Voltage Detector

Abstract

To provide a voltage detection device capable of distinguishing between disconnection of a transmission line relating to a pair of adjacent battery cells and a voltage abnormality of the battery cells themselves more appropriately than before.SOLUTION: A voltage detection device includes: a plurality of discharging circuits that is each connected in parallel to each of a plurality of battery cells connected in series and discharges the battery cells; a plurality of transmission lines that transmits an electrode voltage of the battery cells; and a voltage detection unit that detects a cell voltage of the battery cells on the basis of the electrode voltage input from the transmission lines. The voltage detection device further includes an abnormality distinguishing unit that distinguishes between disconnection of the transmission lines and a voltage abnormality of the battery cells on the basis of, a differential voltage of a pair of cell voltages related to a pair of adjacent battery cells when at least one is discharged and an addition voltage of the pair of cell voltages.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a voltage detection device. [Background technology]

[0002] The following Patent Document 1 describes a voltage detection device that includes a discharge circuit connected in parallel to each of a plurality of battery cells and consisting of a series circuit of a bypass resistor and a switching element, a transmission line that transmits the terminal voltage of each terminal of the battery cell, and a cell voltage detection unit that detects the cell voltage of each battery cell based on the terminal voltage input from the transmission line, and that includes a microcomputer that identifies and determines whether there is a break in the transmission line related to the pair of battery cells or an abnormality in the battery cells themselves based on the cell voltages of the pair of battery cells themselves and the difference between the pair of cell voltages when the discharge circuits of a pair of adjacent battery cells are placed in a discharging state with different duty ratios. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-158269 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the voltage detection device distinguishes between a break in the transmission line for a pair of adjacent battery cells and a voltage abnormality in the battery cells themselves, but this distinction is not always accurate and there is a risk of erroneously detecting both. That is, the voltage detection device determines that a break in the transmission line has occurred when the difference in the voltages of the pair of cells exceeds a predetermined threshold value, but since the difference in the voltage of the pair of cells may also exceed the predetermined threshold value due to a voltage abnormality in the battery cells themselves, the voltage detection device cannot properly distinguish between a break in the transmission line and a voltage abnormality in the battery cells themselves.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide a voltage detection device that can more accurately distinguish between a break in a transmission line for a pair of adjacent battery cells connected in series and a voltage abnormality in the battery cells themselves than has been possible with conventional devices. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the present invention employs, as a first solution relating to a voltage detection device, a plurality of discharge circuits each connected in parallel to a plurality of battery cells connected in series and discharging the battery cells, a plurality of transmission lines transmitting the electrode voltages of the battery cells, and a voltage detection unit detecting the cell voltages of the battery cells based on the electrode voltages input from the transmission lines, the voltage detection device further comprising an abnormality identification unit which identifies a break in the transmission lines and a voltage abnormality in the battery cells based on a differential voltage between a pair of cell voltages for an adjacent pair of the battery cells when at least one of them is discharged and a sum voltage of the pair of cell voltages.

[0007] The present invention provides a second solution related to the voltage detection device, which is the same as the first solution, in that the abnormality identification unit distinguishes between a break in the transmission line and a voltage abnormality in the battery cell when the pair of cell voltages deviate from a predetermined range.

[0008] The present invention employs a third solution related to the voltage detection device, which is the first or second solution described above, in which the abnormality identification unit distinguishes between a break in the transmission line and a voltage abnormality in the battery cell when the differential voltage between the pair of cell voltages exceeds a predetermined differential voltage threshold.

[0009] The present invention employs a fourth solution related to the voltage detection device, in which, in any of the first to third solutions described above, the abnormality identification unit determines that a voltage abnormality has occurred in the pair of battery cells when the absolute value of the amount of change in the differential voltage and the absolute value of the amount of change in the added voltage are equal.

[0010] The present invention provides a fifth solution related to the voltage detection device, which is any of the first to fourth solutions described above, in which the abnormality identification unit determines that the transmission line is disconnected when the absolute value of the amount of change in the differential voltage and the absolute value of the amount of change in the added voltage are not equal. Effect of the Invention

[0011] According to the present invention, it is possible to provide a voltage detection device that can more appropriately distinguish between a break in a transmission line for a pair of adjacent battery cells connected in series and a voltage abnormality in the battery cells themselves than has been possible with the prior art. [Brief description of the drawings]

[0012] [Figure 1] 1 is a circuit diagram showing a configuration of a voltage detection device A according to one embodiment of the present invention. [Diagram 2] FIG. 1A is a characteristic diagram showing the changes in cell voltage, difference voltage, and added voltage when a transmission line is disconnected in a voltage detection device A according to one embodiment of the present invention, and FIG. 1B is a characteristic diagram showing the changes in cell voltage, difference voltage, and added voltage when an abnormality occurs in the voltage of a battery cell. [Diagram 3] 4 is a flowchart showing the operation of a voltage detection device A according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1, a voltage detection device A according to this embodiment is a device that detects, as cell voltages, voltages between electrodes of a plurality of (n) battery cells b1 to bn that constitute the battery pack B. Here, "n" is a natural number of 2 or more.

[0014] The battery pack B is a secondary battery including multiple (n) battery cells b1 to bn, and is mounted on an electric vehicle to supply DC power to a power converter that drives the drive motor. This battery pack B is, for example, a lithium-ion battery or a fuel cell, and supplies a higher voltage DC power (for example, several hundred volts) to the power converter than the lead storage battery (12V) mounted on a typical vehicle.

[0015] The voltage detection device A is an electronic circuit that detects the cell voltages (e.g., several volts) of each of the n battery cells b1 to bn in such a battery pack B, and as shown in the figure, includes a plurality of (n+1) connection terminals T1 to Tn+1, a plurality of (n) discharge circuits H1 to Hn, a plurality of (n+1) CR filters F1 to Fn+1, a cell voltage detection unit K, and a microcomputer M.

[0016] Due to drawing space limitations, FIG. 1 shows only three battery cells b1, b2, bn, three discharge circuits H1, H2, Hn, five transmission lines S1 to S3, Sn, Sn+1, five connection terminals T1 to T3, Tn, Tn+1, and five CR filters F1 to F3, Fn, Fn+1 out of the n battery cells b1 to bn, n discharge circuits H1 to Hn, n+1 transmission lines S1 to Sn+1, n+1 connection terminals T1 to Tn+1, and n+1 CR filters F1 to Fn+1.

[0017] The n battery cells b1 to bn are connected in series in a row, with the positive terminal of battery cell b1 being the positive terminal of battery assembly B, and the negative terminal of battery cell bn being the negative terminal of battery assembly B. In other words, the n battery cells b1 to bn are connected in series in the order of battery cell b1 → battery cell b2 → (omitted) → battery cell bn, and the sum of the cell voltages of the battery cells b1 to bn is the output voltage of battery assembly X.

[0018] One end of each of the n+1 transmission lines S1 to Sn+1 is connected to the n+1 connection terminals T1 to Tn, and the other end is connected to the n battery cells b1 to bn. That is, of the n+1 transmission lines S1 to Sn+1, the first transmission line S1 has one end connected to the first connection terminal T1, and the other end connected to the positive electrode of the first battery cell b1.

[0019] The second transmission line S2 has one end connected to the second connection terminal T2 and the other end connected to the negative electrode of the first battery cell b1 and the positive electrode of the second battery cell b2. The third transmission line S3 has one end connected to the third connection terminal T3 and the other end connected to the negative electrode of the second battery cell b2 and the positive electrode of the third battery cell b3.

[0020] Furthermore, the nth transmission line Sn has one end connected to the nth connection terminal Tn and the other end connected to the negative electrode of the n-1th battery cell bn-1 (not shown) and the positive electrode of the nth battery cell bn. Moreover, the n+1th transmission line Sn+1 has one end connected to the n+1th connection terminal Tn+1 and the other end connected to the negative electrode of the nth battery cell bn.

[0021] Such n+1 transmission lines S1 to Sn+1 are electric wires that transmit each electrode voltage of the n battery cells b1 to bn to the voltage detection device A. That is, the first transmission line S1 transmits the voltage of the positive electrode of the first battery cell b1 as a first electrode voltage V1 to the first connection terminal T1.

[0022] The second transmission line S2 transmits the voltages of the negative electrode of the first battery cell b1 and the positive electrode of the second battery cell b2 as a second electrode voltage V2 to the second connection terminal T2. The third transmission line S3 transmits the voltages of the negative electrode of the second battery cell b2 and the positive electrode of the third battery cell b3 as a third electrode voltage V3 to the third connection terminal T3.

[0023] Furthermore, the nth transmission line Sn transmits the voltage of the negative electrode of the n-1th battery cell bn-1 and the positive electrode of the nth battery cell bn as the nth electrode voltage Vn to the nth connection terminal Tn. The n+1th transmission line Sn+1 transmits the voltage of the negative electrode of the nth battery cell bn as the n+1th electrode voltage Vn+1 to the n+1th connection terminal Tn+1.

[0024] As described above, the n+1 connection terminals T1 to Tn+1 are connected to one end of the n+1 transmission lines S1 to Sn+1, and are also connected to one end of the discharge circuits H1 to Hn and the input end of the CR filters F1 to Fn+1. That is, of the n+1 connection terminals T1 to Tn+1, the first connection terminal T1 is connected to one end of the first transmission line S1, one end of the first discharge circuit H1, and the input end of the first CR filter F1.

[0025] The second connection terminal T2 is connected to one end of the second transmission line S2, one end of the second discharge circuit H2, and the input end of the second CR filter F2, respectively. The third connection terminal T3 is connected to one end of the third transmission line S3, one end of the third discharge circuit H3, and the input end of the third CR filter F3, respectively.

[0026] Furthermore, the nth connection terminal Tn is connected to one end of the nth transmission line Sn, one end of the nth discharge circuit Hn, and the input end of the nth CR filter Fn, respectively. The n+1th connection terminal Tn+1 is connected to one end of the n+1th transmission line Sn+1, one end of the n+1th discharge circuit Hn+1, and the input end of the n+1th CR filter Fn+1, respectively.

[0027] One end of each of the n discharge circuits H1 to Hn is connected to the connection terminals T1 to Tn and the input terminals of the CR filters F1 to Fn, and the other end is connected to the connection terminals T2 to Tn+1, the discharge circuits H1 to Hn+1, and the input terminals of the CR filters F2 to Fn+1. That is, among the n discharge circuits H1 to Hn, the first discharge circuit H1 has one end connected to the first connection terminal T1 and the input terminal of the first CR filter F1, and the other end connected to the second connection terminal T2, one end of the second discharge circuit H2, and the input terminal of the second CR filter F2.

[0028] The second discharge circuit H2 has one end connected to the second connection terminal T2, the other end of the first discharge circuit H2, and the input end of the second CR filter F2, and the other end connected to the third connection terminal T3, one end of the fourth discharge circuit H4 (not shown), and the input end of the third CR filter F3. Furthermore, the nth discharge circuit Hn has one end connected to the nth connection terminal Tn, the other end of the n-1th discharge circuit Hn-1, and the input end of the nth CR filter Fn, and the other end connected to the n+1th connection terminal Tn+1 and the input end of the n+1th CR filter Fn+1.

[0029] These n discharge circuits H1 to Hn are connected in parallel to the battery cells b1 to bn, respectively. That is, the first discharge circuit H1 is connected in parallel to the first battery cell b1, the second discharge circuit H2 is connected in parallel to the second battery cell b2, the third discharge circuit H3 is connected in parallel to the third battery cell b3, and the n-th discharge circuit Hn is connected in parallel to the n-th battery cell bn.

[0030] Each of the n discharge circuits H1 to Hn is a series circuit of a bypass resistor and a switching element, and is in a discharging state when the switching element is in an ON state, and in a non-discharging state when the switching element is in an OFF state. The ON / OFF states of the switching elements in the n discharge circuits H1 to Hn are set by a gate signal input from a microcomputer M as shown in the figure.

[0031] That is, the first discharge circuit H1 puts the first battery cell b1 into a discharge state when the switching element is in an ON state, and puts the first battery cell b1 into a non-discharge state when the switching element is in an OFF state. The second discharge circuit H2 puts the second battery cell b2 into a discharge state when the switching element is in an ON state, and puts the second battery cell b2 into a non-discharge state when the switching element is in an OFF state. Furthermore, the nth discharge circuit Hn puts the nth battery cell bn into a discharge state when the switching element is in an ON state, and puts the nth battery cell bn into a non-discharge state when the switching element is in an OFF state.

[0032] The n+1 CR filters F1 to Fn+1 have input terminals connected to the connection terminals T1 to Tn and the discharge circuits H1 to Hn, output terminals connected to the input terminals IN1 to INn+1 of the cell voltage detection unit K, and a common terminal grounded. That is, of the n+1 CR filters F1 to Fn+1, the first CR filter F1 has an input terminal connected to the first connection terminal T1 and one end of the first discharge circuit H1, an output terminal connected to the first input terminal IN1, and a common terminal grounded.

[0033] The second CR filter F2 has an input terminal connected to the second connection terminal T2 and one end of the second discharge circuit H2, an output terminal connected to the second input terminal IN2, and a common terminal grounded. The third CR filter F3 has an input terminal connected to the third connection terminal T3 and one end of the third discharge circuit H3 (not shown), an output terminal connected to the third input terminal IN3, and a common terminal grounded.

[0034] Furthermore, the nth CR filter Fn has an input end connected to the nth connection terminal Tn and one end of the nth discharge circuit Hn, an output end connected to the nth input terminal INn, and a common end grounded. The n+1th CR filter Fn+1 has an input end connected to the n+1th connection terminal Tn+1 and the other end of the nth discharge circuit Hn, an output end connected to the n+1th input terminal INn+1, and a common end grounded.

[0035] These n+1 CR filters F1 to Fn+1 are low-pass filters equipped with a resistor R and a capacitor C, and remove high-frequency noise contained in the 1st to n+1th electrode voltages V1 to Vn+1. As shown in the figure, one end of the resistor R is an input end of the CR filters F1 to Fn+1, and the other end is an output end of the CR filters F1 to Fn+1. Moreover, one end of the capacitor C is connected to the other end of the resistor R, and the other end is a common end of the CR filters F1 to Fn+1, which is grounded.

[0036] As described above, the voltage detection unit K has n+1 input terminals IN1 to INn+1, and detects the first to n-th cell voltages Vc1 to Vcn for the n battery cells b1 to bn based on the first to n+1th electrode voltages V1 to Vn+1 input from the CR filters F1 to Fn+1, respectively, and outputs the first to n-th cell voltages Vc1 to Vcn to the microcomputer M.

[0037] That is, the voltage detection unit K detects the difference voltage between the first electrode voltage V1 and the second electrode voltage V2, and outputs the difference voltage to the microcomputer M as the first cell voltage Vc1 for the first battery cell b1. The voltage detection unit K also detects the difference voltage between the second electrode voltage V2 and the third electrode voltage V3, and outputs the difference voltage to the microcomputer M as the second cell voltage Vc2 for the second battery cell b2. The voltage detection unit K also detects the difference voltage between the nth electrode voltage Vn and the n+1th electrode voltage Vn+1, and outputs the difference voltage to the microcomputer M as the nth cell voltage Vcn for the nth battery cell bn.

[0038] The microcomputer M is a so-called one-chip microcomputer in which a CPU (Central Processing Unit), memory, an input / output interface, etc. are integrally incorporated, and converts the first to n-th cell voltages Vc1 to Vcn input from the voltage detection unit K into first to n-th cell voltage data Dc1 to Dcn, and outputs the first to n-th cell voltage data Dc1 to Dcn to an external higher-level control device (not shown). Note that this higher-level control device is an electronic control device that controls the charging and discharging of the battery pack B.

[0039] The microcomputer M corresponds to the abnormality identification unit of the present invention. That is, the microcomputer M diagnoses the occurrence of an open circuit in the first to n+1th transmission lines S1 to Sn+1 by processing the first to nth cell voltages Vc1 to Vcn based on a predetermined open circuit detection program. This open circuit diagnosis process is performed by sequentially calculating the difference voltage Vdiff and the sum voltage Vsum in a time series manner based on the first to nth cell voltage data Dc1 to Dcn obtained in a time series manner from the first to nth cell voltages Vc1 to Vcn with the ON / OFF states of the first to nth discharge circuits H1 to Hn appropriately set, and based on the change trends of the difference voltage Vdiff and the sum voltage Vsum.

[0040] Next, the operation of the voltage detecting device A according to this embodiment will be described in detail with reference to FIGS.

[0041] In this voltage detection device A, the first to n+1th electrode voltages V1 to Vn+1 related to the first to n-th battery cells b1 to bn are input to a voltage detection unit K via the first to n+1th transmission lines S1 to Sn+1 and the CR filters F1 to Fn+1. The voltage detection unit K then outputs the first to n-th cell voltages Vc1 to Vcn related to the first to n-th battery cells b1 to bn to a microcomputer M based on the first to n+1th electrode voltages V1 to Vn+1 input to the first to n+1th input terminals IN1 to INn+1, respectively.

[0042] Then, the microcomputer M calculates the difference voltage Vdiff and the sum voltage Vsum for each pair of adjacent battery cells among the first to n-th battery cells b1 to bn. That is, the microcomputer M calculates the difference voltage Vdiff and the sum voltage Vsum for each of the first and second battery cells b1 and b2 adjacent to each other, the second and third battery cells b2 and b3 (not shown) adjacent to each other, (omitted), and the n-1th battery cell bn-1 (not shown) and the nth battery cell bn adjacent to each other.

[0043] Here, the differential voltage Vdiff is a differential voltage between a pair of cell voltages for a pair of adjacent battery cells. For example, for a first battery cell b1 and a second battery cell b2 that are adjacent to each other, the differential voltage Vdiff is a differential voltage (Vc1-Vc2) between a first cell voltage Vc1 and a second cell voltage Vc2.

[0044] On the other hand, the sum voltage Vsum is a sum of a pair of cell voltages for a pair of adjacent battery cells. For example, for a first battery cell b1 and a second battery cell b2 that are adjacent to each other, the sum voltage Vsum is a sum of a first cell voltage Vc1 and a second cell voltage Vc2 (Vc1+Vc2).

[0045] The microcomputer M sequentially stores the first to nth cell voltage data Dc1 to Dcn corresponding to the first to nth cell voltages Vc1 to Vcn in an internal memory at a predetermined time interval, and sequentially calculates the difference voltage Vdiff and the sum voltage Vsum at a predetermined time interval by reading the first to nth cell voltage data Dc1 to Dcn from the internal memory and stores them in the internal memory.

[0046] Here, the properties of the difference voltage Vdiff and the sum voltage Vsum will be described. As explained as a problem with the technology of Patent Document 1, the differential voltage between a pair of cell voltages relating to a pair of adjacent battery cells connected in series, for example, the differential voltage between the first cell voltage Vc1 and the second cell voltage Vc2 relating to the first battery cell b1 and the second battery cell b2, exceeds a predetermined threshold value when the second transmission line S2 commonly connected to the first battery cell b1 and the second battery cell b2 becomes disconnected.

[0047] However, the difference voltage between the pair of cell voltages of a pair of adjacent battery cells exceeds a predetermined threshold even when either the first battery cell b1 or the second battery cell b2 has a voltage abnormality. Therefore, the technology of Patent Document 1 cannot appropriately distinguish between a break in the transmission line and a voltage abnormality (battery abnormality) of a battery cell.

[0048] In contrast, the differential voltage Vdiff and the sum voltage Vsum obtained when at least one of a pair of adjacent battery cells is gradually discharged are characteristic quantities that can appropriately identify a transmission line commonly connecting the pair of adjacent battery cells and a voltage abnormality (battery abnormality) in one of the pair of battery cells, as described below.

[0049] For example, a first battery cell b1 and a second battery cell b2 will be described with reference to Fig. 2. As shown in Fig. 2(a), when the second battery cell b2 is gradually discharged by turning on / off the second discharge circuit H2, which is one of the first discharge circuit H1 and the second discharge circuit H2, at a predetermined duty ratio, the first cell voltage Vc1 does not change even if a break occurs in the second transmission line S2, but the second cell voltage Vc2 gradually decreases when the second transmission line S2 is broken.

[0050] In this case, the difference voltage Vdiff gradually rises when the second transmission line S2 is disconnected. In contrast, the sum voltage Vsum does not change even when the second transmission line S2 is disconnected. In other words, when the second transmission line S2 is disconnected, the difference voltage Vdiff and the sum voltage Vsum have completely different slopes (amounts of change) when graphed.

[0051] On the other hand, as shown in FIG. 2(b), when the second battery cell b2 is gradually discharged by turning the second discharge circuit H2 ON / OFF at a predetermined duty ratio, if a voltage abnormality (battery abnormality) occurs in the second battery cell b2, both the first cell voltage Vc1 and the second cell voltage Vc2 gradually decrease.

[0052] Furthermore, the differential voltage Vdiff gradually rises when a voltage abnormality (battery abnormality) occurs in the second battery cell b2. In contrast, the sum voltage Vsum gradually falls when a voltage abnormality (battery abnormality) occurs in the second battery cell b2. In other words, when a voltage abnormality (battery abnormality) occurs in the second battery cell b2, the differential voltage Vdiff and the sum voltage Vsum have the same absolute value although the directions of the slopes (amounts of change) differ when graphed.

[0053] The microcomputer M utilizes such properties of the difference voltage Vdiff and the sum voltage Vsum to more accurately distinguish between breaks in the first to n+1th transmission lines S1 to Sn+1 and voltage abnormalities (battery abnormalities) in the first to nth battery cells b1 to bn based on the information processing shown in FIG. 3.

[0054] Hereinafter, with reference to FIG. 3, a process of distinguishing between a break in the first to n+1th transmission lines S1 to Sn+1 and a voltage abnormality (battery abnormality) in the first to nth battery cells b1 to bn using the differential voltage Vdiff and the sum voltage Vsum in the microcomputer M will be described.

[0055] 3 relates to a first battery cell b1 and a second battery cell b2, which are one of a pair of adjacent battery cells. The same determination process is performed on the pair of adjacent battery cells other than the first battery cell b1 and the second battery cell b2 as on the first battery cell b1 and the second battery cell b2.

[0056] When the microcomputer M calculates a new differential voltage Vdiff in chronological order for the first battery cell b1 and the second battery cell b2, the microcomputer M adds the new differential voltage Vdiff to the differential voltages Vdiff stored in the internal memory and erases the oldest differential voltage Vdiff in chronological order. That is, the microcomputer M updates and stores the differential voltages Vdiff at multiple times over a predetermined period (step S1).

[0057] Then, when the microcomputer M calculates a new sum voltage Vsum in chronological order for the first battery cell b1 and the second battery cell b2, it adds the new sum voltage Vsum to the sum voltages Vsum stored in the internal memory and erases the oldest sum voltage Vsum in chronological order. That is, the microcomputer M updates and stores the sum voltages Vsum at multiple times over a predetermined period (step S2).

[0058] Next, the microcomputer M determines whether the first cell voltage Vc1 or the second cell voltage Vc2 is equal to or greater than the upper limit value Vmax (step S3). The determination in step S3 is "Yes" if either the first cell voltage Vc1 or the second cell voltage Vc2 exceeds the upper limit value Vmax, and "No" if neither the first cell voltage Vc1 nor the second cell voltage Vc2 exceeds the upper limit value Vmax.

[0059] If the determination in step S3 is "Yes", that is, if either the first cell voltage Vc1 or the second cell voltage Vc2 has become abnormally high, the microcontroller M determines whether the differential voltage Vdiff between the first cell voltage Vc1 and the second cell voltage Vc2 has become equal to or greater than a predetermined differential voltage threshold Vth (step S4).

[0060] That is, the determination in step S4 is "Yes" if the differential voltage Vdiff exceeds the differential voltage threshold Vth, and is "No" if the differential voltage Vdiff does not exceed the differential voltage threshold Vth. The state in which the determination in step S4 is "Yes" indicates a suspected disconnection of the second transmission line S2 commonly connected to the first battery cell b1 and the second battery cell b2, or a suspected voltage abnormality (battery abnormality) in either the first battery cell b1 or the second battery cell b2.

[0061] If the determination in step S4 is "Yes," the microcomputer M determines whether the absolute value |ΔVdiff| of the differential voltage change amount ΔVdiff is approximately equal to the absolute value |ΔVsum| of the added voltage change amount ΔVsum (step S5). That is, based on the differential voltage Vdiff_mm at the latest time tm, the differential voltage Vdiff_m-1 at the time tm-1 immediately before the latest time tm, and the differential voltage Vdiff_m-2 at the time tm-2 immediately before the immediately before time tm-1, the microcomputer M calculates the time change amount of the differential voltage Vdiff over these three times as the differential voltage change amount ΔVdiff, and calculates the absolute value |ΔVdiff| of the differential voltage change amount ΔVdiff. Note that the above "m" is a natural number.

[0062] In addition, based on the sum voltage Vsum_m at the latest time tm, the sum voltage Vsum_m-1 at the time tm-1 immediately before the latest time tm, and the sum voltage Vsum_m-2 at the time tm-2 immediately before the immediately previous time tm-1, the microcontroller M calculates the time change in the sum voltage Vsum over these three times as the sum voltage change ΔVsum, and calculates the absolute value |ΔVsum| of the sum voltage change ΔVsum.

[0063] The microcontroller then determines whether the absolute value |ΔVdiff| of the differential voltage change amount ΔVdiff and the absolute value |ΔVsum| of the added voltage change amount ΔVsum are approximately equal by evaluating whether the difference between the absolute value |ΔVdiff| of the differential voltage change amount ΔVdiff and the absolute value |ΔVsum| of the added voltage change amount ΔVsum is within a predetermined range threshold.

[0064] If the determination in step S5 is "Yes", the microcomputer M determines that a disconnection has occurred in the second transmission line S2 (step S6), and if the determination in step S5 is "No", it determines that a voltage abnormality (battery abnormality) has occurred in the second battery cell b2 (step S7). That is, the microcomputer M distinguishes between a disconnection in the second transmission line S2 and a voltage abnormality (battery abnormality) in the second battery cell b2 based on the differential voltage Vdiff_m and the sum voltage Vsum_m, the differential voltage Vdiff_m-1 and the sum voltage Vsum_m-1, and the differential voltage Vdiff_m-2 and the sum voltage Vsum_m-2 over three times including the most recent.

[0065] Note that even if the determination in step S4 is "No," the microcomputer M determines that a voltage abnormality (battery abnormality) has occurred in the second battery cell b2 (step S7). In this case, since the differential voltage ΔV12 does not exceed the differential voltage threshold ΔVth, no break has occurred in the second transmission line S2, and there is simply a voltage abnormality (battery abnormality) in the second battery cell b2.

[0066] On the other hand, if the determination in step S3 is "No", the microcomputer M determines whether the first cell voltage Vc1 or the second cell voltage Vc2 has fallen below the lower limit Vmin (step S8). The determination in step S8 is "Yes" if either the first cell voltage Vc1 or the second cell voltage Vc2 falls below the lower limit Vmin, and "No" if both the first cell voltage Vc1 and the second cell voltage Vc2 are not below the lower limit Vmin.

[0067] If the judgment in step S8 is "Yes", that is, if either the first cell voltage Vc1 or the second cell voltage Vc2 has become abnormally low, the microcontroller M judges whether the differential voltage Vdiff between the first cell voltage Vc1 and the second cell voltage Vc2 has become equal to or greater than a predetermined differential voltage threshold Vth (step S9).

[0068] That is, the determination in step S9 is "Yes" if the differential voltage Vdiff exceeds the differential voltage threshold Vth, and is "No" if the differential voltage Vdiff does not exceed the differential voltage threshold Vth. The state in which the determination in step S9 is "Yes" is a state in which, like the state in which the determination in step S4 described above is "Yes," there is a suspected break in the second transmission line S2 commonly connected to the first battery cell b1 and the second battery cell b2, or a suspected voltage abnormality (battery abnormality) in either the first battery cell b1 or the second battery cell b2.

[0069] If the determination in step S9 is "Yes," the microcomputer M determines whether the absolute value of the difference voltage change amount and the absolute value of the added voltage change amount are approximately equal, as in step S5 described above (step S10). That is, the microcomputer M calculates the time change amount of the difference voltage Vdiff over these three times as a difference voltage change amount ΔVdiff based on the difference voltage Vdiff_mm at the latest time tm, the difference voltage Vdiff_m-1 at the time tm-1 immediately before the latest time tm, and the difference voltage Vdiff_m-2 at the time tm-2 immediately before the immediately before time tm-1. Then, the microcomputer M calculates the absolute value |ΔVdiff| of the difference voltage change amount ΔVdiff.

[0070] Furthermore, the microcomputer M calculates the amount of change over time of the sum voltage Vsum over these three times as an added voltage change amount ΔVsum based on the added voltage Vsum_m at the latest time tm, the added voltage Vsum_m-1 at the time tm-1 immediately before the latest time tm, and the added voltage Vsum_m-2 at the time tm-2 immediately before the immediately previous time tm-1.The microcomputer M then calculates the absolute value |ΔVsum| of the added voltage change amount ΔVsum.

[0071] Then, the microcontroller M determines whether the absolute value |ΔVdiff| of the differential voltage change amount ΔVdiff and the absolute value |ΔVsum| of the added voltage change amount ΔVsum are approximately equal to each other by evaluating whether the difference between the absolute value |ΔVdiff| of the differential voltage change amount ΔVdiff and the absolute value |ΔVsum| of the added voltage change amount ΔVsum is within a predetermined range threshold.

[0072] If the determination in step S10 is "Yes", the microcomputer M determines that a break in the second transmission line S2 has occurred (step S11), and if the determination in step S10 is "No", the microcomputer M determines that a voltage abnormality (battery abnormality) has occurred in the second battery cell b2 (step S12). That is, even if either the first cell voltage Vc1 or the second cell voltage Vc2 falls below the lower limit Vmin, the microcomputer M distinguishes between a break in the second transmission line S2 and a voltage abnormality (battery abnormality) in the second battery cell b2 in the same way as when either falls below the upper limit Vmax.

[0073] If the determination in step S8 is "No", the microcomputer M determines that the second transmission line S2 and the second battery cell b2 are normal (step S13). In this case, since both the first cell voltage Vc1 and the second cell voltage Vc2 are within the range defined by the upper limit value Vmax and the lower limit value Vmin, neither a break in the second transmission line S2 nor a voltage abnormality (battery abnormality) in the second battery cell b2 has occurred.

[0074] According to the voltage detection device A of this embodiment, the difference voltage Vdiff and sum voltage Vsum for a pair of adjacent battery cells connected in series are used for the 1st to nth battery cells b1 to bn and the 1st to n+1th transmission lines S1 to Sn+1, so that it is possible to distinguish between a break in the transmission line for a pair of adjacent battery cells connected in series and a voltage abnormality in the battery cell itself more appropriately than in the past.

[0075] Furthermore, in the voltage detection device A according to this embodiment, prior to distinguishing between a break in the transmission line and a voltage abnormality in the battery cell (battery abnormality) using the differential voltage Vdiff and the sum voltage Vsum in steps S5 and S10, it is determined in steps S3 and S8 whether the pair of cell voltages deviate from a predetermined range defined by an upper limit value Vmax and a lower limit value Vmin. Such a voltage detection device A makes it possible to more appropriately distinguish between a break in the transmission line related to a pair of adjacent battery cells and a voltage abnormality in the battery cells themselves.

[0076] Furthermore, in the voltage detection device A according to this embodiment, prior to distinguishing between a break in the transmission line and a voltage abnormality in the battery cell (battery abnormality) using the differential voltage Vdiff and sum voltage Vsum in steps S5 and S10, it is determined whether or not the differential voltage between the pair of cell voltages exceeds a predetermined threshold value in steps S4 and S9. Such a voltage detection device A makes it possible to more appropriately distinguish between a break in the transmission line relating to a pair of adjacent battery cells and a voltage abnormality in the battery cell itself.

[0077] The present invention is not limited to the above-described embodiment, and the following modifications are possible. (1) In the above embodiment, a break in the transmission line and a voltage abnormality in a battery cell (battery abnormality) are identified based on the differential voltage Vdiff_m and the sum voltage Vsum_m, the differential voltage Vdiff_m-1 and the sum voltage Vsum_m-1, and the differential voltage Vdiff_m-2 and the sum voltage Vsum_m-2 over three times including the most recent time. However, the present invention is not limited to this.

[0078] For example, a break in the transmission line and a voltage abnormality (battery abnormality) in a battery cell may be identified based on the differential voltage Vdiff and sum voltage Vsum over two times including the most recent time or over four or more times. The accuracy of identification improves as the number of times increases, but there is a disadvantage in that the calculation load on the microcomputer M increases, so it is preferable not to increase the number of times excessively.

[0079] (2) In the above embodiment, the discrimination between a break in the transmission line and a voltage abnormality in the battery cell (battery abnormality) using the differential voltage Vdiff and the sum voltage Vsum in steps S5 and S10 is combined with the judgment processes of steps S3, S4, S8, and S9. However, the present invention is not limited to this.

[0080] That is, in the above embodiment, when the pair of cell voltages deviates from a predetermined range based on the judgment processes of steps S3 and S8, a break in the transmission line and a voltage abnormality in the battery cell (battery abnormality) are identified, but the judgment processes of steps S3 and S8 may be omitted as necessary.

[0081] In the above embodiment, when the differential voltage between a pair of cell voltages exceeds a predetermined threshold value based on the judgment processes of steps S4 and S9, a break in the transmission line and a voltage abnormality in the battery cell (battery abnormality) are identified. However, the judgment processes of steps S3 and S8 may be omitted as necessary.

[0082] (3) In the above embodiment, when at least one of a pair of adjacent battery cells is gradually discharged, for example, when the second battery cell b2 of the first battery cell b1 and the second battery cell b2 is gradually discharged by turning the second battery cell b2 on / off at a predetermined duty ratio, a break in the transmission line and a voltage abnormality (battery abnormality) of the battery cell are distinguished by using the difference voltage Vdiff and the sum voltage Vsum.

[0083] However, the present invention is not limited to this. For example, as described in Patent Document 1, a pair of adjacent battery cells may be discharged with different duty ratios, and the difference voltage Vdiff and sum voltage Vsum may be used to distinguish between a break in the transmission line and a voltage abnormality (battery abnormality) in the battery cell.

[0084] (4) In the above embodiment, the voltage detection device A detects the cell voltage of the battery pack B mounted on an electric vehicle, but the present invention is not limited to this. In other words, the present invention is also applicable to battery packs other than the vehicle-mounted battery pack B. [Explanation of symbols]

[0085] A Voltage detection device B Battery pack b1~bn Battery cells T1~Tn+1 connection terminals H1~Hn discharge circuit F1~Fn+1 CR filter K Cell voltage detection section M Microcomputer (Abnormality Identification Unit) S1~Sn+1 Transmission lines

Claims

1. A voltage detection device comprising: a plurality of discharge circuits each connected in parallel to a plurality of battery cells connected in series, the discharge circuits discharging the battery cells; a plurality of transmission lines transmitting electrode voltages of the battery cells; and a voltage detection unit detecting cell voltages of the battery cells based on the electrode voltages input from the transmission lines, a differential voltage between a pair of cell voltages of an adjacent pair of battery cells when at least one of the battery cells is discharged and an abnormality in the voltage of the pair of cell voltages is identified by an abnormality identification unit that identifies a break in the transmission line and an abnormality in the voltage of the battery cell based on the differential voltage between a pair of cell voltages of the adjacent pair of battery cells when at least one of the battery cells is discharged and the sum of the pair of cell voltages.

2. 2. The voltage detection device according to claim 1, wherein the abnormality identification unit is configured to identify a disconnection of the transmission line and an abnormal voltage of the battery cell when the pair of cell voltages deviates from a predetermined range.

3. 3. The voltage detection device according to claim 1, wherein the abnormality identification unit is configured to identify a disconnection of the transmission line and a voltage abnormality of the battery cell when a difference between the voltages of the pair of cells exceeds a predetermined difference voltage threshold.

4. The voltage detection device according to any one of claims 1 to 3, characterized in that the abnormality identification unit determines that a voltage abnormality has occurred in the pair of battery cells when the absolute value of the change in the differential voltage is equal to the absolute value of the change in the added voltage.

5. The voltage detection device according to any one of claims 1 to 4, characterized in that the abnormality identification unit determines that the transmission line is broken when the absolute value of the change in the differential voltage and the absolute value of the change in the added voltage are not equal.

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