JP2014003777A - Battery state adjusting device and battery pack system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To equalize states of charge among cells at high accuracy and in a short time.SOLUTION: A battery pack system comprising a battery pack composed of a plurality of cells connected in series measures terminal voltages of all of the cells when sufficient time has passed after discharging a load stops, sets a target voltage Vd on the basis of the minimum value of the measured voltage, and sets a cell having a terminal voltage larger than the target voltage Vd as a target cell. After that, the battery pack system executes an equalization discharge action for discharging the target cell while calculating a differential voltage (ΔV1[i]) between the terminal voltages of the target cell (V1[i] and V2[i]) measured before and after the discharge, acquiring a voltage return amount (ΔV2[i]) supposed to be generated after the stop of the discharge from data retained in advance, calculating a correction target voltage (Vd2[i]=Vd-ΔV1[i]-ΔV2[i]) by using the differential voltage and the voltage return amount, and stopping the discharge when the terminal voltage of the target cell has reached the correction target voltage.

Description

  The present invention relates to a battery state adjusting device and an assembled battery system.

  In a battery pack formed by directly connecting a plurality of cells, if the state of charge is different between the plurality of cells, the discharge output of the battery pack is limited by the cell in the lowest state of charge. In view of this, an equalization process that suppresses variations in the state of charge of a plurality of cells has been proposed. Among the proposed methods, there is also an equalization processing method that takes into account the amount of voltage drop due to the internal resistance of the cell (see, for example, Patent Document 1 below). On the other hand, after charging or discharging of the cell is stopped, voltage components due to electrochemical components remain in the cell, and it takes a certain time (for example, several hours) for the cell terminal voltage to stabilize. Is also known. A method of performing equalization processing after waiting for such voltage stabilization, or a method of determining whether or not the equalization has ended after providing a voltage stabilization wait time according to the cell temperature after performing the equalization processing ( For example, see Patent Document 2 below).

JP 2009-159794 A JP 2009-89566 A

  If the equalization is made in consideration of the above voltage component caused by the electrochemical component, the accuracy of the equalization process can be improved. However, in the method of providing the voltage stabilization waiting time described above, the time required for equalization becomes longer.

  Accordingly, an object of the present invention is to provide a battery state adjusting device that contributes to high accuracy and equalization in a short time.

  A battery state adjustment device according to the present invention includes a charge / discharge circuit capable of performing a charge / discharge operation, which is a process of individually charging or discharging a plurality of cells connected in series, and a voltage measurement circuit for measuring a terminal voltage of each cell. A data holding unit that holds data of a voltage return amount when the terminal voltage of each cell transiently returns from the first open voltage to the second open voltage after the charge or discharge of each cell is stopped, and the charge / discharge Based on the terminal voltage of each cell measured before the start of operation, a target voltage is set and a target voltage / target cell setting unit for setting a target cell from among the plurality of cells, and before and after the start of the charge / discharge operation A target voltage correction unit that corrects the target voltage and derives a corrected target voltage based on the terminal voltage of the target cell measured in step S3 and the voltage return amount data; and the charge / discharge operation for the target cell. Started Characterized in that the terminal voltage of the target cell is provided with a charging and discharging control unit to terminate the charging and discharging operation for the target cell when it reaches the corrected target voltage.

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to provide the battery state adjustment apparatus which contributes to an equalization implementation | achievement in accuracy and a short time.

1 is an overall configuration diagram of an assembled battery system according to an embodiment of the present invention. 1 is an overall configuration diagram of an assembled battery system according to an embodiment of the present invention. The internal equivalent circuit diagram (a) of the cell and the equivalent circuit diagram examples (b) and (c) of the impedance circuit in the cell. It is a figure which shows the mode of the change of the terminal voltage of a cell before and after discharge of a cell. It is an operation | movement flowchart of the equalization process which concerns on embodiment of this invention. It is a figure which shows the mode of the change of the terminal voltage of an object cell. It is a flowchart which shows the preparation procedure of voltage return amount data. It is a figure which shows the some cell utilized for preparation of voltage return amount data. It is a figure which shows the structure utilized for preparation of voltage return amount data. It is a wave form chart of a terminal voltage of a cell observed at the time of creation of voltage return amount data. It is a figure which shows the relationship between SOC of a cell, and OCV. It is an internal block diagram of the control circuit which concerns on embodiment of this invention. It is an example of the block diagram of a target voltage correction | amendment part.

  Hereinafter, an example of an embodiment of the present invention will be specifically described with reference to the drawings. In each of the drawings to be referred to, the same part is denoted by the same reference numeral, and redundant description regarding the same part is omitted in principle. In this specification, for simplification of description, a symbol or reference that refers to information, signal, physical quantity, state quantity, member, or the like is written to indicate information, signal, physical quantity, state quantity or Names of members and the like may be omitted or abbreviated.

