JP2010141956A - Capacity regulator for battery packs - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the following problem: it is difficult to quickly and accurately suppress an increase in variation in voltage among the battery cells Ci1, Ci2 comprising a battery pack. <P>SOLUTION: When the voltage of one of the battery cells Ci1, Ci2 is higher than that of the other by a predetermined value defining a dead band width or more, a discharge switch 30 or a discharge switch 34 is turned on to discharge the battery cell corresponding to the higher voltage. The above predetermined value can be increased by turning on a switching element 60. When currents passed through the battery cells Ci1, Ci2 are small, the switching element 60 is turned off to reduce the predetermined value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an assembled battery capacity adjusting device that constitutes an assembled battery as a series connection body of a plurality of battery cells and suppresses voltage variation between unit batteries that are one or a plurality of adjacent battery cells.

As this type of capacity adjustment device, for example, as disclosed in Patent Document 1 below, a device that discharges the charge of a battery cell having a voltage higher than the average value of the voltage of the battery cell constituting the assembled battery has been proposed. . Thereby, the voltage of the battery cell with a high voltage can be reduced to an average value, and the voltage of each battery cell of an assembled battery can be equalized by extension.
JP 2006-50785 A

  By the way, although the voltage of the battery cell depends on the capacity of the battery cell, when a current flows through the assembled battery, the voltage of each battery cell has an electromotive voltage determined according to the capacity and an internal resistance. This is the sum of the voltage drop due to. And this internal resistance has dispersion | variation for every battery cell resulting from an individual difference and a secular change. Therefore, in the case where the process for equalization is performed when the current flows through the assembled battery, the variation in the battery cell voltage can be suppressed under the situation where the assembled battery current has a certain value. There is a possibility that the capacity variation between the battery cells may not be suppressed. In particular, depending on the internal resistance, there is a situation in which the voltage of a cell having a small capacity is increased, and thus, the battery cell having a small capacity is subjected to a discharge treatment, whereby the capacity may be reduced unintentionally.

  Such a situation can be avoided by performing the above-described process for equalization only when the current flowing through the assembled battery is negligibly small, such as when the vehicle is stopped. However, if such a restriction is provided, the opportunity for processing to adjust the capacity of the battery cell is limited, so that the period during which the current flows through the assembled battery is prolonged, such as when the running time of the vehicle becomes long. May increase the variation in the capacity of the battery cells.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to constitute a battery assembly as a series connection body of a plurality of battery cells and to be a unit that is one or a plurality of adjacent battery cells. An object of the present invention is to provide a battery pack capacity adjustment device capable of suitably suppressing an increase in voltage variation between batteries.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

  The invention according to claim 1 constitutes an assembled battery as a series connection body of a plurality of battery cells, and the capacity of the assembled battery suppresses variations in voltage between unit batteries which are one or a plurality of adjacent battery cells. In the adjustment device, when a variation in voltage between the plurality of unit batteries constituting the assembled battery is out of an allowable range, an equalizing unit that performs at least one of the charging process and the discharging process of the unit battery so as to suppress the variation. And an enlarging means for enlarging the allowable range when the amount of current flowing through the assembled battery is large.

  When the current flowing through the assembled battery is large, the voltage variation of each unit battery due to the internal resistance variation between the unit batteries increases. For this reason, even if the voltages of the unit cells are equalized under such circumstances, the capacities of the unit cells may not be equalized by this, and there is a possibility that the variation in capacity may be increased. In the above invention, in view of this point, by expanding the allowable range when there is a large amount of current flowing through the assembled battery, it is difficult to accurately determine the capacity depending on the voltage of the unit battery. It is possible to suitably avoid the equalization process. In addition, by performing the equalization process while expanding the allowable range, it is possible to suppress an increase in capacity variation between unit cells compared to the case where the equalization process is prohibited when there is a large amount of current flowing through the assembled battery. You can also.

  According to a second aspect of the present invention, in the first aspect of the invention, the apparatus further includes an internal resistance variation detecting unit that detects a variation in internal resistance between the unit cells, and the enlarging unit has a variation in the detected internal resistance. If it is larger, the permissible range is expanded.

  When the variation in the internal resistance between the unit cells is large, the current flows through the assembled battery, so that the variation in the voltage becomes large despite the small variation in the capacity between the unit cells. For this reason, when the internal resistance is large, even if the voltages of the unit cells are equalized, the capacity of the unit cells may not be equalized by this, and there is a possibility that the variation of the capacity is increased. In view of this point, in the above invention, when the internal resistance is large, the allowable range is expanded, so that it is difficult to accurately determine the capacity depending on the voltage of the unit battery. Can be suitably avoided.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the internal resistance variation detecting means for detecting the variation in internal resistance between the unit cells, and the variation in the detected internal resistance is not more than a predetermined value. And a prohibiting means for prohibiting the expansion of the allowable range.

