JP2014009946A - Battery monitoring device and failure diagnosis method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery monitoring device and failure diagnosis method for highly accurately detecting a failure in measurement accuracy of a measurement circuit without providing a reference power source.SOLUTION: A microcomputer 40 determines that one of or both of measurement circuits 14, 24 have a failure concerning a battery cell 21 of a module 2 when a difference between a cell voltage V1_4 measured by the measurement circuit 14 and a cell voltage V2_1 measured by the measurement circuit 24 is greater than a threshold. When a difference between a cell voltage V2_4 measured by the measurement circuit 24 and a cell voltage V3_1 measured by a measurement circuit 34 is greater than a threshold concerning a battery cell 31 of a module 3, a microcomputer determines that one of or both of the measurement circuits 24, 34 have a failure. The measurement circuit having a failure is identified by combining the determination results.

Description

  The present invention relates to a battery monitoring device that monitors a battery for operating an electric vehicle such as an electric vehicle (EV) and a hybrid vehicle (Hybrid EV; HEV), and a failure diagnosis method for the battery monitoring device.

  In recent years, lithium ion batteries have been used as secondary batteries for operating electric vehicles. In this lithium ion battery, the battery voltage normal range and the dangerous range are very close, so care must be taken during charging and discharging.

For example, when the battery is fully charged, rapid deterioration progresses, causing a significant decrease in charge capacity. In addition, the amount of charge of the battery cells is not uniform due to variations during manufacturing, variations in self-discharge, and aging, and individual differences occur between the battery cells.
When a lithium ion battery is used in such a state, a specific battery cell is overcharged or overdischarged, and intense heat is generated, which may lead to ignition or rupture in the worst case. For this reason, optimal charge / discharge control is required. To this end, a battery monitoring device that monitors the battery voltage with high accuracy is required. In addition, it is necessary to perform a reliable failure diagnosis that detects a failure of the battery monitoring device with high accuracy.

  A conventional battery monitoring device includes a measurement circuit that is an IC (Integrated Circuit) and a reference power supply that applies a reference voltage to the measurement circuit, and measures each cell voltage of a plurality of battery cells connected in series. In addition, in order to detect a decrease in measurement accuracy and failure of this measurement circuit, the output voltage of the reference power supply was measured by the measurement circuit, and the power supply monitoring device failed when the measured value was outside the preset range. (For example, refer to Patent Documents 1 and 2).

  FIG. 9 shows a configuration example of a conventional battery monitoring device. A plurality of battery cells 11 to 13, 21 to 23, 31 to 33 connected in series are modularized as a set of three, and measurement circuits (monitoring ICs) 14 and 24 for measuring the cell voltage of the battery cells for each module, 34 is connected. The microcomputer 40 (hereinafter referred to as “microcomputer”) starts measurement via SPI (Serial Peripheral Interface) communication periodically with respect to the measurement circuit 14 of the lowest module 1 among the modules 1 to 3 connected in series. Communicate the command. This command is transmitted from the measurement circuit 14 to the upper measurement circuit 24 and from the measurement circuit 24 to the uppermost measurement circuit 34 via inter-IC communication. When the measurement start command is transmitted, the measurement circuit 14 measures the cell voltages V1_1 to V1_3 of the battery cells 11 to 13. Similarly, the measurement circuit 24 measures cell voltages V2_1 to V2_3 of the battery cells 21 to 23, and the measurement circuit 34 measures cell voltages V3_1 to V3_3 of the battery cells 31 to 33, respectively.

  The microcomputer 40 waits for the measurement circuits 14, 24, and 34 to finish measurement, and acquires measurement results of the cell voltage and the reference voltage from these measurement circuits 14, 24, and 34 via inter-IC communication and SPI communication. The microcomputer 40 notifies the acquired cell voltage measurement result to a host device (not shown) via a communication interface (hereinafter referred to as I / F) 41 such as a CAN (Controller Area Network). Further, the microcomputer 40 compares the acquired reference voltage measurement result with a preset threshold value, and determines that it is abnormal when it falls outside the threshold range. If it is determined that there is an abnormality, the microcomputer 40 notifies the host device via the communication I / F 41. Here, the voltage output accuracy of the reference power supplies 15, 25, and 35 is desirably as high as possible from the viewpoint of detecting a failure of the measurement circuits 14, 24, and 34 with high accuracy.

