Battery management system

Abstract

Provided is a battery management system in which functions assigned to a lower-level unit that controls a battery module and a higher-level unit that supervises the lower-level unit are optimized, with consideration given to reuse after mounting on a vehicle. The battery management system comprises: a lower-level unit (CMU) that is associated with each battery module (M) having a plurality of battery cells (C), and controls the battery module (M); and a higher-level unit (BMU) that supervises a plurality of lower-level units (CMU). Each lower-level unit (CMU) determines a state estimation value indicating a state of each battery cell (C), and transmits the state estimation value to the higher-level unit (BMU). The higher-level unit (BMU), on the basis of the respective state estimation values transmitted and received from the plurality of lower-level units (CMU), determines a total state estimation value of an entire pack (P) composed of the plurality of battery modules (M).

Description

Battery Management System 【0008】 【0001】 Embodiments of the present invention relate to a battery management system. 【0002】 Patent Document 1 discloses an invention related to a battery management system that can detect whether or not a battery is discharging according to an instruction from a balancer control circuit. 【0003】 In the battery management system according to the invention, a CMU (Cell Management System) that detects the voltage of battery cells and balances the voltages of battery cells is provided for each group having a certain number of battery cells. In addition, a configuration is adopted in which a unit different from the CMU is responsible for the control function of the entire battery. 【0004】 Japanese Unexamined Patent Application Publication No. 2019-118186 【0005】 However, for example, in the case of a battery mounted on a vehicle, it may be possible to reuse it even after it has finished serving as an in-vehicle battery, such as for a household emergency power supply or storing renewable energy. As the configuration of the in-vehicle battery, a CMU is provided for each battery module having a plurality of battery cells as disclosed in Patent Document 1, and a BMU (Battery Management System) that collectively controls a plurality of CMUs is provided. 【0006】 And, for example, if a battery pack composed of a plurality of battery modules is reused as a whole, the configuration of the battery is not very different from when it is mounted on a vehicle, and it is conceivable that the BMU can control a plurality of CMUs. 【0007】 However, on the other hand, when an in-vehicle battery is reused, it is not always used in the state as it was mounted on the vehicle. That is, for example, when using each battery module according to the reuse mode or when reusing a plurality of battery modules without a unified form such as a battery pack, the BMU used in the battery when mounted on the vehicle cannot be used as it is. 【0008】For example, in the former case mentioned above, a dedicated BMU (Battery Module Unit) needs to be prepared to suit the intended reuse. In the latter case, the BMU is optimized to control multiple battery modules that are bundled together in a battery pack when installed in a vehicle. If the battery pack is disassembled, even if the battery modules are bundled together, control by the vehicle's BMU becomes difficult. Furthermore, if the application is different, it may be difficult to reuse the BMU that was part of the vehicle's battery. 【0009】 The present invention was made to solve the above problems, and the object of the present invention is to provide a battery management system that optimizes the functions assigned to a lower-level unit that controls the battery module and a higher-level unit that oversees the lower-level unit, with the intention of reuse after installation in a vehicle. 【0010】 The battery management system in this embodiment includes a lower-level unit that controls each battery module having multiple battery cells, and a higher-level unit that manages the multiple lower-level units. The lower-level units grasp state estimates indicating the state of each battery cell and transmit them to the higher-level unit. The higher-level unit grasps the total state estimate for the entire pack, which is composed of multiple battery modules, based on the state estimates transmitted from the multiple lower-level units that it receives. 【0011】 Since the present invention employs such a battery management system, it is possible to optimize the functions assigned to the lower-level unit that controls the battery module and the higher-level unit that oversees the lower-level unit, with the understanding that the battery will be reused after being installed in a vehicle. 【0012】This is a block diagram showing the overall configuration of a battery storage system according to an embodiment of the present invention. This is a block diagram showing the internal configuration of a battery management system according to an embodiment of the present invention. This is a block diagram showing the internal configuration of a control device for a BMU (higher-level unit) according to an embodiment of the present invention. This is a block diagram showing the internal configuration of a control device for a CMU (lower-level unit) according to an embodiment of the present invention. This is a flowchart showing the basic control flow of a lower-level unit according to an embodiment of the present invention. This is a flowchart showing the basic control flow of a lower-level unit according to an embodiment of the present invention. This is a flowchart showing the basic control flow of a higher-level unit according to an embodiment of the present invention. This is a flowchart showing the balance control flow in a lower-level unit according to an embodiment of the present invention. This is a flowchart showing the balance control flow in a higher-level unit according to an embodiment of the present invention. This is a flowchart showing the temperature information estimation calculation flow in a lower-level unit according to an embodiment of the present invention. This is a flowchart showing the temperature information estimation calculation flow in a higher-level unit according to an embodiment of the present invention. 【0013】 Embodiments of the present invention will be described in detail below with reference to the drawings. Note that the drawings are schematic and may differ from actual ones. Furthermore, the embodiments of the present invention shown below are illustrative examples of devices and methods for realizing the technical concept of the present invention, and the technical concept of the present invention is not limited to the structure, arrangement, etc., of the components described below. The technical concept of the present invention can be modified in various ways within the technical scope defined by the claims described in the patent claims. 【0014】 The overall configuration of the battery storage system S according to an embodiment of the present invention will be described with reference to Figure 1. As described above, secondary batteries that were originally installed in a vehicle can be reused after they have served their purpose. Various methods can be considered for reusing such secondary batteries. 【0015】Therefore, in the embodiments of the present invention described below, the use of the secondary battery to be reused will be explained using as an example a battery storage system S that is connected to a grid current, can charge with generated power, and can discharge to a load. Figure 1 is a block diagram showing the overall configuration of the battery storage system S according to an embodiment of the present invention. 【0016】 In other words, the battery storage system S is a system that stores grid current generated and transmitted from various power plants such as thermal power plants, or renewable energy sources such as wind power generation, in a battery module M, and transmits the electricity stored in the battery module M to loads such as homes, offices, and factories as needed. The battery storage system S according to an embodiment of the present invention includes a battery module M, a BMU1, an EMS2, and a PCS3. 【0017】 BMU1 is a battery management unit and is a device that manages the CMUs provided for each battery module M. In other words, BMU1 is capable of understanding the status of multiple battery modules M, and estimates the status of multiple battery modules M, including the multiple CMUs managed by BMU1, as a single unit. 【0018】 For example, a PC (personal computer) or a microcontroller can be used as the BMU1. The BMU1 may also be installed near the battery module M, and may be configured for cloud-based management or remote management. The detailed configuration and functions of the BMU1 will be described later. 【0019】 EMS2 is an Energy Management System, which monitors, manages, and optimizes the use of electrical energy. PCS3 is a Power Conditioning System, which performs functions such as converting AC and DC currents between the grid current, load, and battery modules M, and adjusting voltage. 【0020】As mentioned above, the battery module M is a rechargeable battery that was previously installed in a vehicle. Although its role as a vehicle-mounted rechargeable battery has ended, it is a rechargeable battery that can be reused for other purposes and here constitutes part of the battery storage system S. The battery module M has multiple battery cells C connected in series. 【0021】 Although Figure 1 shows only one battery module M, it is assumed that multiple battery modules M will be reused simultaneously in the battery storage system S connected to the embodiment of the present invention. Therefore, the following explanation will be based on the premise that multiple battery modules M are provided. 