JP5466103B2 - Abnormality detection device for battery pack - Google Patents

Description

  The present invention relates to an assembled battery abnormality detection device, and more specifically to a technique for detecting an increase in internal resistance of a battery cell in an assembled battery having a plurality of battery cells connected in series.

  A battery pack in which a large number of battery cells (battery modules) are connected in series is generally used. For example, in a hybrid vehicle or the like, such an assembled battery is used as a power source for driving an electric motor.

  Japanese Patent Laying-Open No. 2005-345124 (Patent Document 1) describes a configuration in which a common A / D converter is shared among a plurality of battery modules in an assembled battery. In particular, in Japanese Patent Laid-Open No. 2005-345124 (Patent Document 1), the first A / D converter for voltage value detection and the second A / D converter for current detection, which are shared among a plurality of battery modules, are asynchronous. A configuration of a data collection device for ensuring the synchronization of the voltage detection value and the current detection value by operating in this manner is disclosed.

  As a result, by detecting the voltage and current of the battery cell (battery module) synchronously, the internal resistance can be accurately detected even if the battery voltage changes depending on the current. Can be prevented.

JP 2005-345124 A

  In order to detect overcharge and overdischarge of each battery cell in the assembled battery, it is necessary to provide a voltage monitoring function for each battery cell. In particular, when the voltage value (analog value) can be obtained for each battery cell, an abnormality (over rise) in internal resistance is detected based on the combination with the current value obtained by the current sensor. Is possible. In Japanese Patent Laid-Open No. 2005-345124 (Patent Document 1), under such a configuration, a voltage detection A / D converter is shared between battery cells (battery modules), and then a current detection value and a voltage are detected. A data collection device for synchronizing detection values is described.

  However, if the voltage detection value can be output for each battery cell, the number of detectors (sensors) arranged and the number of signals to be handled increase, so there is a concern about cost increase due to the complexity of the configuration of the abnormality detection device. Is done.

  Therefore, with respect to the voltage monitoring function for each battery cell, instead of directly handling the voltage detection value, the configuration of outputting only the comparison result with the determination voltage serving as the overcharge / discharge threshold, simplification of the device, That is, cost reduction can be achieved. On the other hand, there is a problem of how to ensure the accuracy of abnormality detection while at the same time simplifying the apparatus.

  Here, each battery cell that is a secondary battery generates an electromotive force by an electrochemical reaction of the electrode active material. While this electrochemical reaction tends to occur near the surface of the electrode active material, a delay time for diffusion occurs in the reaction inside the electrode active material. For this reason, it is known that a dynamic polarization voltage that changes with the passage of time is generated due to an imbalance between the inside of the electrode and the surface portion. The polarization voltage is generated in the negative voltage direction during discharging, and is generated in the positive voltage direction during charging.

  For this reason, the output voltage of the battery cell may be greatly reduced by the polarization voltage even if the internal resistance is normal. In such a case, there is a concern that an abnormality (excessive rise) in internal resistance may be erroneously detected.

  The present invention has been made to solve such problems, and an object of the present invention is to perform a predetermined determination without directly detecting a voltage value as a voltage monitoring function for each battery cell of an assembled battery. In an abnormality detection device that is simply configured to detect a comparison result with a voltage, an erroneous detection of an internal resistance abnormality (over rise) is prevented.

  In one aspect of the present invention, a battery pack abnormality detection device having a plurality of battery cells connected in series includes a plurality of detection units, a current detector, and an abnormality monitoring circuit. The plurality of detection units are provided corresponding to each of the plurality of battery cells, and each is configured to perform a voltage comparison between the output voltage of the corresponding battery cell and a predetermined determination voltage. The current sensor is configured to detect currents of a plurality of battery cells. Whether or not the output voltage of any of the plurality of battery cells has dropped below the determination voltage by sequentially detecting a signal reflecting the result of the voltage comparison while sequentially operating in response to the start trigger. An abnormality detection signal indicating that is output. The abnormality monitoring circuit determines whether or not an internal resistance abnormality has occurred in which the internal resistance rises above the upper limit value in any of the plurality of battery cells based on the signals from the plurality of detection units and the current detection value by the current detector. Configured to monitor. Then, the abnormality monitoring circuit includes a polarization voltage estimation unit for estimating a polarization voltage generated in each battery cell, and a determination current for detecting an internal resistance abnormality according to the estimated polarization voltage as a default value. A determination current setting unit that reduces the current value and a current comparison unit. When the output voltage of any of the plurality of battery cells is lower than the determination voltage when the abnormality detection signal indicates that the current detection value is lower than the determination current, the current comparison unit Configured to detect occurrences.

  Preferably, the determination current setting unit is configured to relatively decrease the determination current when the absolute value of the polarization voltage increases when the estimated polarization voltage is a negative voltage.

  Preferably, the determination current setting unit or the current comparison unit operates to mask detection of the internal resistance abnormality when the estimated polarization voltage is lower than the first reference voltage that is a negative voltage.

  More preferably, the determination current setting unit or the current comparison unit has the polarization voltage higher than the second reference voltage higher than the first reference voltage once the detection of the internal resistance abnormality is masked. Sometimes it operates to resume detection of internal resistance anomalies.

  Particularly in such a configuration, the first reference voltage is set to a higher voltage as the temperature of the plurality of battery cells is lower. Alternatively, the second reference voltage is set to a higher voltage as the temperature of the plurality of battery cells is lower.

  According to the present invention, as a voltage monitoring function for each battery cell of an assembled battery, in an abnormality detection device that is simply configured to detect a comparison result with a predetermined determination voltage without directly detecting a voltage value, It is possible to prevent erroneous detection of abnormal resistance (over rise).

It is a schematic block diagram which shows the structure of the electric system to which the abnormality detection apparatus of the assembled battery by embodiment of this invention is applied. It is a block diagram explaining the structural example of the detection unit shown by FIG. It is a conceptual diagram explaining the detection method of internal resistance abnormality by an abnormality monitoring circuit. It is a conceptual diagram for demonstrating the influence of the polarization voltage with respect to the output voltage of a battery cell. It is a wave form diagram explaining the relationship between the change of a battery current, and the change of a polarization voltage. It is a functional block diagram for realizing internal resistance abnormality detection by the abnormality monitoring circuit. It is a conceptual diagram explaining the structure image of the map which calculates | requires a polarization value based on battery current and battery temperature. It is a wave form diagram explaining the detection method of the cell resistance abnormality which considered the polarization voltage in the abnormality detection apparatus of the assembled battery by embodiment of this invention. It is a conceptual diagram explaining the setting of the reference voltage for polarization determination. It is a flowchart explaining the control processing procedure of the internal resistance abnormality detection by the abnormality detection apparatus of the assembled battery by embodiment of this invention. It is a block diagram which shows the other structural example of the assembled battery to which the abnormality detection apparatus of the assembled battery by this Embodiment is applied.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following, the same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated in principle.

  FIG. 1 is a schematic block diagram showing a configuration of an assembled battery abnormality detection device according to an embodiment of the present invention and an electric system 200 to which the abnormality detection device is applied.

  Referring to FIG. 1, an electric system 200 is mounted on a vehicle having a mechanism capable of generating a vehicle driving force by electric power such as a hybrid vehicle or an electric vehicle. The electric system 200 includes an assembled battery 10, an abnormality detection device 100 for the assembled battery 10, and a load 12.

  The assembled battery 10 includes a plurality of battery cells CL (1) to CL (n) connected in series (n: an integer of 2 or more). The assembled battery 10 supplies DC power to the load 12. Further, the assembled battery 10 is charged with DC power supplied from the load 12. Hereinafter, the battery cells CL (1) to CL (n) are collectively referred to simply as the battery cell CL.

  Load 12 includes a motor and an inverter that drives the motor (both not shown). This motor is configured to generate wheel driving force by a power running operation, or to generate AC power by regenerative braking by being rotated by the wheel driving force. Note that the motor may be used as a motor for generating electric power for starting an engine mounted on the hybrid vehicle and / or charging the battery pack 10. An inverter (not shown) converts DC power from the assembled battery 10 into AC power and supplies it to the motor, or converts AC power generated by the motor into DC power and supplies it to the assembled battery 10.

  Abnormality detection device 100 includes detection units 20 (1) to 20 (n) provided corresponding to battery cells CL (1) to CL (n), a transmission circuit 25, and an abnormality monitoring circuit 30, respectively. .

  The output voltages Vc (1) to Vc (n) of the corresponding battery cells CL (1) to CL (n) are input to the detection units 20 (1) to 20 (n). The detection unit 20 (1) operates in response to the start trigger TRG given from the abnormality monitoring circuit 30, and compares the output voltage Vc (1) of the battery cell CL (1) with a predetermined determination voltage Vx. To do. And detection unit 20 (1) outputs detection signal OD (1) according to a voltage comparison result. Specifically, when the output voltage Vc (1) is lower than the determination voltage Vx (Vc (1) <Vx), the detection unit 20 (1) is at a logic high level (hereinafter also simply referred to as H level). The detection signal OD (1) is output. On the other hand, when the output voltage Vc (1) is not lower than the determination voltage Vx (Vc (1) ≧ Vx), the detection unit 20 (1) has a logic low level (hereinafter also simply referred to as L level). The detection signal OD (1) is output.

  The detection unit 20 (2) operates in response to the detection signal OD (1) being output from the previous detection unit 20 (1), and the output voltage Vc (2) of the battery cell CL (2). A predetermined determination voltage Vx is compared. Then, the detection unit 20 (2) outputs the detection signal OD (2) in a manner in which a logical sum of the voltage comparison result in the detection unit 20 (1) and the voltage comparison result in itself is taken.

  That is, when the detection signal OD (1) is at the H level, the detection unit 20 (2) outputs the detection signal OD (2) at the H level even when Vc (2) ≧ Vx. On the other hand, when the detection signal OD (1) is at the L level, the detection unit 20 (2) follows the comparison result between Vc (2) and the determination voltage Vx, that is, when VC (2) <Vx. Outputs an H level detection signal OD (2), while VC (2) ≧ Vx outputs an L level detection signal OD (2).

  FIG. 2 is a block diagram illustrating a configuration example of the i-th detection unit 20 (i). FIG. 2 shows the configuration of the detection unit 20 (i) with i = 2 to n.

  With reference to FIG. 2, the detection unit 20 (i) includes a voltage comparator 21 and a logic gate 22. The voltage comparator 21 compares the output voltage Vc (i) of the battery cell CL (i) corresponding to the detection unit 20 (i) with a predetermined determination voltage Vx, and Vc (i) <Vx. Sometimes, the output voltage is set to the H level, while when Vc (i) ≧ Vx, the output voltage is set to the L level.

  The logic gate 22 outputs a logical sum (OR) operation result between the output signal of the voltage comparator 21 and the detection signal OD (i−1) from the detection unit 20 (i−1) in the previous stage, as the detection unit 20 ( The detection signal OD (i) of i) is output.

  Referring to FIG. 1 again, a detection signal OD (detection signal) in which a voltage comparison result in each detection unit 20 (detection units 20 (1) to 20 (n) is comprehensively described. The same applies hereinafter) is reflected. OD (1) to OD (n) are comprehensively expressed (hereinafter the same) are sequentially transmitted to the detection unit 20 in the next stage while performing a logical sum operation. As a result, the detection units 20 (1) to 20 (n) sequentially operate in response to the start trigger TRG.

  Since the operation time of each detection unit 20 is the same, as a result, the output voltages Vc (1) to Vc (n) of the corresponding battery cells CL (1) to CL (n) are sequentially changed in a certain cycle. It is compared with the determination voltage Vx. The detection signal OD (n) output from the last-stage detection unit 20 (n) is a series of voltage comparisons between the battery cells CL (1) to CL (n) and the determination voltage Vx in response to the start trigger TRG. , A signal indicating whether or not there is a battery cell whose output voltage is lower than the determination voltage Vx, for example, a 1-bit digital signal.

  The transmission circuit 25 generates a final determination signal FV after insulating the detection signal OD (n) output from the detection unit 20 (n) at the final stage with a photocoupler or the like. That is, the determination signal FV is generated in response to the start trigger TRG and input to the abnormality monitoring circuit 30. As described above, the determination signal FV has an abnormality in which the output voltage is lower than the determination voltage Vx in any one of the battery cells CL (1) to CL (n) (hereinafter also referred to as “cell voltage decrease abnormality”). Whether or not Specifically, when the output voltage is lower than the determination voltage Vx in any one of the battery cells CL (1) to CL (n), the determination signal FV is set to the H level. On the other hand, when all the output voltages of battery cells CL (1) to CL (n) are not lower than the determination voltage Vx, the determination signal FV is set to the L level.

  The current sensor 15 detects a battery current Ib that is a passing current of the assembled battery 10. Since the battery cells CL (1) to CL (n) are connected in series, the battery current Ib is common to the battery cells CL (1) to CL (n). The current sensor 15 can determine the current value of the battery current Ib. The temperature sensor 17 detects the temperature of the assembled battery 10 (battery temperature Tb). The voltage sensor 16 detects the output voltage of the entire battery cells CL (1) to CL (n), that is, the output voltage Vb of the assembled battery 10.

  On the other hand, voltage sensors for detecting voltage values are not arranged for the output voltages Vc (1) to Vc (n) of the battery cells CL (1) to CL (n). Hereinafter, the output voltages Vc (1) to Vc (n) of the battery cells CL (1) to CL (n) are collectively referred to as a cell voltage Vc.

  The abnormality detection device 100 detects the occurrence of an abnormality in the battery cell based on the voltage comparison result between each cell voltage Vc and the determination voltage Vx, not directly based on the voltage value of each battery cell. That is, the abnormality detection apparatus 100 has a simple configuration in which voltage sensors that detect voltage values (analog values) of a large number of battery cells CL (1) to CL (n) are not disposed with respect to voltage monitoring for each battery cell. It is understood that

  Abnormality monitoring circuit 30 performs an abnormality detection operation for battery cells CL (1) to CL (n) in response to a start instruction signal STR from a host ECU (Electronic Control Unit). That is, the abnormality monitoring circuit 30 generates a start trigger TRG to be given to the detection unit 20 (1) in response to the start instruction signal STR.

  Further, the abnormality monitoring circuit 30 determines that the internal resistance is excessively increased when the voltage drop abnormality occurs based on the determination signal FV returned in response to the start trigger TRG and the sampling value of the output of the current sensor 15. Hereinafter, it is determined whether or not an “internal resistance abnormality” has occurred.

  Then, abnormality monitoring circuit 30 outputs a signal RSL indicating abnormality detection results (including at least detection results regarding cell voltage drop abnormality and internal resistance abnormality) of battery cells CL (1) to CL (n) to the host ECU. To do.

  Although not shown because it is not directly related to the detection of the internal resistance abnormality in the present embodiment, the output voltages Vc (1) to Vc (n) of each battery cell are higher than the upper limit voltage (the determination voltage Vx). It is preferable to further provide a detection unit (not shown) for determining whether or not the value exceeds the upper limit. Thereby, the abnormality detection apparatus 100 can be configured so that it is possible to monitor the voltage abnormality on the overcharge side of each of the battery cells CL (1) to CL (n).

  Next, detection of internal resistance abnormality by the abnormality monitoring circuit 30 will be described in detail. The abnormality monitoring circuit 30 can be configured by a microcomputer such as an integrated circuit (IC), and performs software processing by executing a program stored in advance and / or a dedicated electronic circuit (not shown). The abnormality detection operation described below is executed by the hardware processing.

FIG. 3 is a conceptual diagram for explaining a detection method of an internal resistance abnormality by the abnormality monitoring circuit 30.
Referring to FIG. 3, the internal resistance of the battery cell can be detected by a voltage drop from open circuit voltage Vo caused by battery current Ib. That is, the cell voltage Vc decreases according to the increase in the battery current Ib according to the slope corresponding to the internal resistance.

  When the internal resistance of the battery cell increases, the slope (negative value) of the Ib-Vc straight line shown in FIG. 3 becomes steep, and the output voltage Vc at the same battery current Ib decreases. Then, by defining the boundary value of the internal resistance corresponding to the threshold value for detecting the internal resistance abnormality, the current Ix when the internal resistance becomes the cell voltage Vc = Vx under the boundary value can be obtained.

  The current Ix thus determined is compared with the battery current Ib when the output voltage of any one of the battery cells CL (1) to CL (n) falls below the determination voltage Vx, thereby determining the internal resistance abnormality detection. It can be a current. That is, when the battery voltage drop abnormality is detected, the internal resistance abnormality is detected when the battery current Ib <Ix, while the internal resistance abnormality is not detected when Ib ≧ Ix. Even in the abnormality detection operation, it is possible to determine whether or not an internal resistance abnormality has occurred in the abnormality detection device 100 having a configuration in which the voltage sensor for acquiring the voltage is not arranged.

  However, as shown in FIG. 4, if the discharge of a constant current is continued, there is a possibility that the internal resistance abnormality is erroneously detected in the above-described abnormality detection operation due to the generation of a negative polarization voltage.

  Referring to FIG. 4, from time t1, discharging with battery current Ib = I1 (I1 <Ix) is continued. At time t1, the battery voltage Vb decreases from the open voltage Vo due to the generation of a voltage drop ΔV1 that depends on the product of the internal resistance and the battery current. Furthermore, the polarization voltage Vdyn is generated according to the time difference of the electrochemical reaction between the surface and the inside of the electrode active material.

  FIG. 5 is a conceptual waveform diagram for explaining the relationship between the change in battery current and the change in polarization voltage.

  Referring to FIG. 5, when the battery current Ib changes as shown in FIG. 5A, the polarization voltage Vdyn changes in the negative voltage direction as the discharge continues, as shown in FIG. It changes in the positive voltage direction as charging continues. That is, when the battery current Ib> 0 (during discharging), the change amount of the polarization voltage Vdyn at that time is basically negative, and when the battery current Ib <0 (during charging), The amount of change in the polarization voltage Vdyn is basically positive. Further, if a sufficient time elapses while the battery current Ib remains constant, the polarization voltage Vdyn converges to a constant value that depends on the battery current Ib. That is, the polarization voltage Vdyn exhibits a first-order lag behavior having a constant character constant. This time constant corresponds to the diffusion rate of a reaction participating substance (for example, lithium ion) in the electrochemical reaction. The polarization voltage Vdyn generally appears as the sum of first-order lag voltages generated according to a plurality of different time constants.

  Referring to FIG. 4 again, since battery current Ib (Ib = I1) is positive, polarization voltage Vdyn is generated in the negative voltage direction.

  Since the voltage drop due to the internal resistance is large, the cell voltage 102 of the abnormal cell whose internal resistance has increased is lower than the determination voltage Vx immediately after the time t1 when the battery current is generated and when the polarization voltage Vdyn is not generated. To do. At this time, an internal resistance abnormality is detected because I1 <Ix.

  On the other hand, the cell voltage 105 of a normal cell in which the internal resistance has not increased does not fall below the determination voltage Vx due to the influence of a voltage drop due to the internal resistance. For this reason, the internal resistance abnormality is not detected. However, when the discharge with a current smaller than the determination current Ix continues, the cell voltage 105 decreases due to the influence of the polarization voltage. When the cell voltage 105 is lower than the determination voltage Vx, the internal resistance abnormality is erroneously detected because I1 <Ix even though the internal resistance is normal.

  Therefore, in the abnormality detection device 100 according to the present embodiment having a simplified configuration, the following detection method is adopted in order to prevent erroneous detection of the internal resistance abnormality due to the generation of the polarization voltage.

  FIG. 6 shows a functional block diagram for realizing the internal resistance abnormality detection by the abnormality monitoring circuit 30. The function of each block shown in FIG. 6 is realized by software processing and / or hardware processing by the abnormality monitoring circuit 30.

  Referring to FIG. 6, abnormality monitoring circuit 30 includes a current sampling unit 32, a maximum value extraction unit 34, a polarization voltage estimation unit 36, an Ix setting unit 38, and a current comparison unit 40.

  When the start instruction signal STR is input, the current sampling unit 32 generates a start trigger TRG. Furthermore, the current sampling unit 32 samples the battery current Ib detected by the current sensor 15 once or a plurality of times within the operation period of the detection units 20 (1) to 20 (n) in response to the start trigger TRG. .

  The maximum value extraction unit 34 extracts the maximum value from the current sampling values extracted by the current sampling unit 32 and outputs the maximum current Imax. When the number of times of sampling of the current sampling unit 32 is 1, the current sampling value is directly used as the maximum current Imax.

  When the determination signal FV is set to the H level, that is, when the output voltage is lower than the determination voltage Vx in any battery cell, the current comparison unit 40 indicates an abnormality detection signal RSL indicating the presence or absence of an internal resistance abnormality. Is output.

  The current comparison unit 40 compares the maximum current Imax from the maximum value extraction unit 34 with the determination current Ix set by the Ix setting unit 38. When Imax <Ix, the internal resistance abnormality is detected and the abnormality detection signal RSL is set to the H level. On the other hand, when Imax ≧ Ix, current comparison unit 40 sets abnormality detection signal RSL to the L level, so that no internal resistance abnormality is detected.

  The Ix setting unit 38 sets the determination current Ix according to the polarization voltage Vdyn estimated by the polarization voltage estimation unit 36. Specifically, when the absolute value of the negative polarization voltage is increased, the determination current Ix is decreased from the normal value (default value) shown in FIG. 3 to make it difficult to detect the internal resistance abnormality. Preferably, detection of internal resistance abnormality is masked (prohibited) by changing to Ix = 0.

  Here, an example of polarization voltage estimation by the polarization voltage estimation unit 36 will be described. In addition, about the estimation method of a polarization voltage, it is not limited to the following illustrations, It points out clearly that the well-known method can be used suitably.

  The magnitude of the polarization voltage Vdyn is considered to be determined according to the past charge / discharge history. Further, the closer the time is, the greater the influence, and the larger the charge or discharge current amount, the greater the influence. Therefore, the polarization voltage Vdyn can be obtained by the following equation (1).

  In the equation (1), Vdyn (t0) represents a polarization voltage at time t = t0, and τ represents a time constant. The time constant τ can be obtained experimentally so as to correspond to the rate of change of the polarization voltage in the average current state.

  Further, fdyn {st (t)} indicates the dependence of the polarization voltage on the battery state quantity obtained in advance. As will be described below, the battery state quantity here includes at least the battery current Ib, and preferably includes both the battery current Ib and the battery temperature Tb.

  If the battery current Ib remains constant and the time elapses sufficiently, the polarization voltage Vdyn converges to a constant value that depends on the battery current Ib. That is, fdyn {st (t)} corresponds to the convergence value of the polarization voltage Vdyn when a sufficient amount of time has elapsed with the current battery state quantity (at least the battery current Ib) being constant. Hereinafter, this fdyn is also referred to as a polarization value.

  According to the equation (1), the polarization value fdyn is sequentially estimated based on the current battery state quantity, and the estimated polarization value fdyn is integrated along the time axis direction with attenuation by the time constant τ. Thus, the polarization voltage Vdyn (t0) at an arbitrary time point t0 can be obtained.

  Furthermore, in order to sequentially estimate the polarization voltage Vdyn by discrete data processing for each predetermined period Δt by a computer, the following equation (2) is obtained by discretizing equation (1).

  According to the equation (2), if the initial value of the polarization voltage Vdyn is set, then the current polarization value fdyn {st (t0)} and the previous estimated value Vdtn (t0−Δt) of the polarization voltage Vdyn ) Can be used to sequentially estimate the current polarization voltage Vdyn (t0).

  For the polarization value fdyn in the equations (1) and (2), a map for obtaining the polarization value fdyn based on the battery current Ib is obtained by conducting an experiment for measuring the polarization voltage with the battery current Ib constant. It can be created in advance.

  Moreover, even if the battery current Ib is the same, the battery temperature Tb affects the degree of occurrence of polarization. Therefore, it is preferable to estimate the polarization value fdyn based on the battery current Ib and the battery temperature Tb. In this case, a map based on the experimental result can be created in advance for the polarization value fdyn (Ib, Tb) with the battery current Ib and the battery temperature Tb as variables.

  FIG. 7 shows a map image of the polarization value fdyn (Ib, Tb). Basically, fdyn (Ib, Tb) <0 is set during discharging (Ib> 0), and fdyn (Ib, Tb)> 0 is set during charging (Ib <0). Note that the absolute value of the polarization value | fdyn (Ib, Tb) | is set to be relatively large as the current during discharging and charging increases. Regarding the temperature, as the battery temperature Tb is lower, the absolute value | fdyn (Ib, Tb) | of the polarization value is set to be relatively large. Then, based on the battery current Ib and the battery temperature Tb at each time point, the polarization value fdyn (Ib, Tb) corresponding to fdyn {st (t0)} in the equation (5) is obtained by referring to the map. Read out.

  In general, the estimation of the polarization voltage estimation unit 36 is executed as part of the SOC estimation of the battery pack 10. Therefore, the polarization voltage Vdyn is estimated so as to be sequentially updated according to the execution period of the SOC estimation calculation. For this reason, the polarization voltage estimation part 36 can be shared with the functional block for SOC estimation. In this embodiment, a plurality of equations (5) using a plurality of different time constants are used, and the polarization voltage Vdyn is calculated according to the sum of Vdyn (t0) calculated by these equations. Shall. Further, since the polarization voltage Vdyn can be calculated based on the battery current Ib common to each battery cell CL, it can be set to a value common to each battery cell CL.

  FIG. 8 is a waveform diagram for explaining a cell resistance abnormality detection method in consideration of the polarization voltage according to the embodiment of the present invention.

  Referring to FIG. 8, similarly to FIG. 4, a battery current Ib (Ib> 0) smaller than the determination current Ix is continuously generated between times t1 and t3. That is, each battery cell CL is continuously discharged.

  The battery voltage Vb decreases stepwise from the open voltage Vo due to a voltage drop according to the internal resistance at time t1 when the battery current Ib occurs. Furthermore, the battery voltage Vb gradually decreases due to the influence of the polarization voltage as the battery current Ib is continuously discharged. Although no voltage sensor is provided for each of the battery cells CL (1) to CL (n), a voltage drop and a polarization voltage similar to the battery voltage Vb are generated for the cell voltage Vc.

  The polarization voltage Vdyn estimated by the polarization voltage estimation unit 36 (FIG. 6) is generated in the negative direction from time t1. At time t2, the polarization voltage Vdyn becomes lower than the reference voltage V1. The reference voltage V1 serving as a threshold when the polarization determination is changed from off to on is a negative voltage.

  When Vdyn <V1, the Ix setting unit 38 determines that a polarization voltage of a level that leads to erroneous detection is generated in each battery cell CL, and turns on polarization determination. When the polarization determination is turned on, the determination current Ix is lowered from the normal value (default value) shown in FIG. As an example, the Ix setting unit 38 sets Ix = 0 in order to mask (prohibit) detection of abnormal internal resistance while polarization determination is on.

  When masking (prohibiting) the detection of the internal resistance abnormality, instead of setting the determination current Ix = 0, the current detection unit 40 sets the abnormality detection signal RSL to L while the polarization determination is on. You may make it fix to a level.

  From time t3, the assembled battery 10 that has been discharged is charged. That is, after time t3, the state of Ib <0 continues. As a result, the polarization voltage Vdyn that had been decreasing until time t3 increases from time t3. However, the polarization determination is kept on until time t4 when the polarization voltage Vdyn becomes higher than the reference voltage V2. Then, at time t4, the Ix setting unit 38 determines that the polarization voltage at a level leading to erroneous detection has been eliminated, and returns the polarization determination to OFF. When the polarization determination is turned off, the determination current Ix returns to the normal value (default value) shown in FIG. Thereby, normal detection of internal resistance abnormality can be resumed. The reference voltage V2 serving as a threshold when the polarization determination is switched from on to off may be the same as the reference voltage V1, but is preferably set to a voltage higher than the reference voltage V1.

  When the current comparison unit 40 is configured to fix the abnormality detection signal RSL to the L level while the polarization determination is turned on, the fixation is released when the polarization determination is turned off. As a result, the abnormality detection signal RSL is generated according to the normal comparison result between the maximum current Imax and the determination current Ix (default value).

  Further, as described above, the polarization voltage has a temperature dependency that becomes larger at a low temperature with respect to the same current. Therefore, as shown in FIG. 9, the reference voltages V1 and V2 for determining the polarization are preferably set variably according to the battery temperature Tb. Specifically, since the possibility of false detection increases at low temperatures when the polarization voltage increases, the reference voltages V1 and V2 are set relatively high so that the polarization determination can be easily turned on for the negative polarization voltage Vdyn. To do. On the other hand, the reference voltages V1 and V2 are set relatively low so that the polarization determination is difficult to turn on at high temperatures.

  Next, internal resistance abnormality detection by the assembled battery abnormality detection device according to the embodiment of the present invention will be described in the form of a control processing procedure by the abnormality monitoring circuit 30 using a flowchart.

  Referring to FIG. 10, abnormality monitoring circuit 30 determines whether or not the abnormality detection operation for the internal resistance abnormality is started in step S <b> 100. The determination in step S100 is determined based on, for example, whether or not a start instruction signal STR from the host ECU is generated. When the start instruction signal STR is not generated, the subsequent steps S110 to S200 are not executed.

  On the other hand, when the start instruction signal STR is generated, step S100 is determined as YES, and the process proceeds to step S110. In step S110, the abnormality monitoring circuit 30 generates a start trigger TRG for the detection unit 20 (1). In response to the start trigger TRG, the voltage comparison between the battery cells CL (1) to CL (n) and the determination voltage Vx is sequentially performed by the detection units 20 (1) to 20 (n) sequentially operating. Will be.

  Further, the abnormality monitoring circuit 30 detects the battery current Ib detected by the current sensor 15 once or plural times in the operation period of the detection units 20 (1) to 20 (n) in response to the start trigger TRG in step S120. Is sampled. That is, the processing of steps S110 and S120 corresponds to the function of the current sampling unit 32 in FIG.

  When the current sampling process in step S120 ends, the abnormality monitoring circuit 30 proceeds to step S130 and extracts the maximum current Imax that is the maximum value among the acquired current sampling values. When the number of times of sampling is one, the current sampling value is directly used as the maximum current Imax. That is, the processing in step S130 corresponds to the function of the maximum value extraction unit 34 in FIG.

  Further, the abnormality monitoring circuit 30 estimates the polarization voltage Vdyn in step S140. The process by step S140 can be performed similarly to the polarization voltage estimation part 36 of FIG.

  In step S150, the abnormality monitoring circuit 30 determines whether or not a polarization voltage of a level that causes erroneous detection is generated in each battery cell CL based on the polarization voltage Vdyn obtained in step S140. That is, in step S150, the polarization determination is executed according to the comparison between the polarization voltage Vdyn and the reference voltage V1 or V2.

  When the polarization determination is OFF, step S160 is determined to be NO, and therefore the abnormality monitoring circuit 30 sets the determination current Ix to a default value in order to execute normal internal resistance abnormality detection in step S165.

  When the polarization determination is off, step S160 is determined as YES, and therefore the abnormality monitoring circuit 30 reduces the determination current Ix from the default value so that the internal resistance abnormality is hardly detected at step S170. Preferably, determination current Ix = 0 is set in order to mask detection of an internal resistance abnormality.

  In step S180, the abnormality monitoring circuit 30 compares the maximum current Imax obtained in step 130 with the determination current Ix set in step S165 or S170.

  When Imax <Ix (YES in S180), the abnormality monitoring circuit 30 advances the process to step S190, and the internal resistance of any battery cell is higher than the threshold value, that is, the internal resistance is abnormal. As a result, the detection result “abnormal” is output.

  On the other hand, when Imax ≧ Ix (NO in S180), the abnormality monitoring circuit 30 proceeds to step S200, determines that no internal resistance abnormality has occurred, and detects “no abnormality”. Output the result. If the cell voltage drop abnormality is not detected by the determination signal FV, step S180 is NO and it is determined that no internal resistance abnormality has occurred.

  As described above, the assembled battery abnormality detection device according to the present embodiment prevents erroneous detection caused by the occurrence of polarization voltage in a simple configuration in which the voltage value is not directly detected for the voltage monitoring function for each battery cell. It is possible to detect whether or not the internal resistance is higher than a predetermined level (abnormal internal resistance).

  As described in the present embodiment, when polarization determination is turned on, it is preferable to mask (prohibit) the detection of abnormal internal resistance from the viewpoint of preventing erroneous detection. On the other hand, from the viewpoint of securing an opportunity to detect an internal resistance abnormality, the determination current Ix may be decreased from the default value by ΔIx in accordance with the polarization voltage Vdyn while stopping within the range of Ix> 0. For example, ΔIx can be set by dividing the polarization voltage Vdyn by the internal resistance (normal value).

  Further, as shown in FIG. 11, the assembled battery 10 may be configured by combining the battery pack 10 shown in FIG. 1 as one battery block and combining a plurality of such battery blocks (B0 to B7). Good.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention can be applied to detection of excessive increase in internal resistance of a battery cell in an assembled battery in which a plurality of battery cells are connected in series.

  10 battery pack, 12 load, 15 current sensor, 16 voltage sensor, 17 temperature sensor, 20 detection unit, 21 voltage comparator, 22 logic gate, 25 transmission circuit, 30 abnormality monitoring circuit, 32 current sampling unit, 34 maximum value extraction Unit, 36 polarization voltage estimation unit, 38 setting unit, 40 current comparison unit, 100 abnormality detection device, 102, 105 cell voltage transition, 200 electrical system, CL (1) to CL (n) battery cell, ECU host, FV determination Signal, Ib battery current, Imax maximum current, Ix determination current (internal resistance abnormality), OD (1) to OD (n) detection signal, RSL abnormality detection signal, STR start instruction signal, TRG start trigger, Tb battery temperature, V1 , V2 reference voltage (polarization determination), Vb battery voltage, Vc, Vc (1) to Vc (n) cells Voltage, Vdyn polarization voltage, Vo open-circuit voltage, Vx determination voltage (cell voltage drop), fdyn polarization value.

Claims (6)

A battery pack abnormality detection device having a plurality of battery cells connected in series,
A plurality of detection units provided corresponding to each of the plurality of battery cells, each configured to perform a voltage comparison between an output voltage of the corresponding battery cell and a predetermined determination voltage;
A current detector for detecting the current of the plurality of battery cells,
The plurality of detection units sequentially operate in response to a start trigger and sequentially transmit a signal reflecting the result of the voltage comparison, so that the output voltage of any of the plurality of battery cells is higher than the determination voltage. It is configured to output an abnormality detection signal indicating whether or not it has decreased,
The abnormality detection device is:
Based on the signals from the plurality of detection units and a current detection value by the current detector, whether or not an internal resistance abnormality in which the internal resistance rises above an upper limit value has occurred in any of the plurality of battery cells. An abnormality monitoring circuit for monitoring
The abnormality monitoring circuit is
A polarization voltage estimation unit for estimating a polarization voltage generated in each of the battery cells;
In accordance with the estimated polarization voltage, a determination current setting unit that reduces a determination current for detecting the internal resistance abnormality from a default value;
When the abnormality detection signal indicates that the output voltage of any of the plurality of battery cells is lower than the determination voltage, the internal resistance abnormality is detected when the current detection value is lower than the determination current. An abnormality detection device for a battery pack, including a current comparison unit for detecting occurrence of the battery.   The assembled battery abnormality detection according to claim 1, wherein, when the estimated polarization voltage is a negative voltage, the determination current setting unit relatively decreases the determination current when the absolute value of the polarization voltage increases. apparatus.   The determination current setting unit or the current comparison unit operates to mask detection of the internal resistance abnormality when the estimated polarization voltage is lower than a first reference voltage that is a negative voltage. The assembled battery abnormality detection device according to claim 1 or 2.   In the determination current setting unit or the current comparison unit, when the detection of the internal resistance abnormality is masked, the polarization voltage becomes higher than a second reference voltage higher than the first reference voltage. The assembled battery abnormality detection device according to claim 3, wherein the abnormality detection device operates to restart detection of the abnormality in the internal resistance.   The assembled battery abnormality detection device according to claim 3, wherein the first reference voltage is set to a higher voltage as a temperature of the plurality of battery cells is lower.   The assembled battery abnormality detection device according to claim 4, wherein the second reference voltage is set to a higher voltage as a temperature of the plurality of battery cells is lower.

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