  When the variation in internal resistance is small, even if the current flowing through the assembled battery is large, the variation in voltage between unit cells appropriately represents the variation in capacity between unit cells. For this reason, under such a situation, it is possible to suitably equalize the capacities of the unit cells by equalizing the voltages of the unit cells. In the above invention, in view of this point, under such circumstances, it is possible to sufficiently equalize the capacities of the unit cells by prohibiting the expansion of the allowable range.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, further comprising an internal resistance variation detecting means for detecting a variation in internal resistance between the unit cells, wherein the enlarging means comprises: When the product of the quantitative value of the degree of variation in the detected internal resistance and the current flowing through the assembled battery is large, the allowable range is expanded.

  The variation in voltage between unit cells due to the internal resistance increases as the degree of variation in the internal resistance increases and as the current amount increases. In the above invention, in view of this point, it is possible to suitably perform the process of expanding the allowable range by appropriately quantifying the variation in voltage determined by these two factors.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the equalizing means suppresses the variation by a process of discharging a high voltage of the unit cells. It is characterized by being.

  According to the above invention, equalization processing can be realized with a relatively simple configuration.

  According to a sixth aspect of the present invention, in the fifth aspect of the present invention, the equalizing means constitutes the assembled battery and is a resistor for dividing the voltage of a predetermined number of adjacent unit cells by the predetermined number. And the discharge process is performed using the divided voltage value by the resistor and the corresponding positive electrode potential as input.

(First embodiment)
Hereinafter, a first embodiment in which an assembled battery capacity adjusting device according to the present invention is applied to an assembled battery capacity adjusting device mounted on a hybrid vehicle will be described with reference to the drawings.

  FIG. 1 shows a system configuration according to the present embodiment.

  The assembled battery 10 is configured as a series connection body of a plurality of (here, m × n) lithium secondary batteries (battery cells C11 to Cnm).

  On the other hand, the capacity adjustment apparatus according to the present embodiment uses “m (≧ 2)” battery cells C11 to C1m,..., Cn1 to Cnm as one block, and selectively selects voltages at both ends of each block. A flying capacitor 12 is provided for detection. That is, the flying capacitor 12 and both ends of the battery cells Ci1 to Cim (i = 1 to n) of each block can be selectively electrically connected (conducted) by the switching elements S1 to S (n + 1). Yes. The voltage of the flying capacitor 12 is taken into the differential amplifier circuit 14 via the switching elements Sa and Sb. Note that the switching elements S1 to S (n + 1) and the switching elements Sa and Sb are highly insulated from the microcomputer (microcomputer 16) side constituting the in-vehicle low voltage system and the assembled battery 10 side constituting the in-vehicle high voltage system. It is composed of a withstand voltage insulating element. This high breakdown voltage insulating element may be a photo MOS relay, for example. Then, the voltage across the flying capacitor 12 detected by the differential amplifier circuit 14 is taken into the microcomputer 16.

  The microcomputer 16 monitors the state of the assembled battery based on the detected voltage value, the detected current value detected by the current sensor 24, and the like. The microcomputer 16 is supplied with power from the battery 21 via the start switch 18, the relay 20, and the power supply line L <b> 1. Here, the relay 20 short-circuits the battery 21 and the power supply line L1 when the start switch 18 is turned on or a drive signal is input from the signal line L2. For this reason, when the start switch 18 is turned on, the battery 21 and the power supply line L <b> 1 are brought into conduction by the relay 20, so that the power of the battery 21 is supplied to the microcomputer 16.

  On the other hand, the microcomputer 16 monitors the on / off state of the start switch 18 via the signal line L3 when power is supplied from the battery 21. When the start switch 18 is turned off, a drive signal is output to the relay 20 via the signal line L2 in order to continue power supply to the microcomputer 16 until the post-processing performed before the microcomputer 16 is stopped is completed. To do. Thereby, even after the start switch 18 is turned off, the power of the battery 21 is supplied to the microcomputer 16 via the relay 20 and the power supply line L1 until the post-processing is completed in the microcomputer 16.

  The capacity adjustment device further includes equalization units U1 to Un that reduce voltage variations in the block. Each of these equalization units Ui (i = 1 to n) has an input terminal IN to which a command for reducing the variation in voltage is input, and an output terminal OUT that outputs a command signal input from the input terminal IN. (However, the most downstream equalization unit Un is not provided with the output terminal OUT).

  The microcomputer 16 outputs to the equalization units U1 to Un a command signal for reducing the voltage variation in each block. Specifically, the signal is output to the input terminal IN of the most upstream equalizing unit U1 via the photocoupler 22. Here, the photocoupler 22 is an element for taking insulation between the microcomputer 16 driven at a low voltage and the assembled battery 10 side. When the command signal is taken into the most upstream equalizing unit U1, the most upstream equalizing unit U1 outputs this signal to the input terminal IN of the adjacent equalizing unit U2 on the lower potential side. In this way, the same command signal is input up to the most downstream equalization unit Un. A technique for outputting a command signal to the most upstream unit and sequentially transmitting the command signal to the most downstream unit is disclosed in, for example, Japanese Patent Application Laid-Open No. 2007-278913.

  FIG. 2 shows a circuit configuration of the equalization unit Ui. This figure shows an example in which the number of battery cells in each block is “2”.

