JP3624800B2 - Battery capacity adjustment method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an assembled battery capacity adjustment method for correcting variations in cell capacity of an assembled battery.
[0002]
[Prior art]
In an assembled battery composed of a plurality of cells, the voltage of each cell is caused by variations in self-discharge current of the cell or variations in current consumption of a cell voltage detection circuit attached to the cell over the course of use. And vary individually. In an assembled battery in which the battery capacity is in a fixed proportional relationship with the open-circuit voltage, the open-circuit voltage variation itself is a variation in the capacity of each cell.
When charging the battery pack, it is necessary to adjust the capacity according to the variation of each cell as described above to make the capacity uniform.
[0003]
As this capacity adjustment, a capacity adjustment discharge circuit is conventionally provided for each cell, and the average voltage of all the cells of the assembled battery is set as the capacity adjustment target value, and the voltage is higher than the capacity adjustment target value during charging and discharging of the assembled battery. Some cells are made to approach the average voltage of an assembled battery by discharging according to the deviation from the capacity adjustment target value.
Then, during the capacity adjustment, the abnormality determination level is set up and down by a predetermined value based on the above-mentioned capacity adjustment target value, and the abnormality determination of the individual cell is performed depending on whether or not the abnormality determination level is exceeded. It has become.
[0004]
[Problems to be solved by the invention]
However, in the capacity adjustment method as described above, if there is a cell that is not abnormal but has a relatively large voltage drop amount than many other cells, the cell having a relatively large voltage drop amount is erroneously determined to be abnormal. There is a problem that it ends up.
That is, since only cells having a voltage higher than the average cell voltage of the capacity adjustment target value are discharged, as shown in FIG. The large filled cell Cx in the figure eventually exceeds the abnormality determination level set to the lower Vd from the capacity adjustment target value.
[0005]
In FIG. 8, the voltage position of each cell is represented by ◯, and (a), (b), and (c) show changes in the cell voltage over time. In (a), cells Ca, Cb, and Cd that are higher than the capacity adjustment target value are discharged into the state of (b), and (c) shows a state in which more time has passed. Since the cell Cx decreases relatively more than other cells, the cell Cx moves away from the average voltage of all the cells.
[0006]
Furthermore, if a capacity adjustment function abnormality occurs due to a failure in which the capacity adjustment discharge circuit for discharging a cell whose voltage is higher than the target value for capacity adjustment remains off in any cell, the voltage of that cell Since the value may change while maintaining a predetermined deviation with respect to the average voltage of all cells, there is a problem that an abnormality cannot be detected when the deviation is within Vd of the abnormality determination level width.
[0007]
That is, since only the cells having a voltage higher than the average cell voltage of the capacity adjustment target value are discharged, as shown in FIG. 9, from the state of (a), leaving the cells Cy of capacity adjustment function abnormality, The cells Ca and Cb that are higher than the capacity adjustment target value are discharged to enter the state of (b), and then the other cells are adjusted to the capacity adjustment target value while leaving the cell Cy as shown in (c). The abnormally functioning cell Cy changes while maintaining a predetermined deviation from the average voltage of all the cells.
Therefore, a separate detection system for determining on / off failure of the capacity adjustment discharge circuit is required.
[0008]
Accordingly, in view of the above-mentioned conventional problems, the present invention provides a battery pack capacity adjustment method that prevents erroneous determination of cell abnormality and enables detection of abnormality of the capacity adjustment function without a separate detection system. Objective.
[0009]
[Means for Solving the Problems]
For this reason, the present invention of claim 1 is a battery pack capacity adjustment method comprising a plurality of modules connected in series and a plurality of modules connected in series, each having a discharge circuit for each cell. And every predetermined time,
The open circuit voltage of each cell is detected, the cell voltage average value in the module with the lowest module voltage is taken as the capacity adjustment target value, the adjusted discharge time is determined based on the capacity adjustment target value and the open circuit voltage of the cell, and the adjusted discharge The discharge of the cell was repeated for the time.
[0010]
According to the invention of claim 2, in addition to the structure of claim 1, a cell in which the difference between the cell voltage average value and the open circuit voltage exceeds a predetermined threshold value is judged to be abnormal.
More specifically, the invention of claim 3 is a first threshold value applied to a cell having an open circuit voltage whose threshold value is lower than the cell voltage average value, and the difference between the cell voltage average value and the open circuit voltage. Is determined to be abnormal in voltage drop when the first threshold value is exceeded,
The invention according to claim 4 is a second threshold value applied to a cell having an open circuit voltage whose threshold value is higher than the cell voltage average value, and a difference between the cell voltage average value and the open circuit voltage is a second threshold value. Is exceeded, it is determined that the cell has a capacity adjustment function abnormality.
[0011]
According to a fifth aspect of the present invention, the detection of the open circuit voltage of the cell and the discharge for capacity adjustment are performed in parallel for each module.
[0012]
【The invention's effect】
In the invention of claim 1, since the cell voltage average value in the module having the lowest module voltage is set as the capacity adjustment target value, each cell is discharged for the adjusted discharge time determined based on the open circuit voltage and the capacity adjustment target value. It can be brought close to the capacity adjustment target value only by the discharge, and has the effect of quickly equalizing the voltage of each cell regardless of whether charging or discharging, and without discharging the capacity more than necessary. .
[0013]
In the invention of claim 2, the abnormality of the cell can be determined from the cell voltage average value and the threshold value.
For example, the voltage of a cell that has a relatively large voltage drop amount but is not abnormal as compared with a large number of other cells can be obtained by setting the cell voltage average value in the module having the lowest module voltage as the overall capacity adjustment target value. Since the voltage approaches the same level as the voltage of a large number of cells, the open circuit voltage decreases as the cell voltage average value exceeds the first threshold value without approaching the level of the large number of cells. In this case, it can be determined that the voltage drop amount is abnormal, and a cell in a normal voltage drop amount and a cell in which the voltage drop amount is abnormal can be clearly identified.
[0014]
Further, when the open circuit voltage becomes high enough to exceed the second threshold value from the cell voltage average value while a large number of cells gather at the level of the capacity adjustment target value as in claim 4, the capacity adjustment function is A cell in which the capacity adjustment function is functioning normally and a cell in which the capacity adjustment function is in an abnormal state can be determined as abnormal even if a separate detection system for determining a discharge circuit failure or the like of the capacity adjustment is not provided. Can be clearly identified. This simplifies the failure diagnosis program as well as reducing the number of separate detection systems.
[0015]
In the invention of claim 5, since the detection and discharge of the cell voltage are performed in parallel for each module, the processing time is shortened and the capacity adjustment becomes smooth.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described by way of examples.
FIG. 1 is a diagram illustrating a configuration of an assembled battery control device to which the capacity adjustment method of the embodiment is applied. The assembled battery 10 is configured by connecting n modules 11 in series, and each module 11 has m cells 12 connected in series.
A capacity adjusting discharge circuit 14 is connected between both terminals of each cell 12. The capacity adjustment discharge circuit 14 includes a discharge resistor 15 and a switching circuit 16.
In the figure, the numbers in () of the module 11 () indicate the module numbers, and the numbers in () of the cells 12 () indicate the cell numbers in the module.
[0017]
In the module 11, both terminals of each cell 12 are further connected to a cell controller 18. The cell controller 18 includes a cell voltage detection circuit (not shown).
The cell controller 18 of each module 11 is connected to a battery controller 20 that includes a charging unit therein via a communication line.
The battery controller 20 manages various information related to the assembled battery such as charging / discharging information of the assembled battery. Both terminals of the assembled battery are connected to the battery controller 20.
In the figure, only one connection between the cell controller 18 and the cell controller 18 is shown, and the other connections are simply indicated by arrows.
[0018]
The cell controller 18 sequentially obtains an open voltage (cell voltage) Vc of each cell 12 in the module 11 during charging and discharging by the battery controller 20, and the total voltage Vj (hereinafter referred to as module voltage) in each module. ) Is calculated.
In the battery controller 20, the module voltage Vj is inputted from each module 11 and compared, and the module voltage Vj of the module having the lowest module voltage (lowest voltage module) is set as the lowest module voltage value VMIN. Then, the cell voltage average value Vamin in the lowest voltage module is obtained.
[0019]
The battery controller 12 determines whether the cell is abnormal based on the cell voltage average value Vamin, and sets this as the capacity adjustment target value Vg. Then, the adjustment discharge time Tc corresponding to the deviation between the capacity adjustment target value Vg and the open circuit voltage Vc of each cell 12 is calculated, the capacity adjustment discharge circuit 14 is turned on for the adjustment discharge time Tc, and the capacity adjustment target value is obtained. A cell having a voltage higher than Vg is discharged.
In the following, subscripts i (i = 1, 2, ---, m) and j (j = 1, 2, ---, n) are added as necessary to indicate individual cells and modules. To explain.
[0020]
2 and 3 are flowcharts showing the flow of control of capacity adjustment in the cell controller and the battery controller.
First, in step 101, in each cell controller 18j, a variable i for sequentially counting the cells 12ji in the module 11j is set to 1, and the process proceeds to the next step 102.
In step 102, it is checked whether or not the variable i is equal to or less than m corresponding to the total number of cells 12ji in the module 11j. When the variable i is less than or equal to m, the open circuit voltage Vcji of the i-th cell 12ji is detected in step 103, and the variable i is increased by 1 in step 104.
[0021]
The above is repeated while the variable i is less than or equal to m, and when the Vcji detection of all the cells in the module 11j is completed and the variable i exceeds m, the process proceeds from step 102 to step 105.
In step 105, the detected open circuit voltage Vcji is summed to obtain the module voltage Vj in the module 11j.
The battery controller 20 reads the module voltage Vj from each module 11j every predetermined time. In step 106, the module voltage Vj of each module is compared to obtain the module voltage Vj of the lowest voltage module as the module voltage minimum value VMIN.
Subsequently, in step 107, the module voltage minimum value VMIN is divided by the number m of cells constituting the module 11, and the cell voltage average value Vamin of the minimum voltage module is obtained.
[0022]
Thereafter, each cell controller 18j determines an abnormal cell using the cell voltage average value Vamin calculated by the battery controller 20.
First, in step 108, the variable i is reset to 1, and in step 109, it is checked whether the variable i is less than or equal to m.
[0023]
When the variable i is less than or equal to m, it is checked in step 110 whether or not the difference between the open circuit voltage Vcji of the i-th cell 12ji and the cell voltage average value Vamin is less than or equal to zero.
When the difference is 0 or less, the routine proceeds to step 111, where it is checked whether or not the value obtained by inverting the difference is smaller than the preset voltage drop amount abnormality determination threshold value Vd as the first threshold value. If it is within the voltage drop amount abnormality determination threshold value Vd, the variable i is incremented by 1 in step 115 and then the process returns to step 109.
[0024]
If the difference between the cell voltage average value Vamin and the open circuit voltage Vcji is equal to or greater than the voltage drop amount abnormality determination threshold value Vd, a determination output that the cell 12ji is abnormal in voltage drop amount is sent to the battery controller 20 in step 112. The process proceeds to step 115.
The battery controller 20 displays the occurrence of an abnormal cell as necessary.
[0025]
If the difference between the open circuit voltage Vcji of the cell 12ji and the cell voltage average value Vamin is not less than or equal to 0 in the check in the previous step 110, the process proceeds to step 113.
In step 113, it is checked whether or not the difference is smaller than a preset capacity adjustment function abnormality determination threshold value Ve as a second threshold value. The process proceeds to step 115 as it is.
If the difference between the cell open voltage Vcji and the cell voltage average value Vamin is equal to or greater than the capacity adjustment function abnormality determination threshold Ve, a determination output to the effect that the cell 12ji is abnormal in capacity adjustment function is sent to the battery controller 20 in step 114. Go to step 115.
After step 115, the process returns to step 109, and the above steps are repeated until the variable i exceeds m.
[0026]
When the variable i exceeds m, the process proceeds from step 109 to capacity adjustment after step 116.
In each cell controller 18j, first, in step 116, the cell voltage average value Vamin is set as the capacity adjustment target value Vg. In step 117, the variable i is reset to 1 again, and in step 118, it is checked whether the variable i is less than or equal to m.
When the variable i is less than or equal to m, the process proceeds to step 119, where the difference between the open circuit voltage Vcji of the i-th cell 12ji and the capacity adjustment target value Vg is multiplied by a predetermined adjustment coefficient α, and the capacity adjustment voltage amount of the cell Let it be Vaji.
Subsequently, in step 120, using a conversion table prepared in advance as shown in FIG. 4, the capacity adjustment voltage amount Vaj is converted into an adjustment capacity Cji (Ah).
When the difference between the open circuit voltage Vcji of the cell and the capacity adjustment target value Vg is 0 or less, the conversion to the adjustment capacity Cji is not performed.
[0027]
In the next step 121, an adjustment time Tcji (h) corresponding to the adjustment capacity Cji is calculated. The adjustment time is obtained by the following equation.
Tcji = Cji / Id
Note that Id is the value of the current flowing through the capacity adjustment discharge circuit 14ji of the cell, and is determined by the open circuit voltage of the cell and the impedance of the capacity adjustment discharge circuit.
In step 122, the capacity adjustment discharge circuit 14ji of the cell is turned on for the adjustment time Tcji, and the cell voltage (open voltage Vcji) is discharged to match the capacity adjustment target value Vg.
Then, after increasing the variable i by 1 in step 123, the process returns to step 118.
When the difference between the cell open voltage Vcji and the capacity adjustment target value Vg is 0 or less, the conversion to the adjustment capacity Cji is not performed as described above, and the capacity adjustment discharge circuit remains off and is not discharged.
After step 119 is repeated, the control ends when the variable i exceeds m.
[0028]
The transition of the voltage of each cell by the capacity adjustment control described above is shown in FIG. 5, for example.
First, if the cell voltage of each module is distributed as shown in (a) at the start of control, the cell voltage average value Vamin of the lowest voltage module (module voltage lowest value VMIN) is set as the capacity adjustment target value Vg. Each cell having a voltage higher than the capacity adjustment target value Vg is discharged in an adjustment time corresponding to the voltage difference from Vg.
Thereby, after adjustment by discharge, as shown in (b), most of the cell voltages are aligned near the average value level of all the cells.
[0029]
Here, if the filled cell 12a in the previous (a) is not abnormal, but has a relatively large voltage drop amount than many other cells, as shown in (b), Only the cell 12a has dropped to a lower voltage than many other cells.
[0030]
In the state of (b), the module including the filled cell 12a that has dropped to a lower voltage than the other cells becomes the lowest voltage module, and in the next adjustment, the cell voltage average value Vamin ′ of this lowest voltage module is the capacity adjustment target. The value is Vg. Similarly to the above, each cell having a voltage larger than the capacity adjustment target value Vg is discharged in an adjustment time corresponding to the voltage difference from Vg.
Thereafter, since the voltage drop amount of the filled cell 12a is relatively larger than that of many other cells, the cell voltage average value of the module including the cell 12a is set as the capacity adjustment target value Vg. (C) As the adjustment is repeated, the voltage of the filled cell 12a approaches the same level as many other cells. Accordingly, the voltage of the filled cell 12a approaches the cell voltage average value that is a criterion for cell abnormality determination, but the cell 12a that is not abnormal although the voltage drop amount is relatively larger than that of many other cells is erroneously abnormal. This is avoided.
[0031]
On the other hand, when the voltage drop amount of the filled cell 12b shown in FIG. 6A is abnormal, even if the module that does not include the cell becomes the lowest voltage module at first, the subsequent adjustment is as shown in (b). The module including the cell 12a having a large voltage drop amount becomes the lowest voltage module. In the next adjustment, the cell voltage average value Vamin ′ of the lowest voltage module is set as the capacity adjustment target value Vg.
However, while the cells having a higher voltage are discharged toward the capacity adjustment target value Vg, the filled cells 12b continue to decrease in voltage, so that after the discharge of each cell, the same module has the lowest voltage. Even if it is a module, as in any case (c), the difference between the cell voltage average value Vamin "and the voltage of the cell 12b exceeds the voltage drop amount abnormality determination threshold value Vd. Abnormality is reliably detected.
[0032]
Next, in the case of the solid cell 12c shown in FIG. 7A, if, for example, a failure occurs in the capacity adjustment discharge circuit 14 and the capacity adjustment function becomes abnormal, one of the modules becomes the lowest voltage module. Then, when the cell voltage average value Vamin is set as the capacity adjustment target value Vg and cells having a higher voltage are discharged in a predetermined adjustment time, the voltages of a large number of cells are substantially at the same level as shown in FIG. Only the filled cell 12c is left uncharged because it is not discharged.
[0033]
Similarly, when the cell voltage average value Vamin ′ of the lowest voltage module in the state of (b) is set as the capacity adjustment target value Vg and the adjustment is repeated, the average voltage of the other cells excluding the filled cell 12c decreases. Then, the difference between the filled cells 12c and the cell voltage average value of the lowest voltage module increases. Thus, as shown in (c), when the difference between the voltage of the cell 12c and the cell voltage average value Vamin "exceeds the capacity adjustment function abnormality determination threshold Ve, it is detected that the capacity adjustment function is abnormal.
[0034]
This embodiment is configured as described above, and in the assembled battery 10 configured by connecting a plurality of modules each including a plurality of cells 12 in series, the cell voltage average value of the lowest voltage module is set as a capacity adjustment target value Vg, By turning on the capacity adjustment discharge circuit 14 of each cell for an adjustment discharge time Tc corresponding to the deviation between the capacity adjustment target value Vg and the open circuit voltage of the cell, a cell having a voltage higher than the capacity adjustment target value Vg is discharged. Therefore, the voltage of each cell is quickly equalized regardless of charging or discharging. At that time, the capacitance is adjusted within the normal range of the capacity variation without discharging the capacity more than necessary.
[0035]
Further, relative to the cell voltage average value of the lowest voltage module as a reference, it is determined that the deviation between the voltage of each cell and a voltage exceeding a predetermined threshold value is abnormal, so that it is more relative than many other cells. However, it is avoided that a cell that is not abnormal but has a large voltage drop is erroneously determined to be abnormal, and a cell that has an abnormal capacity adjustment function due to a failure of the capacity adjustment discharge circuit or the like is reliably detected.
[0036]
Furthermore, since a cell controller is provided for each module, and the discharge by the detection of the cell voltage and the control of the capacity adjustment discharge circuit is executed in parallel with other modules, the entire processing time is shortened. As a result, the control flow can be repeated in a short time, and the frequency of capacity adjustment increases, so that the change in each cell voltage becomes smooth.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of an assembled battery control device according to an embodiment of the present invention.
FIG. 2 is a flowchart showing a flow of control of capacity adjustment according to the embodiment.
FIG. 3 is a flowchart showing a flow of control of capacity adjustment according to the embodiment.
FIG. 4 is a diagram illustrating a conversion table between a capacity adjustment voltage amount and an adjustment capacity.
FIG. 5 is a diagram showing a transition of voltage of each cell by capacity adjustment control.
FIG. 6 is a diagram showing a transition of a cell voltage when there is a voltage drop amount abnormality;
FIG. 7 is a diagram showing a transition of a cell voltage when there is a capacity adjustment function abnormality;
FIG. 8 is a diagram showing transition of cell voltage in a conventional example.
FIG. 9 is a diagram showing a transition of a cell voltage when there is a capacity adjustment function abnormality in the conventional example.
[Explanation of symbols]
10 assembled battery 11 module 12 cell 14 capacity adjustment discharge circuit (discharge circuit)
15 Discharge resistor 16 Transistor 18 Cell controller 20 Battery controller

Claims (5)

A module in which a plurality of cells are connected in series is configured by connecting a plurality of sets in series, and is a method of adjusting the capacity of a battery pack provided with a discharge circuit for each cell.
Detect the open voltage of each cell,
The cell voltage average value in the module with the lowest module voltage is taken as the capacity adjustment target value.
A method for adjusting a capacity of a battery pack, comprising: determining an adjusted discharge time based on a capacity adjustment target value and an open circuit voltage of the cell, and repeatedly discharging the cell for the adjusted discharge time. A module in which a plurality of cells are connected in series is configured by connecting a plurality of sets in series, and is a method of adjusting the capacity of a battery pack provided with a discharge circuit for each cell.
Detect the open voltage of each cell,
The cell voltage average value in the module with the lowest module voltage is taken as the capacity adjustment target value.
Determine the adjusted discharge time based on the capacity adjustment target value and the open circuit voltage of the cell, and repeatedly discharging the cell for the adjusted discharge time,
A method of adjusting the capacity of a battery pack, comprising determining that a cell in which a difference between the average cell voltage value and the open circuit voltage exceeds a predetermined threshold is abnormal. When the threshold value is a first threshold value applied to a cell having an open circuit voltage lower than the cell voltage average value, and a difference between the cell voltage average value and the open voltage exceeds a first threshold value 3. The battery pack capacity adjustment method according to claim 2, wherein the cell is determined to have a voltage drop amount abnormality. When the threshold value is a second threshold value applied to a cell having an open circuit voltage higher than the cell voltage average value, and the difference between the cell voltage average value and the open voltage exceeds a second threshold value 4. The capacity adjustment method for an assembled battery according to claim 2, wherein the cell is determined to have a capacity adjustment function abnormality. 5. The battery pack capacity adjustment method according to claim 1, wherein detection of an open circuit voltage of the cell and discharge for capacity adjustment are performed in parallel for each of the modules.

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