JP 2011-232171 A JP 2010-249793 A

  Since the conventional battery monitoring apparatus is configured as described above, a reference power supply that outputs a reference voltage is necessary for failure diagnosis. For this reason, there is a problem that the cost increases due to the necessity of adding parts. Further, there is a problem that reliability is lowered due to a complicated circuit configuration.

  The present invention has been made to solve the above-described problems, and provides a battery monitoring device and a failure diagnosis method for detecting a measurement accuracy failure of a measurement circuit with high accuracy without providing a reference power supply. With the goal.

  The battery monitoring device according to the present invention is a battery monitoring device that monitors a battery in which a plurality of battery cells connected in series are modularized for each predetermined number in the connection order, and is provided corresponding to each of the plurality of modules. Each cell voltage of a predetermined number of battery cells in the corresponding module is measured, and the cell voltage of the lowest potential battery cell in the module one level higher than the module or in the module one level lower than the module The difference between the cell voltages of the same battery cell measured by a plurality of measurement circuits that measure the cell voltage of the battery cell having the highest potential and the measurement circuit between adjacent modules is calculated, and the difference is a predetermined threshold value. And a microcomputer for diagnosing that the battery monitoring device is malfunctioning when larger.

  In the failure diagnosis method for a battery monitoring apparatus according to the present invention, a plurality of measurement circuits provided corresponding to a plurality of modules respectively measure the cell voltages of a predetermined number of battery cells in the corresponding module, and The cell voltage of the lowest potential battery cell in the module one level higher than the module or the cell voltage of the highest potential battery cell in the module one level lower than the module is measured and output to the microcomputer. The cell voltage measurement step and the microcomputer calculate the difference between the cell voltages of the same battery cell respectively measured by the measurement circuit between adjacent modules, and when the difference is greater than a predetermined threshold, between the adjacent modules A failure presence / absence determination step for determining that one or both of the measurement circuits have failed, and a microcomputer It is a combination of the determination result of the failure presence determination step performed on all of the plurality of measurement circuits, in which and a fault diagnosis step of identifying the measuring circuit is faulty.

  According to the present invention, since the failure is diagnosed when the difference between the cell voltages of the same battery cell measured by the measurement circuit between adjacent modules is larger than the threshold value, the measurement circuit is provided without a reference power supply. It is possible to provide a battery monitoring device that can detect a failure in measurement accuracy with high accuracy.

  According to this invention, when the difference between the cell voltages of the same battery cell measured by the measurement circuit between adjacent modules is larger than the threshold value, either one or both of the measurement circuits between the adjacent modules are Since it is determined that there is a failure and the measurement circuit that has failed is specified by combining the determination results made for all of the multiple measurement circuits, the measurement accuracy of the measurement circuit can be improved without providing a reference power supply. It is possible to provide a failure diagnosis method capable of detecting a failure with high accuracy and identifying a failed measurement circuit.

It is a circuit diagram which shows the structure of the battery monitoring apparatus which concerns on Embodiment 1 of this invention. 4 is a flowchart showing a failure diagnosis operation of the battery monitoring device according to the first embodiment. It is a circuit diagram which shows the structure of the battery monitoring apparatus which concerns on Embodiment 2 of this invention. 6 is a flowchart showing a failure diagnosis operation of the battery monitoring device according to the second embodiment. It is a circuit diagram which shows the modification of the battery monitoring apparatus which concerns on this invention. It is a circuit diagram which shows the modification of the battery monitoring apparatus which concerns on this invention, and is a structure corresponding to four modules. It is a flowchart which shows the failure diagnosis method (method 1) of the battery monitoring apparatus shown in FIG. It is a figure explaining the failure diagnosis method (method 2) of the battery monitoring apparatus shown in FIG. It is a circuit diagram which shows the structural example of the conventional battery monitoring apparatus.