  FIG. 1 is an overall configuration diagram of an assembled battery system according to an embodiment of the present invention. The assembled battery system includes an assembled battery 1 that is a storage battery module and a charge state equalization device 2. The assembled battery 1 includes n cells 10 connected in series with each other. In FIG. 1, n = 3, but n may be any number as long as it is 2 or more. Each cell 10 forming the assembled battery 1 is an arbitrary type of storage battery, for example, a lithium ion battery or a nickel metal hydride battery. In the present embodiment, discharging and charging means discharging and charging of the assembled battery 1 or the cell 10 unless otherwise specified. A parallel connection circuit of a plurality of cells 10 may be included in the assembled battery 1, or a plurality of series connection circuits of the plurality of cells 10 may be connected in parallel to each other in the assembled battery 1. In the description, attention is paid only to n cells 10 connected in series with each other.

  A power block 3 is connected to the assembled battery 1. The power block 3 includes a load and a power source. The assembled battery 1 can supply discharge power to a load in the power block 3 and can be supplied with charging power from a power source in the power block 3. A power conversion circuit (not shown) may be interposed between the assembled battery 1 and the load and power source in the power block 3. The charging / discharging control circuit (not shown) controls charging and discharging of the assembled battery 1 between the assembled battery 1 and the power block 3. This charge / discharge control circuit may be considered to be included in the components of the assembled battery system, and the power block 3 may be considered to be included in the components of the assembled battery system.

  The charge state equalization apparatus 2 includes a control circuit 20, a discharge circuit 21 provided for each cell 10, and a voltage sensor 22 provided for each cell 10. Each discharge circuit 21 includes a series connection circuit of a resistor R and a switching element SW, and the series connection circuit as each discharge circuit 21 is connected in parallel between the positive electrode and the negative electrode of the corresponding cell 10. Each voltage sensor 22 is connected in parallel between the positive electrode and the negative electrode of the corresponding cell 10, and measures the terminal voltage of the corresponding cell 10 (the positive electrode potential of the cell 10 with reference to the negative electrode potential of the cell 10). A signal indicating the measurement result of each voltage sensor 22 is output to the control circuit 20. The control circuit 20 includes a CPU (central processing unit) and the like, and performs on / off control of each switching element SW based on the measurement result of the voltage sensor 22 and the like. A semiconductor switching element such as a field effect transistor is employed as the switching element SW, but a mechanical switch may be used as the switching element SW. Some switching elements SW may be turned on only when an equalization process described later is executed, and all switching elements SW are turned off when the equalization operation is not executed.

  In the following, as shown in FIG. 2, the n cells 10 connected in series may be referred to by symbols 10 [1] to 10 [n], and the discharge circuit 21 connected in parallel to the cell 10 [i]. And the voltage sensor 22 may be referred to by symbols 21 [i] and 22 [i], respectively, and the resistor R and the switching element SW in the discharge circuit 21 [i] may be referred to by symbols R [i] and SW [i], respectively. The terminal voltage of the cell 10 [i] measured by the voltage sensor 22 [i] may be referred to as a measured voltage and may be referred to by the symbol V [i] (i is an integer). . When the switching element SW [i] is on, the positive electrode and the negative electrode of the cell 10 [i] are connected via the resistor R [i], and the cell 10 [i] is discharged via the resistor R [i]. Is called. When the switching element SW [i] is off, the cell 10 [i] is not discharged through the resistor R [i].

FIG. 3A is an internal equivalent circuit diagram of one cell 10. The cell 10 can be considered as a series connection circuit of a voltage source VS that outputs a constant DC voltage and having zero internal resistance, and an impedance circuit Z including a resistance component and a capacitance component. The circuits Z _A and Z _{B in} FIGS. 3B and 3C are a first example and a second example of the internal circuit of the impedance circuit Z. Circuit Z _A includes a resistor R0, a circuit connected in series with the parallel connection circuit of a resistor R1 and a capacitor C1. The circuit Z _B is a circuit in which a resistor R0, a parallel connection circuit of a resistor R1 and a capacitor C1, and a parallel connection circuit of a resistor R2 and a capacitor C2 are connected in series. Due to the presence of the impedance circuit Z, as shown in FIG. 4, the terminal voltage V [i] of the cell 10 [i] immediately rises by the voltage drop of the resistor R0 immediately after the discharge is stopped, and the voltage V _A [i]. Then, the voltage gradually rises over an appropriate time (for example, several minutes to several hours) and converges to a constant stable voltage V _B [i] that is the output voltage of the voltage source VS (V _A [i ] And V _B [i] are different).

The difference (V _B [i] −V _A [i]) corresponds to a voltage component caused by an electrochemical component remaining in the cell 10 [i], and after the discharge of the cell 10 [i] is stopped. 2 represents the voltage return amount when the terminal voltage V [i] of the cell 10 [i] transiently returns from the voltage V _A [i] to the stable voltage V _B [i]. Since each of the voltages V _A [i] and V _B [i] is a terminal voltage V [i] observed when no current flows between the positive electrode and the negative electrode of the cell 10 [i], the cell 10 [ i] is an open circuit voltage.

