JP6673010B2 - Cell disconnection inspection method - Google Patents

Description

  The present invention relates to a cell disconnection inspection method for inspecting the presence or absence of disconnection of a battery cell in an assembled battery in which a plurality of battery cells each having a plurality of battery cells connected in parallel are connected in series.

  There is known an assembled battery in which a plurality of battery cells are connected in parallel, and a plurality of battery cells are connected in series. In this type of battery pack, it is necessary to inspect the presence or absence of abnormality in the battery cells, but it is uneconomical to provide a voltage sensor or the like for each battery cell. In view of the above, there has been conventionally proposed a technique for inspecting the presence or absence of disconnection of a battery cell based on a voltage change of a battery block.

  For example, Patent Literature 1 discloses a parallel connection that connects battery cells when the amount of change in the open voltage of a plurality of battery blocks is equal to or greater than a predetermined threshold when the voltage value of the entire battery pack changes by a certain amount or more. There is disclosed a technique for determining that the body has an abnormality such as a disconnection.

JP 2009-216448 A

Normally, the fluctuation characteristics of the voltage of the battery block (hereinafter, referred to as “block voltage V _Bn ”) with respect to the charging rate Cas (that is, state of charge) of the assembled battery changes when the disconnection of the battery cell occurs. In the related art, the presence or absence of a disconnection is determined by utilizing such a change characteristic of the block voltage _VBn before and after the disconnection.

Here, the variation characteristics of the block voltage V _Bn for charging rate Cas of the assembled battery is around the charging rate Cas of the battery pack during disconnection occurs, varies. Therefore, for example, when a disconnection occurs when Cas = 30%, the block voltage V _Bn when Cas = 30% does not change before and after the disconnection, but as the charging rate Cas departs from 30%, the block voltage increases. The amount of change before and after the disconnection of _VBn increases. In other words, if the charging rate Cas of the battery pack at the time of performing the disconnection inspection is far from the charging rate Cas at the time of the disconnection occurrence, the influence of the disconnection greatly appears on the block voltage _VBn . On the other hand, when the charging rate Cas at the time of the disconnection inspection is close to the charging rate Cas at the time of the disconnection occurrence, the influence of the disconnection on the block voltage _VBn is reduced, and the effect of the disconnection becomes difficult to detect, so that the inspection accuracy may be reduced. was there

  Therefore, in order to accurately inspect the presence or absence of a disconnection, it is necessary to perform the disconnection inspection at a timing of a charging rate Cas different from the charging rate Cas at the time of disconnection. However, unless some sensor is provided for each battery cell, it is impossible to specify the charging rate Cas at the time of disconnection. As a result, in the related art, the charging rate Cas at the time of disconnection occurrence and the charging rate Cas at the time of inspection are close to each other, and the accuracy of disconnection inspection may be reduced.

  Therefore, an object of the present invention is to provide a cell disconnection inspection method capable of inspecting the presence or absence of disconnection with higher accuracy.

  A cell disconnection inspection method according to the present invention is a cell disconnection inspection for inspecting the presence or absence of disconnection of the battery cell in a battery pack formed by connecting a plurality of battery cells in parallel, and further, in a plurality of battery packs connected in series. A method for determining whether or not a battery cell is disconnected in each battery block based on an open voltage of the battery block, the disconnection inspection step including: equalizing the voltages of the plurality of battery blocks. If the process is performed when the charging rate of the battery pack is in the high charging rate range, the disconnection inspection step is performed when the charging rate is in the low charging rate range lower than the high charging rate range, When the equalization process is performed when the charging rate is in the low charging rate range, the disconnection inspection step is performed when the charging rate is in the high charging rate range.

  In the present invention, the disconnection inspection step is performed in a charging area different from the charging area where the equalization processing is performed, so that the accuracy of the disconnection inspection can be further improved.

FIG. 2 is a diagram illustrating a configuration of a battery system. It is a figure showing composition of an equalization processing part. It is a figure showing the relation between disconnection and block charge rate. 5 is a graph showing a change in block voltage due to disconnection. It is a figure explaining the principle of a disconnection inspection. It is a figure showing change of the fluctuation characteristic of a battery block by equalization processing. FIG. 7 is a diagram illustrating changes in an equalization process, a disconnection inspection execution timing, and a disconnection determination flag. FIG. 6 is a diagram illustrating a change in inter-block voltage deviation due to a difference in a battery pack charging rate. FIG. 4 is a diagram illustrating an example of a map of a correction coefficient. FIG. 7 is a diagram illustrating a correspondence between a comparison block and a reference block. It is a flowchart which shows the flow of a disconnection inspection.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a configuration of a battery system 10 that performs a disconnection inspection method according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a configuration of the equalization processing unit 14.