Embodiment 1 FIG.
As shown in FIG. 1, the battery monitoring apparatus according to the first embodiment monitors a secondary battery composed of a plurality of battery cells 11 to 13, 21 to 23, 31 to 33 connected in series. is there. The secondary battery is mounted on an electric vehicle such as EV and HEV, and operates the electric vehicle. In the example of FIG. 1, nine battery cells connected in series are modularized every three in the order of connection. The battery cells 11 to 13 including the battery cell 11 having the lowest potential are referred to as a module 1, and the battery cells 21 to 23 are replaced. The module 2 is the battery cell 31 to 33 including the battery cell 33 having the highest potential. In FIG. 1, the same or corresponding parts as those in FIG. 9 described above are denoted by the same reference numerals.

  In the battery monitoring device, three measurement circuits 14, 24, and 34, which are the same number as the three modules 1 to 3, are connected in series. The lowest measurement circuit 14 includes cell voltages V1_1 to V1_3 of the battery cells 11 to 13 of the lowest module 1 and a cell voltage V1_4 (V2_1) of the battery cell 21 of the lowest potential in the module 2 one level higher. ). The measurement circuit 24 measures the cell voltages V2_1 to V2_3 of the battery cells 21 to 23 of the module 2 and the cell voltage V3_1 (V2_4) of the battery cell 31 at the lowest potential in the one higher module 3. The highest measurement circuit 34 measures only the cell voltages V3_1 to V3_3 of the battery cells 31 to 33 of the highest module 3.

  Each of these measurement circuits 14, 24, and 34 is composed of an IC and performs inter-IC communication between directly connected ICs. A general IC can measure the cell voltage of 6 to 14 battery cells. When such an IC is used in the first embodiment, the number of battery cells to be modularized can be measured. The number needs to be smaller than the number of cells (6 to 14). For example, when the measurement circuit 14 is an IC capable of measuring the cell voltage of six battery cells, it is modularized with a maximum of five battery cells, and the remaining one is the lowest potential of the upper module 2. This is used for measuring the cell voltage of the battery cell 21.

  The microcomputer 40 is connected to the lowest module 1 and periodically transmits a measurement start command to the module 1 via SPI communication. This command is transmitted from the measurement circuit 14 to the upper measurement circuit 24 and from the measurement circuit 24 to the uppermost measurement circuit 34 via inter-IC communication. When the measurement start command is transmitted, the measurement circuit 14 measures the cell voltages V1_1 to V1_4 of the battery cells 11 to 13 and 21. When the measurement start command is transmitted, the measurement circuit 24 measures the cell voltages V2_1 to V2_4 of the battery cells 21 to 23 and 31. When the measurement start command is transmitted, the measurement circuit 34 measures the cell voltages V3_1 to V3_3 of the battery cells 31 to 33.

  Here, in order for each measurement circuit to perform measurement synchronously, the measurement circuits 14 and 24 require time until a measurement start command is transmitted to the measurement circuit 34, that is, until the measurement circuit 34 starts measurement. After waiting for time, the measurement circuit starts measurement simultaneously by starting measurement.

  After the time required for the measurement of the measurement circuits 14, 24, and 34 has elapsed, the microcomputer 40 performs cell voltages V1_1 to V1-4, V2_1 to V1_1 from the measurement circuits 14, 24, and 34 via inter-IC communication and SPI communication. Measurement results of V2_4, V3_1 to V3_3 are acquired. Then, the microcomputer 40 performs failure diagnosis of the battery monitoring device based on the acquired cell voltages V1_1 to V1-4, V2_1 to V2_4, V3_1 to V3_3. In the microcomputer 40, a predetermined threshold value Vth is set in advance. If the difference between the cell voltages of the same battery cell measured by two directly connected measurement circuits is smaller than the threshold value Vth, the two measurement circuits are normal. Diagnose. If the difference is equal to or greater than the threshold value Vth, it is diagnosed that one or both of the two measurement circuits are faulty (that is, the battery monitoring device is faulty). Details of a failure diagnosis method for identifying a measurement circuit that has failed will be described later.

  The communication I / F 41 is a communication interface for connecting to a vehicle network such as CAN, and the battery monitoring device is connected to the battery management device 50 that is a host device through the communication I / F 41 and CAN. The battery management device 50 is connected to the vehicle control device 51 through CAN or the like.

The battery management device 50 is a so-called BMU (Battery Management Unit) that manages the battery, and determines the remaining battery capacity based on, for example, the measurement result of the cell voltage notified from the battery monitoring device. Further, the battery management device 50 outputs information on the failure diagnosis result notified from the battery monitoring device to the vehicle control device 51, or receives the notification from the vehicle control device 51 to control the operation of the battery monitoring device.
The function of the battery management device 50 can be taken into the battery monitoring device.

  The vehicle control device 51 is a so-called ECU (Electronic Control Unit) that performs integrated control of the entire electric vehicle, and is connected to a charging connector, an ignition switch, a vehicle driving motor, a display, and the like (not shown) through a CAN or the like. The vehicle control device 51, for example, controls the power supply from the battery to each part of the vehicle by detecting the on / off of the ignition switch, or displays the remaining battery capacity and failure diagnosis result information notified from the battery management device 50 Or the connection of the charging gun to the charging connector is detected and the battery management device 50 is notified of the transition to the chargeable state.

  Next, a failure diagnosis method using the microcomputer 40 will be described using the flowchart shown in FIG. Before starting the flowchart of FIG. 2, it is assumed that the measurement results of the cell voltages V1_1 to V1-4, V2_1 to V2_4, V3_1 to V3_3 are already notified from the measurement circuits 14, 24, and 34 to the microcomputer 40. (Cell voltage measurement step).

  In step ST1 (failure presence / absence determination step), the microcomputer 40 calculates the difference between the cell voltage V1_4 measured by the measurement circuit 14 and the cell voltage V2_1 measured by the measurement circuit 24 for the lowest battery cell 21 of the module 2. The difference is compared with the threshold value Vth.

  When the difference between the cell voltages V1_4 and V2_1 of the battery cell 21 is smaller than the threshold value Vth (step ST1 “YES”), the microcomputer 40 determines that the measurement circuit 14 and the measurement circuit 24 have successfully measured the cell voltage. Subsequently, in step ST2, the microcomputer 40 calculates the difference between the cell voltage V2_4 measured by the measurement circuit 24 and the cell voltage V3_1 measured by the measurement circuit 34 for the lowest battery cell 31 of the module 3, and the difference and the threshold value Vth. Compare

When the difference between the cell voltages V2_4 and V3_1 of the battery cell 31 is smaller than the threshold value Vth (step ST2 “YES”), the microcomputer 40 determines that the measurement circuit 24 and the measurement circuit 34 have successfully measured the cell voltage. Therefore, in step ST3 (failure diagnosis step), the microcomputer 40 diagnoses that the measurement circuits 14, 24, and 34 of all the modules 1 to 3 are normal.
On the other hand, when the difference between the cell voltages V2_4 and V3_1 is equal to or greater than the threshold value Vth (step ST2 “NO”), one or both of the measurement circuit 24 and the measurement circuit 34 cannot be measured correctly. At this stage, since it is found that the measurement circuit 24 is normal in the previous step ST1, it is diagnosed that the abnormality has occurred in the measurement circuit 34 of the module 3 (step ST4; Fault diagnosis step).

  On the other hand, when the difference between the cell voltages V1_4 and V2_1 of the battery cell 21 is equal to or greater than the threshold value Vth (step ST1 “NO”), the microcomputer 40 cannot correctly measure either one or both of the measurement circuit 14 and the measurement circuit 24. Judge that Therefore, in the subsequent step ST5 (failure presence / absence determination step), it is specified which of the measurement circuit 14 and the measurement circuit 24 is abnormal. In step ST5, the microcomputer 40 calculates the difference between the cell voltage V2_4 measured by the measurement circuit 24 and the cell voltage V3_1 measured by the measurement circuit 34 for the lowest battery cell 31 of the module 3, and sets the difference and the threshold value Vth. Compare.