  The control circuit 20 can execute an equalization process that equalizes the charge states of the plurality of cells 10 in consideration of the voltage return amount. The state of charge of the cell 10 is expressed as an SOC (State of Charge) of the cell 10. The SOC of the cell 10 is a ratio of the remaining capacity of the cell 10 to the full charge capacity of the cell 10. Since the SOC of the cell 10 depends on the open voltage of the cell 10, in the equalization process, the control circuit 20 equalizes the charge state of the plurality of cells 10 by equalizing the open voltage of the plurality of cells 10. Let

  The content of the equalization process will be described with reference to FIG. FIG. 5 is an operation flowchart of the equalization processing. The control circuit 20 activates the equalization process after a sufficiently long predetermined time (for example, 2 hours) has elapsed since the charging or discharging of the assembled battery 1 between the assembled battery 1 and the power block 3 is stopped. For example, when the assembled battery system is incorporated in a vehicle (not shown) such as an electric vehicle or a hybrid vehicle and the vehicle is driven using the discharge power of the assembled battery 1, the control circuit 20 is used for driving the vehicle. The equalization process is started after a predetermined time (for example, 2 hours) has elapsed since the discharge stopped.

  When the equalization process is started, first, in step S11, the control circuit 20 takes in the output signals of the voltage sensors 22 [1] to 22 [n] to thereby obtain the terminal voltages V [1] to V [n] of all the cells 10. Are measured and acquired, and the target voltage Vd is set based on the measured voltages V [1] to V [n]. In step S11 and later-described steps S12 and S13, all the switching elements SW are turned off. Therefore, each terminal voltage acquired in step S11 is an open circuit voltage of each cell 10, and corresponds to the output voltage of the voltage source VS in FIG. The value of the target voltage Vd is the target value of the open circuit voltage of each cell 10 after the equalization process. The control circuit 20 obtains the maximum voltage Vmax and the minimum voltage Vmin among the measured voltages V [1] to V [n] in step S11, and when the difference (Vmax−Vmin) is equal to or less than a predetermined positive value. The equalization process may be terminated without setting the target voltage Vd.

  For example, the control circuit 20 sets the voltage Vmin or the voltage (Vmin + α) to the target voltage Vd (α> 0). For example, the predetermined value α is set to the same level as the measurement error of the voltage measurement using the voltage sensor 22. When the target voltage Vd set here falls below a predetermined lower limit value, the target voltage Vd is corrected to the lower limit value. The target voltage Vd may be set based on a voltage other than the minimum voltage Vmin. For example, the average voltage Vmean of the measured voltages V [1] to V [n] in step S11 can be set to the target voltage Vd.

  After setting the target voltage Vd, in step S12, the control circuit 20 determines from the cells 10 [1] to 10 [n] based on the measured voltages V [1] to V [n] and the target voltage Vd in step S11. Select and set the target cell. The cell 10 whose measured voltage in step S11 is larger than the target voltage Vd is set as the target cell. That is, when the measured voltage V [i] in step S11 is larger than the target voltage Vd, the cell 10 [i] is set as the target cell, and otherwise, the cell 10 [i] is not set as the target cell. In step S12, one or more target cells are set.

  After setting the target cell, in step S13, the control circuit 20 measures and acquires the terminal voltage of each target cell by capturing the output signal of the voltage sensor 22 corresponding to each target cell. When the cell 10 [i] is the target cell, in step S13, the terminal voltage V [i] of the target cell 10 [i] is acquired as the measurement voltage V1 [i]. The equalization process includes an equalization discharge operation in which the target cell 10 [i] is discharged using the discharge circuit 21 [i], and the measurement voltage V1 [i] is the target cell 10 [j] immediately before the discharge in the equalization discharge operation. i] is the open circuit voltage. The voltage V [i] measured in step S11 may be used as the measurement voltage V1 [i]. In this case, the measurement process in step S13 is omitted.

  After acquiring the measurement voltage V1 [i], in step S14, the control circuit 20 starts to perform the equalization discharge operation for each target cell. That is, only the switching element SW connected in parallel to the target cell is switched from OFF to ON among the switching elements SW [1] to SW [n]. After a predetermined time (for example, 100 milliseconds) has elapsed since the start of the equalization discharge operation, in step S15, the control circuit 20 captures the output signal of the voltage sensor 22 corresponding to each target cell, thereby Measure and acquire the terminal voltage. When the cell 10 [i] is the target cell, in step S15, the terminal voltage V [i] of the target cell 10 [i] is acquired as the measurement voltage V2 [i]. The measurement voltage V2 [i] is a closed circuit voltage of the target cell 10 [i] with respect to the electric circuit of the target cell 10 [i] and the discharge circuit 21 [i]. After the terminal voltage V [i] sharply decreased by turning on the switching element SW [i] is stabilized, the measured voltage V2 [i] is acquired before the terminal voltage of the target cell 10 [i] starts to decrease due to discharge. Thus, the predetermined time is set.

FIG. 6 shows a waveform 300 of the terminal voltage V [i] of the target cell 10 [i], which is one of the target cells. The execution period of the equalizing discharge operation for the target cell 10 [i] is a period from time t _A to time t _B. Therefore, the switching element SW [i] corresponding to the target cell 10 [i] is switched from off to on at time t _A and then switched from on to off at time t _B.

  After the measurement voltages V1 [i] and V2 [i] are acquired for each target cell, in step S16, the control circuit 20 obtains a voltage amount ΔV1 that should be called a first correction amount for each target cell. A voltage amount ΔV1 corresponding to the target cell 10 [i] is represented by a symbol ΔV1 [i]. ΔV1 [i] = V1 [i] −V2 [i]. In subsequent step S <b> 17, the control circuit 20 obtains a voltage amount ΔV <b> 2 that should be called a second correction amount for each target cell. A voltage amount ΔV2 corresponding to the target cell 10 [i] is represented by a symbol ΔV2 [i]. The voltage amount ΔV2 [i] is derived based on voltage return amount data (a ΔV2 table data described later) held by the control circuit 20 (details will be described later).

