JP3649092B2 - Battery pack abnormality detection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an assembled battery abnormality detection device for detecting an abnormality of a driving assembled battery mounted on an electric vehicle or the like.
[0002]
[Prior art]
An assembled battery configured by connecting a plurality of single cells in series is used as a driving battery mounted in an electric vehicle or the like. These single cells constituting an assembled battery are grouped into a module composed of a small number of single cells, and a single cell constituting the module is managed by a controller (hereinafter referred to as a cell controller) provided for each module. Is called. If a failure occurs in a single cell included in the module, for example, if the cell voltage is extremely low compared to other single cells, the module including the single cell should be replaced. ing.
[0003]
A battery controller that manages the entire assembled battery is provided on the vehicle side, and data is transmitted / received to / from each other by serial communication with a cell controller that manages each module. At the start of the vehicle and at the start of charging, the battery controller instructs each cell controller to measure the no-load voltage of all the single cells, and monitors the variation state of the cell voltage. The battery controller calculates the cell average voltage and the standard deviation based on the cell voltage transmitted from the cell controller, and transfers it to each cell controller. Based on these data, capacity adjustment cells are selected and abnormal cells are detected.
[0004]
[Problems to be solved by the invention]
The above-described variation in cell voltage occurs due to deterioration of a single cell or the like, but the cell controller detects an abnormal single cell and monitors the cell voltage so as not to exceed the allowable lower limit value. In the conventional abnormal cell detection, for example, a calculation formula such as the following formula (1) is used, and when the cell voltage satisfies the formula (1), it is determined that there is an abnormality.
[Expression 1]
(Each cell voltage) − (cell average voltage) ≧ 20σ (1)
However, σ is a standard deviation calculated from the aggregated all cell voltages, and a value of about σmin = 10 (mV) is used as the minimum value.
[0005]
However, the above-described abnormal cell determination method has a problem that the degree of abnormality detection is low because the minimum value of the difference between the cell voltage and the cell average voltage when determined to be abnormal is 200 mV. In other words, even when it is determined that there is no abnormality, an abnormal cell may be detected when the cell voltage of each single cell is actually investigated. Note that if σmin is decreased to increase the degree of abnormality detection, it is difficult to improve the degree of abnormality detection by such a method because it causes an inconvenience that an abnormality is determined even if there is a variation in the normal range.
Further, in a region where the SOC (state of chrage) of the assembled battery is low, the cell capacity error tends to increase and the standard deviation σ also increases. Therefore, there is a problem that the correlation between the standard deviation σ and the cell voltage variation is reduced, and it is difficult to appropriately detect the abnormal cell.
[0007]
The objective of this invention is providing the assembled battery abnormality detection apparatus which can detect the cell voltage abnormality of an assembled battery reliably.
[0008]
[Means for Solving the Problems]
The embodiment of the invention will be described in association with FIG.
(1) The invention of claim 1 includes an assembled battery 1 having modules M1 to M12 composed of a plurality of single cells C1 to C96, a first control device B / C that controls the entire assembled battery 1, and a plurality of Are provided for each of the modules M1 to M12, and include second control devices C / C1 to C / C12 for controlling the corresponding modules M1 to M12, and the first control device B / C and the second control device. This is applied to an assembled battery abnormality detecting device for detecting an abnormality of the assembled battery 1 by transmitting / receiving data to / from C / C1 to C / C12, and to the cell voltages of the single cells C1 to C96 in the modules M1 to M12. Based on the calculation means C / C1 to C / C12 for calculating the standard deviation within the module for each of the plurality of modules M1 to M12 , the average value of the standard deviation within the module of the determination target module and the standard deviation within the module of the plurality of modules M1 to M12 based on the bets, determining means B to determine the module whether the determination target module has an abnormal unit cell To achieve the above objective.
(2) The invention of claim 2 is the battery pack abnormality detection device according to claim 1, wherein the first control device B / C is used as the determination means, and the second control devices C / C1 to C / C12 are calculated. It is a means.
[0009]
In the section of the means for solving the above-described problems for explaining the configuration of the present invention, the drawings of the embodiments of the invention are used for easy understanding of the present invention. The form is not limited.
[0010]
【The invention's effect】
According to the first and second aspects of the present invention, the standard deviation in the module is calculated based on the cell voltage in the module, so that if there is a single cell having an abnormal cell voltage, the standard deviation varies greatly. Therefore, by examining the correlation between the standard deviations in the module, it is possible to reliably determine whether or not the module includes an abnormal single cell regardless of the SOC of the assembled battery .