  As shown in the figure, the equalization unit Ui includes a discharge resistor 32 that constitutes the discharge circuit of the battery cell Ci1, and a PNP-type bipolar transistor (discharge switch 30) that opens and closes the discharge circuit. Further, the equalizing unit Ui includes a discharge resistor 36 that constitutes a discharge circuit of the battery cell Ci2, and an NPN bipolar transistor (discharge switch 34) that opens and closes the discharge circuit. Furthermore, the equalization unit Ui includes resistors 46 and 48 for equally dividing the block voltage (the voltage of the series connection body of the battery cells Ci1 and Ci2). Then, the potential at the connection point of the resistors 46 and 48 and the positive potential of the corresponding battery cell Ci2 are input to the comparison circuit 50. The comparison circuit 50 turns on the discharge switch 34 to discharge the battery cell Ci2 when the positive electrode potential is higher than the predetermined potential with respect to the potential at the connection point. When the positive electrode potential is lower than a predetermined value, the discharge switch 30 is turned on to discharge the battery cell Ci1.

  Specifically, a resistor 38, an NPN-type bipolar transistor (transistor 40), a PNP-type bipolar transistor (transistor 42), and a resistor 44 are connected in series to a block (series connection body of battery cells Ci1, Ci2). The body is connected. On the other hand, the comparison circuit 50 includes an operational amplifier 52 having an output terminal connected to the bases of the transistors 40 and 42. The operational amplifier 52 has its non-inverting input terminal connected to the connection point of the resistors 46 and 48, and its inverting input terminal connected to the output terminal via the resistor 56 and via the resistor 54. It is connected to the connection point of the battery cells Ci1, Ci2. Further, a series connection body of a resistor 58 and a switching element 60 is connected to the resistor 56 in parallel. The switching element 60 is of a normally open type, and is turned on / off according to a command signal input from the input terminal IN of the equalization unit Ui.

  According to such a configuration, when the voltage variation of the battery cells Ci1 and Ci2 is greater than or equal to a predetermined value, the cell having the higher voltage can be discharged. Moreover, the threshold value of the variation degree for performing the discharge process can be changed by turning on the switching element 60. In other words, the allowable range of voltage variation can be expanded. This will be described below.

  When the resistance values R1 and R2 of the resistors 54 and 56, the output voltage Vo of the operational amplifier 52, and the voltages V1 and V2 of the battery cells Ci1 and Ci2 are used, the voltage at the inverting input terminal of the operational amplifier 52 and the non-inverting input are caused by an imaginary short. Since the terminal voltages are equal to each other, the following expression (c1) is established.

(Vo−V2) · R1 / (R1 + R2) + V2 = (V1 + V2) / 2 (c1)
The condition for turning on the transistor 42 is expressed by the following equation (c2) when the threshold voltage Vbe of the transistor 42 is used.

V2-Vo> Vbe (c2)
In the above equation (c2), the following equation (c3) is established by removing the output voltage Vo using the above equation (c1).

V2-V1> 2Vbe / (1 + R2 / R1) (c3)
Similarly, the condition for turning on the transistor 40 is expressed by the following expression (c4) using the threshold voltage Vbe of the transistor 40, so the following expression (c5) is established.

Vo−V2> Vbe (c4)
V1-V2> 2Vbe / (1 + R2 / R1) (c5)
According to the above equations (c3) and (c5), when one of the voltages is higher than the other by “2 Vbe / (1 + R2 / R1)” or more, the transistor 40, the discharge switch 30, the transistor 42, and the discharge One of the switches 34 for use is turned on, so that one of the battery cells is discharged. Moreover, since turning on the switching element 60 is equivalent to reducing the resistance value R2 in the above formulas (c3) and (c5), any battery cell can be obtained by turning on the switching element 60. The region where the discharge is not performed (dead zone) is enlarged.

  In FIG. 3, the equalization discharge process aspect by the said equalization unit Ui is shown. Specifically, FIG. 3A shows the transition of the voltages V1 and V2 of the battery cells Ci1 and Ci2, FIG. 3B shows the transition of the operating state of the discharge switch 34 of the battery cell Ci2, and FIG. (C) shows the transition of the operating state of the discharge switch 30 of the battery cell Ci1.

  As shown in the figure, when the voltage V2 of the battery cell Ci2 is higher than the voltage V1 of the battery cell Ci1 by a threshold Δ or more, the discharge switch 34 for discharging the battery cell Ci2 is turned on. Further, when the voltage V2 of the battery cell Ci2 is lower than the voltage V1 of the battery cell Ci1 by a threshold Δ or more, the discharge switch 30 for discharging the battery cell Ci1 is turned on. Here, the threshold Δ differs depending on the state of the switching element 60, and is “2Vbe / (1 + R2 / R1)” when the switching element 60 is in the OFF state.

  According to such a configuration, the dead zone region can be variably set by operating the switching element 60 by the microcomputer 16. In particular, in this embodiment, when the current flowing through the assembled battery 10 is large, the dead zone region is expanded, so that the equalization discharge process by the equalization unit Ui can be made appropriate in accordance with the situation. This will be described below.

  FIG. 4A shows that the internal resistances of the battery cells Ci1 and Ci2 are greatly different from each other even though the capacities of the battery cells Ci1 and Ci2 are equal. In this example, the voltages V1 and V2 of FIG. Incidentally, in FIG. 4, the horizontal axis represents the charge / discharge current of the battery cell, and the vertical axis represents the voltage of the battery cell. The voltage of the battery cells Ci1 and Ci2 depends not only on the state of charge (remaining capacity: SOC) but also on the voltage drop due to the internal resistance. For this reason, when the internal resistance, which is the amount of voltage change with respect to the current change, is different, the voltage is different as long as the current amount is not zero even if the SOC is the same. However, in the present embodiment, when the current flowing through the assembled battery 10 is large, the dead zone region (in the drawing, the alternate long and short dash line and the broken line) is enlarged, so that the equalizing discharge process is not performed. In the present embodiment, the dead zone region is enlarged when the current flowing through the assembled battery 10 is large. FIG. 4A shows an example in which the dead zone region is enlarged in the entire current zone for convenience.

  On the other hand, FIG. 4B shows a case where an equalization request is generated at the time when the absolute value of the discharge current increases (I = I0) because the SOCs of the battery cells Ci1 and Ci2 are different. In this case, as shown in FIG. 4C, the voltage difference between the battery cells Ci1 and Ci2 at zero current can be reduced, and the difference in SOC can be reduced.

  On the other hand, as shown in FIG. 4D, when the dead zone region is not enlarged even when the absolute value of the discharge current becomes large (I = I0), the SOCs of the battery cells Ci1 and Ci2 are equal. Regardless, there is a demand for equalization due to variations in internal resistance. For this reason, as shown in FIG.4 (e), a difference arises in SOC between battery cell Ci1, Ci2 by equalization discharge processing.

  FIG. 5 shows a procedure of the dead zone region variable setting process according to the present embodiment. This process is repeatedly executed by the microcomputer 16 at a predetermined cycle, for example.

In this series of processing, first, in step S10, it is determined whether or not there is a request to reduce the dead zone width. Here, it is determined whether or not the current flowing through the assembled battery 10 is under a situation that is assumed to be equal to or lower than an upper limit value that does not cause voltage variation due to internal resistance. Specifically, for example, it may be determined whether or not at least one of the following conditions is satisfied.
a. Disconnection from power conversion circuit: The assembled battery 10 is connected to a rotating machine as an in-vehicle power generation device via an inverter or the like as a power conversion circuit, and the low-voltage battery via a DCDC converter as a power conversion circuit. 21 is connected. Here, between the assembled battery 10 and the power conversion circuit, a conduction control means such as a relay for electrically connecting and disconnecting between them is provided. The condition is that the battery pack 10 and the power conversion circuit are disconnected by the conduction control means.
b. Condition that the start switch 18 of the in-vehicle control device (microcomputer 16) is turned off: In this case, since it is considered that the charge / discharge current of the assembled battery 10 will be very small or zero thereafter, this condition may be adopted.
c. The condition that the detected value of the current flowing through the assembled battery 10 (detected value by the current sensor 24) is equal to or less than the threshold value: Here, the threshold value is set to the upper limit value or less that does not make the voltage variation due to the internal resistance noticeable. It is desirable to do.

  If it is determined in step S10 that there is a request for reducing the dead band width, in step S12, the switching element 60 of the equalization unit Ui is turned off to reduce the dead band width. On the other hand, if a negative determination is made in step S10, the switching element 60 of the equalization unit Ui is turned on in step S14 to increase the dead zone width. When the processes in steps S12 and S14 are completed, this series of processes is temporarily terminated.

  Incidentally, even after the microcomputer 16 is stopped, since the equalization unit Ui is in a power supply state by the corresponding battery cells Ci1 to Cim, the equalization discharge is performed when the voltage variation is out of the dead zone region. The At this time, since the switching element 60 is turned off, the dead zone region is reduced.

  According to the embodiment described in detail above, the following effects can be obtained.

  (1) When the amount of current flowing through the battery pack 10 is large, the allowable range (dead zone) of voltage variation was expanded. Accordingly, it is possible to preferably avoid the excessive voltage equalization process being performed in a situation where it is difficult to accurately determine the capacity of the battery cell depending on the voltage. In addition, by performing the equalization process while expanding the dead zone, it is possible to suppress an increase in the capacity variation between the battery cells compared to the case where the equalization process is prohibited when the current flowing through the battery pack 10 is large. (FIG. 4 (c)).

  (2) The switching element 60 for expanding the dead zone region is of a normally open type. Thereby, the dead zone region can be reduced under the situation where the microcomputer 16 is stopped. For this reason, in a situation where the current flowing through the assembled battery 10 is small and the capacity can be equalized with high accuracy by the equalizing discharge process, high accuracy is equalized based on the reduced dead band width regardless of the stop of the microcomputer 16. Processing can be performed.

(Second Embodiment)
Hereinafter, the second embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  FIG. 6 shows a circuit configuration of the equalization unit Ui according to the present embodiment.

  As illustrated, the comparison circuit 50 of the present embodiment includes a series connection body of a resistor 58a and a switching element 60a, a series connection body of a resistor 58b and a switching element 60b, and a series connection of a resistor 58c and a switching element 60c. A connection body is provided, and these are connected in parallel to the resistor 56. Thereby, the dead band width can be variably set in four stages according to how many of the switching elements 60a to 60c are turned on.

  FIG. 7 shows the procedure of the dead zone region variable setting process according to the present embodiment. This processing is repeatedly executed by the microcomputer 16 for each block, for example, at a predetermined cycle.

  In this series of processing, first, in step S20, the internal resistance Rr of the target block is detected. This processing is performed internally using a regression analysis method or the like based on a plurality of sets of the detected value of the block voltage performed using the flying capacitor 12 and the differential amplifier circuit 14 and the current flowing through the assembled battery 10 at that time. What is necessary is just to set it as the process which calculates resistance Rr. In the subsequent step S22, it is determined whether or not the absolute value of the difference between the normal internal resistance Rn and the detected internal resistance Rr for the block is equal to or less than a threshold value ΔR. This process is for determining whether or not the variation in internal resistance between the battery cells constituting the block is greater than or equal to a predetermined value. That is, when the internal resistance Rr of the block deviates from the normal internal resistance Rn, it is considered that the internal resistances of the battery cells constituting the block also vary. For this reason, based on the internal resistance of the block deviating from the normal internal resistance Rn, it is estimated that the internal resistance between the battery cells in the block has varied.

  If an affirmative determination is made in step S22, it is considered that there is no variation in the internal resistance between the battery cells constituting the block. Therefore, in step S30, the dead zone width W is set to the minimum width W1. That is, all the switching elements 60a to 60c are turned off. This is a setting in view of the fact that when there is no variation in internal resistance, the variation in SOC between battery cells can be grasped with high accuracy by the voltage variation between battery cells.

  On the other hand, when a negative determination is made in step S22, in steps S24 to S28, the absolute value of the charge / discharge current detection value (current I) of the battery pack 10 is compared with the threshold values α, β, and γ. . Then, as the current I increases, the dead zone width W is increased (steps S30 to S36). That is, when the absolute value of the charge / discharge current is equal to or less than the threshold value α (step S24: YES), the dead zone width W is set to the width W1 (step S30), and the absolute value of the charge / discharge current is greater than the threshold value α and less than the threshold value β. In the case (step S26: YES), the dead zone width W is set to the width W2 (> W1) (step S32). If the absolute value of the charging / discharging current is larger than the threshold β and not more than the threshold γ (step S28: YES), the dead zone width W is set to the width W3 (> W2) (step S34), and the absolute value of the charging / discharging current is When larger than the threshold value γ (step S28: NO), the dead zone width W is set to the width W4 (> W3) (step S36). This is because when the internal resistance varies, the estimation accuracy of the SOC variation between the battery cells due to the voltage variation between the battery cells decreases as the current flowing through the assembled battery 10 increases.

  In addition, when the process of step S30-S36 is completed, this series of processes are once complete | finished.

  As described above, in the present embodiment, as the absolute value of the current I increases, the dead zone width W is increased, so that the positive correlation coefficient between the voltage variation between the battery cells and the SOC variation between the battery cells decreases. The dead zone width can be expanded. For this reason, it is possible to perform the equalizing discharge process as much as possible while suitably avoiding an inappropriate equalizing discharge process. In particular, in this embodiment, when it is estimated that the variation in internal resistance between battery cells is small, the dead band width W is set to the minimum width W1 regardless of the absolute value of the current I, as shown in FIG. In addition, the capacity can be equalized with high accuracy.

  According to this embodiment described above, the following effects can be obtained in addition to the effects (1) and (2) of the first embodiment.

  (3) The dead zone width W was increased as the current flowing through the battery pack 10 increased. Thereby, the equalizing discharge process can be performed as much as possible while suitably avoiding an inappropriate equalizing discharge process.

  (4) When the variation of the battery cells Ci1 and Ci2 is equal to or less than a predetermined value, the expansion of the dead zone width W is prohibited. Thereby, the capacity | capacitance of battery cell Ci1, Ci2 can fully be equalized.

(Third embodiment)
Hereinafter, the third embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  FIG. 9 shows the procedure of the dead zone region variable setting process according to the present embodiment. This processing is repeatedly executed by the microcomputer 16 for each block, for example, at a predetermined cycle. In FIG. 9, the same steps as those shown in FIGS. 5 and 7 are given the same step numbers for the sake of convenience.

  As shown in the figure, in the present embodiment, the dead zone width W is increased as the internal resistance variation of the battery cells Ci1 and Ci2 is considered to be large. That is, when the negative determination is made in step S10 and the absolute value of the difference between the normal internal resistance Rn and the detected internal resistance Rr for the block is equal to or smaller than the threshold value ΔR1 (step S40: YES), the dead zone width W is increased. W2 is set (step S32). If the absolute value of the difference between the normal internal resistance Rn and the detected internal resistance Rr for the block is larger than the threshold ΔR1 and equal to or smaller than the threshold ΔR2 (step S42: YES), the dead zone width W is set to the width W3. (Step S34). Further, when the absolute value of the difference between the normal internal resistance Rn and the detected internal resistance Rr for the block is larger than the threshold value ΔR2 (step S42: NO), the dead zone width W is set as the width W4 (step S36).

  According to this embodiment described above, the following effects can be obtained in addition to the effects (1) and (2) of the first embodiment.

  (5) The dead zone width W was increased so that the variation in internal resistance between the battery cells Ci1 and Ci2 was considered large. Thereby, it is possible to suitably avoid the process of equalizing the excessive voltage in a situation where it is difficult to accurately determine the capacity depending on the voltage of the battery cells Ci1 and Ci2.

(Fourth embodiment)
Hereinafter, the fourth embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  FIG. 10 shows the procedure of the dead zone region variable setting process according to the present embodiment. This processing is repeatedly executed by the microcomputer 16 for each block, for example, at a predetermined cycle. In FIG. 10, the same steps as those shown in FIG. 7 are given the same step numbers for the sake of convenience.

  As shown in the figure, in the present embodiment, the difference between the normal internal resistance Rn, which is a parameter quantifying the variation between the internal resistances of the battery cells Ci1, Ci2, and the detected internal resistance Rr flow through the assembled battery 10. The larger the absolute value of the product with the current I, the wider the dead band width W.

  That is, when the absolute value of the product is equal to or smaller than the threshold value ΔV1 (step S50: YES), the dead zone width W is set as the width W1 (step S30), and the absolute value of the product is larger than the threshold value ΔV1 and equal to or smaller than the threshold value ΔV2. (Step S52: YES), the dead zone width W is set as the width W2 (step S32). When the absolute value of the product is larger than the threshold value ΔV2 and equal to or smaller than the threshold value ΔV3 (step S54: YES), the dead zone width W is set as the width W3 (step S34), and the absolute value of the product is larger than the threshold value ΔV3. (Step S54: NO), the dead zone width W is set as the width W4 (step S36).

  According to this embodiment described above, the following effects can be obtained in addition to the effects (1) and (2) of the first embodiment.

  (6) The dead zone width W was increased as the absolute value of the product of the quantitative value of the degree of variation of the battery cells Ci1 and Ci2 and the current flowing through the battery pack 10 increased. Thereby, the expansion process of dead zone width W can be performed suitably.

(Fifth embodiment)
Hereinafter, a fifth embodiment will be described with reference to the drawings, focusing on differences from the first embodiment.

  FIG. 11 shows a circuit configuration of the equalization unit Ui according to the present embodiment. In FIG. 11, members corresponding to those shown in FIG. 2 are given the same reference numerals for convenience.

  As shown in the figure, in this embodiment, the number of battery cells Cij constituting the block is set to “3”, and the equalization unit Ui performs a process of reducing the voltage variation of the three battery cells Ci1, Ci2, Ci3.

  Specifically, a series connection body of resistors 70a, 70b, 70c having the same resistance value is provided at both ends of the battery cells Ci1, Ci2, Ci3 in order to equally divide the block voltage by the number of battery cells constituting the block voltage. Connected in parallel. Each battery cell Ci1, Ci2, Ci3 has a series connection body of discharge switches 72a, 72b, 72c, which are PNP type bipolar transistors, and discharge resistors 74a, 74b, 74c, respectively. Connected in parallel. Resistors 76a, 76b, and 76c are connected between the emitters and bases of the discharge switches 72a, 72b, and 72c. The bases of the discharge switches 72a, 72b, 72c are connected to the corresponding battery cells Ci1, Ci2 via the resistors 78a, 78b, 78c and the collectors and emitters of the switching elements 80a, 80b, 80c as NPN bipolar transistors. , Ci3 are connected to the negative electrode.

  Resistors 82a, 82b, and 82c are connected between the bases and emitters of the switching elements 80a, 80b, and 80c. The base of the switching element 80c is connected to the positive side of the battery cell Ci3 to be discharged by the discharge switch 72c through the resistor 84c and the collector and emitter of the PNP bipolar transistor (transistor 100). . The base of the transistor 100 includes the positive electrode of the battery cell Ci3 to be discharged by the discharge switch 72c and the resistors 70a. It is connected to the output of the comparison circuit 50 which receives the potential at the connection point 70b as an input. Thus, when the voltage of the battery cell Ci3 is higher than the average value of the voltage of the battery cells Ci1, Ci2, Ci3, which is the potential of the connection point, the transistor 100 is turned on. As a result, the switching element 80c is also turned on, and consequently the discharge switch 72c is turned on, so that both ends of the battery cell Ci3 are connected by the series connection body of the discharge switch 72c and the discharge resistor 74c. Ci3 is discharged.

  The base of the switching element 80a is connected to the positive electrode of the battery cell Ci1 to be discharged by the discharge switch 72a through the resistor 84a and the collector and emitter of a PNP bipolar transistor (switching element 86a). A resistor 88a is connected between the emitter and base of the switching element 86a, and the base is connected to the discharge switch 72a via the resistor 90a and the collector and emitter of the NPN bipolar transistor (transistor 92a). Is connected to the negative electrode side of the battery cell Ci1 to be discharged. The output voltage of the comparison circuit 50 that receives the potential at the connection point of the battery cells Ci1 and Ci2 and the potential at the connection point of the resistors 70a and 70b is applied to the base of the transistor 92a. As a result, when the average voltage of the battery cells Ci1 to Ci3 is twice or more higher than the total voltage of the battery cells Ci2 and Ci3 (the connection point potential of the resistors 70a and 70b) is greater than a predetermined value, the transistor 92a is turned on. it can. Thus, the switching elements 86a and 80a are turned on, and the discharge switch 72a is turned on, so that both ends of the battery cell Ci1 are connected by the series connection body of the discharge switch 72a and the discharge resistor 74a. Battery cell Ci1 is discharged.

  On the other hand, the base of the switching element 80b is connected to the positive electrode of the battery cell Ci2 to be discharged by the discharge switch 72b via the resistor 84b and the collector and emitter of the PNP bipolar transistor (switching element 86b). A resistor 88b is connected between the emitter and base of the switching element 86b, and the base is discharged via the diode 102, the resistor 90b and the collector and emitter of the NPN bipolar transistor (transistor 92b). It is connected to the negative electrode side of the battery cell Ci2 to be discharged by the switch 72b. The output voltage of the comparison circuit 50 that receives the potential at the connection point between the positive electrode of the battery cell Ci3 and the resistors 70b and 70c is applied to the base of the transistor 92b. Furthermore, the cathode side of the diode 102 is connected to the positive electrode of the battery cell Ci3 on the high potential side via the collector and emitter of a PNP bipolar transistor (switching element 94). A resistor 96 is connected between the emitter and base of the switching element 94, and the base is connected to the collector of the transistor 92a via the resistor 98.

  Thereby, the battery cell Ci2 is used when the voltage of the battery cell Ci3 is lower than the average voltage and the total voltage of the battery cell Ci2 and the battery cell Ci3 on the lower potential side is higher than twice the average voltage. It will be discharged. That is, in this case, the transistors 92b, 86b, and 80b are turned on, and the discharge switch 72b is turned on, so that both ends of the battery cell Ci2 are connected by the series connection body of the discharge switch 72b and the discharge resistor 74b. The battery cell Ci2 is discharged. On the other hand, even when the voltage of the battery cell Ci3 is lower than the average voltage, the total voltage of the battery cell Ci2 and the battery cell Ci3 on the lower potential side is lower than twice the average voltage. When the transistor 92a is turned on, the switching element 94 is turned on, and the cathode side of the diode 102 is at a higher potential than the anode side, so that the switching element 86b is not turned on. For this reason, the discharge switch 72b is not turned on, and the discharge of the battery cell Ci2 is prohibited.

  As described above, in the present embodiment, for the intermediate battery cell Ci2 among the battery cells Ci1 to Ci3 constituting the block, when the high-potential side battery cell Ci3 is discharged, a prohibition unit for prohibiting the discharge is provided. Prepared. As a result, the voltage of the block voltage is compared by using means (comparing circuit 50) for comparing the voltage value obtained by equally dividing the block voltage with the resistors of the number of battery cells constituting the block and the positive potential of the corresponding battery cell. A process for discharging high battery cells can be performed.

(Other embodiments)
Each of the above embodiments may be modified as follows.

  In the first embodiment, the microcomputer 16 may not perform the process shown in FIG. Even in this case, when the start switch 18 is turned off, the dead zone width W is reduced.

  In FIG. 2, the resistor 58 and the switching element 60 constituting the comparison circuit 50 are connected in parallel to the resistor 56, but the present invention is not limited thereto, and may be connected in parallel to the resistor 54, for example. In this case, however, the dead zone is reduced by turning on the switching element.

  In FIG. 6, the resistors 58 a, 58 b, 58 c and the switching elements 60 a, 60 b, 60 c constituting the comparison circuit 50 are connected in parallel to the resistor 56, but not limited thereto, for example, in parallel to the resistor 54. You may connect. In this case, however, the dead zone is reduced by turning on the switching element.

  In FIG. 6, the configuration in which the dead zone width can be variably set in four stages is illustrated, but the present invention is not limited to this, and may be three stages or five stages or more.

  In the previous fifth embodiment, the number of battery cells to be equalized is not limited to three and may be four or more. In this case, the discharge condition of the intermediate battery cell may be a condition that the corresponding divided voltage is larger than the negative electrode potential and that the high-potential battery cell is not discharged. desirable.

  -Based on the comparison of each divided voltage (potential of the connection point of the resistors) obtained by dividing the total voltage of three or more battery cells by the number of battery cells, and the positive potential of the corresponding battery cell The equalizing unit that discharges the battery cells having a high height is not limited to that illustrated in FIG. For example, you may change the structure illustrated by Unexamined-Japanese-Patent No. 2002-325370 so that a dead zone width can be variably set.

  The method for detecting the internal resistance of the battery cell Cij is not limited to the method for detecting the average internal resistance of the battery cells constituting the block. For example, the degree of deterioration over time of the battery pack 10 is quantified based on the travel distance of the vehicle, the charge / discharge time of the battery pack 10, the integrated amount of the absolute value of the charge / discharge current, etc. Variations may be estimated. That is, when the deterioration with time progresses, the variation in internal resistance is considered to increase, so it can be estimated that the variation in internal resistance increases as the deterioration with time progresses. Further, for example, by setting the voltage detection target by the voltage detection means configured to include the flying capacitor 12 and the differential amplifier circuit 14 as a battery cell, based on a set of detected values of the voltage and current of each battery cell. The internal resistance may be calculated.

  In each of the embodiments described above, the dead band width is instructed to one equalization unit so that the command is sequentially notified from the equalization unit to which the command has been issued to another equalization unit. However, the present invention is not limited thereto, and the microcomputer 16 may issue a command to each equalization unit.

  In each of the above embodiments, the present invention is applied to equalize the battery cells in the block. However, the present invention is not limited to this. For example, the equalization target of the equalization unit may be all the battery cells constituting the assembled battery, and the present invention may be applied when performing the equalization process.

  In each of the above embodiments, the equalization unit is always supplied with power from the corresponding block, so that the equalization discharge by the equalization unit is always possible. However, the present invention is not limited to this. For example, a switch may be provided between the block and the corresponding equalization unit, and power may be supplied from the block to the equalization unit only when the switch is closed.

  In each of the above embodiments, the present invention is applied when equalizing the battery cells in the block, but the present invention is not limited to this. For example, you may apply this invention to equalization of the blocks which comprise an assembled battery. In this case, for example, the microcomputer 16 may perform equalization discharge by turning on all the discharge circuits of the corresponding equalization unit in accordance with the degree of deviation between the voltages of the respective blocks. Further, at this time, the threshold values for determining whether or not the equalizing discharge is performed are variably set according to the internal resistance detected based on the combination of the block voltage and the current. It is also possible to apply the method of the embodiment.

  In each of the above embodiments, the voltage detection means is configured by the flying capacitor 12 and the differential amplifier circuit 14. However, the present invention is not limited to this. For example, a resistor that divides the target voltage and an analog-digital converter (A / D converter) ).

  The battery cell is not limited to a lithium secondary battery but may be a nickel hydride secondary battery, for example.

  In each of the above-described embodiments, the present invention is applied to the assembled battery mounted on the hybrid vehicle. However, the present invention is not limited thereto, and may be applied to, for example, a battery mounted on an electric vehicle.

1 is a system configuration diagram according to a first embodiment. FIG. The circuit diagram which shows the circuit structure of the equalization unit concerning the embodiment. The time chart explaining operation | movement of the said equalization unit. The figure which illustrates the equalization aspect of the said embodiment. The flowchart which shows the procedure of the equalization process concerning the embodiment. The circuit diagram which shows the circuit structure of the equalization unit concerning 2nd Embodiment. The flowchart which shows the procedure of the equalization process concerning the embodiment. The figure which shows the effect of the same embodiment. The flowchart which shows the procedure of the equalization process concerning 3rd Embodiment. The flowchart which shows the procedure of the equalization process concerning 4th Embodiment. The circuit diagram which shows the circuit structure of the equalization unit concerning 5th Embodiment.

Explanation of symbols

  10 ... assembled battery, 16 ... microcomputer, Ui ... equalization unit, Cij ... battery cell.

Claims (6)

In an assembled battery capacity adjustment device that constitutes an assembled battery as a series connection body of a plurality of battery cells and suppresses variation in voltage between unit batteries that are one or a plurality of adjacent battery cells,
Equalization means for performing at least one of the charging process and the discharging process of the unit cell so as to suppress the variation when the variation in voltage between the plurality of unit cells constituting the assembled battery is out of an allowable range;
An assembled battery capacity adjusting device comprising: an enlarging means for enlarging the allowable range when the amount of current flowing through the assembled battery is large. An internal resistance variation detecting means for detecting variation in internal resistance between the unit cells;
2. The battery pack capacity adjustment device according to claim 1, wherein the expansion means expands the allowable range when the variation in the detected internal resistance is large. Internal resistance variation detecting means for detecting variation in internal resistance between the unit cells;
The assembled battery capacity adjustment device according to claim 1, further comprising a prohibiting unit that prohibits the expansion of the allowable range when the detected variation in the internal resistance is equal to or less than a predetermined value. An internal resistance variation detecting means for detecting variation in internal resistance between the unit cells;
The expansion means expands the permissible range when the product of the quantitative value of the degree of variation in the detected internal resistance and the current flowing through the assembled battery is large. The capacity adjustment apparatus of the assembled battery of 1 item | term.   The capacity of the assembled battery according to any one of claims 1 to 4, wherein the equalizing means suppresses the variation by a process of discharging a high voltage of the unit batteries. Adjustment device.   The equalizing means includes a resistor that constitutes the assembled battery and divides the voltage of a predetermined number of adjacent unit cells by the predetermined number, and a positive potential corresponding to a divided value by the resistor, 6. The capacity adjustment apparatus for an assembled battery according to claim 5, wherein the discharging process is performed with the input as a power source.

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