JP6805837B2 - How to detect disconnection of the assembled battery - Google Patents

Description

The present invention relates to a method for detecting a disconnection of a parallel connection line of an assembled battery in which cell blocks in which a plurality of cells are connected in parallel are connected in series in a plurality of stages.

As a secondary battery mounted on a vehicle, an assembled battery in which cell blocks in which a plurality of cells are connected in parallel are connected in series in multiple stages is often used.

In Patent Document 1, in such an assembled battery, the voltage or resistance value of each cell block is compared, and a part of the cells connected in parallel of each cell block is dropped or the parallel connection line is broken. The method of detection is described as follows.

That is, the open circuit voltage (Open Circuit Voltage: OCV) of each cell block is measured in the test period before charging and the period before discharging after full charging, and the voltage difference between the terminal voltage at the time of charging and discharging and the OCV is measured. The internal resistance of each cell block is calculated by dividing by the charge / discharge current. When the cell block is parallel to two cells, the internal resistance of the cell block is R (Ω) in the normal state, and if one of the parallel connections of the two cells is dropped or one of the parallel connection lines is broken, it is double the normal state. It is used that it becomes 2 × R (Ω).

Japanese Unexamined Patent Publication No. 2008-027658

The method of detecting disconnection described in Patent Document 1 is a disconnection cell in which some of the parallel connection lines are disconnected in an assembled battery in which cell blocks in which a plurality of cells are connected in parallel by parallel connection lines are connected in series in multiple stages. This is based on the fact that the internal resistance of the block is larger than the internal resistance of the normal cell block by the resistance increase rate calculated by the following (Equation 1).
Resistance increase rate = (number of parallels) / (number of parallels-number of disconnections) ... (Equation 1)
In this (Equation 1), the resistance increase rate of the disconnected cell block is calculated on the premise that the internal resistance of each cell does not change even if the current value flowing through each cell increases due to the disconnection.

On the other hand, some cells have a characteristic that the internal resistance value decreases as the current increases. When a disconnection occurs in an assembled battery configured using such a cell, the internal resistance value of each cell decreases as the current flowing through each cell increases, so that the resistance increase rate of the disconnected cell block is as follows: The value is smaller than the value calculated in 1). Therefore, it may be difficult to accurately detect the disconnection of the assembled battery by the method described in Patent Document 1 depending on the characteristics of the cell.

Therefore, an object of the present invention is to detect disconnection of the assembled battery with high accuracy.

The disconnection detection method of the present invention is a disconnection detection method for the parallel connection line of an assembled battery in which cell blocks in which a plurality of cells are connected in parallel by a parallel connection line are connected in series in a plurality of stages, and has a time interval of 100 to 200 msec . When the current of the assembled battery is detected and the product of the current first current value and the second current value at the previous detection timing is negative, and the first current value and the second current value are negative. When the absolute value of the current value difference from the current value exceeds a predetermined threshold value, the disconnection detection of the parallel connection line is executed.

In the disconnection detection method of the present invention, each voltage value of each cell block is detected at the same time as the current of the assembled battery is detected, and the execution of the disconnection detection is one with each current first voltage value of each cell block. The disconnection determination may be executed based on the resistance ratio between the cell blocks calculated based on the voltage value difference of each second voltage value at the previous detection timing.

Further, in the disconnection detection method of the present invention, the resistance ratio between the cell blocks may be calculated based on the voltage value difference and the current value difference.

INDUSTRIAL APPLICABILITY The present invention can detect disconnection of an assembled battery with high accuracy.

It is a system diagram which shows the structure of the electric vehicle to which the disconnection detection method of embodiment of this invention is applied. It is a top view which shows the parallel bus bar and the connection bus bar of the positive electrode of the cell block which comprises the assembled battery shown in FIG. It is a top view which shows the parallel bus bar and the connection bus bar of the negative electrode of the cell block which comprises the assembled battery shown in FIG. It is sectional drawing of the normal cell block shown in FIG. 1 and the disconnection cell block in which disconnection occurred. It is a graph which shows the relationship between the voltage and the current density of the cell which comprises the assembled battery shown in FIG. It is a graph which shows the current change of the assembled battery while the electric vehicle shown in FIG. 1 is running. It is explanatory drawing which shows the change of the variation of the internal resistance value of a cell block with respect to the absolute value of the current value difference. It is a flowchart of the disconnection detection method of this embodiment. It is a flowchart of the disconnection detection method of another embodiment. It is a flowchart of the current control method of the assembled battery which applied the disconnection detection method of this embodiment.

<Structure of an electric vehicle to which the disconnection detection method of the present embodiment is applied>
Hereinafter, the configuration of the electric vehicle 100 to which the disconnection detection method of the present embodiment is applied will be described with reference to the drawings. In the following description, the electric vehicle 100 is a hybrid vehicle driven by the motor generator 14 and the engine 16, and is capable of EV traveling traveling only by the motor generator 14, and is mounted by an external power source. Although the battery 10 will be described as a rechargeable plug-in hybrid vehicle, the present invention can be applied to other electric vehicles such as electric vehicles.

The electric vehicle 100 includes an assembled battery 10, an inverter 13 connected to the assembled battery 10 via a positive electrode line 11 and a negative electrode line 12, a motor generator 14 for driving a vehicle driven and controlled by the inverter 13, and an engine 16. Includes a control unit 70 that controls the operation of the inverter 13, the motor generator 14, the engine 16, and the charging / discharging of the assembled battery 10. Further, a start switch 19 for starting and stopping the electric vehicle 100 is attached to the driver's seat of the electric vehicle 100. The start switch 19 is connected to the control unit 70.

The output shaft of the motor generator 14 and the output shaft of the engine 16 are connected to a power dividing mechanism 15 that divides the output of the engine 16 into a driving force for the wheels 18 and a driving force for driving the motor generator 14 as a generator. There is. The output shaft of the power split mechanism 15 is configured to drive the wheels 18 via the differential gear 17.

The assembled battery 10 is formed by connecting cell blocks 20, 30, 40, 50 in series, in which a plurality of cells 21, 31, 41, 51 of a rechargeable secondary battery such as a lithium ion battery are connected in parallel. Hereinafter, the structures of the cell blocks 20, 30, 40, and 50 will be described using the cell block 20 as an example. The structures of the cell blocks 30, 40, and 50 are the same as those of the cell block 20, and for the same parts, the cell block 30 has the same ones digit in the 30s, and the cell block 40 has the same ones digit in the 40s. The cell block 50 is coded in the 50s with the same ones digit.

The cell block 20 is composed of a plurality of cylindrical lithium-ion battery cells 21, a positive electrode parallel bus bar 24, a positive electrode connection bus bar 25, a negative electrode parallel bus bar 27, and a negative electrode connection bus bar 26.

As shown in FIG. 2A, the positive electrode parallel bus bar 24 has openings 24a arranged on a flat metal plate according to the arrangement of cells 21, and a plurality of openings 24a are arranged from the peripheral edge of each opening 24a toward the center of each opening 24a. The positive electrode connection bus bar 25 is extended. As shown in FIG. 3A, the positive electrode connecting bus bar 25 is an elongated plate that is bent diagonally downward from the positive electrode parallel bus bar 24 toward the positive electrode 22 of the cell 21. As shown in FIGS. 2A and 3A, the tip 28 of the positive electrode connection bus bar 25 is connected to the positive electrode 22 by resistance welding. In this way, the positive electrodes 22 of the plurality of cells 21 are connected in parallel by the positive electrode parallel bus bars 24 and the plurality of positive electrode connection bus bars 25.

As shown in FIGS. 2B and 3A, the structures of the negative electrode parallel bus bar 27 and the negative electrode connection bus bar 26 are the same as those of the positive electrode parallel bus bar 24 and the positive electrode connection bus bar 25, and the negative electrode connection bus bar 26 is the negative electrode parallel bus bar 27. It is an elongated plate formed by bending diagonally upward from the peripheral edge of the opening 27a toward the negative electrode 23 of the cell 21. As shown in FIGS. 2B and 3A, the tip 29 of the negative electrode connection bus bar 26 is connected to the negative electrode 23 by resistance welding. The negative electrode 23 of the plurality of cells 21 is connected in parallel to the negative electrode parallel bus bar 27 and the plurality of negative electrode connection bus bars 26. Therefore, the positive electrode parallel bus bar 24 and the plurality of positive electrode connection bus bars form a parallel connection line on the positive electrode side, and the negative electrode parallel bus bar 27 and the plurality of negative electrode connection bus bars 26 form a parallel connection line on the negative electrode side. There is.

FIG. 3B shows a case where the negative electrode connection bus bar 26 of the cell 21 shown in FIG. 3A is disconnected. Hereinafter, as shown in FIG. 3B, a cell in which a disconnection has occurred will be referred to as a disconnection cell 21a, and a cell block including the disconnection cell 21a will be described as a disconnection cell block 20a.

As shown in FIG. 1, the positive electrode parallel bus bar 24 of the cell block 20 is connected to the positive electrode line 11 of the assembled battery 10, and the negative electrode parallel bus bars 27, 37, 47 of the cell block 20 to the cell block 40 are connected to the cell from the cell block 30. It is connected to the positive electrode parallel bus bars 34, 44, 54 of the block 50 by series bus bars, respectively. Further, the negative electrode parallel bus bar 57 of the cell block 50 is connected to the negative electrode line 12 of the assembled battery 10. In this way, the cell blocks 20, 30, 40, 50 are connected in series.

As shown in FIG. 1, between the positive electrode parallel bus bars 24, 34, 44, 54 of each cell block 20, 30, 40, 50 and the negative electrode parallel bus bars 27, 37, 47, 57, each cell block Voltage sensors 64, 65, 66, 67 that detect each block voltage value V1, V2, V3, V4 of 20, 30, 40, 50 are attached. Further, a voltage sensor 61 for detecting the voltage value V of the assembled battery 10 is attached between the positive electrode line 11 and the negative electrode line 12 of the assembled battery 10, and the current value I of the assembled battery 10 is attached to the positive electrode line 11. A current sensor 62 for detecting the voltage is attached. Further, a temperature sensor 63 for detecting the temperature T of the assembled battery 10 is attached to the assembled battery 10. Further, as shown in FIG. 1, a connector 90 that can be connected to an external power source is connected to the positive electrode line 11 and the negative electrode line 12.

The control unit 70 is a sensor to which a CPU 71 that performs information processing and calculation internally, a memory 72 that stores a control program, control data, and the like, a voltage sensor 61, 64 to 67, a current sensor 62, and a temperature sensor 63 are connected. It is a computer having a device interface 73, and the CPU 71, the memory 72, and the sensor / device interface 73 are connected to each other by a data bus 74.

The motor generator 14 receives the electric power output from the assembled battery 10 to drive the electric vehicle 100, converts the kinetic energy generated during braking of the electric vehicle 100 into electric power, and charges the assembled battery 10. Therefore, while the electric vehicle 100 is running, the assembled battery 10 is repeatedly charged and discharged. The current value I of the assembled battery 10 is such that the discharge current is positive (+) and the charge current is negative (−).

<Outline of current density characteristics and disconnection detection method for cell voltage>
Next, with reference to FIGS. 4 to 6, the characteristics of the current density j with respect to the voltage η of the cells 21, 31, 41, and 51 shown in FIG. 1 and the outline of the disconnection detection method of the cell blocks 20, 30, 40, and 50. Will be described. Since the cells 21, 31, 41, and 51 have the characteristics of the current density j with respect to the same voltage η, the cell 21, the cell block 20 will be described in the following description. In FIG. 4, the current density j at the time of discharging the cell 21 is positive (+), and the current density j at the time of charging is negative (−).

As shown in FIG. 4, in the range A where the current density j of the cell 21 is between + j0 and −j0, the voltage η and the current density j have a linear relationship. This means that when the current density j is in the range A, the internal resistance of the cell 21 is substantially constant. On the other hand, in the range where the current density j of the cell 21 is larger than + j0 and the current density j is smaller than −j0, the voltage η and the current density j have a non-linear relationship. As shown in FIG. 4, in the range where the current density j is larger than + j0, the degree of increase in the voltage η decreases as the current density j increases. Further, in the range where the current density j is smaller than −j0, the degree of decrease in the voltage η decreases as the current density j decreases. This means that in the range where the current density j is larger than + j0 or smaller than −j0, the larger the absolute value of the current density j, the smaller the internal resistance of the cell 21.

