3. Alternatively, the SOC may be calculated from the integrated current during charging and discharging of battery 3. The battery controller 100 compares the calculated SOC with the lower limit SOC. The lower limit SOC is the lower limit of the usable range of SOC set to prevent over-discharge of battery 3. If the SOC of battery 3 is below the lower limit SOC, the vehicle controller 200 implements a large output limit to prevent over-discharge of battery 3. The output limit to prevent over-discharge is a control that minimizes power consumption while ensuring, for example, the minimum capacity necessary to reach the nearest charging facility. Therefore, the amount of limit imposed by the output limit to prevent over-discharge is large.

[0031] The output limiting performed in the control flow of step S4 is smaller than the output limiting required to protect battery 3 from over-discharge; in other words, the limiting amount of the output limiting in step S4 is smaller than the limiting amount of the output limiting for over-discharge protection. Furthermore, in other words, the output value of battery 3 after the output limiting in step S4 (discharge current, discharge voltage, or available power) is higher than the output value of battery 3 after the output limiting for over-discharge protection. For example, if output limiting is performed by current control, the current value limited in the control flow of step S4 is smaller than the current value limited by reaching the lower limit of SOC (the current limiting amount is small). Note that output limiting is not limited to current control; it may also be performed by voltage control.

[0032] If the voltage difference (ΔV) is less than the limiting threshold (V1), the battery controller 100 and the vehicle controller 200 do not perform output limiting in step S5.

[0033] In step S6, the battery controller 100 compares the calculated voltage difference (ΔV) with the voltage difference threshold (V2) and determines whether the voltage difference (ΔV) is less than the voltage difference threshold (V2). The voltage difference threshold (V2) corresponds to the limit release threshold. If the voltage difference (ΔV) is less than the voltage difference threshold (V2), the battery controller 100 and the vehicle controller 200 execute the control flow of step S6. If the voltage difference (ΔV) is greater than or equal to the voltage difference threshold (V2), the battery controller 100 and the vehicle controller 200 terminate the control flow shown in Figure 3.

[0034] In step S7, the vehicle controller 200 determines whether the vehicle speed is 0 [km / h]. If the vehicle speed is 0 [km / h], In Step S8, The vehicle controller 200 releases the output limit. Then, the battery controller 100 and the vehicle controller 200 terminate the control flow shown in Figure 3. Thus, if the voltage difference (ΔV) during the execution of the output limit is less than the voltage difference threshold (V2) and the vehicle speed is 0 [km / h], the battery controller 100 and the vehicle controller 200 release the output limit. On the other hand, if the vehicle speed is not 0 [km / h], the battery controller 100 and the vehicle controller 200 terminate the control flow shown in Figure 3. Note that in the determination in step S7, the pre-set vehicle speed threshold is not limited to 0 [km / h], but may be a low speed such as 10 [km / h] or 20 [km / h].

[0035] Next, the output restriction and subsequent release of the output restriction when a cell low-temperature phenomenon occurs during high-speed vehicle operation will be explained with reference to the control flow described above. When a cell low-temperature phenomenon occurs during high-speed vehicle operation, the temperature of some cells becomes lower than that of other cells, and the voltage of the low-temperature cells decreases, causing the voltage difference (ΔV) to exceed the voltage difference threshold (V1). The vehicle controller 200 executes output restriction through the control process in step S4. When output restriction is executed, the discharge current of the battery 3 decreases, so the voltage difference (ΔV) during output restriction becomes smaller than the voltage difference threshold (V1). After executing the control process in step S4, output restriction is executed while the vehicle is running. Then, when the vehicle stops or parks (vehicle speed = 0 [km / h]), the output restriction is released.

[0036] In this way, the output limiting (control processing in step S4) reduces the discharge current from the low-temperature cells, which are at a lower temperature than other cells, thus suppressing the decrease in the SOC of the low-temperature cells. As a result, during high-speed driving, the output limiting of battery 3 can be executed before the SOC reaches the lower limit, which would otherwise lead to a large output limiting. Furthermore, it prevents the phenomenon of the calculated SOC value becoming extremely low in a short period of time during high-speed driving.

[0037] Next, referring to Figure 4, we will explain the temporal changes in the voltage and state of charge (SOC) of battery 3 while the vehicle is running (under power). Figure 4 is a graph showing the voltage characteristics (a) and SOC characteristics (b) of battery 3. The voltage of battery 3 is the open-circuit voltage (OCV). Note that in the graph of Figure 4, for illustrative purposes, the OCV is shown until it reaches 0V and the SOC reaches 0%, but in actual vehicle control, the output of battery 3 is controlled by the output limit of battery 3 so that the OCV and SOC of battery 3 do not become zero.

[0038] When driving starts with battery 3's SOC at 100%, the average voltage of battery 3 gradually decreases over time as power is consumed during vehicle operation, as shown in graph a of Figure 4(a). The minimum voltage of battery 3 changes with different characteristics depending on whether or not cell low temperature occurs. When cell low temperature does not occur, the minimum voltage of battery 3 changes as shown in graph b of Figure 4(a). On the other hand, when cell low temperature occurs, the minimum voltage of battery 3 changes as shown in graph c of Figure 4(a). The voltage difference between the average voltage and the minimum voltage of battery 3 increases as the SOC decreases, but the voltage difference when cell low temperature occurs is greater than the voltage difference when cell low temperature does not occur.

[0039] The State of Charge (SOC) of battery 3 gradually decreases over time, as shown in graph a of Figure 4(b). b If the above conditions are met, the State of Charge (SOC) is calculated from the average voltage of battery 3.

[0040] SOC b When it reaches (time t1 or t3 in Figure 4), the method for calculating the State of Charge (SOC) of battery 3 switches from calculating it using the average voltage to calculating it using the average voltage and the minimum voltage. а When this point is reached (at time t4 or t5 in Figure 4), the method for calculating the State of Charge (SOC) of battery 3 switches from calculating it using the average voltage and the minimum voltage to calculating it using only the minimum voltage.

[0041] If the cell low-temperature phenomenon does not occur, the SOC of battery 3 progresses as shown in graph a. On the other hand, if the cell low-temperature phenomenon occurs, the SOC of battery 3 progresses as shown in graph b. In this embodiment, when the cell low-temperature phenomenon occurs, at time t2, the power difference becomes greater than or equal to the voltage difference threshold (V1), so the output limit of battery 3 is executed. As a result, the discharge current of the low-temperature cell is suppressed, the voltage drop of the low-temperature cell is suppressed, and the decrease in the SOC (calculated value) of battery 3 is also suppressed. On the other hand, in a comparative example different from this embodiment, the output limit of battery 3 is not executed even at time t2. As high-speed driving continues, the temperature of the low-temperature cell becomes even lower, and the minimum voltage of battery 3 (voltage of the low-temperature cell) becomes even lower. As a result, as shown by the dotted arrows, the calculated value of SOC becomes extremely low in a short time.

[0042] As described above, the battery control method and battery control device according to this embodiment detect the voltage of each of the multiple cells 1, calculate the voltage difference between the highest and lowest voltages of the multiple cells 1 based on the detected voltages, and if the voltage difference is greater than or equal to a predetermined first voltage difference threshold (corresponding to the limiting execution threshold (V1)), the output limit of the battery 3 is executed. As a result, the battery output limit is executed before a large output limit that would prevent over-discharge is reached, thus preventing unnecessarily large output limits from being applied to normal cells.

[0043] Furthermore, the battery control method and battery control device according to this embodiment release the output restriction when the voltage difference during output restriction is less than the second voltage difference threshold (corresponding to the restriction release threshold (V2)) and the vehicle speed of the mobile body equipped with the battery 3 falls below a predetermined vehicle speed threshold. This allows the system to determine that output restriction is no longer necessary and release the restriction. As a result, the period during which the operation of the mobile body is restricted can be minimized.

[0044] Furthermore, the battery control method and battery control device according to this embodiment calculate the State of Charge (SOC) of the battery 3, and if the calculated SOC is below a predetermined lower limit SOC, it performs output limiting on the battery 3. In addition, the first limit amount of output limiting performed when the voltage difference is above a first voltage difference threshold is smaller than the second limit amount of output limiting performed when the calculated SOC is below a predetermined lower limit SOC. This makes it possible to perform small output limits on the battery 3 before large output limits are reached, thereby suppressing the decrease in the SOC of the battery 3.

[0045] In this embodiment, the battery controller 100 may use the voltage of the cells located in the part of the battery 3 that is exposed to the airflow as the minimum voltage of the battery 3. When a vehicle equipped with the battery 3 is running, the parts exposed to the airflow are somewhat fixed, and the cells that are prone to cell low-temperature phenomena are also fixed. Therefore, the minimum voltage can be measured from the detected voltage of the cells in the part exposed to the airflow. As a result, since the cell low-temperature phenomenon due to the airflow occurs only in specific cells, by targeting only specific cells for measuring the minimum voltage, it is possible to exclude voltage drops due to causes other than temperature drops due to the cell low-temperature phenomenon.

[0046] As a modification of this embodiment, the battery controller 100 measures the State of Charge (SOC) of each of the multiple cells 1 and calculates the SOC difference between the average SOC and the minimum SOC of the multiple cells 1 based on the measured SOCs. The vehicle controller 200 may then perform battery output limiting if the calculated SOC difference is greater than or equal to a predetermined SOC difference threshold. The battery controller 100 detects the voltage of each of the multiple cells 1 and calculates the SOC of the corresponding cell 1 from each detected voltage. By using a standardized SOC, even if the battery 3 is composed of different types of cells, such as those with different maximum voltages, the same measurement value can be used to determine whether output limiting is necessary.

[0047] As a modification of this embodiment, the battery controller 100 detects temperature at multiple detection points in the battery 3 and calculates the temperature difference between the highest and lowest temperatures of multiple cells 1 based on the detected temperatures. The vehicle controller 200 may then limit the output of the battery 3 if the temperature difference is greater than or equal to a predetermined temperature difference threshold. The highest and lowest temperatures of the multiple cells 1 can be determined from the detection values ​​of multiple temperature sensors installed in the battery 3. Alternatively, the vehicle controller 200 may calculate the temperature distribution of the battery 3 from the detection values ​​of the temperature sensors, the ambient temperature of the battery 3, and the driving conditions of the vehicle, and use the temperatures of the highest and lowest parts of the calculated temperature distribution as the highest and lowest temperatures of the multiple cells 1. This allows for the determination of whether output limiting is necessary based on the temperature difference.

[0048] ≪Second Embodiment≫ Next, a second embodiment will be described based on the drawings. Figure 5 shows the output limiting threshold (V c1 , V c2 , V c3 This is a graph showing the relationship between the limit value and the value. Figure 6 is a flowchart showing the control flow of the battery controller 100 and the vehicle controller 200. In this embodiment, Battery controller 100 Although some control of the vehicle controller 200 differs, the configuration of the battery control system is the same as in the first embodiment. Below, the parts of the second embodiment that differ from the control of the first embodiment will be described, and parts that have the same configuration as in the first embodiment will be denoted by the same reference numerals and their description will be omitted. Furthermore, the description of the first embodiment will be appropriately referenced for similar configurations and control.

[0049] In this embodiment, the threshold is V to perform output limiting. c1 , V c2 , V c3 There are three of them. Output limiting threshold (V c1 , V c2 , V c3 ) is a threshold value compared to the voltage difference (ΔV), and the output limiting threshold (V c1 ) is smallest, and the output limiting threshold (V c3) is the largest. Also, the voltage difference (ΔV) is the output limiting threshold (V c1 Output limiting threshold (V) is above ) c2 If the voltage difference (ΔV) is less than the output limiting threshold (V), the first stage of output limiting is performed, and the upper limit of the output of battery 3 is reduced to limit value A. c2 Output limiting threshold (V) is above ) c3 If the voltage difference (ΔV) is less than the output limiting threshold (V), the second stage of output limiting is performed, and the upper limit of the output of battery 3 is reduced to limit value B (< limit value A). Furthermore, if the voltage difference (ΔV) is less than the output limiting threshold (V c3 If the value is above (V), the upper limit of the output of battery 3 is reduced to zero. In other words, the output limiting threshold (V) c1 , V c2 , V c3 The relationship between the output and the limit is shown in the graph in Figure 5. In Figure 5, the vertical axis represents the permitted output of battery 3, and the horizontal axis represents the voltage difference. Thus, the larger the voltage difference, the greater the limit on the output of battery 3. In the graph in Figure 5, the limit corresponds to the difference between the maximum allowable output and the limit when battery 3 is not under output limiting.

[0050] Next, the control methods for the battery controller 100 and the vehicle controller 200 will be described with reference to Figure 6. The control processes in steps S11 and S12 are the same as those in steps S1 and S2 according to the first embodiment.

[0051] In step S13, the calculated voltage difference (ΔV) and the output limiting threshold (V) c1 ) is compared with the output limiting threshold (V c1 Determine whether the voltage difference (ΔV) is greater than or equal to the output limiting threshold (V). c1 If the value is less than ), in step S14, the vehicle controller 200 does not perform output limiting. The control flow proceeds to step S20.

[0052] The voltage difference (ΔV) is the output limiting threshold (V c1If it is determined to be greater than or equal to ), in step S15, the voltage difference (ΔV) and the output limiting threshold (V c2 ) is compared with the output limiting threshold (V c2 Determine whether the voltage difference (ΔV) is greater than or equal to the output limiting threshold (V). c2 If it is determined that the voltage difference (ΔV) is not greater than or equal to the output limiting threshold (V), then the voltage difference (ΔV) is less than or equal to the output limiting threshold (V c1 Output limiting threshold (V) is above ) c2 If the value is less than A, the vehicle controller 200 performs output limiting by limit value A. Then the control flow proceeds to step S20.

[0053] The voltage difference (ΔV) is the output limiting threshold (V c2 If it is determined to be greater than or equal to ), in step S17, the voltage difference (ΔV) and the output limiting threshold (V c3 ) is compared with the output limiting threshold (V c3 Determine whether the voltage difference (ΔV) is greater than or equal to the output limiting threshold (V). c3 If it is determined that the voltage difference (ΔV) is not greater than or equal to the output limiting threshold (V), then the voltage difference (ΔV) is less than or equal to the output limiting threshold (V c2 Output limiting threshold (V) is above ) c3 If the value is less than B, the vehicle controller 200 performs output limiting by limit value B. Then the control flow proceeds to step S20.

[0054] The voltage difference (ΔV) is the output limiting threshold (V c3 If it is determined that the value is greater than or equal to ), in step S19, the vehicle controller 200 performs output limiting so that the output of battery 3 becomes zero. Note that in the control process of step S19, the upper limit when limiting the output may be a value greater than zero. The control processes of steps S20 to S22 are the same as the control processes of steps S6 to S8 according to the first embodiment. The battery controller 100 and the vehicle controller 200 are shown in Figure 6 The control flow shown is terminated.

[0055] As described above, in this embodiment, the greater the voltage difference between the highest and lowest voltages of multiple cells, the greater the limit on the output of the battery 3. This allows output limiting to be performed with a limit that corresponds to the voltage difference.

[0056] The battery controller 100 and the vehicle controller 200 correspond to the "controllers" of the present invention.

[0057] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit it. Therefore, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention. [Explanation of symbols]

[0058] 1 cell 2 Inverters 3 Batteries 4. Relay switch 5 Motors 6. Total voltage sensor 7 Current Sensor 8. Temperature sensor 100 Battery Controllers 200 Vehicle Controller

Claims

1. A method for controlling a battery including multiple cells, which is executed by a processor, The aforementioned processor, The voltage of each of the aforementioned multiple cells is detected, From among the detection voltages of the plurality of cells, the highest voltage of the plurality of cells is identified. From the detected voltage of the cell located in the part of the battery that is exposed to the airflow while driving, the lowest voltage of the plurality of cells is identified. The voltage difference between the aforementioned highest voltage and the aforementioned lowest voltage is calculated, A battery control method that performs output limiting of the battery when the voltage difference is greater than or equal to a predetermined first voltage difference threshold.

2. In the battery control method described in claim 1, A battery control method that releases the output limit when the voltage difference during the execution of the output limit is less than a second voltage difference threshold which is lower than the first voltage difference threshold, and the vehicle speed of the mobile body equipped with the battery becomes less than or equal to a predetermined vehicle speed threshold.

3. In the battery control method according to claim 1 or 2, The SOC of each of the aforementioned multiple cells is measured, Based on the measured SOC, the SOC difference between the average SOC and the lowest SOC of the multiple cells is calculated. A battery control method that performs output limiting of the battery when the SOC difference is greater than or equal to a predetermined SOC difference threshold.

4. In the battery control method according to any one of claims 1 to 3, The temperature is detected at multiple detection points in the aforementioned battery, Based on the detected temperatures, the temperature difference between the highest and lowest temperatures of the multiple cells is calculated. A battery control method that performs a limit on the output of the battery if the temperature difference is greater than or equal to a predetermined temperature difference threshold.

5. In the battery control method according to any one of claims 1 to 4, A battery control method that increases the limit on the battery's output as the voltage difference increases.

6. In the battery control method according to any one of claims 1 to 5, The State of Charge (SOC) of the aforementioned battery is calculated, If the calculated SOC is below a predetermined lower limit SOC, the output limit of the battery will be implemented. A battery control method in which the first limit amount of the output limit, which is performed when the voltage difference is greater than or equal to the first voltage difference threshold, is smaller than the second limit amount of the output limit, which is performed when the calculated SOC is less than or equal to a predetermined lower limit SOC.

7. In the battery control method according to claim 1, The battery control method involves positioning the part of the battery that is exposed to the airflow while driving at the front of the vehicle.

8. In the battery control method according to any one of claims 1 to 7, A battery control method that sets the voltage of the cell located at the front of the vehicle to the minimum voltage.

9. In the battery control method according to any one of claims 1 to 7, A battery control method in which a specific cell among the plurality of cells is targeted for measuring the lowest voltage.

10. A battery containing multiple cells, The system includes a controller that controls the output of the aforementioned battery, The aforementioned controller, The voltage of each of the aforementioned multiple cells is detected, From among the detection voltages of the plurality of cells, the highest voltage of the plurality of cells is identified. From the detected voltage of the cell located in the part of the battery that is exposed to the airflow while driving, the lowest voltage of the plurality of cells is identified. The voltage difference between the highest voltage and the lowest voltage is calculated, A battery control device that limits the output of the battery if the voltage difference is greater than or equal to a predetermined first voltage difference threshold.

11. In the battery control device according to claim 10, The aforementioned controller, A battery control device that releases the output limit when the voltage difference during the execution of the output limit is less than a second voltage difference threshold which is lower than the first voltage difference threshold, and the vehicle speed of the mobile body equipped with the battery becomes less than or equal to a predetermined vehicle speed threshold.

12. In the battery control device according to claim 10 or 11, The aforementioned controller, The SOC of each of the aforementioned multiple cells is measured, Based on the measured SOC, the SOC difference between the average SOC and the lowest SOC of the multiple cells is calculated. A battery control device that performs output limiting of the battery if the SOC difference is greater than or equal to a predetermined SOC difference threshold.

13. In the battery control device according to any one of claims 10 to 12, The aforementioned controller, The temperature is detected at multiple detection points in the aforementioned battery, Based on the detected temperatures, the temperature difference between the highest and lowest temperatures of the multiple cells is calculated. A battery control device that limits the output of the battery if the temperature difference is greater than or equal to a predetermined temperature difference threshold.

14. A battery control device according to any one of claims 10 to 13, The aforementioned controller, A battery control device that increases the limit on the battery's output as the voltage difference increases.

15. A battery control device according to any one of claims 10 to 14, The aforementioned controller, The State of Charge (SOC) of the aforementioned battery is calculated, If the calculated SOC is below a predetermined lower limit SOC, the output limit of the battery will be implemented. A battery control device in which the first limit amount of the output limit, which is performed when the voltage difference is greater than or equal to the first voltage difference threshold, is smaller than the second limit amount of the output limit, which is performed when the calculated SOC is less than or equal to a predetermined lower limit SOC.

16. In the battery control device according to claim 10, The part of the battery that is exposed to the airflow while driving is the battery control unit located at the front of the vehicle.

17. In the battery control device according to any one of claims 10 to 16, A battery control device that sets the voltage of the cell located at the front of the vehicle to the minimum voltage.

18. In the battery control device according to any one of claims 10 to 16, A battery control device that targets a specific cell among the aforementioned plurality of cells for measuring the lowest voltage.

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