When the difference between the cell voltages V2_4 and V3_1 of the battery cell 31 is smaller than the threshold value Vth (step ST5 “YES”), it is determined that the measurement circuit 24 and the measurement circuit 34 have successfully measured the cell voltage. Accordingly, the microcomputer 40 diagnoses that the abnormality has occurred in the measurement circuit 14 of the module 1 (step ST6; failure diagnosis step).
On the other hand, when the difference between the cell voltages V2_4 and V3_1 is greater than or equal to the threshold value Vth (step ST5 “NO”), one or both of the measurement circuit 24 and the measurement circuit 34 cannot be measured correctly. Since this step ST5 is a process for specifying which of the measurement circuit 14 and the measurement circuit 24 is abnormal, the microcomputer 40 is supposed to have an abnormality in the measurement circuit 24 of the module 2. Diagnose (step ST7; failure diagnosis step).

  After performing the above fault diagnosis, the microcomputer 40 manages the battery voltage V1_1 to V1-3, V2_1 to V2_3, V3_1 to V3_3, and the result of the fault diagnosis via the communication I / F 41. Notify the device 50.

  The timing for performing the failure diagnosis may be arbitrary, but the cell voltage is likely to fluctuate during charge / discharge control. Therefore, it is desirable to perform the failure diagnosis during a period other than during charge / discharge control in order to avoid erroneous diagnosis. For example, when the vehicle control device 51 detects that the charging gun is not connected to the charging connector and that the electric vehicle is stopped (ignition switch off), the battery control device 51 passes through the battery management device 50 to the battery monitoring device. Notification of failure diagnosis start command.

  As described above, according to the first embodiment, the battery monitoring device monitors a battery in which a plurality of battery cells 11 to 13, 21 to 23, and 31 to 33 connected in series are modularized for each predetermined number in the connection order. The device is provided corresponding to each of the plurality of modules 1 to 3, measures each cell voltage of a predetermined number of battery cells in the corresponding module, and is the highest in the module one level higher than the module. The difference between the cell voltages of the same battery cell respectively measured by the plurality of measurement circuits 14, 24, and 34 that measure the cell voltage of the battery cell at the lower potential and the measurement circuit between adjacent modules is calculated, and the difference is predetermined. And a microcomputer 40 that diagnoses that the battery monitoring device is out of order when the threshold value Vth is larger. For this reason, it is possible to diagnose a failure of the measurement circuit with high accuracy without providing a known high-accuracy reference power supply as in the prior art. Therefore, it is not necessary to add parts and the cost can be reduced. Further, the circuit configuration is not complicated, and the reliability can be improved.

  Further, according to the first embodiment, the microcomputer 40 calculates the difference between the cell voltages of the same battery cells measured by the measurement circuits between adjacent modules among the plurality of measurement circuits 14, 24, and 34, When the difference is larger than the threshold value Vth, it is determined that one or both of the measurement circuits between the adjacent modules are faulty, and the determination is made for all of the plurality of measurement circuits 14, 24, and 34. Combining the results, it was configured to identify the faulty measurement circuit. For this reason, it is possible to specify a measurement circuit that has failed without providing a conventional reference power supply.

Embodiment 2. FIG.
FIG. 3 is a circuit diagram showing a configuration of the battery monitoring apparatus according to the second embodiment. In FIG. 3, the same or corresponding parts as in FIG. In the module 1, a discharge circuit including a discharge circuit switch SW <b> 11 and a resistor R <b> 11 connected in series is provided in parallel with the battery cell 11. Similarly, a discharge circuit switch SW12 and a resistor R12 connected in series are provided in parallel with the battery cell 12, and a discharge circuit switch SW13 and a resistor R13 connected in series are provided in parallel with the battery cell 13. Similarly, in the modules 2 and 3, a discharge circuit switch and a resistor connected in series are provided in parallel with each battery cell.

  The battery cells 11 to 13, 21 to 23, and 31 to 33 are not necessarily uniform in charge amount due to variations in manufacturing, variations in self-discharge, and aging, and individual differences occur depending on the battery cells. Therefore, when variation occurs in the cell voltage of each of the battery cells 11 to 13, 21 to 23, and 31 to 33, the discharge circuit is selectively operated to discharge the battery cells having a high cell voltage, and between the battery cells. Equalize cell voltage. Since a method for equalizing cell voltages between battery cells using a discharge circuit is a known technique, detailed description thereof is omitted.