  The battery system 10 is mounted on an electric vehicle (for example, a hybrid vehicle or an electric vehicle). The battery system 10 has an assembled battery 12 in which a plurality of battery blocks Bn (n = 1, 2,..., Bmax) are connected in series. Each battery block Bn is configured by connecting a plurality of battery cells Ek (k = 1, 2,..., Cmax) in parallel. The battery cell Ek is a chargeable / dischargeable secondary battery, for example, a lithium ion secondary battery, a nickel hydride battery, or the like. The battery pack 12 is connected to a motor generator 24 via a system main relay 20 and an inverter 22. The motor generator 24 functions as a drive source of the electric vehicle, and functions as an electric motor that outputs power using electric power from the battery pack 12. The motor generator 24 also functions as a power generator that receives power and generates electric power, and the assembled battery 12 is charged with the electric power generated by the motor generator 24.

The battery system 10 further includes a current sensor 13 that detects a current flowing through the battery pack 12 (hereinafter, referred to as “battery current Ib”), a voltage Vas of the battery pack 12 (hereinafter, referred to as “battery voltage Vas”), and a battery block Bn. a voltage detecting unit 16 for detecting a voltage V _{Bn (hereinafter} referred to as "block voltage V _Bn") of, a, and equalization processing unit 14 to equalize the block voltage V _Bn between battery blocks Bn.

Equalization processing section 14 is a portion to equalize variations in the block voltage V _Bn between battery blocks Bn. That is, the amount of self-discharge of the battery cell Ek varies, and due to the variation, the voltage of each battery cell Ek, and eventually, the block voltage _VBn also varies. When the variation of the block voltage _VBn occurs, the deterioration of the battery cell Ek proceeds at an accelerated rate, or the amount of available energy decreases. To avoid such problems, to discharge certain battery block Bn optionally, equalization processing unit 14 to reduce the block voltage V _Bn of the particular battery blocks Bn are provided. The equalization processing unit 14 includes equalization circuits 26 connected in parallel with the battery blocks Bn by the number of the battery blocks Bn. The equalizing circuit 26 is a circuit in which a resistance element R and a switching element SW are connected in series, as shown in FIG.

When the block voltage V _Bn of the specific battery block Bn is higher than the block voltage V _Bn of another battery block Bn, the controller 18 turns on / off the switching element connected in parallel with the specific battery block Bn. By switching, a specific battery block Bn is discharged. Then, the discharge process, that block voltage V _Bn is performed with respect to high battery blocks Bn all above a certain, it is possible to align uniformly the block voltage V _Bn plurality of battery blocks Bn. Hereinafter, the process to align the variation of the block voltages V _Bn between battery blocks Bn, referred to as "equalization processing."

The voltage detector 16 outputs a potential difference between the voltage detection lines 28 connected to each battery block Bn as a block voltage _VBn . The voltage detection unit 16 includes, for example, a capacitor connected in parallel with the corresponding battery block Bn, and a comparator (both not shown) connected to each voltage detection line 28 via a sampling switch. In the case of the voltage detection unit 16, when the sampling switch corresponding to the battery block Bn to be detected is turned on, the voltage value of the battery block Bn (the voltage value of the corresponding capacitor) is output from the comparator. Further, the voltage detection unit 16 has a capacitor and a sampling switch connected in parallel with the entire assembled battery 12, and also detects the assembled battery voltage Vas. The voltage values V _Bn and Vas detected by the voltage detector 16 are input to the controller 18 after A / D conversion. The current sensor 13 detects a current flowing through the battery pack 12, that is, a battery current Ib. The battery current Ib detected by the current sensor 13 is output to the controller 18. Note that the block voltage _VBn and the battery pack voltage Vas used in the following description are both open-circuit voltages (OCV) detected in a no-load state.

  The controller 18 includes a CPU and a memory (both not shown), and performs various calculations and transmission / reception of control signals as necessary. More specifically, the controller 18 controls the driving of the equalization processing unit 14 and calculates the charging rate of the battery pack 12. The assembled battery charging rate is a value indicating the ratio of the current charged amount to the fully charged amount of the assembled battery 12, and is generally called SOC (state of charge). The controller 18 calculates the charging rate of the battery pack 12 from the open voltage (battery voltage Vas) of the battery pack 12 and the battery current Ib. That is, generally, the charging rate C of the battery pack 12 has a fixed relationship with the battery pack voltage Vas, and is substantially proportional to the battery pack voltage Vas. Therefore, when the battery pack voltage Vas is obtained, the controller 18 calculates the charging rate of the battery pack 12 based on the battery pack voltage Vas. When the load is connected to the assembled battery 12 (the system main relay 20 is turned on) and it is difficult to obtain the open circuit voltage (assembled battery voltage Vas), the controller 18 uses the most recently obtained assembled battery voltage Vas. The sum of the obtained charging rate of the battery pack 12 and the variation of the charging rate C obtained from the integrated current value Ah is calculated as the charging rate of the battery pack 12.

Incidentally, as the charging rate, there is a charging rate for each battery block Bn in addition to the charging rate for the entire assembled battery 12. Hereinafter, the charging rate of the entire battery pack 12 is referred to as “battery charging rate Cas”, and the charging rate of each battery block Bn is referred to as “block charging rate C _Bn ”.

In addition, the controller 18 also performs an inspection for the presence / absence of disconnection of the battery cell Ek based on the block voltage _VBn detected by the voltage detection unit 16. The disconnection inspection of the battery cell Ek will be described in detail. The disconnection of the battery cell Ek means that the connection line connecting the plurality of battery cells Ek in parallel is disconnected in the middle, and the electrical connection between some of the battery cells Ek and the remaining battery cells Ek is impaired. For example, when a disconnection occurs at the position P1 in FIG. 2, the electrical connection between the battery cell E1 in the vicinity and another battery cell Ek is damaged, and the battery cell E1 does not function electrically. In this case, since the battery capacity of the battery block Bn is reduced, the fluctuation characteristics of the block charging rate C _{Bn and} , consequently, the block voltage V _Bn change before and after the disconnection.

FIG. 3 is a schematic diagram illustrating a difference in the block charging rate C _Bn depending on the presence or absence of a disconnection. As shown in FIG. 3, a case is considered where two battery blocks Ba and Bb are connected in series, and each battery block Ba and Bb is configured by connecting five battery cells E1 to E5 in parallel. As shown in FIG. 3, it is assumed that the battery cells E4 of the battery block Bb are disconnected when the block charging rates C _Ba and C _Bb of the two battery blocks Ba and _Bb are both 60%. In this case, the battery capacity of the battery block Bb is lower than that of the battery block Ba. Therefore, when the battery pack 12 is continuously discharged, the block charging rate C _Bb of the battery block Bb having a small capacity is lower than the block charging rate C _Ba of the battery block Ba having a large capacity.

Here, the block charging rate _{CBb_af} of the battery block Bb after the occurrence of the disconnection can be expressed by the following equation 1.
C _{Bb_af} = C _{Bb_be-} (C _{Bb_be} -C _Ba ) × (num1 / num2) Equation 1
In Formula _{1, C Bb_be} and _{C Bb_af} are block charge rate after disconnection occurs and then break occurrence of the battery block Bb which has been _{disconnected, C Ba} is blocked charging rate of the normal rechargeable battery block Ba disconnection has not occurred Num1 is the parallel number of the battery cells Ek before the disconnection occurs, and num2 is the parallel number of the battery cells Ek after the disconnection occurs. Thus, in the example of FIG. 2, the block charging rate _{C Ba} of the battery block Ba continues to discharge of the battery pack 12 until the 30% block charging rate _{C Bb} of the battery blocks Bb is reduced to 22.5%. That is, it can be said that the fluctuation characteristic of the block charging rate _CBn changes before and after the disconnection. Here, the block charging rate C _Bn is substantially proportional to the open voltage of the battery block Bn, that is, the block voltage V _Bn . Therefore, it can be said that the fluctuation characteristic of the block voltage _VBn changes before and after the disconnection.