【0022】 However, there are various ways in which secondary batteries installed in vehicles are reused. Therefore, in addition to cases where multiple battery modules M are reused, as in the battery storage system S in the embodiment of the present invention, the following explanation also applies when only one battery module M is used, depending on the method of reuse. 【0023】 As will be described later, in the embodiment of the present invention, each of the multiple battery modules M constituting the battery storage system S is provided with one CMU, and the battery module M is controlled by the CMU. The BMU1 then manages the multiple CMUs, which are provided in equal numbers to the number of battery modules M. 【0024】 However, the relationship between the battery module M and the CMU does not necessarily have to be one-to-one. For example, a single battery module M may be divided into multiple groups, and a CMU may be provided for each group. In this case, multiple CMUs may be provided within a single battery module M. Alternatively, a single CMU may control multiple battery modules M. The detailed configuration of the battery module M will be described later. 【0025】In the battery storage system S according to the embodiment of the present invention, AC current from power plants such as thermal power plants or grid currents such as renewable energy sources is converted into DC current in the PCS 3, and output to the load or stored in the battery module M. 【0026】 In the BMU1, as described later, the CMU, which oversees the entire battery pack P consisting of multiple battery modules M, estimates the state of the entire battery pack P, and the EMS2 issues an operation command according to the state of the battery pack P. This operation command is further transmitted to the PCS3, which charges and discharges the battery modules M as appropriate and outputs to the load as described above. 【0027】 Here, as shown in Figure 1, in the embodiment of the present invention, four components of the battery storage system S are listed: BMU1, EMS2, PCS3, and battery module M. However, the components of the battery storage system S are not limited to these. 【0028】 In Figure 1, each component is connected by an arrow or a solid line. Here, the arrows indicate the flow of information, with information being transmitted in the direction of the arrow. On the other hand, the solid line indicates the flow of electric current. Therefore, the power transmitted from the grid current enters the PCS3, where the processing described above takes place, and the battery module M is charged. Then, the power stored in the battery module M is discharged and transmitted to the load. 【0029】 Furthermore, in the embodiments of the present invention, the BMU1 and CMU will be collectively referred to as BMS (Battery Management System) as appropriate below. In addition, in the embodiments of the present invention, the CMU that controls the battery module M corresponds to a "lower unit." On the other hand, the BMU1, which oversees these CMUs, corresponds to a "higher unit." 【0030】 Furthermore, as mentioned above, in addition to BMU1 issuing operation commands to EMS2, EMS2 may also perform its own control over BMS when, for example, reusing a secondary battery (battery module M). Therefore, EMS2 may issue commands to BMU1 and CMU, and BMU1 and CMU may execute processing based on those commands. 【0031】 Therefore, such an EMS2 will be referred to as an "external unit" as appropriate. While EMS2 is used here as an example of an "external unit," it is also conceivable that processes such as the state estimation of the battery module M, which is performed in the BMU1 as described later, could be performed in the cloud. In such a case, the cloud would be considered an "external unit." 【0032】 The computing power of the BMU in a secondary battery originally installed in a vehicle is not abundant. Therefore, even if functions are newly allocated between the upper and lower units, as in the embodiment of the present invention, it is unlikely that the computing power of the BMU will dramatically improve. 【0033】 Therefore, in such cases, by using an external unit such as a cloud as a higher-level unit of the BMU, the computational functions can be transferred from the BMU to the external unit which has abundant computing power, and the BMU itself can also be configured to receive computation results from the external unit, thereby enabling the acquisition of more accurate computation results. 【0034】 Next, the BMS in an embodiment of the present invention will be described with reference to Figure 2. Figure 2 is a block diagram showing the internal configuration of a battery management system (BMS) according to an embodiment of the present invention. In addition to the BMS, Figure 2 also shows the EMS2 and PCS3 shown in Figure 1. 【0035】 As described above, the BMS in the embodiment of the present invention consists of a BMU1 and a CMU. The BMU1 manages multiple CMUs. On the other hand, as will be described later, the CMU is associated with each battery module M and controls the battery module M. As shown in Figure 2, in the embodiment of the present invention, three battery modules M are connected in series. 【0036】 Therefore, the CMU plays the role of understanding and controlling the state of the associated battery module M, and the BMU1 calculates a total state estimate that indicates the overall state of the battery pack P, which includes the battery module M, based on the state estimates transmitted from the multiple CMUs that it oversees. 【0037】 In other words, the BMU1 controls the entire battery pack P, which consists of multiple battery modules M, while each CMU controls only its own battery module M. This division of functions allows for the reuse of secondary batteries installed in a vehicle, not as a complete battery pack, but as individual battery modules. Details of the division of functions between the BMU1 and CMU will be described later. 【0038】 Furthermore, a current measuring device 4 is connected in series with the three battery modules M within the BMS. The current measuring device 4 includes a current detection circuit 41 that receives the value of the current passing through the multiple battery modules M detected by the current sensor A, and a communication circuit 42 that transmits the detected current value to the BMU 1 and the CMU provided in each battery module M. 【0039】 In Figure 2, the current value transmitted from the communication circuit 42 is shown to be received by both the BMU 1 and each CMU. However, instead of this configuration, for example, the current value may be transmitted from the communication circuit 42 to the BMU 1 first, and then from the BMU 1 to each CMU. 【0040】 The BMU1 includes a BMU control device 11 and a communication circuit 12. The communication circuit 12 transmits and receives information, for example, between the BMUs provided in the multiple battery modules M and between the BMU1 and the EMS2. 【0041】 Figure 3 is a block diagram showing the internal configuration of the control device of the BMU (higher-level unit) 1 according to an embodiment of the present invention. The BMU control device 11 includes an information acquisition unit 111, an aggregation calculation unit 112, a balancing target setting unit 113, a battery diagnostic unit 114, and an information transmission unit 115. 【0042】Incidentally, in FIG. 2, the BMU 1 consists of a BMU control device 11 and a communication circuit 12, and the internal configuration of the BMU control device 11 is as shown in FIG. 3. However, these configurations only show the configurations necessary for explaining the function of the BMU 1 in the embodiment of the present invention, and other configurations may be provided. 【0043】 The information acquisition unit 111 acquires information transmitted from each CMU provided in a plurality of battery modules M to be aggregated and information transmitted from the EMS 2 which is an external unit. The aggregation calculation unit 112 calculates the total state estimation value for the entire battery pack P instead of the state of each individual battery module M based on the state estimation values described later calculated in each CMU. 【0044】 The balancing target setting unit 113 sets the target value for the cell balancing process in the plurality of battery modules M constituting the battery pack P based on the state of the battery cells C in each battery module M transmitted from each CMU. As described above, each battery module M is provided with a CMU, but what the CMU can grasp is only the state of the battery module M in which it is provided. 【0045】 On the other hand, information from the CMUs provided in the plurality of battery modules M constituting the battery pack P is collected by the BMU 1. Therefore, the BMU 1 can grasp the state of each battery module M. The balancing process is, for example, a process of discharging a battery cell with a high charge rate to match a battery cell with a low charge rate when there are a plurality of battery cells C. 【0046】 Therefore, when executing the balancing process for the plurality of battery modules M, the BMU control device 11 acquires the state estimation values transmitted from the plurality of CMUs under its control, considers the balance of each battery module M, and sets the target value when executing the balancing process in the balancing target setting unit 113. Thus, it is reasonable to set the target value required for the balancing process executed in the plurality of battery modules M on the BMU 1 side instead of setting it in each CMU. 【0047】The battery diagnosis unit 114 diagnoses the state of the battery module M or the battery pack P based on the state estimation values and the like of each battery module M transmitted from each CMU acquired by the information acquisition unit 111. Specifically, for example, temperature monitoring is performed to prevent overheating of the battery pack P. 【0048】 The information transmission unit 115 transmits, for example, the target values in the balancing process set by the balancing target setting unit 113 to each battery module M (CMU). Alternatively, when there is an external unit higher than the BMU1 as will be described later, the total state estimation value aggregated and calculated in the BMU1 may be transmitted in order to have a more accurate estimation of the degradation state of the battery. 【0049】 Returning to FIG. 2, in the BMS according to the embodiment of the present invention, three battery modules M are connected in series. In FIG. 2, the first battery module M1, the second battery module M2, and the third battery module M3 are shown from the left side to the right side. 【0050】 Note that the configurations of these first battery module M1 to third battery module M3 are all the same here. Therefore, hereinafter, the first battery module M1 will be described as an example. However, in the case of an explanation applicable to any of the first battery module M1 to third battery module M3, it will be appropriately expressed as "battery module M" as before. 【0051】 The first battery module M1 includes a plurality of battery cells C and a CMU1. The plurality of battery cells C are connected in series as shown in FIG. 2. In the battery module M shown in FIG. 2, it is shown that four battery cells C are stacked on top of each other, but this is only for convenience of illustration. 【0052】In other words, the number of these battery cells C stacked, and the number of stacked battery cells C that make up one battery module M, can be arbitrarily set according to the battery capacity required for the battery module M. Hereafter, whether referring to individual battery cells or multiple battery cells contained in the battery module M, the term "battery cell C" will be used as appropriate. 【0053】 Furthermore, a temperature sensor T is provided near the battery cell C. The temperature sensor is installed in a location where the highest and lowest temperatures can be measured, for example, in order to detect the highest and lowest temperatures. Because it is positioned in this way, it is not designed to measure the temperature of each individual battery cell C, unlike, for example, a voltage sensor. 【0054】 As shown in Figure 2, in the BMS of the embodiment of the present invention, a temperature sensor T is provided in each battery module M. However, it is not necessary for a battery module M without the temperature sensor T to be connected. 【0055】 The CMU1 is equipped with a communication circuit M11, a CMU control device M12, a voltage detection circuit M13, a balance circuit M14, and a temperature detection circuit M15. The communication circuit M11 plays the role of transmitting various information acquired in the first battery module M1 and calculated state estimates to, for example, the BMU1. 【0056】 The CMU control unit M12 has the function of controlling the entire first battery module M1. Details of the functions of the CMU control unit M12 will be described later. The voltage detection circuit M13 detects the voltage of each of the multiple battery cells C provided in the first battery module M1. 【0057】Furthermore, the balance circuit M14 performs the balancing process described above in order to balance (equalize the voltage of) each battery cell C. Specifically, based on a command from the cell balancing control unit M124, which will be described later, the balance circuit M14 consumes power using an ON / OFF resistor and controls the voltage of each battery cell C to a value set as the cell balancing target value. 【0058】 The temperature detection circuit M15 acquires information from the temperature sensor T that detects the temperature of the battery cell C and transmits it to the CMU control device M12. 【0059】 In Figure 2, each CMU has the configuration described above. However, these configurations only show the configurations necessary to explain the function of the VMU in the embodiment of the present invention, and other configurations may also be included. The same applies to the internal configuration of the CMU control device M12 described below. 【0060】 Figure 4 is a block diagram showing the internal configuration of the CMU control device M12 of the CMU (sub-unit) M1 according to an embodiment of the present invention. The CMU control device M12 includes a measurement value acquisition unit M121, a cell state estimation unit M122, a cell balancing target setting unit M123, a cell balancing control unit M124, a battery cell diagnostic unit M125, and an information transmission unit M126. 【0061】 The measurement value acquisition unit M121 acquires, for example, the voltage value detected by the voltage detection circuit M13 for each battery cell C. Similarly, the measurement value acquisition unit M121 acquires temperature information measured by the temperature sensor T via the temperature detection circuit M15. 【0062】 The cell state estimation unit M122 estimates the state of each battery cell C and calculates a state estimation value. The values ​​used to estimate the state of the battery cell C are, for example, values ​​indicating at least one of the following: state of charge (SOC), state of health (SOH), upper limit charging power, or upper limit discharging power. 【0063】Furthermore, as state estimates, you may calculate each value and then use these four types of indicators in appropriate combinations, or you may use all four types of indicators, or you may use indicators other than these. 【0064】 Conventional CMUs simply transmit measured values ​​from various sensors to the BMU, which then performs calculations to estimate the state of each battery module based on these measurements. In contrast, the CMU in the embodiment of the present invention calculates state estimates in the cell state estimation unit M122 and then transmits these state values ​​to the BMU 1 as state values ​​that allow the BMU 1 to grasp the overall state of the battery pack P. 【0065】 The cell state estimation unit M122 calculates the state estimate for each of the multiple battery cells C provided in the first battery module M1. Therefore, for example, the state estimates for the second module M2 and the third battery module M3 are calculated in the respective CMU2 and CMU3. 【0066】 The cell balancing target setting unit M123 sets a target value when the balancing process is performed in the first battery module M1 via the balance circuit M14. Here, a target value is set in the first battery module M1, but as will be described later, if a target value is set in the balancing target setting unit 113 of the BMU1, for example, this target value is received as a correction value, and this correction value is set as the target value in the first battery module M1. 【0067】 In the following explanation, it is assumed that the value transmitted from the balancing target setting unit 113 of the BMU1 is a correction value, and that the target value set by the cell balancing target setting unit M123 is corrected based on this correction value. However, instead of this process, for example, a process may be performed in which the target value set by the cell balancing target setting unit M123 is replaced with the correction value transmitted from the BMU1. 【0068】The cell balancing control unit M124 controls the cell balancing process performed in the first battery module M1. When performing the cell balancing process, the target value set in the cell balancing target setting unit M123 is used. Commands from the cell balancing control unit M124 are transmitted to the balance circuit M14 via the information transmission unit M126, and the balancing process for each battery cell C is performed. 【0069】 The battery cell diagnostic unit M125 diagnoses the state of the battery cells C based on estimated values ​​of the battery cell C's state, etc. Alternatively, it may diagnose the state of the first battery module M1 based on estimated values ​​of the state of each individual battery cell C, etc. 【0070】 The information transmission unit M126 transmits information such as state estimates obtained from various parts of the CMU control device M12, such as the cell state estimation unit M122, to the BMU1, for example. Alternatively, if the BMS is also connected to an external unit, the information may be transmitted directly to the external unit. 【0071】 As explained above, the functions assigned to BMU1 (higher-level unit) and each CMU (lower-level unit) are different. Therefore, next, we will explain the exchange of information between the higher-level unit and the lower-level units in different cases. Here again, we will use CMU1 of the first battery module M1 as an example of the CMU. 【0072】 First, the CMU1 performs various processes to obtain state estimates. Specifically, for example, it obtains the voltage of each battery cell C from the voltage detection circuit M13. It also obtains the current value passing through each battery cell C from the current measuring device 4. As described above, the current value measured by the current sensor A is detected by the current detection circuit 41 and input to the CMU1 via the communication circuit 42. 【0073】Furthermore, the temperature of the battery cell C measured by the temperature sensor T is input to the CMU control device M12 via the temperature detection circuit M15. The process for acquiring this temperature information will be explained separately. Specifically, these voltage values, current values, and temperature information are input to, for example, the cell state estimation unit M122 via the measurement value acquisition unit M121. 【0074】 The measurement value acquisition unit M121 further acquires, for example, state correction values ​​from the BMU1 to correct the state estimate values. Here, "state correction values" refer to correction values ​​for the charge rate, capacity degradation rate, upper limit charging power, or upper limit discharge power, which represent the state estimate values. Note that there are some types of state correction values ​​for which the BMU1 does not necessarily acquire state correction values. In this case, depending on the type of state estimate value, the BMU1 may not transmit the values ​​to the CMU1. 【0075】 The cell state estimation unit M122 calculates each of the above-mentioned state estimates based on various measurement values ​​obtained from the battery cell C and the state correction value received from the BMU1. In other words, if a state correction value has not been received for the state estimate, the state estimate of the first battery module M is calculated based on the various measurement values ​​obtained. 【0076】 On the other hand, for state estimates for which state correction values ​​have been obtained in CMU1, the state estimates calculated in the cell state estimation unit M122 are corrected with the obtained state correction values, and the corrected values ​​are treated as the calculated state estimates. 【0077】 For example, regarding the State of Health (SOH), the cell state estimation unit M122 calculates the total input / output current by accumulating the absolute values ​​of the current passing through the battery cells C from the time of manufacture of the battery module M. This total input / output current value may be stored in a memory device, for example, not shown in the diagram. Then, the SOH of each battery cell C is calculated from the relationship between the total input / output current and the SOH of the cell, which has been determined in advance through experiments. 【0078】The state of charge (SOC) is estimated by the cell state estimation unit M122 from the integrated value of the current passing through the battery cell C. Furthermore, the upper limit of charging power is estimated, for example, from the relationship between the temperature of the battery cell C, which has been determined in advance through experiments, and the upper limit of charging power relative to the SOC of the battery cell C. 【0079】 On the other hand, the cell state estimation unit M122 estimates the upper limit discharge power from, for example, the relationship between the temperature of the battery cell C and the upper limit discharge power relative to the state of charge (SOC) of the battery cell C, which has been determined in advance through experiments. 【0080】 After calculating all of the four types of state estimates mentioned above, the calculated state estimates are transmitted to the BMU1 via the information transmission unit M126. This completes the state estimate calculation process in the CMU1. 【0081】 Meanwhile, the BMU1 receives estimated state values ​​for each battery module M from multiple CMUs located in the multiple battery modules M it oversees. In this state, if there is a connected higher-level external unit, the BMU1 obtains state correction values ​​from that external unit. 【0082】 If a state correction value is obtained from an external unit, that state correction value is sent to the multiple CMUs that manage it. As mentioned above, when a CMU receives a state correction value, it refers to it as appropriate when estimating the state estimate. 【0083】 BMU1 is the higher-level unit from the perspective of the multiple CMUs that oversee it. Therefore, as the higher-level unit, BMU1 aggregates the state estimation values ​​transmitted from the multiple CMUs, which are lower-level units, in the aggregation calculation unit 112. 【0084】 For example, when calculating the total State of Health (SOH) of the battery pack P, the aggregation calculation unit 122 calculates it by averaging the SOH values ​​transmitted from multiple CMUs that it oversees. Note that calculating the average value is merely an example, and any calculation method suitable for calculating the total SOH of the battery pack P may be adopted. 【0085】For the overall SOC of the battery pack P, the aggregation calculation unit 122 calculates the lowest value among the SOC values ​​transmitted from each CMU and uses this as the overall SOC of the battery pack P. 【0086】 Regarding the upper limit charging power and upper limit discharging power, the aggregation calculation unit 122 calculates the minimum value of the upper limit charging power or upper limit discharging power transmitted from multiple CMUs, and sets the value obtained by multiplying these calculated minimum values ​​by the number of battery cells C that make up all the battery modules M constituting the battery pack P as the upper limit charging power or upper limit discharging power. 【0087】 The reason why BMU1 aggregates the state estimates transmitted from multiple CMUs is that BMU1 has the role of understanding the overall state of the battery pack P, which has multiple battery modules M, based on these aggregated state estimates. Therefore, for each state estimate, the state estimates transmitted from multiple CMUs are aggregated, and a total state estimate for the battery pack P is calculated based on each state estimate. 【0088】 By performing this process, the overall state of the battery pack P can be determined. The estimated total state, which represents the overall state of the battery pack P, may be transmitted to an external unit, which is a higher-level unit. 【0089】 The BMU1 then transmits the estimated total state of the entire battery pack P to an external unit. For example, if the external unit is a cloud, the advanced computing power of that cloud can be utilized. By performing this processing, it becomes possible to estimate the state of the battery module M with higher accuracy. 【0090】 Furthermore, in the embodiments of the present invention, unlike the case where the battery module M is mounted on a vehicle, the example given is that the battery module M is incorporated into a battery storage system S. Therefore, for example, if the EMS2 shown in Figure 1 is an external unit, there is a possibility that control specific to the battery storage system S will be performed on the battery module M. 【0091】Therefore, by transmitting the estimated total state of the battery pack P from the BMU1 to the external unit EMS2, it becomes possible to issue commands that enable more appropriate control of the battery modules M that constitute the battery storage system S. 【0092】 Next, the cooperation between the CMU and BMU1 will be explained using the balancing process for the battery cells C that make up the battery module M as an example. First, in the CMU1, the measurement value acquisition unit M121 acquires the voltage value of each battery cell C and transmits the voltage value information to the cell balancing target setting unit M123. The cell balancing target setting unit M123 calculates the lowest value among the acquired voltage values ​​and sets it as the balancing target value. 【0093】 CMU1 transmits the calculated balancing target value to BMU1. BMU1 receives the balancing target value transmitted from CMU1. The balancing target setting unit 113 sets the lowest value as the balancing target value for the battery module M, based on the respective balancing target values ​​of the multiple battery modules M that it manages. 【0094】 If BMU1 is connected to an external unit, which is a higher-level unit, BMU1 receives a correction value for the balancing target value from the external unit. If a correction value exists, BMU1 applies the received correction value to the calculated balancing target value. On the other hand, if there is no correction value, the value calculated by the balancing target setting unit 113 is used as the balancing target value. BMU1 then transmits the calculated balancing target value, or the corrected balancing target value, to CMU1. 【0095】 CMU1 receives a correction value for the balancing target value from BMU1. If a correction value exists, it is applied to the balancing target value calculated by the cell balancing target setting unit M123. On the other hand, if no correction value exists, it is not applied to the balancing target value calculated by the cell balancing target setting unit M123. In other words, the balancing target value set by the cell balancing target setting unit M123 is used as is. 【0096】 Then, based on the balancing target value set by the cell balancing target setting unit M123, or the corrected balancing target value, the cell balancing control unit M124 performs balancing processing on the battery cell C via the balance circuit M14. 【0097】 Furthermore, we will explain the temperature estimation process in the BMS. Temperature has a significant impact when calculating state estimates in the CMU. Therefore, we will explain the coordination of temperature-related processing between the CMU and BMU1. 【0098】 First, it is checked whether a temperature sensor T is provided in the first battery module M1, which is equipped with the CMU1. In the multiple battery modules M in the embodiment of the present invention, it is assumed that a temperature sensor T is provided in all of them. On the other hand, as mentioned above, a temperature sensor T is not necessarily provided in the battery module M. 【0099】 This verification may only be performed the first time a BMS is installed in the battery storage system S. Alternatively, information regarding the presence or absence of temperature sensors T may be stored in a memory device (not shown) in advance in each CMU. In this case, this verification becomes unnecessary. 【0100】 If a temperature sensor T is installed in the battery module M, information regarding the temperature measured by the temperature sensor T is input to the CMU 1 via the temperature detection circuit M15. The cell state estimation unit M122 of the CMU 1 uses the temperature detected by the temperature sensor T to estimate the temperature of each battery cell C and transmits the estimated value to the BMU 1 as temperature information. 【0101】 On the other hand, if the battery module M is not equipped with a temperature sensor T, the cell state estimation unit M122 estimates the temperature of the battery cell C in the battery module M using, for example, a preset fixed temperature value. The estimated value is then transmitted to the BMU1 as temperature information. 【0102】The BMU1 receives temperature information transmitted from the CMU1, and if it is connected to an external unit which is a higher-level unit, it also receives temperature information for each battery cell C from that external unit. 【0103】 In the BMU1, when temperature information is received from an external unit, if temperature information is available for each battery cell C, the aggregation calculation unit 122 applies the temperature information obtained from the external unit as an estimated temperature value for each battery cell C to estimate the temperature of each battery cell C. 【0104】 On the other hand, if temperature information is not obtained from an external unit, the aggregation calculation unit 122 estimates the temperature of each battery cell C based on the temperature information transmitted from each CMU of the multiple battery modules M. Specifically, for example, the temperature is estimated from the mounting position of the temperature sensor in the battery pack P and its physical structure. 【0105】 The aggregation calculation unit 122 transmits the temperature information of each battery cell C to each CMU via the information transmission unit 115. It also transmits the same temperature information to the external unit, which is a higher-level unit. 【0106】 Upon receiving temperature information transmitted from the higher-level unit BMU1, CMU1 checks whether it contains temperature information for each battery cell C in the first battery module M1. If temperature information for each battery cell C is available, CMU1 applies the temperature information received from BMU1 as the temperature for each battery cell C. CMU1 then uses the temperature information applied when calculating, for example, the state estimate. 【0107】 [Operation] Next, we will explain the various processes centered on the BMS of the battery storage system S described above, following the flow of the process. First, we will explain the basic flow of the process using Figures 5 to 8. Figures 5 and 6 are flowcharts showing the basic control flow of the lower unit (CMU) according to an embodiment of the present invention. Figures 7 and 8 are flowcharts showing the basic control flow of the upper unit (BMU) according to an embodiment of the present invention. 【0108】In BMS processing, the processing is carried out based on the functions assigned to the lower-level unit, the CMU, and based on the functions assigned to the higher-level unit, the BMU. During these processes, information is exchanged between BMU1 and CMU as needed. Therefore, although the flowchart shown in the diagram separates the processing of BMU1 and CMU, in the following explanation of the control flow, the processing of BMU1 and CMU will be explained together as needed, following the flow of information. 【0109】 Furthermore, this explanation assumes that the aforementioned external unit is connected as a higher-level unit to the BMU1. Therefore, the BMU1 exchanges information with the external unit as needed. In addition, as before, the battery module M will be explained using the first battery module M1 as an example. 【0110】 First, the CMU1 performs various processes to obtain state estimates. Specifically, for example, it obtains the voltage of each battery cell C from the voltage detection circuit M13 (ST1). It also obtains the current value passing through each battery cell C from the current measuring device 4 (ST2). Furthermore, the temperature of each battery cell C, measured by the temperature sensor T, is input to the CMU control device M12 via the temperature detection circuit M15, thereby detecting the temperature of each battery cell C (ST3). 【0111】 The measurement value acquisition unit M121 further acquires, for example, a state correction value from the BMU1 to correct the state estimate (ST4). However, as mentioned above, the state correction value is not always acquired by the BMU1, and depending on the type of state estimate, it may not be transmitted from the BMU1 to the CMU1. 【0112】 The cell state estimation unit M122 first calculates the SOH value in the battery cell C, for example, using the method described above (ST5). Then, it determines whether or not it has received the SOH state correction value as the state correction value described above from the BMU1 (ST6). 【0113】If a state correction value for SOH is received (YES in ST6), the state correction value is applied to the SOH value calculated by the cell state estimation unit M122 (ST7). Therefore, the corrected SOH value is treated as the calculated state estimation value. 【0114】 If a state correction value for SOH has not been received (NO in ST6), the SOH value calculated by the cell state estimation unit M122 in the previous process will be used as the state estimation value. 【0115】 Next, the cell state estimation unit M122 calculates the SOC value in the battery cell C (ST8). Then, it determines whether or not it has received the SOC state correction value as the state correction value from the BMU1 (ST9). 【0116】 If a state correction value related to the State of Control (SOC) is received (YES in ST9), the state correction value is applied to the SOC value calculated by the cell state estimation unit M122 (ST10). Therefore, the corrected SOC value is treated as the calculated state estimation value. 【0117】 If no state correction value for SOC has been received (ST9 NO), the SOC value calculated by the cell state estimation unit M122 in the previous process will be used as the state estimation value. 【0118】 Furthermore, the cell state estimation unit M122 calculates the value of the upper limit charging power in the battery cell C (ST11 in Figure 6). Then, it determines whether or not it has received the state correction value for the upper limit charging power as the state correction value from the BMU1 (ST12). 【0119】 If a state correction value related to the upper limit charging power is received (YES in ST12), the state correction value is applied to the upper limit charging power value calculated by the cell state estimation unit M122 (ST13). Therefore, the corrected upper limit charging power value is treated as the calculated state estimation value. 【0120】If a state correction value for the upper limit charging power has not been received (NO in ST12), the value of the upper limit charging power calculated by the cell state estimation unit M122 in the previous process will be used as the state estimation value. 【0121】 Then, the cell state estimation unit M122 calculates the value of the upper limit discharge power in the battery cell C (ST14). After that, it determines whether or not it has received the state correction value for the upper limit discharge power as the state correction value from the BMU1 (ST15). 【0122】 If a state correction value related to the upper limit discharge power is received (YES in ST15), the state correction value is applied to the upper limit discharge power value calculated by the cell state estimation unit M122 (ST16). Therefore, the corrected upper limit discharge power value is treated as the calculated state estimation value. 【0123】 If a state correction value for the upper limit discharge power has not been received (NO in ST15), the value of the upper limit discharge power calculated by the cell state estimation unit M122 in the previous process will be used as the state estimation value. 【0124】 Once four types of state estimates for each battery cell C of the first battery module M1 have been calculated in this manner, the information transmission unit M126 transmits these state estimates to the BMU1 (ST17). This completes the state estimate calculation process in the CMU. 【0125】 Next, the BMU1 receives state estimates for each battery module M from multiple CMUs located in the multiple battery modules M it manages (ST31 in Figure 7). Furthermore, the BMU1 obtains state correction values ​​from the connected higher-level external unit (ST32). 【0126】If a state correction value is obtained from an external unit (YES in ST33), the state correction value is transmitted to the CMUs provided by the multiple battery modules M that manage it (ST34). The transmission of the state correction value from BMU1 to each CMU here leads to the process of obtaining the state correction value from the BMU as described above (ST4 in Figure 5). As described above, the CMU receives the state correction value and refers to it as appropriate when estimating the state value. 【0127】 As described above, BMU1 receives state estimates from the CMUs of each of the multiple battery modules M it manages, and aggregates the state estimates of the battery pack P consisting of these multiple battery modules M. 【0128】 Specifically, the state estimate values ​​transmitted from multiple CMUs are aggregated in the aggregation calculation unit 112. Then, the state estimate value for the battery pack P is calculated based on the calculation method for each state estimate value as described above. 【0129】 Specifically, the aggregation calculation unit 112 first calculates the SOH value in the battery pack P (ST35). Then, it determines whether or not it has received the SOH state correction value as the state correction value from the external unit (ST36). 【0130】 If a state correction value related to SOH is received (YES in ST36), the state correction value is applied to the SOH value calculated by the aggregation calculation unit 112 (ST37). Therefore, the corrected SOH value is treated as the calculated total state estimate. 【0131】 If the state correction value for SOH has not been received from an external unit (NO in ST36), the SOH value calculated by the aggregation calculation unit 112 in the previous process will be used as the estimated state value for the entire battery pack P. 【0132】 Next, the aggregation calculation unit 112 calculates the SOC value in the battery pack P (ST38). Then, it determines whether or not it has received the SOC state correction value as the state correction value from the external unit (ST39). 【0133】If a state correction value related to the SOC is received from an external unit (YES in ST39), the state correction value is applied to the SOC value calculated by the aggregation calculation unit 112 (ST40). Therefore, the corrected SOC value is treated as the calculated total state estimate. 【0134】 If no state correction value for SOC has been received (NO in ST39), the SOC value calculated by the aggregation calculation unit 112 in the previous process will be used as the estimated state value for the entire battery pack P. 【0135】 Furthermore, the aggregation calculation unit 112 calculates the value of the upper limit charging power in the battery pack P (ST41 in Figure 8). Then, it determines whether or not the state correction value for the upper limit charging power has been received from the external unit as the state correction value mentioned above (ST42). 【0136】 If a state correction value related to the upper limit charging power is received (YES in ST42), the state correction value is applied to the upper limit charging power value calculated by the aggregation calculation unit 112 (ST43). Therefore, the corrected upper limit charging power value is treated as the calculated total state estimate. 【0137】 If a state correction value for the upper limit charging power has not been received (NO in ST42), the value of the upper limit charging power calculated by the aggregation calculation unit 112 in the previous process will be used as the estimated state value for the entire battery pack P. 【0138】 Then, the aggregation calculation unit 112 calculates the value of the upper limit discharge power in the battery pack P (ST44). After that, it determines whether or not the state correction value of the upper limit discharge power has been received from the external unit as the state correction value mentioned above (ST45). 【0139】 If a state correction value related to the upper limit discharge power is received from an external unit (YES in ST45), the state correction value is applied to the upper limit discharge power value calculated by the aggregation calculation unit 112 (ST46). Therefore, the corrected upper limit discharge power value is treated as the calculated total state estimate. 【0140】If the state correction value for the upper limit discharge power has not been received from an external unit (NO in ST45), the value of the upper limit discharge power calculated by the aggregation calculation unit 112 in the previous process will be used as the state estimate value. 【0141】 BMU1 transmits the calculated total estimated state value of the battery pack P to the higher-level external unit (ST47). This completes the calculation process of the total estimated state value for the battery pack P in BMU1. 【0142】 The order in which the state estimates, or the total state estimates, are calculated for BMU1 and CMU was explained as follows: SOH, SOC, upper limit charging power, and upper limit discharging power. However, the order in which these information estimates are calculated does not matter; they may be processed in parallel. 【0143】 Next, the balancing process flow will be explained using Figures 9 and 10. Figure 9 is a flowchart showing the balancing control flow in a lower-level unit (CMU) according to an embodiment of the present invention. On the other hand, Figure 10 is a flowchart showing the balancing control flow in a higher-level unit (BMU) according to an embodiment of the present invention. 【0144】 As mentioned above, we will use the CMU1 in the first battery module M1 as an example of a lower-level unit, and since information is exchanged between the BMU1 and the CMU1, we will explain by combining the processing of the BMU1 and the CMU1 as appropriate. Furthermore, it is also true that an external unit exists as a higher-level unit of the BMU1. 【0145】 First, the CMU1 acquires the voltage value of each battery cell C in the measurement value acquisition unit M121 and transmits the voltage value information to the cell balancing target setting unit M123 (ST61 in Figure 9). The cell balancing target setting unit M123 calculates the lowest value among the acquired voltage values ​​and sets it as the balancing target value (ST62). 【0146】CMU1 transmits the calculated balancing target value to BMU1 (ST63). BMU1 then receives the balancing target value transmitted from CMU1 (ST71 in Figure 10). The balancing target setting unit 113 calculates the lowest value based on the respective balancing target values ​​of the multiple battery modules M it manages, and sets it as the balancing target value for the battery module M (ST72). 【0147】 The BMU1 receives a correction value for the balancing target value from an external unit, which is a higher-level unit (ST73). The BMU1 then determines whether or not it has received the balancing target value from the external unit (ST74), and if it has received a correction value (YES in ST74), it applies the received correction value to the calculated balancing target value (ST75). 【0148】 On the other hand, if no correction value has been received (NO in ST74), the value calculated by the balancing target setting unit 113 is used as the balancing target value. The BMU 1 then transmits the calculated balancing target value, or the corrected balancing target value, to the CMU 1 (ST76). In addition, the BMU 1 transmits the corrected balancing target value to the external unit, which is a higher-level unit (ST77). 【0149】 CMU1 receives a correction value for the balancing target value from BMU1 (ST64 in Figure 9). The cell balancing target setting unit M123 of CMU1 determines whether or not a balancing target value has been transmitted from BMU1 (ST65). If a balancing target value has been transmitted (YES in ST65), the cell balancing target setting unit M123 applies the said balancing target value to the balancing target value calculated by M123 (ST66). 【0150】 On the other hand, if the cell balancing target setting unit M123 determines that no balancing target value has been transmitted (NO in ST65), the balancing target value calculated by the cell balancing target setting unit M123 is used in the cell balancing process. 【0151】Then, based on the balancing target value set by the cell balancing target setting unit M123, or the corrected balancing target value, the cell balancing control unit M124 performs balancing processing on the battery cell C via the balance circuit M14 (ST67). 【0152】 Furthermore, the flow of temperature estimation processing in the BMS will be explained using Figures 11 and 12. Figure 11 is a flowchart showing the flow of temperature information estimation calculation in a lower-level unit (CMU) according to an embodiment of the present invention. Figure 12 is a flowchart showing the flow of temperature information estimation calculation in a higher-level unit (BMU) according to an embodiment of the present invention. 【0153】 As before, we will use the CMU1 in the first battery module M1 as an example of a lower-level unit, and since information is exchanged between the BMU1 and CMU1, we will explain the process by combining the processing of the BMU1 and the CMU1 as appropriate. Furthermore, it will also be the case that an external unit exists as a higher-level unit of the BMU1. 【0154】 First, it is checked whether a temperature sensor T is provided in the first battery module M1 equipped with the CMU1 (ST81). In the multiple battery modules M in the embodiment of the present invention, as described above, it is assumed that a temperature sensor T is provided in all of them. 【0155】 If a temperature sensor T is installed in the battery module M (YES in ST81), information regarding the temperature measured by the temperature sensor T is input to the CMU 1 via the temperature detection circuit M15 (ST82). The cell state estimation unit M122 of the CMU 1 estimates the temperature of each battery cell C using the temperature detected by the temperature sensor T (ST83). 【0156】The CMU1 then transmits the estimated value to the BMU1 as temperature information (ST84). If the battery module M does not have a temperature sensor T installed (NO in ST81), the cell state estimation unit M122 estimates the temperature of the battery cell C using a preset fixed temperature value. It then transmits the estimated value to the BMU1 as temperature information. 【0157】 The temperature information transmitted from CMU1 is received by BMU1 (ST91 in Figure 12). In addition to the temperature information transmitted from CMU1, BMU1 also receives temperature information for each battery cell C from an external unit, which is a connected higher-level unit (ST92). The aggregation calculation unit 122 checks whether or not temperature information from the external unit is present (ST93). 【0158】 If the aggregation calculation unit 122 determines that it has not received temperature information from an external unit (NO in ST93), it estimates the temperature of each battery cell C based on the temperature information transmitted from each CMU of the multiple battery modules M (ST94). 【0159】 On the other hand, if the aggregation calculation unit 122 determines that it has received temperature information from an external unit (YES in ST93), the aggregation calculation unit 122 applies the temperature information obtained from the external unit as the estimated temperature value for each battery cell C to estimate the temperature of each battery cell C (ST95). 【0160】 Then, the aggregation calculation unit 122 transmits the temperature information of each battery cell C to each CMU via the information transmission unit 115 (ST96). In addition, it also transmits the same temperature information to the external unit, which is a higher-level unit (ST97). 【0161】Upon receiving temperature information transmitted from the higher-level unit BMU1 (ST86 in Figure 11), CMU1 checks whether temperature information for each battery cell C in the first battery module M1 is included (ST87). If temperature information for each battery cell C is present (YES in ST87), the temperature information received from BMU1 is applied as the temperature for each battery cell C (ST88). Then, CMU1 uses the temperature information applied when calculating the state estimate, for example. 【0162】 Up until now, we have used a battery storage system S as an example to explain how to reuse secondary batteries installed in vehicles. However, the allocation of functions between upper and lower units is not only effective in the case of reuse. For example, the above-mentioned allocation of functions may have been made while the batteries were installed in the vehicle. 【0163】 Furthermore, by assigning functions between the upper and lower units from this stage onward, there are advantages in vehicle control, and the system can be easily reused without requiring major modifications during the reuse phase. 【0164】 Furthermore, in the explanations above, it is assumed that all the information necessary to perform the functions assigned to the CMU can be obtained by the CMU itself. Therefore, it is assumed that the CMU has all the necessary components. 【0165】 However, it is not always necessary to have all of these configurations; for example, the necessary information could be obtained via the BMU. In such cases, the functions described above can be achieved by modifying the existing CMU to add the necessary functions. Consequently, the convenience of using a single or multiple battery modules during reuse is improved. 【0166】[Effects of the embodiment] (1) The battery management system comprises a lower unit that controls the battery module and is associated with each battery module having multiple battery cells, and a higher unit that manages the multiple lower units. The lower unit grasps a state estimate value indicating the state of each of the multiple battery cells and transmits it to the higher unit. The higher unit grasps the total state estimate value of the entire battery pack, which is composed of multiple battery modules, based on the state estimate values ​​transmitted from the multiple lower units that it has received. 【0167】 By adopting such a battery management system, it is possible to optimize the functions assigned to the lower-level unit that controls the battery module and the higher-level unit that oversees the lower-level unit, with the understanding that the battery will be reused after being installed in the vehicle. 【0168】 In this way, by transferring some of the functions originally possessed by the higher-level unit to the lower-level unit, it becomes possible for the lower-level unit to control the state of the battery module in which it is installed. Therefore, when a secondary battery is reused, it can be used without major modifications, regardless of whether the battery module itself is being reused or not. This promotes the reuse of secondary batteries. 【0169】 (2) In the battery management system described in (1) above, the state estimate is calculated in a lower unit and is at least one of the charge rate, capacity degradation rate, upper limit charge power, or upper limit discharge power. This means that even if the upper unit becomes unusable due to reuse, each battery module can be reused. 【0170】(3) In the battery management system described in (1) or (2) above, the lower unit comprises: a cell state estimation unit that calculates a state estimate value for the corresponding battery module; a cell balancing target setting unit that sets a cell balancing target value when performing balancing control for the battery cells of the battery module; and a cell balancing control unit that controls the balancing process in the battery module according to the cell balancing target value set by the cell balancing target setting unit. 【0171】 Of the functions originally possessed by the higher-level unit, the lower-level unit includes the function to estimate the state of the battery module, the function to set the cell balancing target values ​​necessary for performing the balancing process, and the function to perform the balancing process. This allows the battery module to be reused with minimal modifications, regardless of the form in which it is reused. 【0172】 (4) In the battery management system described in (3) above, the battery management system includes a temperature sensor provided on at least one battery module, and the cell state estimation unit grasps a state estimate based on the temperature information detected by the temperature sensor. 【0173】 With the function for estimating the state of the battery module now assigned to a lower-level unit, temperature information can also be received by that unit. This makes it easier to calculate the estimated state value. 【0174】 (5) In the battery management system described in any of (1) to (4) above, the upper unit includes an aggregation calculation unit that calculates a total state estimate for the entire battery pack, which is composed of multiple battery modules, based on state estimates transmitted from multiple lower units. 【0175】 In the battery management system according to the embodiment of the present invention, based on the allocation of functions to the upper and lower units, the upper unit oversees the lower units and aggregates the estimated state values ​​calculated by the lower units. This makes it possible to understand the overall state of the battery pack. 【0176】(6) In any of the battery management systems described in (1) to (5) above, the higher-level unit further includes a balancing target setting unit that sets a correction value for the cell balancing target value for the battery cells of the multiple battery modules constituting the battery pack, based on the cell balancing target values ​​transmitted from the multiple lower-level units. 【0177】 By having a balancing target setting unit in the upper-level unit, the BMU control unit can acquire state estimates transmitted from multiple CMUs under its control and perform balancing processing that takes into account the balance of each battery module M. 【0178】 (7) In the battery management system described in (5) or (6) above, the aggregation calculation unit acquires temperature information detected by a temperature sensor provided in at least one battery module and transmits the temperature information to the lower unit so that the cell state estimation unit of the lower unit can use the temperature information as information to consider when calculating the state estimate. 【0179】 The system is designed so that the temperature information necessary for calculating state estimates in lower-level units can be acquired by the higher-level unit and transmitted to the lower-level unit. This ensures that even if the lower-level unit cannot acquire temperature information, it can still reliably obtain and refer to it when calculating state estimates. 【0180】 (8) In the battery management system described in any of (3) to (7) above, the balancing target setting unit in the upper unit transmits a correction value of the set cell balancing target value to all lower units connected to the upper unit, the cell balancing target setting unit of the lower unit sets the cell balancing target value again based on the received correction value of the cell balancing target value, and the cell balancing control unit controls the balancing process in the battery module using the set corrected cell balancing target value. 【0181】The higher-level unit receives cell balancing target values ​​from multiple CMUs (Cell Management Units) that it oversees. Then, as needed, it sets its own balancing target values ​​based on the balancing target values ​​sent from multiple lower-level units. This ensures that the balancing process for the entire battery module is executed more accurately. 【0182】 (9) In the battery management system described in any of (1) to (8) above, either or both of the lower unit and / or upper unit receive a correction value relating to at least one of the state estimate or cell balancing target value obtained by an external unit connected to the battery management system, and corrects the state estimate or cell balancing target value using the received correction value. 【0183】 When reusing a system, it is conceivable that an external unit may exist even higher up than the higher-level unit. In such cases, the ability to exchange information with the external unit allows for control that is more suitable for the mode of reuse, and also enables the appropriate use of the computing power of the external unit if it has advanced computing capabilities. 【0184】 (10) In the battery management system described in (9) above, the external unit acquires temperature information detected by a temperature sensor provided on at least one battery module of the battery management system, transmits the temperature information to either or both of the lower unit and / or upper unit, and either or both of the lower unit and / or upper unit take the received temperature information into consideration when calculating the state estimate. 【0185】 When an external unit is connected that enables information exchange between the upper and lower units, temperature information can be acquired by the external unit and transmitted to the upper unit or the directly connected lower unit. Therefore, even if the lower unit does not have a temperature sensor, temperature information can be acquired as needed for reuse and the state estimate can be calculated. 【0186】 1...BMU, 11...BMU control unit, 111...Information acquisition unit, 112...Aggregation calculation unit, 113...Balancing target setting unit, 114...Battery diagnostic unit, 115...Information transmission unit, 12...Communication circuit, 2...EMS, 3...PCS, 4...Current measuring device, 41...Current detection circuit, 42...Communication circuit, A...Current sensor, C...Battery cell, M...Battery module, M1...First battery module, M11...Communication circuit, M12...CMU control unit, M121...Measurement value acquisition unit, M122...Cell state estimation unit, M123...Cell balancing target setting unit, M124...Cell balancing control unit, M125...Battery cell diagnostic unit, M126...Information transmission unit, M13...Voltage detection circuit, M14...Balance circuit, M15...Temperature detection circuit, P...Pack, T...Temperature sensor

Claims

1. A battery management system comprising: a lower unit associated with each battery module having multiple battery cells and controlling the battery module; and a higher unit that manages the multiple lower units, wherein the lower unit grasps a state estimate value indicating the state of each of the multiple battery cells and transmits it to the higher unit; and the higher unit grasps a total state estimate value for the entire battery pack composed of the multiple battery modules based on the state estimate values ​​transmitted from the multiple lower units that it has received.

2. The battery management system according to claim 1, characterized in that the state estimate is at least one of the charge rate, capacity degradation rate, upper limit charge power, or upper limit discharge power.

3. The battery management system according to claim 1, wherein the lower unit comprises: a cell state estimation unit that calculates the state estimation value for the corresponding battery module; a cell balancing target setting unit that sets a cell balancing target value when performing balancing control for the battery cells of the battery module; and a cell balancing control unit that controls the balancing process in the battery module according to the cell balancing target value set by the cell balancing target setting unit.

4. The battery management system according to claim 3, wherein the battery management system comprises a temperature sensor provided in at least one of the battery modules, and the cell state estimation unit grasps the state estimation value based on the temperature information detected by the temperature sensor.

5. The battery management system according to claim 1, characterized in that the upper unit includes an aggregation calculation unit that calculates the total estimated state value of the entire battery pack composed of a plurality of battery modules based on the estimated state values ​​transmitted from a plurality of lower units.

6. The battery management system according to claim 1, further comprising a balancing target setting unit that sets a correction value for the cell balancing target value for the battery cells of the plurality of battery modules constituting the battery pack, based on the cell balancing target values ​​transmitted from the plurality of lower units.

7. The battery management system according to claim 5 or 6, characterized in that the aggregation calculation unit acquires temperature information detected by a temperature sensor provided in at least one battery module, and transmits the temperature information to the lower unit so that the cell state estimation unit of the lower unit can use the temperature information as information to be considered when calculating the state estimate value.

8. The battery management system according to claim 7, characterized in that the balancing target setting unit in the upper unit transmits a correction value of the set cell balancing target value to all lower units connected to the upper unit, the cell balancing target setting unit of the lower unit sets the cell balancing target value again based on the received correction value of the cell balancing target value, and the cell balancing control unit controls the balancing process in the battery module using the set corrected cell balancing target value.

9. The battery management system according to claim 1, characterized in that either or both of the lower unit or the upper unit receive a correction value relating to at least one of the state estimate value or the cell balancing target value obtained by an external unit connected to the battery management system, and correct the state estimate value or the cell balancing target value using the received correction value.

10. The battery management system according to claim 9, wherein the external unit acquires temperature information detected by a temperature sensor provided in at least one of the battery modules of the battery management system, transmits the temperature information to either or both of the lower unit and / or the upper unit, and either or both of the lower unit and / or the upper unit take into consideration the received temperature information when calculating the state estimate.

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