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram for explaining an assembled battery abnormality detection device according to the present invention, and is a block diagram of the device. The assembled battery 1 shown in FIG. 1 includes 96 single cells C1 to C96 connected in series, and the eight single cells C1 to C96 are grouped to form modules M1,..., M12. Yes. In addition, the number of unit cells which comprise an assembled battery and each module is not limited to the above-mentioned number. The cell controllers C / C1, C / C2,..., C / C12 provided in each module M1,..., M12 manage single cells on a module basis, and power is supplied from each module M1 to M12. The
[0012]
Cell controllers C / C1 to C / C12 detect the voltage and temperature of each single cell, as well as calculate battery status such as module voltage, sensor abnormalities, and cell controllers C / C1 to C / C12 themselves These data are stored in the RAM 11 (described later). The cell controllers C / C1 to C / C12 are activated when an activation signal from a battery controller B / C, which will be described later, is turned on. When the activation signal is turned off, the power from the modules M1 to M12 is also turned off.
[0013]
B / C is a battery controller that controls each cell controller C / C1 to C / C12 to manage the entire assembled battery 1. The battery controller B / C is mounted on the vehicle side, and the cell controllers C / C1 to C / C12 are serially connected via the interface I / F6. Battery controller B / C has CPU3, RAM4, ROM5, transmission terminal SD, and reception terminal RD, and controls each cell controller C / C1-C / C12 by serial communication and each cell controller C / C1-C / Receive data from C12.
[0014]
In the present embodiment, cell voltage information transmitted from each cell controller C / C1 to C / C12 to the battery controller B / C in order to reduce the amount of transmission data is the individual cell of each single cell. The module voltage Vm obtained by averaging the cell voltage Vc in the module instead of the voltage Vc was used. As will be described later, the abnormality diagnosis of each of the modules M1 to M12 is performed based on the module voltage Vm and the standard deviation σm for each module calculated by the cell controllers C / C1 to C / C12.
[0015]
The data transmitted from each of the cell controllers C / C1 to C / C12 is stored in the RAM 4 (backup RAM) of the battery controller B / C, and the battery controller B / C is based on these data. Controls C / C12, calculates remaining battery capacity, diagnoses battery abnormality, etc. The vehicle is provided with a display device 8 for displaying the remaining capacity and battery abnormality, and is connected to the CPU 3 of the battery controller B / C via the interface I / F 7. The battery controller B / C uses the auxiliary battery 2 as a power source, and is turned on / off in conjunction with turning on / off the ignition switch of the vehicle and charging of the assembled battery 1.
[0016]
FIG. 2 is a diagram showing the configuration of the cell controller C / C1, and includes a CPU 10, a RAM 11, a ROM 12, an A / D converter 13, and an interface I / F 14. Although not described, the other cell controllers C / C2 to C / C12 have the same configuration. The A / D converter 13 converts the terminal voltages of the single cells C1 to C8 into digital signals and sends them to the CPU 10. The cell voltage data is temporarily stored in the RAM 11, and the above-described calculation and diagnosis are performed based on these data. The calculation and diagnosis results are stored in the RAM 11 and sent to the battery controller B / C by serial communication after an instruction from the battery controller B / C.
[0017]
<Description of abnormal voltage cell detection method>
Next, an abnormal voltage cell detection method will be described using the flowchart shown in FIG. FIG. 3 is a flowchart showing an abnormality diagnosis operation of the cell controller C / C and the battery controller B / C. For example, when the vehicle is activated, the battery controller B / C and the cell controller C / C start the operation shown in FIG.
[0018]
In step S1, the battery controller B / C transmits a cell voltage measurement instruction signal to each of the cell controllers C / C1 to C / C12. When each cell controller C / C1 to C / C12 receives the instruction signal from the battery controller B / C, it measures the cell voltage Vc of each single cell in step S11. In the subsequent step S12, the module standard deviation σm, which is the standard deviation of the module voltage Vm and the cell voltage in the module, is calculated based on the cell voltage Vc. In step S13, the calculated module voltage Vm and the in-module standard deviation σm are transmitted from each of the cell controllers C / C1 to C / C12 to the battery controller B / C.
[0019]
When the battery controller B / C receives the module voltage Vm and the in-module standard deviation σm from each of the cell controllers C / C1 to C / C12, in step S2, the battery controller B / C calculates the standard deviation σtotal for the entire assembled battery based on the module voltage Vm. calculate. Step S3 is a step of determining whether or not the in-module standard deviation σm satisfies the following expression (2) with respect to the average σmave of the standard deviation σm and the standard deviation σtotal of the entire assembled battery.
[Expression 2]
σm ≧ χ {σmave−σtotal} (2)
In equation (2), σtotal is a standard deviation calculated using the module voltage Vm. The coefficient χ is a constant determined by the number of batteries included in the modules M1 to M12 and the type of battery.
[0020]
If it is determined in step S3 that σm satisfies the expression (2), the process proceeds to step S4, and a flag indicating that the module includes an abnormal cell is set. On the other hand, if it is determined in step S3 that σm does not satisfy the expression (2), the process proceeds to step S5 to set a flag indicating that the module is normal. Step S6 is a step for determining whether or not the abnormality determination has been completed for all the modules M1 to M12. If it is determined that the determination has not been completed, the process returns to step S3. finish.
[0021]
In the above description, the abnormality diagnosis process shown in FIG. 3 is performed when the vehicle is started. However, this abnormality diagnosis process can be executed in both the vehicle stop state and the traveling state. However, in order to accurately determine the abnormality, it is preferable to execute it at the time of no-load when starting the vehicle or charging, or at the time of steady load traveling.
[0022]
FIG. 4 shows an example of the cell voltage Vc of a single cell included in each of the modules M1 to M12. The cell voltage Vc of the sixth single cell included in the module M1 is about 10% lower than that of other single cells included in the assembled battery. In general, this single cell is regarded as abnormal. It is. However, according to the conventional diagnosis method using equation (1), an inequality such as equation (3) holds, and in this case, cell abnormality determination is not made.
[Equation 3]
Maximum cell voltage (V): 4.15
Minimum cell voltage (V): 3.6
Average cell voltage (V): 4.098688
Average value−minimum value (mV): 498.8755 ← (1) left side standard deviation σ (mV): 54.42738
Abnormality judgment value 20σ (mV): 1088.548 ← right side of equation (1) {left side of equation (1)} <{right side of equation (1)} (3)
[0023]
On the other hand, when the abnormality determination is performed based on the standard deviation σm within the module as in the present embodiment, the standard deviations σm1 to σm12 within the modules M1 to M12 have values as shown in FIG. This is shown in the graph in FIG. The in-module standard deviation σm1 of the module M1 including an abnormal single cell with the cell voltage Vc = 3.6 (V) is significantly larger than the in-module standard deviations σm2 to σm12 of the other modules M2 to M12. FIG. 6 shows reference data. The standard deviation σm1 in the module when the cell voltage of the sixth single cell of the module M1 is 3.9 (V), 4 (V), 4.03 (V). The value is shown.
[0024]
As can be seen from FIGS. 4 and 6, the in-module standard deviation σm changes significantly as the cell voltage Vc departs from the average value. As described above, in the present embodiment, the correlation between the standard deviations σm calculated in each module and the standard deviation σtotal of the entire assembled battery is observed, and a normal module and an abnormality are detected. An abnormal module including a single cell can be reliably discriminated, and a cell voltage abnormality is not overlooked as in the prior art.
[0025]
Further, since there is a correlation between σm and σm and σtotal even in a low SOC region where the cell capacity error increases, an abnormal module can be detected even in a low SOC region.
[0026]
In the correspondence between the embodiment described above and the elements of the claims, the battery controller B / C is the first control device and the determination means, and the cell controllers C / C1 to C / C12 are the second control device and Each calculation means is configured.
[0027]
[Brief description of the drawings]
FIG. 1 is a block diagram of an assembled battery abnormality detection device according to the present invention.
FIG. 2 is a diagram showing a configuration of a cell controller C / C1.
FIG. 3 is a flowchart for explaining an abnormality diagnosis procedure;
FIG. 4 is a diagram showing an example of a cell voltage Vc of a single cell included in each module M1 to M12.
FIG. 5 is a graph showing the distribution of an in-module standard deviation σm.
FIG. 6 is a diagram for explaining a change in an in-module standard deviation σm with respect to a change in a cell voltage of the module M1.
[Explanation of symbols]
1 battery pack
B / C battery controller
C1-C96 single cell
C / C1 to C / C12 cell controller
M1 to M12 Module σm, σm1 to σm12 Standard deviation in module

Claims (2)

An assembled battery having a plurality of modules each composed of a plurality of single cells, a first control device that controls the entire assembled battery, and a second control that is provided for each of the plurality of modules and controls a corresponding module An assembled battery abnormality detection device that detects an abnormality of the assembled battery by transmitting and receiving data to and from each other between the first control device and the second control device.
A calculation means for calculating a standard deviation in a module based on a cell voltage of a single cell in the module for each of the plurality of modules;
Based on the average value of the module within the standard deviation of the standard deviation and the plurality of modules in the module of the determination target module, and a determining means for determining whether the module whether or not the determination target module has an abnormal unit cell An assembled battery abnormality detection device characterized by that. In the assembled battery abnormality detection device according to claim 1,
The assembled battery abnormality detection device, wherein the determination means is the first control device, and the calculation means is the second control device.

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