FIG. 4 is a graph showing a change in the block voltage _VBn . In FIG. 4, the horizontal axis represents the integrated current value Ah, and the vertical axis represents the block voltage _VBn . The current is negative in the discharging direction and positive in the charging direction. Therefore, in FIG. 4, the charging rate increases as the position approaches the right. In FIG. 4, the solid line indicates the block voltage _{VBn_be} before the battery cell Ek is disconnected.

As shown in FIG. 4, the block voltage _{VBn_be} of the battery block Bn has a fluctuation characteristic that increases as the integrated current value Ah increases. In this battery block Bn, it is assumed that the battery cell Ek is broken at a specific integrated current value Ah_a. In that case, the variation characteristic of the block voltage _{V Bn} is changed to the characteristic _{V Bn_af} as shown by the broken line in FIG. 4. Specifically, when a disconnection occurs, the curve indicating the fluctuation characteristic shrinks only in the horizontal axis direction around the integrated current value Ah_a at which the disconnection has occurred.

Here, the integrated current value Ah_a on the horizontal axis in FIG. 4 can be considered by replacing the charging rate of the entire assembled battery 12, that is, the assembled battery charging rate Cas. That is, the battery pack charging rate Cas is a value that increases and decreases according to the increase and decrease of the integrated current value Ah. Strictly speaking, if the cell disconnection occurs, the capacity of the assembled battery charging rate Cas decreases accordingly. Therefore, it can be said that the assembled battery charging rate Cas with respect to the integrated current value Ah changes. However, unlike the battery block Bn, the effect of one battery cell Ek on the entire battery pack 12 is very small. Therefore, the capacity decrease of the battery pack 12 due to the cell disconnection can be substantially ignored, and the value of the battery pack charging rate Cas with respect to the integrated current value Ah can be regarded as being constant. Then, in such a case, the horizontal axis in FIG. 4 can be replaced with the battery pack charging rate Cas. In the example of FIG. 4, the position of the integrated battery charge rate Cas = 100% when the integrated current value Ah = Ah_b according to the battery capacity of the battery pack 12, and the position of the integrated battery charge rate Cas = 0 when the position of the integrated current value Ah = 0. %. The variation characteristics of this case, the block voltage V _Bj comparison block Bj for battery pack charging rate Cas can be said to vary with the disconnection. In the present embodiment, the presence / absence of disconnection of the battery cell Ek is inspected using the change in the fluctuation characteristic of the block voltage _VBj due to such disconnection. This will be described with reference to FIG.

In FIG. 5, the horizontal axis represents the battery pack charging rate Cas, and the vertical axis represents the block voltage _VBn . In FIG. 5, the two-dot chain line indicates the block voltage V _Bi of the reference block Bi where no disconnection has occurred, the solid line indicates the block voltage V _{Bj_be} before disconnection of the comparison block Bj to be _inspected , and the broken line indicates The block voltage _{VBj_af} after the disconnection of the comparison block Bj is shown.

When inspecting the presence / absence of disconnection, the controller 18 sets the block voltages V _Bi , V _Bj of the reference block Bi and the comparison block Bj at the timing when the assembled battery charging rate Cas becomes close to a predetermined inspection charging rate C_c. get. Then, the difference between the block voltages V _Bi and V _Bj of the two battery blocks Bi and Bj and the inter-block voltage deviation ΔV _i−j = | V _Bi −V _Bj | are obtained. The value of the inter-block voltage deviation ΔV _ij does not change even if charging and discharging are repeated, as long as the battery pack charging rate Cas is the same. However, when a cell disconnection occurs in the comparison block Bj, as described above, the fluctuation characteristic of the block voltage _VBj changes, so that the value of the inter-block voltage deviation ΔV _i-j also changes. In the example of FIG. 5, the inter-block voltage deviation ΔV _ij is D1 before the disconnection, but becomes D2 after the disconnection (D2> D1). Therefore, by monitoring the change in the block voltage difference [Delta] V _i-j, it is possible to determine the presence or absence of cell breakage.

Therefore, in this embodiment, the controller 18 includes a inter current block voltage deviation ΔV _i-j [t], the difference value between between previous block voltage deviation _{ΔV i-j [t-1} ], check value A _ij [t] = | ΔV _ij [t] −ΔV _ij [t−1] | Then, when the obtained inspection value A _ij [t] exceeds a predetermined reference inspection value Adef, the controller 18 determines that a disconnection has occurred in the comparison block Bj.

Note that such an inspection procedure is based on the premise that no disconnection has occurred in the reference block Bi. However, actually, there is a possibility that a disconnection occurs in the reference block Bi. In this case, from the single inspection value A _ij , which of the reference block Bi and the comparison block Bj is disconnected? Can not judge. However, normally, the reference block Bi is compared with a plurality of comparison blocks Bj. Therefore, when the check value A _i-j in which a plurality of comparison blocks Bj all that is compared may be determined that disconnection is obtained, rather than the comparison block Bj, disconnection reference block Bi is the possibility of the occurrence Can be determined to be high. Then, in that case, another battery block Bn may be reset as a new reference block Bi and a disconnection inspection may be performed.

By the way, as described with reference to FIG. 4, the fluctuation characteristic of the block voltage _VBn changes around the integrated current value Ah (assembly battery charging rate Cas) in which the cell disconnection has occurred. Therefore, the amount of change in the block voltage _VBn due to the disconnection is smaller as the battery pack charging rate Cas at the time of the disconnection (hereinafter, referred to as “disconnection charging rate C_b”) becomes smaller, and becomes larger as the distance from the disconnection charging rate C_b increases. Become. The accuracy of the disconnection inspection according to the above-described procedure increases as the amount of change in the block voltage _VBn due to the disconnection increases. Therefore, in order to increase the accuracy of the disconnection inspection, it is desirable to set the battery pack charging rate (inspection charging rate C_c) at the time of performing the disconnection inspection to a value apart from the disconnection charging rate C_b. For example, in the example of FIG. 5, if a disconnection occurs when the battery pack charging rate Cas is relatively low C_b, the disconnection inspection may be performed when the battery pack charging rate Cas is relatively high C_c. It is desirable.

However, actually, it is not possible to specify the timing at which the disconnection has occurred, and it is not possible to specify the disconnection charging rate C_b. Therefore, in the present embodiment, in order to improve the inspection accuracy without specifying the disconnection charging rate C_b, an equalization process for equalizing the variation of the block voltage _VBn is performed, and a set when the equalization process is performed is performed. At the battery pack charging rate Cas apart from the battery charging rate (hereinafter referred to as “equalized charging rate C_e”), the presence or absence of disconnection is checked. This will be described with reference to FIG. In FIG. 6, the upper part shows the fluctuation characteristics of the block voltage _VBj before the equalization processing, and the lower part shows the fluctuation characteristics of the block voltage _VBj after the equalization processing. In FIG. 6, the solid line _indicates the fluctuation characteristics of the block voltage _{VBj_be} before the disconnection occurs, and the broken line _indicates the fluctuation characteristics of the block voltage _{VBj_af} after the disconnection occurs.

In FIG. 6, it is assumed that the battery cell Ek is disconnected when Cas = C_b in the comparison block Bj. As described repeatedly, and as shown in the upper part of FIG. 6, the occurrence of disconnection changes the fluctuation characteristics of the block voltage _VBj . As a result, the block voltage V _Bj when Cas = C_e is V2 before the disconnection, but drops to V1 after the disconnection. It is assumed that the equalization process is performed in all the battery blocks Bn including the comparison block Bj after the disconnection so that the block charging rate C _Bn becomes C_e. In this case, the variation characteristic of the block voltage V _Bj comparison block Bj, as shown by the broken line in the lower part of FIG. 6, as the block voltage V _Bj when the Cas = C_e is V2, the curve showing the variation characteristics , Shifted to the left as a whole. And, thereby, in the assembled battery charging rate Cas high region (right region), the change amount of the block voltage V _Bj comparison block Bj associated with disconnection increases. As a result, if the inspection for the presence / absence of disconnection is performed in an area where the battery pack charging rate Cas is high, the accuracy of the inspection can be improved. Then, the battery pack charging rate (equalized charging rate C_e) at the time of performing the equalizing processing can be reliably obtained, unlike the disconnection charging rate C_b.

  Therefore, in the present embodiment, the inspection of the presence / absence of disconnection is performed in the charging area where the assembled battery charging rate C_e and the charging area when the equalization processing is performed are reversed, thereby improving the inspection accuracy. That is, if the equalization process is performed when the battery pack charging rate Cas is within the high charging rate range, the disconnection inspection is performed when the battery pack charging rate Cas is within the low charging rate range, and the equalization process is performed. When the charging rate is within the low charging rate range, the disconnection inspection is performed when the battery pack charging rate Cas is within the high charging rate range.

  FIG. 7 is a diagram illustrating the relationship between the execution timing of the equalization processing and the disconnection inspection, and the disconnection determination flag Fb. In FIG. 7, the upper part is a diagram showing the execution timing of the equalization processing and the disconnection inspection, the vertical axis shows the battery pack charging rate Cas, and the horizontal axis shows the time. In the upper part, the black circles indicate the execution timing of the disconnection inspection, and the black diamonds indicate the execution timing of the equalization processing. The lower row shows a disconnection determination flag Fb. When the controller 18 determines that a disconnection has occurred, the disconnection determination flag Fb is turned ON (HIGH).

In the example shown in FIG. 7, the equalization process is performed when the battery pack charging rate Cas is in the low charging range, and the disconnection inspection is performed when the battery pack charging rate Cas is in the high charging range. It is assumed that a cell disconnection has occurred at time t5 after the second equalization process and before the third disconnection inspection. This cell disconnection occurs when the battery pack charging rate Cas is relatively high, as shown in FIG. In this case, even subjected to disconnection whether inspection at time t6 just after the order variation of the block voltages V _Bj comparison block Bj is small, it is difficult to determine the disconnection has occurred. Therefore, at time t6, the disconnection determination flag Fb remains OFF (LOW).

Thereafter, at time t7, the the equalization process is performed, the variation characteristics of the block voltage V _Bj comparison block Bj is, as shown in the lower part of FIG. 6, the deviation to the left, the battery pack charging rate Cas is a high charge region The inspection accuracy at a certain time will be improved. Therefore, at time t8, if the disconnection inspection is performed while the battery pack charging rate Cas is within the high charging range, the inspection value A _ij becomes a large value, and it is reliably detected that the disconnection has occurred. be able to. Therefore, at time t8, the disconnection determination flag Fb is turned ON (HIGH).

As is clear from the above description, in the present embodiment, the assembled battery charging rate C_e when performing the equalization processing is separated from the assembled battery charging rate C_c when performing the disconnection inspection. Therefore, it is possible to increase the change amount of the block voltage V _Bj comparison block Bj associated with disconnection in the test charging rate C_C, can improve inspection accuracy.

Incidentally, it is desirable that the assembled battery charging rate Cas at the time of performing such a disconnection inspection, that is, the inspection charging rate C_c is always the same. However, the block voltage _VBn used in the disconnection inspection is an open voltage obtained when the charge / discharge current is zero, and the timing at which it can be obtained is limited. Therefore, the execution timing of the disconnection inspection is limited to some extent, and it is difficult to always make the inspection charging rate C_c the same.

Therefore, actually, the inspection charging rate C_c slightly varies. Therefore, the obtained block voltages V _Bi and V _Bj include not only the change due to the disconnection but also the change due to the difference in the test charging rate C_c. Such a change in the block voltages V _Bi and V _Bj due to the difference in the inspection charging rate C_c causes a decrease in inspection accuracy. Therefore, in the present embodiment, the inter-block voltage deviation ΔVi _-j is corrected according to the difference in the test charging rate C_c.

FIG. 8 is a diagram for explaining this correction. 8, the solid line indicates the block voltage V _Bi of the reference block Bi, and the broken line indicates the block voltage V _Bj of the comparison block Bj.

If no disconnection has occurred and the battery pack charging rate Cas is the same, the inter-block voltage deviation ΔVi _-j will always be the same. However, when the battery pack charging rate Cas changes, as shown in FIG. 8, the inter-block voltage deviation ΔVi _-j also changes. In the example of FIG. 8, the inter-block voltage deviation ΔV _i-j is D1 when Cas = c1, and changes to D2 when Cas = c2. The inter-block voltage deviation ΔV _i-j increases when the assembled battery charging rate Cas shifts to the high charging rate side, and decreases when the assembled battery charging rate Cas shifts to the low charging rate side. Such a change in the inter-block voltage deviation ΔV _i-j resulting from the change in the battery pack charging rate Cas causes a detection error.

Therefore, it is conceivable to calculate the correction amount L in accordance with the deviation amount of the assembled battery charge (inspection charging rate C_c) to be subjected to the disconnection inspection, and to add the correction amount L to the inter-block voltage deviation ΔVi _-j . As a method of calculating the correction amount L, for example, the required correction amount per 1% of the deviation of the inspection charging rate C_c is stored as the correction coefficient l, and the deviation C_c [t] = C_c of the actual inspection charging rate C_c is stored. The correction amount L is calculated by multiplying [t] -C_c [t-1] by the correction coefficient l. In this case, the correction coefficient 1 may be a fixed value, but is preferably a variable value that changes according to the ratio between the comparison block Bj and the reference block Bi. FIG. 9 is a diagram illustrating an example of a map of the correction coefficient l. In FIG. 9, the vertical axis indicates the value of the correction coefficient 1 and the horizontal axis indicates the ratio of the capacity of the reference block Bi and the comparison block Bj, that is, (capacity of Bi / capacity of Bj).

When correcting the inter-block voltage deviation ΔV _ij [t], the controller 18 first compares the battery capacity of the comparison block Bj to be inspected with the map of FIG. 9 to obtain the correction coefficient l corresponding to the comparison block Bj. To get. Subsequently, a difference value ΔC_c [t] = C_c [t] −C_c [t−1] between the current inspection charging rate C_c [t] and the previous inspection charging rate C_c [t−1] is calculated. Then, the correction value L is obtained by multiplying the difference value ΔC_c [t] by the correction coefficient l. Subsequently, the corrected inter _- block voltage deviation ΔV _ij [t] is obtained by adding the correction amount L to the inter _- block voltage deviation ΔV _ij [t]. Normally, the block voltage _{V Bi} and the battery pack charging rate Cas without a break reference block Bi is in a fixed relationship, the assembled battery charging rate Cas is substantially proportional to the block voltage _{V Bi.} Therefore, when calculating the correction amount L, the deviation amount ΔC_c of the inspection charging rate may be changed to the change amount ΔV _Bi = V _Bi [t] −V _Bi [t−1] of the block voltage V _Bi of the reference block. .

Next, selection of the reference block Bi and the comparison block Bj will be described. In the present embodiment calculates a comparison block Bj to be inspected, and the reference block Bi serving as a reference, the amount of change in the block voltage difference [Delta] V _i-j as check value A _i-j, the check value A _i The presence or absence of a disconnection is determined based on _-j . Here, in order to reduce the influence of the error, it is desirable that the two battery blocks Bi and Bj to be compared have similar battery characteristics, for example, battery resistance and battery capacity. Many of the differences in battery characteristics are due to deterioration and due to temperature characteristics, and the deterioration is also sensitive to temperature. Therefore, if the temperature characteristics of the two battery blocks Bn are close to each other, the battery characteristics of the two battery blocks Bn are often similar. Therefore, in the present embodiment, a battery block whose temperature characteristic is close to the reference block Bi is set as the comparison block Bj.

  FIG. 10 is a diagram illustrating an example of the correspondence between the reference block Bi and the comparison block Bj. As shown in FIG. 10, when cooling air is supplied from the near side of the drawing, the cooling is difficult to be performed and the battery temperature tends to increase as going from the near side to the far side. In other words, it can be said that the battery blocks Bn having the same position in the depth direction have similar temperature characteristics and, consequently, battery characteristics. For this reason, as shown in the lower part of FIG. 10, at the time of the disconnection inspection of the battery blocks B8, B9, and B13 located on the front side, the battery block B1 located on the front side is also selected as the reference block. Further, at the time of the disconnection inspection of the battery blocks B5, B12, B12 located at the innermost side, the battery block B4 located at the innermost side is similarly selected as the reference block. Then, the controller 18 stores such a correspondence table between the reference block Bi and the comparison block Bj in advance, and refers to the correspondence table for the reference block Bi corresponding to the comparison block Bj during the disconnection inspection. Identify.

  Next, a flow of the disconnection inspection processing in the present embodiment will be described with reference to FIG. FIG. 11 is a flowchart illustrating the flow of the disconnection inspection process. As shown in FIG. 11, first, the controller 18 determines whether the battery pack charging rate Cas is within a predetermined inspection range, the equalization execution determination is ON, and it is possible to acquire the open-circuit voltage OCV. Is determined (S10). Here, the inspection range is a range of the assembled battery charging rate in which the execution of the disconnection inspection is permitted, and the assembled battery charging rate (equalized charging rate C_e) apart from the assembled battery charging rate at which the equalization execution processing is executed. Range of rates. The equalization execution determination is a flag that is turned on after the completion of the equalization processing. Whether or not the open-circuit voltage OCV can be obtained is determined based on whether or not the battery no-load time has continued for a certain period of time. If any one of these three conditions is No, the controller 18 proceeds to step S36. In step S36, the controller 18 determines whether or not the equalization processing has been completed (S36). If it is determined that the equalization processing has been completed, the equalization execution determination is set to ON (S38), and the process returns to step S10. On the other hand, if the equalization processing has not been completed, the process returns to step S10 without changing the equalization execution determination.

On the other hand, in step S10, when it is determined Yes, the controller 18, after set to OFF equalization determination (S12), and acquires the block voltage _{V Bn} of all battery blocks Bn. Then, the controller 18 performs a disconnection inspection for each of the battery blocks B1 to Bbmax (S16 to S34).

Specifically, the controller 18 specifies the reference block Bi corresponding to the comparison block Bj with reference to the correspondence table stored in the memory (S18). Next, an inter-block voltage deviation ΔV _ij [t] between the reference block Bi and the comparison block Bj is calculated (S20). Since the inter-block voltage deviation ΔV _ij [t] obtained here includes an error due to a deviation amount of the inspection charging rate C_c, the controller 18 subsequently calculates a correction amount L for correcting the error. (S22). The correction amount L is obtained by multiplying a change amount ΔV _Bi [t] = V _Bi [t] −V _Bi [t−1] of the block voltage V _Bi of the reference block Bi by a specified correction coefficient l.

If the correction amount L is obtained, the correction amount L is added to the inter-block voltage deviation ΔV _ij [t], and the value after the addition is treated as the inter-block voltage deviation ΔV _ij [t] (S24). . Next, a difference value between the obtained block-to-block voltage deviation ΔV _ij [t] and the previous block-to-block voltage deviation ΔV _ij [t-1] is acquired as a test value A _ij [t]. (S26). When the inspection value A _ij [t] is obtained, the inspection value A _ij [t] is compared with a predetermined reference inspection value Adef (S28). As a result of the comparison, when the inspection value A _ij [t] is larger than the reference inspection value Adef, the controller 18 determines that there is a disconnection in the battery block Bj. On the other hand, if A _ij [t] ≦ Adef, the controller 18 determines whether the inspection has been completed for all battery blocks (S32). If the inspection of all the battery blocks Bn is completed, that is, if j = bmax, the process returns to step S10. If j ≠ bmax, j = j + 1 (S34), and the process returns to step S18.

As is clear from the above description, in the present embodiment, the disconnection inspection is permitted only when the assembled battery charging rate Cas is within the inspection range apart from the assembled battery charging rate Cas when the equalization processing is performed. ing. As a result, the amount of change in the block voltage _VBn due to the disconnection increases, and the inspection accuracy can be improved.

Reference Signs List 10 battery system, 12 assembled battery, 13 current sensor, 14 equalization processing unit, 16 voltage detection unit, 18 controller, 20 system main relay, 22 inverter, 24 motor generator, 26 equalization circuit, 28 voltage detection line, Bn battery Block, Bi reference block, Bj comparison block, Ek battery cell, R resistance element, SW switching element.

Claims (1)

A battery disconnection inspection method for inspecting the presence / absence of disconnection of the battery cell, further comprising: a battery block in which a plurality of battery cells are connected in parallel, and further, in an assembled battery in which a plurality of battery cells are connected in series,
Based on the open voltage of the battery block, including a disconnection inspection step to determine the presence or absence of disconnection of the battery cells in each battery block,
If the equalization process for equalizing the voltage of each of the plurality of battery blocks is performed when the charge rate of the battery pack is within the high charge rate area, the disconnection inspection step is performed when the charge rate is in the high charge rate area. If the charge rate is within the low charge rate range, and if the equalization process is performed when the charge rate is within the low charge rate range, the disconnection inspection step is performed when the charge rate is within the high charge rate range. Run on
A cell disconnection inspection method, characterized in that: