WO2013176087A1

WO2013176087A1 - Battery-state determination method, battery control device, and battery pack

Info

Publication number: WO2013176087A1
Application number: PCT/JP2013/063956
Authority: WO
Inventors: 博之野村; 守倉石; 宏昌吉澤; 隆広都竹; 正清松井
Original assignee: 株式会社豊田自動織機
Priority date: 2012-05-22
Filing date: 2013-05-20
Publication date: 2013-11-28
Also published as: JP2013243880A; JP5949146B2

Abstract

A battery pack has a plurality of batteries installed therein which are connected in series and equipped with a current-interrupting mechanism and a battery body. A battery-control ECU calculates a time derivative (S1) by using a current value detected by a current sensor, and determines whether the absolute value of the time derivative is larger than a prescribed threshold (S2). When the absolute value is determined to be larger than the threshold (Y at S2), an estimation of the internal-resistance value of the battery is made (S3), and it is determined whether the estimated value falls within a prescribed range (S4). As a result, when the time derivative is larger than the threshold and the estimated value of the internal-resistance value falls outside the prescribed range (Y at S4), the battery-control ECU determines the current-interrupting mechanism is operating (S5).

Description

Battery state determination method, battery control device, and battery pack

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

Rechargeable batteries (secondary batteries) are now 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 in series the battery which is a battery used as a component is employ | adopted.

In secondary batteries, deterioration of characteristics increases due to overdischarge and overcharge. Unbalanced battery capacity between batteries leads to a reduction in battery capacity of the entire battery. For this reason, in an apparatus using a battery having a configuration in which batteries are connected in series, overdischarge or overcharge is performed by monitoring the voltage for each battery and reflecting the monitoring result in each control of discharge and charge. It is designed to suppress the deterioration of the characteristics due to.

Even if discharge and charge are controlled by voltage monitoring, there is a possibility that the control cannot be performed properly for some reason. For this reason, batteries are often equipped with a current interruption mechanism (CID: Current Interrupt Device).

The current interrupting mechanism is a safety device that operates, for example, due to an increase in pressure inside the battery, and interrupts the current due to an increase in internal pressure. For this reason, 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 and the supply of current from the battery can be interrupted by the current interruption mechanism. Thereby, when a battery equipped with a current interruption mechanism is used, higher safety can be ensured.

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, in the operation of the current interruption function, in addition to the possibility that charge control cannot be performed properly, the state of any battery may be extremely deteriorated, for example, its characteristics may be significantly deteriorated. Sex is also conceivable. Either possibility is highly undesirable considering safety. Therefore, it seems important to detect 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 the present invention is to provide a technique for detecting (determining) the operation of a current interruption mechanism mounted on a battery with high accuracy.

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, detecting a current value flowing through the battery, and using the detected current value, a time of the current value The differential value is calculated, and based on the time differential value obtained by the calculation, it is determined as a battery state whether or not the current interruption mechanism mounted on the battery is operating.

Another aspect of the present invention is a battery control device that controls a plurality of batteries to be charged / discharged, and obtains a current value flowing through a first battery that is a battery having a current interrupting mechanism. Based on the current value acquisition means, the current value detected by the current value acquisition means, a time differential value of the current value, and a time differential value calculated by the calculation means. State determination means for determining whether or not the current interruption mechanism is operating.

Still another aspect of the present invention is a battery pack including a plurality of connected batteries and a battery to be charged / discharged, and detecting a current value flowing through a first battery that is a battery including a current interrupting mechanism. Based on the current value detection means, the current value detected by the current value detection means, the time differential value of the current value, the calculation means for calculating the time differential value of the current value of the first battery State determination means for determining whether or not the current interrupting mechanism is operating, and a path provided for charging to the current and discharging from the battery, and the current flowing through the path can be turned on / off And a relay unit, and a control unit that controls the relay unit to turn off the current flowing through the path when the state determination unit determines that the current interrupting mechanism is operating.

In the present invention, the operation of the current interrupt mechanism mounted on the battery can be detected (determined) with high accuracy.

It is a figure explaining the structural example of the battery pack by this embodiment. It is a figure explaining the voltage value accompanying the action | operation of an electric current interruption mechanism, and the time change of an electric current value. It is a flowchart of a CID operation 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 a 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, the battery pack 1 includes a battery control ECU (Electronic Control Unit) 11, a plurality of batteries 120, a battery 12 connected in series, an SMR (System Main Relay) 13, a current sensor 14, and a temperature sensor. 15 is provided.

The 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 computer (data processing apparatus) including a CPU (Central Processing Unit), a memory, a recording medium storing a program (firmware) executed by the CPU, and 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.

Each battery 120 constituting the battery 12 includes a battery main body 121 and a current interruption mechanism (CID) 122, as shown in FIG. 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 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 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 120. In addition to the determination of the operation of the current interruption mechanism 122, overdischarge and overcharge are prevented, It is also used for applications such as balancing battery capacity between batteries 120.

In the present embodiment, the battery 12 has a configuration in which a plurality of the batteries 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 batteries 120 including the current interrupting mechanism 122 and a plurality of battery modules connected in series are connected in parallel. In the case where the arrangement of the battery 120 that is difficult to deteriorate in characteristics is known in advance, the battery 120 that does not include the current interruption mechanism 122 may be used as the battery 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 is a generator that generates electric power when 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 is assumed to have a function of switching current on / off in the SMR 13 as necessary.

The current sensor 14 is a 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 120. The current value and voltage value input to the battery control ECU 11 are used to determine whether or not the current interruption mechanism 122 of the battery 120 is operating. As a result, the battery control ECU 11 is activated by the current value acquisition means for acquiring the current value detected by the current sensor 14, the voltage value acquisition means for acquiring the voltage value detected by each voltage sensor 16, and the current interruption mechanism 122. It functions as a state determination means for determining whether or not there is.

FIG. 2 is a diagram for explaining the time change (a) of the voltage value and the time change (b) of the current value accompanying the operation of the current interrupt mechanism. (A) shows an example of the time change of the voltage value detected by the voltage sensor 16 of the battery 120 in which the current interrupting mechanism (CID) 122 is operated, and (b) shows the current value detected by the current sensor 14. An example of time change is shown. The current interruption mechanism 122 is activated at time t1.

The voltage value detected by the voltage sensor 16 becomes indefinite after time t1 with the stop of the current flow accompanying the operation of the current interrupt mechanism 122. In other words, the value is not reliable. However, the current value detected by the current sensor 14 suddenly decreases from the previous value to 0 as the current flow is stopped due to the operation of the current interrupt mechanism 122. The current interrupt mechanism 122 operates when the pressure inside the battery body 121 rises. In a situation where a current for charging or discharging is flowing, the current sensor 14 shifts from a state in which the current is detected to a state in which the current cannot be detected in a short time with the operation of the current cutoff mechanism 122. Become.

In the present embodiment, paying attention to this, the time differential value of the current value detected by the current sensor 14, for example, the difference value between the current value detected by the current sensor 14 and the current value detected this time is calculated. It is determined whether or not the current interruption mechanism 122 has been operated using the difference value. Thereby, for example, when the absolute value of the calculated difference value is larger than a predetermined threshold value, the battery control ECU 11 considers that the current interrupt mechanism 122 may have been activated. The difference value (time differential value) to be calculated is hereinafter referred to as “current change value”. The battery control ECU 11 functions as a calculation unit that calculates a current change value (time differential value).

The direction of the current flowing through the battery 12 is different between discharging and charging. This is why the absolute value of the difference value is compared with a threshold value. The time change (b) of the current value shown in FIG. 2 corresponds to an example of the time change of the current value detected by the current sensor 14 during discharging.

The battery control ECU 11 performs control by voltage monitoring. Therefore, normally, the current interrupt mechanism 122 does not operate. Accordingly, it is considered that the current interruption mechanism 122 is likely to be caused by the deterioration of the characteristics of the battery main body 121 unless the temperature detected by the temperature sensor 15 is high. From this, in this embodiment, when the difference value is larger than the threshold value, the internal resistance value of the battery 120 is estimated using the voltage value detected by the temperature sensor 16 and the current value detected by the current sensor 14, It is further confirmed whether or not the estimated internal resistance value is within a predetermined range. By performing the confirmation, in the present embodiment, when there is a battery 120 in which the difference value is larger than the threshold and the estimated internal resistance value is not within the predetermined range, the current interrupting mechanism 122 is activated. I try to see it. The internal resistance value can be estimated by, for example, dividing the voltage value by the current value (estimated value of internal resistance value = voltage value / current value). Since the internal resistance value is estimated, the battery control ECU 11 functions as a resistance value estimating means.

Thus, in this embodiment, the operation of the current interrupt mechanism 122 is determined through a two-stage comparison. As a result, even if the current value detected by the current sensor 14 is temporarily relatively fluctuated, it is possible to suppress erroneous determination that the current interrupt mechanism 122 has been activated. For this reason, the operation of the current interrupt mechanism 122 can be determined with higher accuracy. Since the current change value is used for the operation determination of the current interrupt mechanism 122, the determination can be made quickly.

Note that it is desirable to estimate the internal resistance value using the voltage value detected by the voltage sensor 16 before the situation where the difference value is confirmed to be larger than the threshold value. This is because the voltage value detected by the voltage sensor 16 is indefinite when the current is interrupted. As the battery 120 for estimating the internal resistance value, the battery 120 having the highest voltage value detected by the voltage sensor 16 may be selected. The determination of the operation of the current interrupt mechanism 122 may not be performed using the estimation result of the internal resistance value. For example, when the current interrupting mechanism 122 is activated, the absolute value of the current value detected by the current sensor 14 is close to 0. Therefore, the current interrupting mechanism 122 indicates that the absolute value of the current value is equal to or less than a predetermined threshold value. It may be one of the conditions for determining the operation. A straight line 21 shown in the time variation (b) of the current value in FIG. 2 is an example of the current value as the threshold value.

In this embodiment, only one type of threshold value is compared with the current change value, but multiple types of threshold values may be prepared. For example, when two types of threshold values are prepared, the current interrupt mechanism 122 may be determined to be activated when it is confirmed that the current change value is larger than the larger threshold value. If the current change value is equal to or smaller than the larger threshold value and larger than the smaller threshold value, it is determined whether the current interrupting mechanism 122 is further operated using the estimated value of the internal resistance value or the absolute value of the current value. It may be determined.

FIG. 3 is a flowchart of the CID operation determination process. This determination process is a process for the battery control ECU 11 to detect that the current interruption mechanism 122 of any one of the batteries 120 is activated. For example, the battery control ECU 11 is a constant determined from the sampling time for the current sensor 14 to sample the current value. Executed whenever time passes. Next, the process executed by the battery control ECU 11 to determine the operation of the current interrupt mechanism 122 as described above will be described in detail with reference to FIG.

First, in S1, the battery control ECU 11 acquires a current value from the current sensor 14, and calculates a current change value using the acquired current value and a current value acquired in the past. In FIG. 3, “current change value = d (current value) dt” is expressed as a formula for calculating the current change value. In next S2, the battery control ECU 11 determines whether or not the absolute value of the calculated current change value is larger than the threshold value. If the absolute value of the current change value is larger than the threshold value, the determination in S2 is Y (Yes), and the process proceeds to S3. If the absolute value of the current change value is equal to or smaller than the threshold value, the determination in S2 is N (No), and it is determined that there is no possibility that the current interrupting mechanism 122 has been operated.

In S <b> 3, the battery control ECU 11 extracts the maximum voltage value from the voltage values acquired immediately before from each voltage sensor 16, and divides the extracted voltage value by the current value acquired immediately before. Estimate the resistance value. In subsequent S4, the battery control ECU 11 determines whether or not the estimated value of the internal resistance value is within a predetermined range. When the estimated value of the internal resistance value is within the range, that is, the estimated value is larger than the lower limit of the range (indicated as “internal resistance value lower limit” in FIG. 3) and the upper limit of the range (in FIG. 3) If it is smaller than “internal resistance value upper limit”), the determination in S4 is Y, and it is determined that the current interrupt mechanism 122 is not operating, and the CID operation determining process is terminated here. If the estimated value of the internal resistance value is not within the range, that is, if the estimated value is equal to or less than the lower limit of the internal resistance value or equal to or greater than the upper limit of the internal resistance value, the determination in S4 is N and the process proceeds to S5. To do.

The above range may be stored in the battery control ECU 11 as data in advance, but the battery control ECU 11 may estimate the internal resistance value of the battery 120, and the battery control ECU 11 may set the range based on the estimation result. good. The battery control ECU 11 may acquire data representing a range from an external device such as the vehicle ECU 2.

In S5, the battery control ECU 11 determines that the current blocking mechanism 122 of the battery 120 whose internal resistance value has been estimated is in operation, and performs control for blocking the connection by the SMR 13, notification of the determination result to the vehicle ECU 2, and the like. . Thereafter, the CID operation determination process ends.

By disconnecting the connection by the SMR 13, neither discharging from the battery 12 nor charging to the battery 12 can be performed. For this reason, by cutting off the connection by the SMR 13, it is possible to suppress further deterioration of the state of the battery 120 in which the current interruption mechanism 122 is activated by discharging from the battery 12 or charging the battery 12. By notifying the vehicle ECU 2 of the operation of the current interruption mechanism 122, it is possible to cause the vehicle ECU 2 to respond to the operation of the current interruption mechanism 122. For example, a display device (not shown) that informs the user that a highly urgent problem has occurred in the battery 12 under the control of the vehicle ECU 2 or requests that the vehicle is stopped at a safe place, or This can be done using an audio output device. In some cases, the safety of the user can be ensured more reliably. Since the connection by the SMR 13 is cut off, the battery control ECU 11 functions as a control unit that cuts off the connection of the path used for charging the battery 12 and discharging from the battery 12.

In the present embodiment, the battery control device 11 is mounted on the battery control ECU 11 in the battery pack 1. However, 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 addition, when an alternative function that replaces the SMR 13 exists outside the battery pack 1, the alternative function may be operated in cooperation with the battery pack 1 and a device that controls the alternative function. In some cases, various modifications can be made.

Claims

A method for determining by a computer the state of a battery that is charged and discharged,
Detecting a current value flowing through the battery;
Using the detected current value, the time differential value of the current value is calculated,
Based on the time differential value obtained by the calculation, as a state of the battery, it is determined whether or not a current interruption mechanism mounted on the battery is operating,
The battery state determination method characterized by the above-mentioned.
The determination that the current interrupting mechanism is operating is performed when the absolute value of the time differential value is greater than a predetermined threshold value.
The battery state determination method according to claim 1.
Determination of whether or not the current interruption mechanism is operating is performed using at least one of the detected current value and the estimated internal resistance value of the battery in addition to the time differential value.
The battery state determination method according to claim 2.
When it is determined that the current interrupting mechanism is operating, the connection to the path used for charging the battery and discharging from the battery is interrupted.
The battery state determination method according to any one of claims 1 to 3, wherein:
In a battery control device that controls a plurality of batteries to be charged / discharged,
Current value acquisition means for acquiring a current value flowing in the first battery, which is a battery provided with a current interruption mechanism;
Using the current value acquired by the current value acquisition means, calculating means for calculating a time differential value of the current value;
State determining means for determining whether or not the current interrupting mechanism of the first battery is operating based on the time differential value calculated by the calculating means;
A battery control device comprising:
Control means for interrupting connection of a path used for charging to the battery and discharging from the battery when the state determination means determines that the current interruption mechanism is operating;
The battery control device according to claim 5, further comprising:
Voltage value acquisition means for acquiring a voltage value between terminals of the first battery for each first battery;
Using the voltage value acquired by the voltage value acquisition means and the current value acquired by the current value acquisition means, further comprising resistance value estimation means for estimating the internal resistance value of the first battery,
The state determination means determines whether or not the current interrupting mechanism is operating using the time differential value and the internal resistance value estimated by the resistance value estimation means.
The battery control device according to claim 5 or 6,
The state determination means operates when a current interruption mechanism mounted on the first battery is activated when the time differential value is larger than a predetermined threshold value and the internal resistance value is outside a predetermined range. It is determined that
The battery control device according to claim 7.
The state determination means determines whether or not the current interrupting mechanism is operating using the time differential value and the current value detected by the current value detection means.
The battery control device according to claim 5 or 6,
In a battery pack provided with a plurality of batteries to be charged / discharged,
A current value detecting means for detecting a current value flowing in the first battery which is a battery provided with a current interrupting mechanism;
Using the current value detected by the current value detection means, a calculation means for calculating a time differential value of the current value;
State determining means for determining whether or not the current interrupting mechanism of the first battery is operating based on the time differential value calculated by the calculating means;
Relay means provided on a path used for charging to the current and discharging from the battery, and capable of turning on / off the current flowing through the path;
Control means for controlling the relay means to turn off the current flowing through the path when the state determination means determines that the current interrupting mechanism is operating;
A battery pack comprising: