JP5949147B2 - Battery state determination method, battery control device, and battery pack - Google Patents

Description

  The present invention relates to a technique for using a battery (battery cell) equipped with a current interruption mechanism.

  Currently, rechargeable batteries (secondary batteries) are widely used. Actually, the voltage obtained between the terminals of one battery is relatively small. For this reason, in the battery which needs to generate a higher voltage, the structure which connected the several battery cell which is a battery used as a component in series is employ | adopted.

  In the secondary battery, the deterioration of characteristics increases due to overdischarge and overcharge. Unbalanced battery capacity between battery cells leads to a decrease in battery capacity of the entire battery. In this case, in an apparatus using a battery having a configuration in which battery cells are connected in series, voltage monitoring is performed for each battery cell, and the monitoring result is reflected in each control of discharging and charging. The characteristic deterioration due to overcharge is suppressed.

  Even if discharging and charging are controlled by voltage monitoring, there is a possibility that the control cannot be performed properly for some reason. For this reason, battery cells are often equipped with a current interrupt device (CID: Current Interrupt Device).

  The current interruption mechanism is, for example, a safety device that operates due to an increase in pressure inside the battery cell, and interrupts the current due to an increase in internal pressure. Therefore, at a high temperature at which the internal pressure increases, for example, at the time of overcharging or when an overcurrent is generated, the supply of current to the battery cell and the supply of current from the battery cell can be blocked by the current blocking mechanism. Thereby, when a battery cell equipped with a current interruption mechanism is used, higher safety can be ensured.

The charge control by voltage monitoring is usually performed so that the current interrupt mechanism does not operate, that is, the current is not interrupted. For this reason, there is a possibility that charge control cannot be performed properly in the operation of the current interrupt function. Accordingly, in a device equipped with a battery, when a current interrupting mechanism is activated, it is common to disconnect the path used for discharging from the battery and charging the battery.
The activated current interrupting mechanism is automatically deactivated, for example, when the internal pressure is lowered. By releasing the operation, the battery returns to a state in which a current can flow and can be used. In a device equipped with a battery, it is possible to remove a restriction (for example, a restriction that the device cannot be used) due to the operation of the current interrupt mechanism. From this, it seems important to detect the release of the operation of the current interruption mechanism with high accuracy.

JP-A-8-191544 Japanese Patent Laid-Open No. 10-270091 JP 2011-200071 A JP 2000-236247 A

  An object of this invention is to provide the technique for detecting (determining) the operation | movement cancellation | release of the electric current interruption mechanism mounted in the battery cell with high precision.

  One aspect of the present invention is a method for determining a state of a battery in which charging / discharging is performed by a computer, the computer detects a voltage value between terminals of the battery, and uses the detected voltage value, A time differential value of the voltage value is calculated, and based on the time differential value obtained by the calculation, it is determined as a state of the battery whether or not a current interrupting mechanism mounted on the battery has been deactivated.

  Another aspect of the present invention is a battery control apparatus that controls a plurality of battery cells to be charged / discharged, and each battery cell having a current interrupting mechanism is provided for each first battery cell. Voltage value acquisition means for acquiring a voltage value between terminals of the first battery cell; calculation means for calculating a time differential value of the voltage value using the voltage value acquired by the voltage value acquisition means; and the calculation State determining means for determining whether or not the current interrupting mechanism of the first battery cell has been deactivated based on the time differential value calculated by the means.

  Yet another embodiment of the present invention is a battery pack including a plurality of connected battery cells to be charged / discharged, and for each first battery cell that is a battery cell including a current interrupting mechanism, A voltage value detecting means for detecting a voltage value between terminals of the first battery cell; a calculating means for calculating a time differential value of the voltage value using the voltage value detected by the voltage value detecting means; State determining means for determining whether or not the current interrupting mechanism of the first battery cell has been deactivated based on the time differential value calculated by the means.

  In the present invention, it is possible to detect (determine) the operation release of the current interrupt mechanism mounted on the battery or the battery cell with high accuracy.

It is a figure explaining the structural example of the battery pack by this embodiment. It is a figure explaining the time change of the voltage value accompanying an action | operation of an electric current interruption | blocking mechanism, and action | operation cancellation | release, and an electric current value. It is a flowchart of a CID operation release determination process.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating a configuration example of the battery pack according to the present embodiment.
The battery pack 1 is assumed to be mounted on a vehicle such as an electric vehicle (EV) or a plug-in hybrid vehicle (PHV). As shown in FIG. 1, a battery pack 1 includes a battery control ECU (Electronic Control Unit) 11, a plurality of battery cells 120, a battery 12 connected in series, an SMR (System Main Relay) 13, a current sensor 14, and a temperature. A sensor 15 is provided.

  A vehicle on which the battery pack 1 is mounted is provided with an ECU (noted as “HV / PHV ECU” in FIG. 1, hereinafter referred to as “vehicle ECU”) 2 that controls the entire vehicle system. . When the battery pack 1 is mounted on a vehicle, the battery control ECU 11 of the battery pack 1 becomes communicable with the vehicle ECU 2, and power is supplied to the battery control ECU 11 from, for example, the power supply 3 of the vehicle body. With this power supply, the battery control ECU 11 becomes operable and performs an operation in accordance with an instruction from the vehicle ECU 2. The power supply to the battery control ECU 11 may be performed from one or more than the power source 3. The type and number of power supplies that supply power to the battery control ECU 11 are not particularly limited.

  The battery control ECU 11 is, for example, a CPU (Central Processing Unit), a memory, a recording medium storing a program (firmware) executed by the CPU, and a computer (data processing device) including a plurality of interfaces. The battery control device according to the present embodiment is realized by being mounted on the battery control ECU 11. The battery state determination method according to the present embodiment is also executed by the battery control ECU 11.

  As shown in FIG. 1, each battery cell 120 constituting the battery 12 includes a battery cell main body 121 and a current interruption mechanism (CID) 122. The current interruption mechanism 122 is a safety device that forcibly disconnects the electrical connection due to, for example, an increase in the internal pressure of the battery cell body 121. The internal pressure increases as the temperature increases. The temperature rises due to heating by heat transfer from the heating element, overcharge, overdischarge, or overcurrent generation (for example, short circuit). The current interruption mechanism 122 suppresses a decrease in safety due to such a cause.

  Each battery cell 120 is provided with a voltage sensor 16 for detecting a voltage value between its terminals. This voltage sensor 16 is a voltage value detection means for detecting the voltage value between the terminals of each battery cell 120. In addition to the determination of the release of the operation of the current interrupt mechanism 122, overdischarge and overcharge prevention, Further, it is used for applications such as balancing the battery capacity between the battery cells 120.

  In the present embodiment, the battery 12 has a configuration in which a plurality of battery cells 120 including the current interrupting mechanism 122 are connected in series, but may have a different configuration. That is, the battery 12 may have a configuration in which, for example, a plurality of battery cells 120 including the current interrupting mechanism 122 and a plurality of battery modules connected in series are connected in parallel. When the arrangement of the battery cell 120 that is difficult to deteriorate in characteristics is known in advance, the battery cell 120 that does not include the current interruption mechanism 122 may be used as the battery cell 120. For this reason, the battery 12 mounted on the battery pack 1 is not limited to the one shown in FIG.

  The battery 12 is used for power supply to a motor (not shown). The rated voltage of the battery 12 is lower than the rated voltage of the motor. For this reason, the electric power generated by the discharge from the battery 12 is supplied to a step-up converter (not shown) via the SMR 13.

  The motor becomes a generator that generates electric power during charging. The electric power generated by the motor is stepped down by, for example, a step-up converter and supplied to the battery 12 for charging via the SMR 13. Accordingly, the SMR 13 functions as a relay unit that can turn on / off a current provided on a path for discharging from the battery 12 and charging the battery 12. The battery control ECU 11 functions as a control unit that switches current on and off in the SMR 13 as necessary.

  The current sensor 14 is current value detection means for detecting a current value supplied to the battery 12 or a current value supplied from the battery 12. The temperature sensor 15 is temperature detection means for detecting the temperature in the battery pack 1. The current value detected by the current sensor 14 and the temperature detected by the temperature sensor 15 are input to the battery control ECU 11 and processed in the same manner as the voltage value detected by the voltage sensor 16 of each battery cell 120. Thereby, the battery control ECU 11 functions as current value acquisition means for acquiring the current value detected by the current sensor 14 and voltage value acquisition means for acquiring the voltage value detected by each voltage sensor 16.

  The direction of the current flowing through the battery 12 differs between discharging and charging. Thereby, the sign of the current value detected by the current sensor 14 changes depending on the direction of the current. When the current interrupting mechanism 122 is activated, no current flows through the battery 12, so that the current value detected by the current sensor 14 is 0 or a value close to 0. The increase in the internal pressure of the battery cell main body 121 that operates the current interrupting mechanism 122 is usually caused by the current flowing through the battery cell main body 121 unless it is heated by heat transfer from some heating element. The battery control ECU 11 can recognize a situation in which a current flows through the battery 12 based on a notification or an instruction from the vehicle ECU 2. From this, the battery control ECU 11 determines that the current interrupting mechanism 122 has been activated when the current value detected by the current sensor 14 becomes 0 or a value close to 0 when a current flows through the battery 12. The SMR 13 is turned off, that is, the connection by the SMR 13 is cut off, and the determination result is notified to the vehicle ECU 2.

  When the SMR 13 is turned off, no current flows through the battery 12 even when the current interrupt mechanism 122 is deactivated. Further, the vehicle ECU 2 that is notified of the operation of the current interrupt mechanism 122 can perform control so that no current flows through the battery 12. For this reason, in this embodiment, it is determined whether to release the operation of the current interrupting mechanism 122 using the voltage value detected by the voltage sensor 16 provided for each battery cell 120. Thereby, the battery control ECU 11 functions as a state determination unit that determines whether to release the operation of the current interruption mechanism 122 of the battery 12 (battery cell 120). A method for determining the release of the operation of the current interrupt mechanism 122 will be specifically described with reference to FIG.

  FIG. 2 is a diagram for explaining the time change of the voltage value and the current value accompanying the operation of the current interrupting mechanism and the cancellation of the operation. FIG. 2A shows an example of the time change of the voltage value detected by the voltage sensor 16 of the battery cell 120 in which the current interruption mechanism (CID) 122 is operated, and FIG. 2B is detected by the current sensor 14. The example of the time change of the made electric current value is represented. The current interrupting mechanism 122 was activated at time t1, and the operation was released at time t2. The release of the operation of the current interrupt mechanism 122 is described as “CID re-conduction”.

  The voltage value detected by the voltage sensor 16 becomes indefinite after time t1 as the current flow is stopped due to the operation of the current interrupt mechanism 122. In other words, the value is not reliable. On the other hand, the current value detected by the current sensor 14 rapidly decreases from the previous value to 0 as the current flow is stopped due to the operation of the current interrupt mechanism 122.

  When the operation of the current interrupting mechanism 122 is not generated by heat transfer from the outside, the generation of Joule heat is stopped by the current interrupting, and the internal pressure of the battery cell body 121 in which the current interrupting mechanism 122 is operated decreases. As a result, the activated current interrupting mechanism 122 is deactivated at time t2.

  Even if the current interrupting mechanism 122 is deactivated, the current value detected by the current sensor 14 remains 0 because the SMR 13 is off. However, the voltage value detected by the voltage sensor 16 is a value that represents the voltage between the terminals of the battery cell 120 because the voltage is generated between the terminals of the battery cell 120 with the release of the operation of the current interrupt mechanism 122. For this reason, even if the voltage value detected by the voltage sensor 16 is an unreliable value due to the cessation of the current flow accompanying the operation of the current interruption mechanism 122, the voltage sensor 16 immediately before the operation of the current interruption mechanism 122 is released. As long as the voltage value detected by is not an appropriate value, a relatively large difference occurs in the voltage value detected by the voltage sensor 16 before and after the operation of the current interrupting mechanism 122 is released. This embodiment pays attention to this, and determines the release of the operation of the current interrupt mechanism 122.

  The battery control ECU 11 determines a time differential value of the voltage value detected by the voltage sensor 16, for example, the voltage value detected last time by the voltage sensor 16 and the voltage value detected this time in order to determine the release of the operation of the current interrupt mechanism 122. Calculate the difference value. Thereby, battery control ECU11 functions as a calculating means which calculates a time differential value.

  The battery control ECU 11 compares the calculated absolute value of the difference value with a predetermined threshold value, and if the absolute value is larger than the threshold value, the battery control ECU 11 considers that the current interrupt mechanism 122 may have been released. The reason why the absolute value is compared with the threshold value is that the voltage value detected by the voltage sensor 16 becomes indefinite when the flow of current stops with the operation of the current interrupt mechanism 122. In FIG. 2A, the portion where the voltage value is indefinite is represented by changing from the solid line to the broken line, but the change in the voltage value represented by the broken line is an example, and the voltage detected during the period of indefiniteness. The value is not necessarily in a downward trend. Thereby, the sign of the difference value can be either positive or negative. The difference value (time differential value) is hereinafter referred to as “voltage change value”.

  Focusing on the fact that the voltage value detected by the temperature sensor 16 of the battery cell 120 in which the current interruption mechanism 122 is activated becomes indefinite, the battery cell 120 in which the current interruption mechanism 122 has been activated can be identified. The specification can be performed by extracting the battery cell 120 in which the voltage value detected by the voltage sensor 16 changes unnaturally. This is because, in a situation where no current flows through the battery 12, it is unlikely that the detected voltage value will change relatively large other than the battery cell 120 in which the current interrupt mechanism 122 is operating. Therefore, the determination of the release of the operation of the current interruption mechanism 122 may be performed only on the specified battery cell 120, that is, the battery cell 120 on which the possibility that the current interruption mechanism 122 may be operating. As described above, since it is possible to identify the battery cell 120 that is considered to have the possibility that the current interrupting mechanism 122 is operating, it is assumed that the battery cell 120 that should be determined to release the operation of the current interrupting mechanism 122 is known.

  In the present embodiment, in order to determine the cancellation of the operation of the current interrupt mechanism 122 with higher accuracy, when the absolute value of the voltage change value is larger than the threshold value, it is confirmed whether or not the detected voltage value is within a predetermined range. Like to do. This range is, for example, a range from a voltage value at which discharge of the battery cell 120 is stopped (hereinafter referred to as “normal lower limit threshold”) to a rated voltage value of the battery cell 120 (hereinafter referred to as “normal upper limit threshold”). Thereby, the determination of the release of the operation of the current interruption mechanism 122 is performed when the absolute value of the voltage change value is larger than the threshold value and the detected voltage value is within the range.

  In this way, in this embodiment, it is determined whether or not the current interrupting mechanism 122 is released through a two-stage comparison. Thereby, even if the voltage value detected by the voltage sensor 16 temporarily fluctuates relatively large, it is possible to suppress erroneous determination that the current interrupt mechanism 122 has been deactivated. For this reason, the operation release of the current interrupt mechanism 122 can be determined with higher accuracy. Since the voltage change value is used for the operation release determination of the current interrupt mechanism 122, the determination can be performed quickly.

  By determining (detecting) the release of the operation of the current interrupt mechanism 122 with high accuracy, the use of the battery 12 in a usable state can be restarted in a timely manner while ensuring safety. The battery control ECU 11 can shift to a state in which the battery 12 can be discharged or charged by switching the SMR 13 from off to on. When the vehicle ECU 2 has issued a warning or speed limit by notifying the operation of the current interrupting mechanism 122 from the battery control ECU 11, the vehicle ECU 2 cancels the operation by notifying the operation of the current interrupting mechanism 122 from the battery control ECU 11. be able to. For this reason, the user can use the vehicle more comfortably while ensuring safety.

  It is not always necessary to use the detected voltage value to determine whether to release the operation of the current interrupt mechanism 122. For example, in a situation where no current flows through the battery 12, the voltage value of the battery cell 120 in which the current interruption mechanism 122 is activated is determined when the current interruption mechanism 122 is deactivated unless the temperature detected by the temperature sensor 15 is increased. It is unlikely that it is rising. This is because if the temperature detected by the temperature sensor 15 is not increased, the internal pressure of the battery cell body 121 is considered to have decreased due to the temperature decrease. If the temperature is lowered, the voltage value between the terminals of the battery cell 120 is usually small. In addition, the voltage value detected by the voltage sensor 16 when the current is interrupted is unlikely to rapidly change in an increasing direction even if it is indefinite. Therefore, in consideration of the direction in which the voltage value detected by the voltage sensor 16 changes and the amount of the change, the operation of the current interrupting mechanism 122 is canceled when the voltage value changes relatively large in the increasing direction. May be determined. That is, two threshold values are prepared, and when it is confirmed that the voltage change value is larger than the larger threshold value, the current interrupt mechanism 122 may determine that the operation is cancelled. If the voltage change value is less than or equal to the larger threshold value and greater than the smaller threshold value, it may be determined whether or not the current interrupting mechanism 122 is further deactivated using the detected voltage value. .

  FIG. 3 is a flowchart of the CID operation release determination process. This determination process is a process for the battery control ECU 11 to detect the release of the operation of the current interrupt mechanism 122 operated by the battery cell 120, and for example, a certain time determined from the sampling time for the voltage sensor 16 to sample the voltage value. It is executed every time. Next, the process executed by the battery control ECU 11 to determine the release of the operation of the current interrupt mechanism 122 as described above will be described in detail with reference to FIG.

  As described above, the battery cell 120 that should be determined to release the operation of the current interrupt mechanism 122 can be specified in advance. The number of specified battery cells 120 is not necessarily one. However, in FIG. 3, for the sake of convenience, it is assumed that the number of specified battery cells 120 is only one, and the flow of processing is shown.

  First, in S1, the battery control ECU 11 determines whether or not the current interruption mechanism 122 of any battery cell 120 is operating. When the battery control ECU 11 determines that the current interrupting mechanism 122 has been activated, the battery control ECU 11 saves this as a history in a memory (not shown) and identifies a battery cell 120 that may have the possibility of the current interrupting mechanism 122 being activated. Then, the identification information representing the specified battery cell 120 is stored in the memory. Recording in the memory that the current interruption mechanism 122 has been deactivated is performed when it is confirmed that the current interruption mechanism 122 has been deactivated in all of the battery cells 120 represented by the stored identification information. From this, if the recording that the current interrupting mechanism 122 has been released is not recorded after the recording that the current interrupting mechanism 122 that was stored immediately before is activated, the determination of S1 is Y (Yes). To S2. When the recording that the operation of the current interrupting mechanism 122 has been released has been performed, the determination of S1 is N (No). In this case, since it is not necessary to determine whether to release the operation of the current interrupt mechanism 122, the CID operation release determination process ends here.

  In S2, the battery control ECU 11 takes in a voltage value from each voltage sensor 16 and calculates a voltage change value for each battery cell 120 in which the identification number is stored. The calculation of the voltage change value is performed by subtracting the previously acquired voltage value from the currently acquired voltage value. In FIG. 3, “voltage change value = d (voltage value) dt” is expressed as a formula for calculating the voltage change value.

  In S3 following S2, the battery control ECU 11 determines whether or not the absolute value of the voltage change value is larger than a threshold value (denoted as “CID reconducting threshold value” in FIG. 3). If the voltage change value is larger than the threshold value, the determination in S3 is Y and the process proceeds to S4. If the voltage change value is less than or equal to the threshold value, the determination in S3 is N, and the CID operation release determination process ends here.

  In S4, the battery control ECU 11 determines whether or not the voltage value acquired this time is within a range limited by the normal lower limit threshold and the normal upper limit threshold. If the acquired voltage value is equal to or lower than the normal lower limit threshold or equal to or higher than the normal upper limit threshold, the determination in S4 is N, and the CID operation release determination process ends here. On the other hand, if the acquired voltage value is greater than the normal lower limit threshold and less than the normal upper limit threshold, the determination in S4 is Y, and the process proceeds to S5.

  In S <b> 5, the battery control ECU 11 records the fact in the memory as a history and notifies the vehicle ECU 2 of the determination result, etc., assuming that the operated current interrupting mechanism 122 is released. Thereafter, the CID operation release determination process ends.

  As described above, when the vehicle ECU 2 has issued a warning or a speed limit by notifying the operation of the current interrupting mechanism 122 from the battery control ECU 11, the vehicle ECU 2 receives an operation canceling notification of the current interrupting mechanism 122 from the battery control ECU 11. Let them be lifted. Thereby, it is possible for the user to use the vehicle more comfortably while ensuring safety.

  In the present embodiment, the battery control device is mounted on the battery control ECU 11 in the battery pack 1, but the battery control device may be mounted on a data processing device outside the battery pack 1. Although the battery pack 1 is assumed to be mounted on a vehicle, the battery pack 1 may be mounted on a device other than the vehicle. In some cases, various modifications can be made.

1 Battery pack 11 Battery control ECU
12 batteries 13 SMR
DESCRIPTION OF SYMBOLS 14 Current sensor 15 Temperature sensor 16 Voltage sensor 120 Battery cell 121 Battery cell main body 122 Current interruption | blocking mechanism (CID)

Claims (5)

A method for determining by a computer the state of a battery that is charged and discharged,
Detecting a voltage value between terminals of the battery;
Using the detected voltage value, the time differential value of the voltage value is calculated,
When the absolute value of the time differential value obtained by the calculation is greater than a predetermined threshold, it is determined that the current interruption mechanism mounted on the battery has been deactivated as the state of the battery.
The battery state determination method characterized by the above-mentioned. The determination as to whether or not the current interrupt mechanism has been released is performed using the detected voltage value in addition to the time differential value.
The battery state determination method according to claim 1. In a battery control apparatus that controls a plurality of battery cells to be charged / discharged,
Voltage value acquisition means for acquiring a voltage value between terminals of the first battery cell for each first battery cell that is a battery cell provided with a current interruption mechanism;
Using the voltage value acquired by the voltage value acquisition means, a calculation means for calculating a time differential value of the voltage value;
When the absolute value of the time differential value calculated by the calculation means is larger than a predetermined threshold value, the state determination means for determining that the current interruption mechanism of the first battery cell has been deactivated,
A battery control device comprising: The state determination means determines whether or not the current interrupting mechanism has been deactivated using the time differential value and the voltage value acquired by the voltage value acquisition means.
The battery control device according to claim 3. In a battery pack comprising a plurality of battery cells to be charged / discharged and connected,
Voltage value detecting means for detecting a voltage value between terminals of the first battery cell for each first battery cell that is a battery cell having a current interrupting mechanism;
Using the voltage value detected by the voltage value detection means, a calculation means for calculating a time differential value of the voltage value;
When the absolute value of the time differential value calculated by the calculation means is larger than a predetermined threshold value, the state determination means for determining that the current interruption mechanism of the first battery cell has been deactivated,
A battery pack comprising:

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