  After derivation of the voltage amounts ΔV1 and ΔV2, in step S18, the control circuit 20 obtains a corrected target voltage Vd2 for each target cell based on Vd, ΔV1, and ΔV2. The corrected target voltage Vd2 corresponding to the target cell 10 [i] is represented by the symbol Vd2 [i]. Vd2 [i] = Vd−ΔV1 [i] −ΔV2 [i].

  After deriving the corrected target voltage Vd2 for each target cell, the control circuit 20 monitors the terminal voltage (closed circuit voltage) of each target cell using the output signal of the voltage sensor 22 corresponding to each target cell. When the terminal voltage (closed circuit voltage) V [i] of the target cell 10 [i] falls to the correction target voltage Vd2 [i], the control circuit 20 turns off the switching element SW [i] in step S19. Thus, the equalizing discharge operation for the target cell 10 [i] is terminated. The equalization process ends when the equalization discharge operation for all target cells is completed.

With reference to FIG. 6 again, a change in the terminal voltage of the target cell 10 [i], which is one of the target cells, will be described. When the equalized discharge operation is started at time t _A (when the switching element SW [i] is turned on), a discharge current flows through the discharge circuit including the target cell 10 [i] and the discharge circuit 21 [i]. As a result, a large voltage drop occurs due to the internal resistance of the target cell 10 [i] and the terminal voltage V [i] rapidly decreases. The difference voltage ΔV1 [i] between the measured voltages V1 [i] and V2 [i] acquired before and after the start of the equalizing discharge operation is regarded as a voltage drop due to the internal resistance of the target cell 10 [i]. Can do.

  Temporarily, the correction target voltage Vd ′ [i] is obtained according to “Vd ′ [i] = Vd−ΔV1 [i]”, and the equalizing discharge operation is performed when the terminal voltage V [i] reaches Vd ′ [i]. If completed, the equalization process can be performed in a manner that compensates for the inter-cell variation such as the internal resistance. However, in this case, the terminal voltage V [i] immediately after the end of the equalizing discharge operation coincides with the target voltage Vd, but the terminal voltage V [i] is set to the target voltage over a corresponding time (for example, 2 hours). It rises to a voltage obtained by adding the voltage return amount (see FIG. 4) to Vd and stabilizes. That is, an error corresponding to the voltage return amount occurs between the terminal voltage V [i] and the target voltage Vd. Since the amount of voltage return depends on the degree of cell degradation and the like, and the degree of cell degradation and the like may vary among a plurality of cells, the terminal voltage may vary after the equalization processing.

  Therefore, when aiming at high accuracy of the equalization processing, the above-described voltage return amount should be taken into consideration. In the present embodiment, the correction target voltage Vd2 [i] is calculated using not only the difference voltage ΔV1 [i] but also the voltage amount ΔV2 [i] corresponding to the voltage return amount of the target cell 10 [i]. . For this reason, equalization processing (equalization of charge states of the plurality of cells 10) can be realized with very high accuracy. In FIG. 6, the terminal voltage V [i] of the target cell 10 [i] suddenly increases from the corrected target voltage Vd2 [i] by the voltage amount ΔV1 [i] along with the end of the equalizing discharge operation. It is shown that the voltage is gradually increased by a voltage amount ΔV2 [i] over time (converged to the target voltage Vd). That is, since the error between the terminal voltage V [i] after the equalization process and the target voltage Vd becomes zero or very small, the charge states of the plurality of cells 10 are equalized with high accuracy. Further, as in Patent Document 2, it is not necessary to wait for a predetermined voltage stabilization waiting time after the equalization process is performed once, and to determine whether or not the equalization has ended or to perform the equalization process again. Can be completed in a short time.

[How to create voltage return data]
The voltage return amount data used for deriving the voltage amount ΔV2 [i] is created in advance at the design stage of the assembled battery system. A method for creating the voltage return amount data will be described. FIG. 7 is a flowchart showing a procedure for creating voltage return amount data.

  First, in step S31, a plurality of cells 10 having different degrees of deterioration are prepared in stages. Here, for the sake of concrete explanation, it is assumed that a total of 20 cells 10 having the first to twentieth deterioration degrees are prepared as cells C [1] to C [20] (see FIG. 8). . The number of cells prepared may be other than 20. The first to twentieth deterioration levels are different from each other. The degree of deterioration of the cell C [i] is expressed using, for example, SOH (State Of Health) of the cell C [i]. That is, for example, the deterioration degree of the cell C [i] is the ratio of the current full charge capacity of the cell C [i] to the reference capacity defined for the cell C [i], or a value based on the ratio. is there. The reference capacity of the cell C [i] is an initial value of the full charge capacity of the cell C [i] or a rated capacity predetermined for the cell C [i]. Each of the cells C [1] to C [20] is connected to a discharge circuit 51 and a voltage sensor 52 equivalent to the discharge circuit 21 and the voltage sensor 22, as shown in FIG. The data acquisition device 50 can execute / stop the discharge of the cell C [i] by performing on / off control of the switching element SW in the discharge circuit 51. The voltage sensor 52 connected to the cell C [i] measures the terminal voltage of the cell C [i]. Note that the cell C [i] can be charged to a desired charge state using a charging circuit (not shown).

  In step S32 following step S31, the data acquisition device 50 measures the full charge capacities FCC [1] to FCC [20] of the cells C [1] to C [20]. A known measurement method can be used as a method for measuring the full charge capacity of the cell. For example, starting from a state in which the cell C [i] is fully charged, the cell C [i] is discharged until the cell C [i] reaches a discharge end state, and the cell C [i] in the discharge process is discharged. The total amount of discharged electricity can be acquired as the full charge capacity FCC [i]. Alternatively, the cell C [i] is charged until the cell C [i] is fully charged starting from the state in which the cell C [i] is in the discharge end state, and the cell C [i] in the charging process is charged. The total charge electricity amount can be acquired as the full charge capacity FCC [i].

  In step 33, the data acquisition apparatus 50 derives the deterioration degree variable f and assigns 1 to the variable f. Then, in step 34, the data acquisition apparatus 50 derives the temperature variable k and assigns 1 to the variable k. In 35, the OCV variable j is derived and 1 is substituted into the variable j. In the processing of steps S36 to S45, which will be described later, the variable f takes an integer value from 1 to a predetermined deterioration degree type number F, and the variable k takes an integer value from 1 to a predetermined temperature type number K. , Variable j takes an integer value from 1 to a predetermined number of OCV types J. The number of types of degradation F is the number of types of cell degradation when creating voltage return amount data, and is 20 in this example. As will be understood from the following description, the temperature type number K is the number of types of cell temperature conditions when creating the voltage return amount data, and is an integer of 2 or more. The first to Kth temperatures are different from each other. The OCV type number J is the number of types of cell open-circuit voltage conditions when creating the voltage return amount data, and is an integer of 2 or more. The first to Jth open-circuit voltages (hereinafter also referred to as OCV) are different from each other.

  After step S35, the processes of steps S36 to S39 are sequentially executed. In step S36, the data acquisition device 50 sets and maintains the temperature (for example, the surface temperature) of the cell C [f] having the f-th degradation level at the k-th temperature using a temperature adjustment mechanism (not shown). This maintenance is continued during the execution period of the process of step S37. In step S37, the data acquisition device 50 uses the discharge circuit 51 from the state where the SOC of the cell C [f] is higher than the jth SOC until the SOC of the cell C [f] becomes the jth SOC. The discharge of the cell C [f] is stopped after the discharge of the cell C [f], and the terminal voltage Ve of the cell C [f] at the time when the first predetermined time has elapsed from the stop of the discharge and the first time after the discharge is stopped. 2 The terminal voltage Ve2 of the cell C [f] at the time when a predetermined time has elapsed is measured and acquired using the voltage sensor 52. Here, the second predetermined time (for example, 2 hours) is considerably longer than the first predetermined time (for example, 100 milliseconds). FIG. 10 shows the relationship between the voltages Ve and Ve2. In order to recognize the SOC of the cell C [f] at each time, the full charge capacity FCC [f] is used.

The voltages Ve and Ve2 are equivalent to the voltages V _A [i] and V _B [i] in FIG. 4, respectively, and the difference (Ve2−Ve) is the difference between the cell C [f] after the discharge of the cell C [f] is stopped. ] Represents a voltage return amount when the terminal voltage transiently returns from the first open circuit voltage Ve to the second open circuit voltage Ve2. Each of the voltages Ve and Ve2 is a terminal voltage of the cell C [f] observed when no current flows between the positive electrode and the negative electrode of the cell C [f]. It is a kind.

  As shown in FIG. 11, the SOC of the cell C [f] depends on the OCV of the cell C [f]. In step S <b> 38, the data acquisition device 50 converts the j-th SOC into the j-th OCV using a previously known relationship between the SOC and the OCV. In the subsequent step S39, the data acquisition device 50 uses the voltages Ve and Ve2 acquired in the most recent step S37, and follows the equations “ΔV2 [f, j, k] = Ve2−Ve” according to the equations “ΔV2 [f, j, k] = Ve2−Ve”. The voltage return amount data ΔV2 [f, j, k], which is a function of When the cell 10 having the f-th degradation degree is discharged at the k-th temperature until the OCV becomes the j-th OCV, the voltage return amount (Ve2-Ve) observed after the discharge is stopped is V2. [F, j, k].

  ΔV2 [f, j, k] acquired when f = j = k = 1 is ΔV2 [1,1,1]. In the process of FIG. 7, ΔV2 [1, 1, 1] to ΔV2 [F, J, K] are sequentially acquired. That is, after step S39, it is confirmed whether or not the variable j matches the OCV type number J (step S40). If the variable j matches the OCV type number J, the transition to step S42 is made. If this is not the case, 1 is added to the variable j (step S41), the process returns to step S36, and the processes of steps S36 to S39 are repeatedly executed. In step S42, it is confirmed whether or not the variable k matches the number of temperature types K. If the variable k matches the number of temperature types K, a transition to step S44 occurs. First, 1 is added to the variable k (step S43), the process returns to step S35, and the processes of steps S35 to S41 are repeatedly executed. In step S44, it is confirmed whether or not the variable f matches the deterioration degree type number F. If the variable f matches the deterioration degree type number F, the process of creating the voltage return amount data ends. Otherwise, 1 is added to the variable f (step S45), the process returns to step S34, and the processes of steps S34 to S43 are repeatedly executed.

  As a result, at the end of the voltage return amount data creation process, data ΔV2 [f, f for all combinations of integers f, j and k satisfying 1 ≦ f ≦ F, 1 ≦ j ≦ J and 1 ≦ k ≦ K. j, k], that is, a total of “F × J × K” pieces of data ΔV2 [1,1,1] to ΔV2 [F, J, K]. All the acquired data ΔV2 [f, j, k] are collectively referred to as ΔV2 table data.

  For example, a total of F deterioration degrees obtained by equally dividing the upper limit value and the lower limit value of the deterioration degree assumed for the cell 10 by (F-1) may be set as the first to Fth deterioration degrees. it can. Similarly, for example, a total of J SOCs obtained by equally dividing (J-1) between the SOC upper limit value and the SOC lower limit value within the use range of the cell 10 may be set as the first to Jth SOCs. it can. More specifically, for example, the first to Jth SOCs are set by extracting 90% to 10% SOC in 5% increments. In this case, J = 17, and the first to seventeenth SOCs are 90%, 85%, 80%,..., 10%, respectively. Similarly, for example, a total of K temperatures obtained by equally dividing the temperature upper limit value and the temperature lower limit value within the use range of the cell 10 by (K-1) may be set as the first to Kth temperatures. it can. More specifically, for example, the first to Kth temperatures are set by extracting the temperature from −30 ° C. to 60 ° C. in increments of 5 ° C. In this case, K = 19, and the first to nineteenth temperatures are −30 ° C., −25 ° C., −20 ° C.,. The flowchart in FIG. 7 is an example, and as long as ΔV2 table data is obtained, each data ΔV2 [f, j, k] may be acquired in any order.

[Detailed configuration of control circuit]
FIG. 12 shows an internal block diagram of the control circuit 20 that holds and uses the voltage return amount data obtained as described above. The control circuit 20 includes a voltage return amount estimation unit 60 including a data holding unit 61 and a ΔV2 calculation unit 62. The data holding unit 61 holds ΔV2 table data created in advance. The ΔV2 calculation unit 62 performs the process of step S17 in FIG. That is, the ΔV2 calculation unit 62 uses the ΔV2 table data (voltage return amount data) held in the data holding unit 61 based on the deterioration degree of the target cell 10 [i], the target voltage Vd, and the temperature of the target cell 10 [i]. Is used to derive the voltage amount ΔV2 [i]. The voltage return amount estimation unit 60 estimates the voltage amount ΔV2 [i] as a voltage return amount (see FIG. 4) generated in the target cell 10 [1] after the equalizing discharge operation is completed.

  The deterioration degree of the target cell 10 [i] is derived by the deterioration degree deriving unit 69. The temperature of the cell 10 [i] is measured by a temperature sensor (not shown) provided in the assembled battery system. A temperature sensor may be provided for each cell 10 so that the temperature of each cell 10 can be measured individually, or only one temperature sensor for measuring the temperature of the entire assembled battery 1 may be provided. When a temperature sensor that measures the temperature of the entire assembled battery 1 is provided, the temperature measured by the temperature sensor may be used as the detected temperature of all the cells 10.

  As is apparent from the above description, the ΔV2 table data is given as a function of the degradation degree, OCV, and temperature of the cell 10. The ΔV2 calculating unit 62 substitutes the deterioration degree of the target cell 10 [i], the target voltage Vd, and the temperature of the target cell 10 [i], which are function variables, into the function given as the ΔV2 table data, thereby obtaining ΔV2 [I] is obtained (note that the target voltage Vd is the target open circuit voltage of the target cell 10 after the equalization process).

For example, deterioration degree of the object cell 10 [i], the temperature of the target voltage Vd and the target cell 10 [i] is, respectively, the deterioration degree of the f _A, OCV of the j _A, consistent with the temperature of the k _A (F _A , j _A and k _A are integers satisfying 1 ≦ f _A ≦ F, 1 ≦ j _A ≦ J and 1 ≦ k _A ≦ K), the ΔV2 calculating unit 62 calculates ΔV2 [f _A , j _A , k _A ] may be extracted from the data holding unit 61 as ΔV2 [i]. Deterioration degree of the object cell 10 [i] is not also coincide in any degree of deterioration of the first to F, are deterioration degree between the deterioration degree and the deterioration degree of the (f _B +1) of the f _B If (F _B is an integer satisfying 1 ≦ f _B ≦ F−1), ΔV2 [i] is obtained using ΔV2 [f _B , j, k] and ΔV2 [f _B + 1, j, k]. Good. The same applies when the target voltage Vd does not match any of the first to Jth OCVs, and the same applies when the temperature of the target cell 10 [i] does not match any of the first to Kth temperatures. .

  As shown in FIG. 12, the control circuit 20 is also provided with each part referred to by reference numerals 63 to 69. The target voltage setting unit 63 and the target cell setting unit 64 set the target voltage Vd and the target cell by performing the processes of steps S11 and S12 in FIG. 5, respectively. The ΔV1 calculating unit 65 obtains the voltage amount ΔV1 [i] of each target cell by performing the processing of steps S13, S15, and S16 in FIG. The target voltage correction unit 66 obtains the corrected target voltage Vd2 [i] of each target cell by performing the process of step S18 of FIG. As illustrated in FIG. 13, the ΔV1 calculation unit 65 and the ΔV2 calculation unit 62 may be considered to be inherent in the target voltage correction unit 66. In any case, the target voltage correction unit 66 uses the terminal voltages V1 [i] and V2 [i] of the target cell 10 [i] measured before and after the start of the equalizing discharge operation, and ΔV2 that is data of the voltage return amount. Based on the table data, the corrected target voltage Vd2 [i] is derived by correcting the target voltage Vd for each target cell. The charge / discharge control unit 67 performs the processes of steps S14 and S19 in FIG.

  The full charge capacity measuring unit 68 measures the full charge capacity of each cell 10 every predetermined period (for example, one month). The method for measuring the full charge capacity of the cell 10 [i] is the same as the method for measuring the full charge capacity of the cell C [i] described above. For the measurement of the full charge capacity, a current sensor (not shown) for detecting the current flowing through each cell 10 [i] may be provided in the charge state equalizing device 2. The deterioration degree deriving unit 69 obtains a deterioration degree for each cell 10 based on the latest full charge capacity measured for each cell 10 by the measuring unit 68. The degree of degradation of the cell 10 [i] is expressed using, for example, the SOH (State Of Health) of the cell 10 [i]. Therefore, for example, the deterioration degree deriving unit 69 calculates the ratio of the current full charge capacity of the cell 10 [i] to the reference capacity determined for the cell 10 [i] or a value based on the ratio as the cell 10 [i]. ] As the degree of deterioration. The reference capacity of the cell 10 [i] is an initial value of the full charge capacity of the cell 10 [i] or a rated capacity predetermined for the cell 10 [i].

  The voltage return amount shown in FIG. 4 greatly depends on the deterioration degree of the cell, and the voltage return amount is different if the deterioration degree of the cell is different. The voltage return amount also changes depending on the OCV and temperature of the cell. Considering this, as described above, the voltage return amount data (ΔV2 table data) is previously obtained and held as a function of the degree of deterioration of the cell, the OCV, and the temperature. Then, during actual operation, the voltage return amount (ΔV2) corresponding to the degree of deterioration of the cell or the like is estimated using the data, and the terminal voltage of the equalizing discharge operation is taken into consideration with the voltage return amount (ΔV2). The correction target voltage Vd2 is determined. As a result, the end terminal voltage of the equalization discharge operation is determined in consideration of an accurate voltage return amount, and therefore, equalization processing (equalization of charge states of the plurality of cells 10) is realized with very high accuracy. Can do.

<< Deformation, etc. >>
The embodiment of the present invention can be appropriately modified in various ways within the scope of the technical idea shown in the claims. The above embodiment is merely an example of the embodiment of the present invention, and the meaning of the term of the present invention or each constituent element is not limited to that described in the above embodiment. The specific numerical values shown in the above description are merely examples, and as a matter of course, they can be changed to various numerical values. As annotations applicable to the above-described embodiment, notes 1 to 5 are described below. The contents described in each comment can be arbitrarily combined as long as there is no contradiction.

[Note 1]
The ΔV2 table data described above is given as a function dependent on the first to third variables, with the degree of deterioration, OCV and temperature of the cell 10 being the first to third variables, respectively. It may be given as a function that depends only on one arbitrary variable among the third variables, or may be given as a function that depends only on two arbitrary variables. In response to this, the ΔV2 calculating unit 62 responds to at least one of the first index that is the degree of deterioration of the target cell, the second index that is the target voltage Vd, and the third index that is the temperature of the target cell. Thus, the voltage amount ΔV2 [i] may be derived. However, since the voltage return amount corresponding to the voltage amount ΔV2 [i] particularly depends on the deterioration degree of the cell 10, the ΔV2 table data is given as a function of at least the first variable (deterioration degree of the cell 10). During operation, it is desirable to derive the voltage amount ΔV2 [i] according to at least the first index.

[Note 2]
In the above-described embodiment, among the cells 10 [1] to 10 [n], a cell having a relatively high terminal voltage is set as a target cell, and each of the target cells is discharged, thereby charging the plurality of cells 10 in a charged state. Although equalization is performed, on the contrary, by setting a cell having a relatively low terminal voltage as the target cell and charging each target cell, the charge states of the plurality of cells 10 are equalized. good.

  In this case, instead of the discharge circuits 21 [1] to 21 [n], the charge state equalization apparatus 2 is provided with a charging circuit (not shown) for each cell 10, and the cells 10 [1] to 10 [n]. ] Can be charged individually. For example, in steps S11 and S12 in FIG. 5, the control circuit 20 sets the voltage Vmax, (Vmax−α) or Vmean to the target voltage Vd, and the measurement voltage in step S11 is smaller than the target voltage Vd. What is necessary is just to perform the equalization charge operation which sets the cell 10 to an object cell and charges the object cell using the said charging circuit after that instead of the equalization discharge operation. Also in this case, ΔV1 [i] and ΔV2 [i are based on the terminal voltages V1 [i] and V2 [i] of the target cell 10 [i] measured before and after the start of the equalization charging operation and the ΔV2 table data. ] Is derived, and the corrected target voltage Vd2 [i] is derived based on Vd, ΔV1 [i], and ΔV2 [i]. The control circuit 20 equalizes the target cell 10 [i] when the terminal voltage V [i] of the target cell 10 [i] rises to the corrected target voltage Vd2 [i] after the start of the equalization charging operation. The charging operation may be terminated. When charging is considered, the voltage amount ΔV2 [i] derived from the ΔV2 table data indicates that the terminal voltage V [i] of the cell 10 [i] is transiently first released after the charging of the cell 10 [i] is stopped. The voltage return amount when returning from the voltage to the second open circuit voltage (stable voltage) is shown. It should be noted that both the discharge circuit 21 and the charging circuit are provided in the charge state equalizing apparatus 2, and the charge states of the plurality of cells 10 are equalized using both the equalized discharge operation and the equalized charge operation. Good.

[Note 3]
When there are a plurality of target cells, the equalizing discharge operation or the equalizing charging operation may be simultaneously performed for all the target cells, or one or two or more predetermined numbers for the plurality of target cells. The equalizing discharge operation or the equalizing charging operation may be performed.

[Note 4]
The control circuit 20 can be configured by hardware or a combination of hardware and software. Of the functions realized by the control circuit 20, an arbitrary specific function is described as a program, the program is stored in a flash memory that can be mounted on the control circuit 20, and the program is stored in the control circuit 20. The specific function may be realized by executing it on an arithmetic processing unit (for example, a microcomputer that can be mounted on the control circuit 20).

[Note 5]
For example, it can be considered as follows. The discharge circuit 21 that can be provided for each cell 10, the above-described charging circuit that can be provided for each cell 10, or both circuits perform a charge / discharge operation including an equalization discharge operation and / or an equalization charge operation. A possible charge / discharge circuit is formed. The voltage detection circuit that measures the terminal voltage of each cell 10 includes voltage sensors 22 [1] to 22 [n]. The charge state equalization device 2 can also be called a battery state adjustment device or a charge state adjustment device that adjusts the charge state of each cell 10. The data acquisition device 50 in FIG. 9 may be considered to be included in the constituent elements of the charge state equalization device 2 or the assembled battery system.

DESCRIPTION OF SYMBOLS 1 assembled battery 2 charge condition equalization apparatus 10, 10 [i] cell 20 control circuit 21, 21 [i] discharge circuit 22, 22 [i] voltage sensor 60 voltage return amount estimation part 61 data holding part 62 (DELTA) V2 calculation part 63 Target voltage setting unit 64 Target cell setting unit 65 ΔV1 calculation unit 66 Target voltage correction unit 67 Charge / discharge control unit 68 Fully charged capacity measurement unit 69 Degradation degree derivation unit

Claims (6)

A charge / discharge circuit capable of performing a charge / discharge operation which is a process of charging or discharging a plurality of cells connected in series individually;
A voltage measurement circuit for measuring the terminal voltage of each cell;
A data holding unit for holding data of a voltage return amount when the terminal voltage of each cell transiently returns from the first open voltage to the second open voltage after the charging or discharging of each cell is stopped;
Based on the terminal voltage of each cell measured before the start of the charge / discharge operation, a target voltage / target cell setting unit for setting a target voltage and setting a target cell from among the plurality of cells;
A target voltage correction unit that corrects the target voltage and derives a corrected target voltage based on the terminal voltage of the target cell measured before and after the start of the charge / discharge operation, and the voltage return amount data;
A charge / discharge control unit for starting the charge / discharge operation for the target cell and ending the charge / discharge operation for the target cell when a terminal voltage of the target cell reaches the correction target voltage. Battery condition adjusting device characterized. The voltage return amount data held in the data holding unit is given as a function of the degree of deterioration of the cell,
The target voltage correction unit derives the correction target voltage using a voltage return amount corresponding to a degree of deterioration of the target cell, which is obtained from data held in the data holding unit. Battery condition adjustment device. The deterioration level deriving unit for deriving a deterioration level of the target cell based on a ratio of a full charge capacity of the target cell to a reference capacity determined for the target cell. Battery condition adjustment device. The voltage return amount data held in the data holding unit is given as a function of the open circuit voltage of the cell,
The target voltage has a target value of the open voltage of the target cell,
The said target voltage correction | amendment part derives | leads-out the said correction | amendment target voltage using the voltage return amount according to the said target voltage obtained from the holding | maintenance data of the said data holding | maintenance part. The battery state adjusting device according to any one of the above. The voltage return amount data held in the data holding unit is given as a function of the cell temperature,
The said target voltage correction | amendment part derives | leads-out the said correction | amendment target voltage using the voltage return amount according to the temperature of the said object cell obtained from the holding | maintenance data of the said data holding | maintenance part. 4. The battery state adjusting device according to any one of 4 above. An assembled battery having a plurality of cells connected in series;
An assembled battery system comprising: the battery state adjusting device according to any one of claims 1 to 5.

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