When the positive electrode connection bus bar 25 or the negative electrode connection bus bar 26 of the cell block 20 composed of the cells 21 having the characteristics of voltage η and current density j as shown in FIG. 4 is disconnected as shown in FIG. 3 (b). think of. When a disconnection occurs, no current flows through the disconnection cell 21a, so that the number of cells 21 through which the current flows in the disconnection cell block 20a decreases. Therefore, the current density j of the cell 21 of the disconnection cell block 20a becomes large. When the current density j of the cell 21 is in the range A between + j0 and −j0 shown in FIG. 4, the internal resistance of the cell 21 does not change even if the current density j of the cell 21 changes. Therefore, the relationship between the resistance increase rate of the disconnection cell block 20a and the number of disconnections is as described above (Equation 1).

Resistance increase rate = (number of parallels) / (number of parallels-number of disconnections) ... (Equation 1)

Further, the resistance increase rate is calculated from the block voltage value V1 of the disconnection cell block 20a detected by the voltage sensor 64 and the block voltage value V2 of another normal cell block 30 without disconnection detected by the voltage sensor 65. it can. Therefore, when the current density j of the cell 21 is in the range A between + j0 and −j0 shown in FIG. 4, the number of disconnections can be calculated from (Equation 1) by detecting the block voltage values V1 and V2. it can.

On the other hand, in the range where the current density j of the cell 21 is larger than + j0 or smaller than −j0, the larger the absolute value of the current density j, the smaller the internal resistance of the cell 21, so the resistance increase rate and the number of disconnections. , The relationship between the number of parallels is as shown in (Equation 2) below.

Resistance increase rate = (number of parallels) / (number of parallels-number of disconnections) -C ... (Equation 2)

In (Equation 2), C is a term representing a decrease in the resistance increase rate due to a change in the current density j. C varies depending on the current density j, the temperature of the cell 21, and the like, and is not constant. Therefore, in the range where the current density j of the cell 21 is larger than + j0 or smaller than −j0, even if the resistance increase rate can be calculated by detecting the block voltage values V1 and V2, the C term is unknown. Therefore, the number of disconnections cannot be calculated from (Equation 2). Further, when the number of disconnections is calculated using (Equation 1), an error is generated in the number of disconnections by the amount of the C term, and the disconnection cannot be detected accurately.

Therefore, the accuracy of the disconnection detection can be improved by executing the disconnection detection in a state where the current density j of the cell 21 is small and the internal resistance does not change due to the current density j. Therefore, in the present embodiment, as shown in FIG. 5, the current value I of the assembled battery 10 and the block voltage values V1 to V4 are detected at a short predetermined time interval Δt, and the first current value I at the present time (t) is detected. The first condition for executing the disconnection detection is that the product of (t) and the second current value I (t-1) at the previous detection timing (t-1) becomes negative.

On the other hand, when the current density j of the cell 21 is very small, the internal resistance values of the cell blocks 20, 30, 40, and 50 can vary, so that the disconnection cannot be detected with high accuracy. Therefore, in the present embodiment, as shown in FIG. 6, the first current value I (t) at the present time (t) calculated by the following (Equation 3) and the detection timing (t-1) immediately before are set. Current value difference ΔI from the second current value I (t-1)

ΔI = | I (t-1) -I (t) | ... (Equation 3)

The second condition for executing disconnection detection is that the value exceeds the predetermined threshold value S1.

Then, when the first condition and the second condition are satisfied, the resistance between the cell blocks 20, 30, 40, 50 is based on the block voltage values V1 to V4 of the cell blocks 20, 30, 40, 50. The ratio is calculated, and the number of disconnections is calculated based on the calculated resistance ratio.

<Details of disconnection detection method>
Hereinafter, a disconnection detection method when the electric vehicle 100 is traveling will be described with reference to FIG. 7. In the following description, it is assumed that the disconnection detection method of the present embodiment is executed by the control unit 70 of the electric vehicle 100 executing each step operation shown in the flowchart shown in FIG. 7.

When the electric vehicle 100 is traveling, as shown in FIG. 5, the assembled battery 10 repeats discharging and charging. As shown in steps S101, S102, and FIG. 5 shown in FIG. 7, the control unit 70 detects the current value I of the assembled battery 10 and the block voltage values V1 to V4 at predetermined time intervals Δt. The control unit 70 stores the detected current value I of the assembled battery 10 and each block voltage value V1 to V4 in the memory 72. The predetermined time interval Δt is, for example, a short time of about 100 to 200 msec.

In step S103 of FIG. 7, the control unit 70 sets the first current value I (t) at the present time (t) and the second current value I (t-1) at the previous detection timing (t-1). It is read from the memory 72, its product (I (t-1) × I (t)) is calculated, and it is determined whether or not the product (I (t-1) × I (t)) is negative. Then, when the product (I (t-1) × I (t)) is negative, the previous detection timing (t-1) and the current time (t) are as shown between the times t0 and t1 in FIG. The current of the assembled battery 10 is switched from discharging to charging, and the previous detection timing (t-1) and the current time (t) are short predetermined time intervals after the current is switched from discharging to charging. It is determined that the value is within Δt and both the first current value I (t) and the second current value I (t-1) are close to zero. Further, when the product (I (t-1) × I (t)) is negative, the control unit 70 has the previous detection timing (t-1), such as between the times t2 and t3 in FIG. The current of the assembled battery 10 is switched from charging to discharging between and the current time (t), and the previous detection timing (t-1) and the current time (t) are after the current is switched from charging to discharging. It is determined that the first current value I (t) and the second current value I (t-1) are both within a short predetermined time interval Δt and are close to zero.

Then, if YES in step S103 of FIG. 7, the control unit 70 determines that the first condition of the disconnection detection execution is satisfied, and proceeds to step S104 of FIG. On the other hand, if NO in step S103 of FIG. 7, the control unit 70 determines that the first condition for executing the disconnection detection is not satisfied, and ends the routine without executing the disconnection detection. Then, the control unit 70 returns to step S101 of FIG. 7 and detects the current value I and the block voltage values V1 to V4 at the next detection timing after Δt.

In step S104 of FIG. 7, the control unit 70 reads the current (t) first current value I (t) from the memory 72 and the second current value I (t) at the previous detection timing (t-1). The current value difference ΔI (= | I (t-1) -I (t) |) in the absolute value of the difference of -1) is calculated. Then, the control unit 70 proceeds to step S105 of FIG. 7 and determines whether or not the current value difference ΔI exceeds the predetermined threshold value S1. Since the resistance value of the cell 21 changes depending on the temperature of the cell 21, the threshold value S1 may be changed based on the temperature T of the assembled battery 10 detected by the temperature sensor 63.

If the control unit 70 determines YES in step S105 of FIG. 7, it determines that the second condition of the disconnection detection execution is satisfied, and proceeds to step S106 of FIG. On the other hand, if NO is determined in step S105 of FIG. 7, the control unit 70 determines that the second condition for executing the disconnection detection is not satisfied, and ends the routine without executing the disconnection detection. Then, the control unit 70 returns to step S101 of FIG. 7 and detects the current value I and the block voltage values V1 to V4 at the next detection timing after Δt.

From step S106 to step S109 shown in FIG. 7, the control unit 70 executes disconnection detection as described below. First, in step S106 of FIG. 7, the control unit 70 has the voltage values V1 (t) to V4 (t) of the first block at the present time (t) of each cell block 20, 30, 40, 50, which is one before. Each block voltage value difference ΔV1 to ΔV4 of each second block voltage value V1 (t-1) to V4 (t-1) at the detection timing (t-1) is calculated as follows.

ΔV (n) = | Vn (t-1) -Vn (t) | ... (Equation 4)
(N is the number of the detected block voltage, 1 to 4)

After calculating each block voltage value difference ΔV1 to ΔV4, the control unit 70 proceeds to step S107 in FIG.

Next, as shown in step S107 of FIG. 7, the control unit 70 calculates the resistivity ratio between the cell blocks 20, 30, 40, and 50 by the following (formula 5).

Resistivity i = (ΔV (n) / ΔV (n + 1)) ... (Equation 5)

The resistivity ratio i using (Equation 5) is calculated for each combination of cell blocks 20, 30, 40, and 50 for which resistance values are compared. i is the number of the combination to be calculated, and is an integer of 1 or more. For example, when comparing the resistance value of the cell block 20 and the resistance value of the cell block 30, the resistance ratio 1 = (ΔV (1) / ΔV (2)), the resistance value of the cell block 40 and the resistance value of the cell block 50. When comparing with the resistance value, the resistance ratio 2 = (ΔV (3) / ΔV (4)) is calculated. The combination of the cell blocks 20, 30, 40, 50 for calculating the resistance ratio i is arbitrary, but for example, the resistance ratio i may be calculated for all the combinations of the plurality of cell blocks 20, 30, 40, 50. Then, the resistivity ratio i may be calculated for a specific combination determined in advance. After calculating the resistance ratio i, the control unit 70 proceeds to step S108 of FIG.

In step S108 of FIG. 7, the control unit 70 calculates the resistivity ratio i for comparison as follows and stores it in the memory 72. As shown in (Equation 6) below, the control unit 70 calculates the value of the resistivity ratio i using (Equation 5) when the resistivity ratio i calculated using (Equation 5) is 1 or more. It is stored in the memory 72 as the resistivity ratio i for comparison. Further, as shown in the following (Equation 7), the control unit 70 stores the reciprocal of the resistance ratio i calculated using (Equation 5) as the comparison resistance ratio i when the resistance ratio i is less than 1. Store in 72.

Comparison resistance ratio i = resistance ratio i (resistor ratio i ≧ 1) ・ ・ ・ (Equation 6)
Comparison resistance ratio i = 1 / resistance ratio i (resistor ratio i <1) ... (Equation 7)

Then, in step S108 of FIG. 7, the control unit 70 sets the maximum value in the comparison resistance ratio i as the maximum resistance ratio, as shown in the following (Equation 8).

Maximum resistivity = MAX (comparative resistivity i) ... (Equation 8)

After calculating the maximum resistance ratio, the control unit 70 proceeds to step S109 of FIG.

The control unit 70 executes the abnormality detection process in step S109 of FIG. The abnormality detection process is, for example, a process of outputting a signal of disconnection when the maximum resistance ratio exceeds a predetermined threshold value, or a process of calculating the number of disconnections from the maximum resistance ratio and (Equation 1) and outputting. This is a process such as a process of identifying and outputting a cell block in which a disconnection has occurred.

As shown in FIG. 5, the disconnection detection method of the embodiment described above detects the current value I and the block voltage values V1 to V4 of the assembled battery 10 at a short predetermined time interval Δt, and is the current (t) th. The first condition that the product of the first current value I (t) and the second current value I (t-1) at the previous detection timing (t-1) is negative, and the current state (t) The second condition that the current value difference ΔI between the first current value I (t) and the second current value I (t-1) at the previous detection timing (t-1) exceeds a predetermined threshold value S1. When both of the above are satisfied, the disconnection detection is executed. As a result, the current densities j of the cells 21, 31, 41, 51 are small and the internal resistance does not change due to the current densities j, and the current densities j of the cells 21, 31, 41, 51 are the cell blocks 20, 30, Since the disconnection detection is executed in a state where the internal resistance values of 40 and 50 are large enough not to vary, the accuracy of the disconnection detection of the assembled battery 10 can be improved.

<Other disconnection detection methods>
Next, another embodiment of the present invention will be described with reference to FIG. The same operations as those described with reference to FIG. 7 are designated by the same reference numerals and the description thereof will be omitted.

In the embodiment shown in FIG. 8, as shown in steps S201 to S202 of FIG. 8, the current value difference ΔI calculated in (Equation 3) in step S104 of FIG. 8 and (Equation 4) in step S106 of FIG. 8 ΔR (n) is calculated from the calculated block voltage value difference ΔV (n), and the maximum resistance ratio is calculated using this ΔR (n).

The control unit 70 calculates ΔR (n) by the following (Equation 9) in step S201 of FIG.

ΔR (n) = ΔV (n) / ΔI ・ ・ ・ (Equation 9)
(N is the number of the detected block voltage, 1 to 4)

After calculating ΔR (n), the control unit 70 proceeds to step S202 of FIG.

In step S202 of FIG. 8, the control unit 70 calculates the resistance ratio i for each combination of the cell blocks 20, 30, 40, and 50 for which the resistance values are compared according to the following (Equation 10).

Resistivity i = (ΔR (n) / ΔR (n + 1)) ... (Equation 10)
(I is the number of the combination to be calculated, and is an integer of 1 or more)

After calculating the resistance ratio i, the control unit 70 proceeds to step S108 in FIG.

In step S108 of FIG. 8, the control unit 70 calculates the resistivity ratio i for comparison in (Equation 6) and (Equation 7) in the same manner as described above with reference to FIG. 7, and uses (Equation 8) to maximize. Calculate the resistivity. Then, the abnormality detection process is performed in step S109 of FIG.

This embodiment has the same effect as that of the embodiment described above with reference to FIG. 7.

<Current control method of the assembled battery to which the disconnection detection method of the embodiment is applied>
Next, with reference to FIG. 9, a current control method of the assembled battery 10 to which the disconnection detection method of the present embodiment described with reference to FIG. 7 is applied will be described. The operation from step S101 to step S108 in FIG. 9 is the same as the disconnection detection method of the present embodiment described with reference to FIG. 7. The current control method shown in FIG. 9 executes current control in step S301 of FIG. 9 as follows.

As described above, the disconnection detection method of the present embodiment can accurately obtain the maximum resistivity. The maximum resistance ratio is the ratio of the resistance value of the cell block in which no disconnection has occurred to the resistance value of the cell block having the largest number of disconnections, and can be calculated by the following (Equation 11).

Maximum resistivity = (number of parallels) / (number of parallels-maximum number of disconnections) ... (Equation 11)

Further, the cell current flowing through the cell 21 of the disconnected cell block 20a having the largest number of disconnections is the maximum resistance ratio of the current value I detected by the current sensor 62, and this current flows through the cells 21, 31, 41, 51. It becomes the maximum current.

Maximum cell current value = detected current value x maximum resistivity ratio ... (Equation 12)

From the above, when the cells 21, 31, 41, 51 are lithium ion secondary batteries, the current is limited when the control current value shown in the following (Equation 13) reaches the limit current of lithium precipitation. , Lithium precipitation suppression control can be performed in consideration of disconnection.

Control current value = Detected current value x (maximum resistance ratio + setting error) ... (Equation 13)

Further, in the high rate suppression current control of the lithium ion battery, the cell internal overheat protection control, etc., by controlling the current limit etc. by the control current value calculated by (Equation 13), the high rate suppression in consideration of disconnection and the cell internal Overheat protection can be performed.

In this way, the maximum resistance ratio is accurately obtained by the disconnection detection method of the present embodiment, and the current of the assembled battery 10 is limited based on the maximum resistance ratio to suppress the current in consideration of the disconnection of the assembled battery 10. , Lithium precipitation, deterioration, etc. can be effectively suppressed.

10 sets of batteries, 11 positive electrode line, 12 negative electrode line, 13 inverter, 14 motor generator, 15 power split mechanism, 16 engine, 17 differential gear, 18 wheels, 19 start switch, 20, 30, 40, 50 cell block, 20a disconnection Cell block, 21,31,41,51 cell, 21a disconnection cell, 22 positive electrode, 23 negative electrode, 24,34,44,54 positive electrode parallel bus bar, 24a, 27a opening, 25,35,45,55 positive electrode connection bus bar, 26 , 36, 46, 56 Negative electrode connection bus bar, 27, 37, 47, 57 Negative electrode parallel bus bar, 28, 29 Tip, 61, 64-67 Voltage sensor, 62 Current sensor, 63 Temperature sensor, 70 Control unit, 71 CPU, 72 Memory, 73 sensor / equipment interfaces, 74 data buses, 90 electrodes, 100 electric vehicles.

Claims (1)

This is a method for detecting disconnection of the parallel connection line of an assembled battery in which cell blocks in which a plurality of cells are connected in parallel by a parallel connection line are connected in series in multiple stages.
The current of the assembled battery is detected at a time interval of 100 to 200 msec , and the current is detected.
When the product of the current first current value and the second current value at the previous detection timing is negative, and the absolute value of the current value difference between the first current value and the second current value is predetermined. A disconnection detection method for executing disconnection detection of the parallel connection line when the threshold value of is exceeded.

Images