  On the other hand, the battery monitoring device supplies power for operating the measurement circuits 14, 24, and 34 from the modularized battery cells. The battery cell 21 at the lowest potential of the module 2 is connected not only to the measurement circuit 24 of the module 2 but also to the measurement circuit 14 of the module 1 that is one level lower, and power is supplied to the two measurement circuits 14 and 24. Supply. Therefore, the battery cell 21 consumes twice as much power as the other battery cells 22 and 23. As a result, cell voltage variations are likely to occur between the lowest battery cell 21 and the other battery cells 22, 23. For the same reason, also in the module 3, the cell voltage easily varies between the lowest battery cell 31 and the other battery cells 32 and 33.

  Therefore, in the battery monitoring device according to the second embodiment, each of the battery cells 11 to 13 and 21 to 21 is selectively operated by selectively operating discharge circuits other than the battery cells 21 and 31 having the lowest potential of the modules 2 and 3. 23, 31 to 33 are equalized.

  The microcomputer 40 includes an operation time calculation circuit 42 for calculating the operation time of the battery monitoring device. A storage circuit 43 that stores the calculated operation time is connected to the microcomputer 40. Predetermined reference operation time and discharge time calculated based on the power consumed by the battery cells 11 to 13, 21 to 23, and 31 to 33 are set in the operation time calculation circuit 42 in advance. The reference operation time is, for example, the length of time that the cell voltage variation between the battery cells 21 and 31 having the lowest potential and the other battery cells 11 to 13, 22, 23, 32, and 33 exceeds an allowable range. And The discharge time is, for example, the length of time required to equalize the cell voltage variations between the battery cells 21 and 31 at the lowest potential and the other battery cells 11 to 13, 22, 23, 32, and 33.

Next, the cell voltage equalization method by the microcomputer 40 will be described using the flowchart shown in FIG.
When the vehicle is started and the battery monitoring device is activated, in step ST11, the operation time calculation circuit 42 acquires the operation time stored in the storage circuit 43 at the end of the previous operation. Accumulate operating time to time.

  When the operation time exceeds the reference operation time ("YES" in step ST12), the operation time calculation circuit 42 discharges battery cell discharge circuit switches SW11 to SW13, SW22, except for the lowest battery cells 21 and 31 of the modules 2 and 3. A command to turn on SW23, SW32, and SW33 is transmitted to the module 1 via SPI communication. This command is transmitted to the measurement circuits 14, 24, and 34 via SPI communication and inter-IC communication. In step ST13, the measurement circuit 14 turns on the discharge circuit switches SW11 to SW13, and causes the power of the battery cells 11 to 13 to be consumed by the resistors R11 to R13. On the other hand, the measurement circuit 24 turns on the discharge circuit switches SW22 and SW23, and heats the power of the battery cells 22 and 23 excluding the lowest battery cell 21 through the resistors R22 and R23. Similarly, the measurement circuit 34 turns on the discharge circuit switches SW32 and SW33, and heats the power of the battery cells 32 and 33 excluding the lowest battery cell 31 through the resistors R32 and R33.

  The operation time calculation circuit 42 is configured to turn off the discharge circuit switches SW11 to SW13, SW21 to 23, and SW31 to 33 of all the battery cells when the discharge circuit switch on time has passed the discharge time (“YES” in step ST14). To communicate. This command is transmitted to the measurement circuits 14, 24, and 34 via SPI communication and inter-IC communication. In step ST15, the measurement circuits 14, 24, and 34 turn off the discharge circuit switches SW11 to SW13, SW21 to 23, and SW31 to 33. In subsequent step ST16, the operation time calculation circuit 42 resets the operation time and starts measuring the operation time anew.

  By repeating the above processing, each time the reference operation time elapses, the discharge circuit operates for a predetermined discharge time, and the cell voltages of the battery cells 11 to 13, 21 to 23, and 31 to 33 are equalized. . When the operation of the battery monitoring device ends, the operation time at that time is output from the operation time calculation circuit 42 to the storage circuit 43 and stored in the storage circuit 43.

  In the configuration example of FIG. 3, the discharge circuit is provided for each battery cell. However, the present invention is not limited to this, and the discharge circuit for the lowest battery cells 21 and 31 of the modules 2 and 3 can be omitted. is there.

  As described above, according to the second embodiment, the battery monitoring device includes battery cells 11 to 11 whose cell voltages are measured by one measurement circuit among the plurality of battery cells 11 to 13, 21 to 23, and 31 to 33. 13, 22, 23, 32, and 33 are provided with a discharge circuit that selectively discharges power, and the operation time calculation circuit 42 of the microcomputer 40 measures the operation time of the battery monitoring device, and the operation time Each time a predetermined reference operation time elapses, the discharge circuit is operated for a predetermined discharge time, and the cell voltages of the plurality of battery cells 11 to 13, 21 to 23, and 31 to 33 are equalized. For this reason, the cell voltage between the battery cells 11 to 13, 22, 23, 32, 33 supplying power to one measurement circuit and the battery cells 21, 31 supplying power to two measurement circuits is reduced. Variations can be equalized.

  In the first and second embodiments, the cell voltage of the lowest battery cell of the arbitrary module is measured by the measuring circuit of the arbitrary module and the measuring circuit of the lower module, respectively, and the difference between the measured values is a threshold value. However, the present invention is not limited to this, and the cell voltage of the uppermost battery cell of an arbitrary module is measured with the measurement circuit of the arbitrary module and the measurement circuit of the one higher module. May be configured to measure each of them and compare the difference between the measured values with a threshold value to diagnose a failure. A specific example is shown in FIG.

  In the battery monitoring device shown in FIG. 5, the lowest measurement circuit 14 measures the cell voltages V1_1 to V1_3 of the battery cells 11 to 13 of the lowest module 1. The measurement circuit 24 measures the cell voltages V2_2 to V2_4 of the battery cells 21 to 23 of the module 2 and the cell voltage V2_1 of the battery cell 13 having the highest potential in the module 1 one level lower. The highest measurement circuit 34 measures the cell voltages V3_2 to V3_4 of the battery cells 31 to 33 of the highest module 3 and the cell voltage V3_1 of the battery cell 23 of the highest potential in the module 2 one level lower. To do. In the microcomputer 40, the difference between the cell voltages of the same battery cell (difference between the cell voltages V1_3 and V2_1 of the battery cell 13) measured by two directly connected measurement circuits (for example, the measurement circuits 14 and 24) is greater than the threshold value Vth. If it is smaller, the two measurement circuits are diagnosed as normal, while if the difference is equal to or greater than the threshold value Vth, it is diagnosed that one or both of the two measurement circuits are faulty. Further, the microcomputer 40 may identify the measurement circuit that has failed in the same procedure as the flowchart shown in FIG. 2 (however, the cell voltage numbers for threshold comparison are different).

  In addition, the battery to which the battery monitoring device is applied is not limited to the configuration in the illustrated example, and the number of battery cells and the number of modules may be arbitrary. The number of measurement circuits of the battery monitoring device may be determined according to the number of modules on the battery side. When the number of measurement circuits increases, for example, the measurement circuit shown in FIG. 2 may be repeated by setting three measurement circuits connected in series as one set to identify a measurement circuit that has failed, which will be described below. You may identify the measurement circuit which has failed by the method 1 or the method 2.

  Here, as shown in FIG. 6, a battery monitoring device having a configuration corresponding to four modules 1 to 4 will be described as an example. This battery monitoring apparatus includes a measurement circuit 44 corresponding to the module 4 in addition to the measurement circuits 14, 24, and 34 corresponding to the modules 1 to 3 shown in FIG. The measurement circuit 44 measures the cell voltages V4_1 to V4_3 of the battery cells 41 to 43 of the module 4, and the measurement circuit 34 is connected to the cell voltages V3_1 to V3_3 of the battery cells 31 to 33 of the module 3 by one higher side. The cell voltage V3_4 (V4_1) of the battery cell 41 having the lowest potential in the module 4 is measured.

(Method 1)
FIG. 7 shows a flowchart of a failure diagnosis method (method 1) by the battery monitoring device of FIG. In this method 1, a failure presence / absence determination step is added according to the increased number of modules. In FIG. 7, a step ST21 for newly determining whether or not a module 4 has failed is added to the flowchart shown in FIG. ing. Since the measurement circuits 14, 24, and 34 are found to be normal in the previous steps ST1 and ST2, in step ST21, if the difference between the cell voltages V3_4 and V4_1 of the battery cell 41 is equal to or greater than the threshold value Vth (step ST21 “NO”), it is possible to diagnose that an abnormality has occurred in the measurement circuit 44 of the module 4 (step ST22). On the other hand, when the difference is smaller than the threshold value Vth (step ST21 “YES”), it can be diagnosed that all the measurement circuits 14, 24, 34, 44 are normal (step ST3).

(Method 2)
FIG. 8 is a table for explaining a failure diagnosis method (method 2) by the battery monitoring apparatus of FIG. The microcomputer 40 acquires the measurement result of the cell voltage, performs the processes of step ST1, steps ST2 and ST5, and step ST21 shown in FIG. Subsequently, the microcomputer 40 applies numbers (0 to 7) to the table of FIG. 8A by applying the determination result of the failure of each group to the table of FIG. 8A, and based on the calculated numbers, the table of FIG. 8B. By mapping to, it is possible to identify the measurement circuit that has failed.

  In addition to the above, within the scope of the invention, the invention of the present application can be freely combined with each embodiment, modified any component of each embodiment, or omitted any component in each embodiment. Is possible.

  1-4 modules, 11-13, 21-23, 31-33, 41-43 battery cells, 14, 24, 34, 44 measurement circuit, 15, 25, 35 reference power supply, 40 microcomputer, 41 communication I / F, 42 operation time calculation circuit, 43 storage circuit, 50 battery management device, 51 vehicle control device.

Claims (4)

A battery monitoring device for monitoring a battery in which a plurality of battery cells connected in series are modularized every predetermined number in the connection order,
Each of the modules is provided corresponding to each of the plurality of modules, measures each cell voltage of the predetermined number of battery cells in the corresponding module, and determines the lowest potential battery cell in the module one level higher than the module. A plurality of measurement circuits for measuring a cell voltage or a cell voltage of a battery cell having the highest potential in a module one level lower than the module;
A microcomputer that calculates a difference between cell voltages of the same battery cell respectively measured by the measurement circuit between the adjacent modules, and diagnoses that the battery monitoring device has failed when the difference is greater than a predetermined threshold; A battery monitoring device comprising: A discharge circuit that selectively discharges a battery cell whose cell voltage is measured by one measurement circuit among the plurality of battery cells and consumes heat, and
The microcomputer measures the operation time of the battery monitoring device, operates the discharge circuit for a predetermined discharge time each time the operation time exceeds a predetermined reference operation time, and operates the cell voltages of the plurality of battery cells. The battery monitoring device according to claim 1, wherein:   The microcomputer calculates a difference between the cell voltages of the same battery cell measured by the measurement circuit between the adjacent modules, and when the difference is larger than the threshold, the measurement circuit between the adjacent modules The determination circuit according to claim 1 or 2, wherein one or both of them are determined to be faulty, and a faulty measurement circuit is identified by combining the judgment results made for all of the plurality of measurement circuits. Item 3. The battery monitoring device according to Item 2. A failure diagnosis method for a battery monitoring device for monitoring a battery in which a plurality of battery cells connected in series are modularized every predetermined number in the connection order,
A plurality of measurement circuits provided corresponding to the plurality of modules respectively measure the cell voltages of the predetermined number of battery cells in the corresponding module, and the highest in the module one level higher than the module. A cell voltage measuring step of measuring the cell voltage of the lower potential battery cell or the cell voltage of the highest potential battery cell in the module one level lower than the module, and outputting the measured cell voltage to the microcomputer;
The microcomputer calculates a difference between cell voltages of the same battery cell respectively measured by the measurement circuit between the adjacent modules, and the measurement circuit between the adjacent modules when the difference is larger than a predetermined threshold A failure presence / absence determination step for determining that one or both of the failure has occurred;
The microcomputer includes a failure diagnosis step of identifying a measurement circuit that has failed by combining the determination results of the failure presence / absence determination step performed on all of the plurality of measurement circuits. Device failure diagnosis method.

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