JP2014176184A - Voltage equalization device, and voltage equalization method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voltage equalization device and a voltage equalization method, easily obtaining an offset voltage used in cross control of an active type cell balance with high accuracy according to a use pattern of batteries.SOLUTION: In cross control cell balance processing to make a current flow from one battery to the other battery so as to equalize voltages of first and second batteries, to estimate a voltage change by polarization of each battery, and to make the current flow from the one battery to the other battery until reaching an offset voltage corresponding to an amount corresponding to the voltage change by the polarization even after the voltages of the batteries become equal, an offset voltage correction part 122 refers to a use pattern time table 121 of the batteries, predicts a time during a use stop until the first and second batteries are used for power supply in time of cross control, multiplies the offset voltage by a correction coefficient corresponding to the time during the use stop to correct the offset voltage, and stops the cross control cell balance processing at a time point when having reached the corrected offset voltage.

Description

  The present invention relates to a voltage equalizing apparatus and a voltage equalizing method for equalizing the voltages of a plurality of batteries.

  Conventionally, passive cell balance processing has been employed as cell balance processing for equalizing the voltages of a plurality of batteries. The passive cell balancing process is to discharge batteries other than the battery with the lowest voltage so that the voltages of the plurality of batteries are aligned with the battery with the lowest voltage. However, in this passive cell balance process, when a plurality of batteries are charged from an external charger, it is difficult to discharge the batteries, and it is difficult to equalize the voltages of the batteries.

  As a related technique, a charge state equalization apparatus that equalizes the charge state of each cell for an assembled battery formed by connecting a plurality of cells in series is known from Patent Document 1 below. Further, a battery charger that performs equal charge at an optimal timing is known from Patent Document 2 below. Further, a vehicle charging reservation system that enables charging reservation is known from Patent Document 3 below.

JP 2009-159794 A JP 2012-120263 A JP2012-110122A

  The present invention has been made in view of the above circumstances, and provides a voltage equalization apparatus and a voltage equalization method for easily and accurately obtaining an offset voltage used in cross control in active cell balance processing. For the purpose.

  A voltage equalization apparatus which is one embodiment includes a voltage measurement unit, a time measurement unit, and a control unit. The voltage measuring unit measures the voltages of the first and second batteries. When the cell balance process for equalizing the voltages of the first and second batteries is started, the time measuring unit starts measuring the elapsed time from the start time.

  The control unit controls execution of cell balance processing that performs cross control. In addition, the control unit measures a cross time, which is an elapsed time until the voltage range in which it is determined that the voltage of the first battery and the voltage of the second battery match after starting the cell balance process. .

  Subsequently, the control unit specifies an offset voltage corresponding to the measured cross time with reference to an offset voltage information table in which the cross time and the offset voltage for stopping execution of the cross control are stored in association with each other. Subsequently, the control unit stops the execution of the cross control when the voltage difference between the average voltage of the first and second batteries and the voltage of the first or second battery reaches the specified offset voltage.

  Further, the ratio of the polarization change voltage at the time of depolarization of the first or second battery to the total polarization voltage, which is a change voltage that changes with the complete polarization elimination time of the first or second battery, is calculated as a polarization correction coefficient. Then, the polarization correction coefficient is stored in the polarization correction coefficient table in association with the elapsed time when the polarization of the first or second battery is released, and the polarization correction coefficient table is held in the storage unit.

  The control unit estimates the elapsed time at the time of depolarization of the first or second battery from the predicted stoppage time after the execution of the cross control is stopped until the first and second batteries are used, The polarization correction coefficient corresponding to the elapsed time when the polarization is eliminated is specified with reference to the polarization correction coefficient table, and the execution of cross control is stopped for the offset voltage corrected by multiplying the polarization correction coefficient by the offset voltage. This is calculated as the offset voltage.

  According to the embodiment, there is an effect that the offset voltage used in the cross control of the active type cell balance process can be easily obtained with high accuracy in accordance with the use state of the battery.

It is a figure which shows the structural example of the voltage equalization apparatus of one Embodiment. It is a figure which shows the relationship between 1 set of the battery to discharge, and the battery to charge. It is a figure which shows an example of the change of the battery voltage in cross control. FIG. 3 is a flowchart showing an example of the operation of the voltage equalization apparatus in the first embodiment. It is a figure which shows an example of an offset voltage information table. 10 is a flowchart showing an example of the operation of the voltage equalization apparatus in Embodiment 2. FIG. It is a figure which shows an example of the offset voltage information table at the time of charge. It is a figure which shows an example of the offset voltage information table at the time of discharge. FIG. 10 is a flowchart showing an example of the operation of the voltage equalization apparatus in Embodiment 3. It is a figure which shows an example for the offset voltage information table for the charge and discharge used in Embodiment 3. It is a figure which shows an example of usage patterns, such as an electric vehicle. It is a figure which shows an example of the functional block of the voltage equalization apparatus of Embodiment 4, and a polarization correction coefficient. It is a figure which shows an example of the change of the battery voltage at the time of polarization elimination. FIG. 10 is a flowchart showing an example of the operation of the voltage equalization apparatus in Embodiment 4.

  As a method of equalizing the battery voltage in a shorter time than the time required for equalizing the battery voltage by the conventional active cell balance process, a cell balance process for performing cross control (hereinafter also referred to as “cross control cell balance process”). ) Has been proposed.

  In the conventional active type cell balance processing, as one factor that the time required for equalizing the battery voltage is not shortened, the battery voltage equalized by the cell balance processing is shifted by the influence of polarization which is one of the battery characteristics. To occur.

  Conventionally, in order to eliminate this battery voltage deviation, the cell balance process was repeatedly performed until the influence of polarization disappeared, and thus it took a long time for the battery voltages to be equalized. Here, the term “polarization” means a deviation from the standard electrode potential, including the influence due to the internal resistance in addition to the chemical reaction of the battery.

  Cross control does not stop the cell balance process even after the battery voltage becomes equal in the process of cell balance process, estimates the voltage shift due to the influence of polarization, and continues the cell balance process until it reaches the voltage As a result, the time for equalizing the battery voltage is shortened as compared with the prior art.

  Here, in the case of a battery to be charged, the deviation voltage in the cross control is a voltage obtained by adding a deviation voltage (offset voltage) due to the estimated polarization effect to the average voltage of the battery. In the case of a discharged battery, it is a voltage obtained by subtracting a deviation voltage (offset voltage) due to the estimated polarization effect from the average voltage of the battery.

  However, it is not easy to accurately estimate the offset voltage, which is a deviation voltage due to the influence of polarization, and a method for easily and accurately estimating the offset voltage is desired.

  Under such circumstances, the present inventor found that there is a correlation between the offset time and the cross time, which is the elapsed time from the start of the cell balance process until the battery voltage becomes equal. Provided is a method for easily and accurately estimating an offset voltage using correlation. Hereinafter, embodiments will be described in detail with reference to the drawings.

  FIG. 1 shows a configuration example of a voltage equalization apparatus according to an embodiment. The configuration example of the voltage equalization apparatus illustrated in FIG. 1 includes a cell balance circuit for the assembled battery. In the assembled battery, a plurality of batteries 3a to 3d are connected in series. The cell balance circuit includes a control unit 1, a storage unit 2, voltage measurement units 4a to 4d, current measurement units 5a to 5d, coils L1 to L3, and switches SW1 to SW7.

  In the cell balance circuit of the active system shown in FIG. 1, the on / off of the switches SW1 to SW6 is controlled by pulse width modulation (PWM) by the control unit 1, and between the adjacent batteries of the batteries 3a to 3d. The current is charged and discharged through one of the coils L1 to L3, and the voltages of the batteries 3a to 3d are made equal.

  The control unit 1 can be configured using a CPU (Central Processing Unit), a multi-core CPU, and a programmable device (FPGA (Field Programmable Gate Array), PLD (Programmable Logic Device), etc.). For the storage unit 2, for example, a memory element such as a read only memory (ROM) or a random access memory (RAM), a hard disk, or the like can be used as appropriate. Note that the storage unit 2 may store data such as parameter values and variable values, or may be used as a work area during execution of the cell balance process.

  The batteries 3a to 3d can be secondary batteries or capacitors. The secondary battery can be, for example, a lithium ion secondary battery, a nickel hydride secondary battery, or the like. Although four batteries are shown in FIG. 1, the voltage equalization apparatus according to the present embodiment is not limited to the one that targets four batteries.

  For the voltage measuring units 4a to 4d, for example, a voltmeter or a voltage sensor is used to measure the voltage of each of the batteries 3a to 3d. The voltages measured by the voltage measuring units 4 a to 4 d are output to the control unit 1. Each of the current measuring units 5a to 5d measures the current of each of the batteries 3a to 3d. For example, an ammeter or a current sensor is used. The current measured by the current measuring units 5 a to 5 d is output to the control unit 1.

  In the configuration example of FIG. 1, the current flowing through each of the batteries 3 a to 3 d is obtained by measuring with the current measuring units 5 a to 5 d provided at the illustrated positions, but the current flowing through each of the batteries 3 a to 3 d. The method of obtaining is not limited to the configuration example of FIG. For example, as another configuration example, each ammeter may be connected in series to the negative electrode side of each of the batteries 3a to 3d, and the current flowing through each of the batteries 3a to 3d may be measured and obtained.

  The coils L1 to L3 and the switches SW1 to SW7 are used to charge and discharge current from one battery to the other battery in each set of two adjacent batteries connected in series. A current discharged from one battery of a set of two adjacent batteries connected in series through one of the switches SW1 to SW7 is temporarily stored in one of the coils L1 to L3. The current accumulated in one of the coils L1 to L3 is charged via one of the switches SW1 to SW7 to the other battery in the set of two adjacent batteries connected in series. For example, MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) and relays can be used for the switches SW1 to SW7.

  Here, the configuration of the cell balance circuit of the voltage equalization apparatus in FIG. 1 will be described. In the cell balance circuit of the voltage equalizing apparatus, the voltage measuring units 4a to 4d are connected to both ends of the batteries 3a to 3d. Further, one terminal of the switch SW7 is connected to the load side or the external power source side, and the other terminal of the switch SW7 is connected to one terminal of the current measuring unit 5a.

  The other terminal of the current measuring unit 5a is connected to the positive terminal of the battery 3a. The negative terminal of the battery 3a is connected to the positive terminal of the battery 3b and one terminal of the current measuring unit 5b. The other terminal of the current measuring unit 5b is connected to one terminal of the coil L1. The other terminal of the coil L1 is connected to one terminal of the switches SW1 and SW2. The other terminal of the switch SW1 is connected to the positive terminal of the battery 3a. The other terminal of the switch SW2 is connected to the negative terminal of the battery 3b.

  The negative terminal of the battery 3b is connected to the positive terminal of the battery 3c and one terminal of the current measuring unit 5c. The other terminal of the current measuring unit 5c is connected to one terminal of the coil L2. The other terminal of the coil L2 is connected to one terminal of the switches SW3 and SW4. The other terminal of the switch SW3 is connected to the positive terminal of the battery 3b. The other terminal of the switch SW4 is connected to the negative terminal of the battery 3c.

  The negative terminal of the battery 3c is connected to the positive terminal of the battery 3d and one terminal of the current measuring unit 5d. The other terminal of the current measuring unit 5d is connected to one terminal of the coil L3. The other terminal of the coil L3 is connected to one terminal of the switches SW5 and SW6. The other terminal of the switch SW5 is connected to the positive terminal of the battery 3c. The other terminal of the switch SW6 is connected to the negative terminal of the battery 3d. The negative terminal of the battery 3d is connected to the load side or the external power source side.

  Embodiment 1 of a voltage equalizing apparatus and a voltage equalizing method will be described with reference to FIGS. FIG. 2 shows a set of adjacent batteries connected in series. As an example, a battery 3b to be discharged and a battery 3a to be charged are shown. FIG. 3 shows a change in the battery voltage when the cross control is executed. FIG. 4 shows an example of an operation flow of the cross control cell balance process in the first embodiment. FIG. 5 shows an example of the offset voltage information table.

  In the operation flow of FIG. 4, the control unit 1 obtains the voltage Vc of the battery 3a and the voltage Vd of the battery 3b before the start of the cell balance process in step S401, and the voltage Vc of the battery 3a and the voltage Vd of the battery 3b. Find the difference V1.

  In step S402, it is determined whether or not the voltage difference V1 is greater than or equal to a predetermined threshold value Vth. When the voltage difference V1 is greater than or equal to the threshold value Vth (Yes), the process proceeds to step S403. When the voltage difference V1 is smaller than the threshold value Vth (No), it is determined that the voltages of the batteries 3a and 3b are equal, and step S402. Migrate to The predetermined threshold Vth is a threshold for determining whether to start the cell balance process.

  In step S403, cell balance processing is started. In the cell balance process, the switch SW2 is turned on, the switch SW1 is turned off, and a current is supplied from the battery 3b to the coil L1, and then the switch SW1 is turned on and the switch SW2 is turned off, and the current is supplied from the coil L1 to the battery 3a. The constant current is controlled to flow from the battery 3b to the battery 3a. The above-described on / off control of the switches SW1 and SW2 is performed from the cell balance processing start time t0 in FIG. 3 to the time t1 when the voltages of the batteries 3a and 3b become substantially equal.

  In step S404 in FIG. 4, the measurement of the elapsed time from the start time of the cell balance process is started. In the example of FIG. 3, the start time of the elapsed time measurement is t0. In step S405, the voltage difference V2 between the voltages of the batteries 3a and 3b after the start of the cell balance process is obtained. In the example of FIG. 3, the voltage difference V2 is obtained in a period from time t0 to time t1.

  In step S406, it is determined whether or not the voltage difference V2 is within the predetermined voltage range Vrng. If it is within the voltage range Vrng (in the case of Yes), the process proceeds to step S407. When the voltage difference V2 is outside the voltage range Vrng (in the case of No), it is determined that the voltages of the batteries 3a and 3b are not substantially matched, the process proceeds to step S404, and the voltages of the batteries 3a and 3b are substantially matched. The cell balance process is continued while measuring the elapsed time until the voltage is within the determined voltage range Vrng.

  In step S407, the elapsed time measured from the start time t0 of the cell balance process to the time t1 when it is determined that the voltages of the batteries 3a and 3b substantially match is acquired as the cross time Tcls. In the example of FIG. 3, the cross time Tcls is acquired at time t1.

  In step S408, the offset voltage Vofs is specified using the acquired cross time Tcls. The offset voltage Vofs is specified by referring to a preset offset voltage information table and specifying the offset voltage corresponding to the acquired cross time Tcls. The offset voltage information table is a table in which the cross time Tcls and the offset voltage Vofs for stopping the cross control cell balance process are associated with each other.

  FIG. 5 shows an example of the offset voltage information table. As shown in FIG. 5, the offset voltage information table 501 stores, for example, cross times Tcls every 10 seconds, and stores offset voltages Vofs corresponding to the cross times Tcls in association with the cross times Tcls. .

  In this example, 10, 20, 30, 40, 50, 60,... 1800, 1810, 1820, 1830... Are stored as each cross time Tcls. The offset voltage Vofs includes offset voltages Vofs_10, Vofs_20, Vofs_30, Vofs_40, Vofs_50, Vofs_60... Vofs_1800, Vofs_1810, Vofs_1820, Vofs_1820,. Are stored in association with each other. Information stored in the offset voltage information table 501 is obtained by experiments or simulations and stored in the storage unit 2 in advance.

  In step S409 of FIG. 4, after the magnitude relationship between the voltages of the battery 3a and the battery 3b is reversed at the time t1, the average voltage Vavg of the voltages of the batteries 3a and 3b and the voltage of either the battery 3a or the battery 3b are The voltage difference V3 is obtained. In the example of FIG. 3, the difference between the voltage of the battery 3a and the average voltage Vavg is obtained as the voltage difference V3.

  In step S410, it is determined whether or not the voltage difference V3 is equal to or greater than the specified offset voltage Vofs. If the voltage difference V3 is equal to or greater than the offset voltage Vofs (V3 ≧ Vofs) (Yes), the process proceeds to step S411. To do. When the voltage difference V3 is smaller than the offset voltage Vofs (in the case of No), the process proceeds to step S409, and the cross control cell balance process is continued until the voltage difference V3 between the batteries 3a and 3b becomes equal to or higher than the offset voltage Vofs. In step S411, the cross control cell balance process is stopped.

  According to the first embodiment, the offset voltage used in the cross control cell balance process can be easily obtained. Further, since the cross control is performed, the cell balance processing time can be shortened.

  Next, Embodiment 2 will be described with reference to FIGS. 2, 3, and 6 to 8. FIG. 6 shows an example of the operation flow of the second embodiment. The two batteries that are subjected to the cross control cell balance process are divided into a charge side and a discharge side. In the second embodiment, the cross control cell balance process is performed on the charge side or the discharge side. Alternatively, it may be performed on the charge side and the discharge side, and the cross control cell balance processing may be terminated when one of the voltages reaches the offset voltage first.

  For a battery that is being charged, an offset voltage is specified using a charging offset voltage information table, which will be described later, stored in the storage unit 2. For a battery that is being discharged, an offset voltage is specified using a discharge offset voltage information table, which will be described later, stored in the storage unit 2.

  The processes shown in steps S601 to S606 in FIG. 6 are the same as the processes in steps S401 to S406 in FIG. In step S607 of the second embodiment, the control unit 1 acquires the charge / discharge information, the cross time Tcls, and the charge rate at the start of the cross control cell balance process.

  The charge / discharge information is information indicating whether the batteries 3a and 3b are on the charge side or the discharge side. The charging rate is SOC (State of Charge), which is a value indicating the ratio (charging rate) of the remaining capacity to the full charging capacity of the battery 3a or the battery 3b at the start of the cross control cell balance process.

  In step S608, the offset voltage Vofs is specified using the charging offset voltage information table for the charging side, and the offset voltage Vofs is specified using the discharging offset voltage information table for the discharging side.

  FIG. 7 shows an example of information stored in the charging offset voltage information table. As shown in FIG. 7, the charging offset voltage information table 701 associates the cross time Tcls and the offset voltage Vofs corresponding to the cross time Tcls for each charging rate at the start of the cross control cell balance process. Storing.

  In this example, the charge rate (SOC) at the start of the cross control cell balance process is 0 [%], 10 [%], 20 [%],... 90 [%], 100 [%]. For each, an offset voltage Vofs corresponding to the cross time Tcls is stored. In the example of FIG. 7, each time of 10, 20, 30, 40, 50, 60,..., 1800, 1810, 1820, 1830,.

  The offset voltage Vofs with SOC = 0 [%] in FIG. 7 is associated with each cross time Tcls, 10, 20, 30, 40, 50, 60,..., 1800, 1810, 1820, 1830, on the charging side. Vofs0_10_c, Vofs0_20_c, Vofs0_30_c, Vofs0_40_c, Vofs0_50_c, Vofs0_60_c,... Vofs0_1_80_c,...

  In the SOC = 10 [%] offset voltage Vofs in FIG. 7, information Vofs10_10_c, Vofs10_20_c, Vofs10_30_c, Vofs10_40_c, and Vofs10_50_c indicating the offset voltage when the charging rate is 10% in the case of the charging side in association with each cross time Tcls. , Vofs10_60_c,... Vofs10_1800_c, Vofs10_1810_c, Vofs10_1820_c, Vofs10_1830_c,.

  In the offset voltage information table at the time of charging in FIG. 7, the offset voltage Vofs of SOC = 20 [%] or more is similarly associated with each cross time Tcls, and the offset corresponding to each charging rate during charging. The voltage is stored.

  FIG. 8 shows an example of information stored in the discharge offset voltage information table. As shown in FIG. 8, the discharge offset voltage information table 801 stores the cross time Tcls and the offset voltage Vofs corresponding to the cross time Tcls for each charging rate at the start of the cell balance process for performing the cross control. ing.

  In this example, the charge rate at the start of the cell balance process for performing the cross control is SOC = 0 [%], SOC = 10 [%], SOC = 20 [%],... "SOC = 90 [%] , SOC = 100 [%], the offset voltage Vofs corresponding to the cross time Tcls ”is stored. As the cross time Tcls, information 10, 20, 30, 40, 50, 60,... 1800, 1810, 1820, 1830.

  The SOC = 0 [%] offset voltage Vofs in FIG. 8 is associated with each cross time Tcls (10, 20, 30, 40, 50, 60,... 1800, 1810, 1820, 1830), and is on the discharge side. In this case, offset voltages Vofs0_10_d, Vofs0_20_d, Vofs0_30_d, Vofs0_40_d, Vofs0_50_d, Vofs0_60_d,...

  In the offset voltage information table at the time of discharge in FIG. 8, the offset voltage Vofs of SOC = 10 [%] or more is similarly associated with each cross time Tcls, and the offset corresponding to each charging rate during discharging. The voltage is stored.

  The information stored in the charging offset voltage information table 701 and the discharging offset voltage information table 801 is obtained by, for example, experiments or simulations, and stored in the storage unit 2 in advance.

  The processes shown in steps S609 to S611 of FIG. 6 are the same as the processes of steps S409 to S411 of FIG. According to the second embodiment, the offset voltage used in the cross control cell balance process can be easily and accurately obtained. Further, since the cross control is performed, the cell balance processing time can be shortened.

  Next, Embodiment 3 will be described with reference to FIG. 2, FIG. 3, FIG. 9, and FIG. FIG. 9 shows an example of the operation flow of the third embodiment. In the third embodiment, the cross control cell balance process is performed using a charging offset voltage information table or a discharging offset voltage information table corresponding to the temperature of the battery or the ambient temperature of the battery.

  When the battery 3a or 3b is charged, the offset voltage is specified by using a charging offset voltage information table (to be described later) corresponding to the temperature of the battery stored in the storage unit 2 or the ambient temperature of the battery. When the battery 3a or 3b is discharged, the offset voltage is specified using a discharge offset voltage information table described later corresponding to the battery temperature or the battery ambient temperature stored in the storage unit 2. .

  The processes shown in steps S901 to S906 in FIG. 9 are the same as the processes in steps S401 to S406 in FIG. In step S907 of the third embodiment, the control unit 1 acquires charge / discharge information, a cross time Tcls, a charge rate at the start of the cross control cell balance process, and a temperature Tmp around the battery or the battery.

  The charge / discharge information is information indicating whether it is the charge side or the discharge side. As the charging rate, a value such as SOC indicating the charging rate of the battery 3a or the battery 3b at the start of the cross control cell balance process can be used. The battery or the temperature Tmp around the battery is a temperature measured by a temperature measurement unit (not shown).

  In step S908, in the case of the charging side, the offset voltage is specified using the charging offset voltage information table corresponding to the charging rate and the battery temperature or the battery ambient temperature. In the case of the discharge side, the offset voltage is specified using a discharge offset voltage information table corresponding to the charging rate and the battery temperature or the battery ambient temperature.

  FIG. 10 shows an example of information stored in the charging offset voltage information table and discharging offset voltage information table used in the third embodiment. For example, when the charge / discharge information indicates the charge side and the temperature of the battery 3a or 3b or the ambient temperature is −40 ° C., the charging offset voltage information table 1001 is selected.

  When the charge / discharge information indicates the charge side and the temperature of the battery 3a or 3b or the ambient temperature is −30 ° C., the charging offset voltage information table 1002 is selected. When the charge / discharge information indicates the charge side and the temperature of the battery 3a or 3b or the ambient temperature is 0 ° C., the charging offset voltage information table 1003 is selected. Similarly, when the charge / discharge information indicates the charge side and the temperature of the battery 3a or 3b or the ambient temperature is 25 ° C., 70 ° C., or 80 ° C., the charge offset voltage information tables 1004, 1005, and 1006 are selected.

  When the discharge information indicates the discharge side and the temperature of the battery 3a or 3b or the ambient temperature is −40 ° C., the discharge offset voltage information table 1007 is selected. When the charge / discharge information indicates the discharge side and the temperature of the battery 3a or 3b or the ambient temperature is −30 ° C., the discharge offset voltage information table 1008 is selected.

  When the charge / discharge information indicates the discharge side and the temperature of the battery 3a or 3b or the ambient temperature is 0 ° C., the discharge side offset voltage information table 1009 is selected. Similarly, when the charge / discharge information indicates the discharge side and the temperature of the battery 3a or 3b or the ambient temperature is 25 ° C., 70 ° C., or 80 ° C., the discharge offset voltage information tables 1010, 1011 and 1012 are selected.

  Subsequently, information for specifying the offset voltage is selected from the selected charging offset voltage information table or discharging offset voltage information table based on the charging rate at the start of the cross control cell balance process. The information stored in the charge offset voltage information table and the discharge offset voltage information table according to the third embodiment is obtained by experiment or simulation, and is stored in the storage unit 2 in advance.

  The processes shown in steps S909 to S911 of FIG. 9 are the same as the processes of steps S409 to S411 of FIG. According to the third embodiment, the offset voltage used in the cross control cell balance process can be easily and accurately determined according to the battery or the temperature around the battery. Further, since the cross control is performed, the cell balance processing time can be shortened.

  Next, Embodiment 4 will be described with reference to FIGS. 2, 3, and 11 to 13. In the cross control cell balance processing, the method of determining the offset voltage Vofs according to the cross time Tcls has been described as the first to third embodiments.

  After the cross-control cell balance process, it is desirable that the electric vehicle or the like is left without being operated until the polarization of the battery is sufficiently eliminated, and the voltage of each battery is set in a state where the polarization of the battery is eliminated. . However, when the electric vehicle or the like is operated after the cross-control cell balance process is performed and before the polarization of the battery is eliminated, it is desirable that the voltages of the respective batteries are aligned at the timing when the electric vehicle is operated. .

  In particular, in the case of a battery that takes a long time to eliminate polarization, the offset voltage Vofs of the cross-control cell balance process is set so that the voltage of each battery is aligned at the timing when the electric vehicle is operated in accordance with the operating status of the electric vehicle or the like. Is required to be determined with high accuracy. The voltage equalizing apparatus according to the fourth embodiment determines the offset voltage Vofs of the cross control cell balance process so that the voltages of the respective batteries are aligned at the timing when the electric vehicle or the like is operated according to the operating state of the electric vehicle or the like. Is.

  An externally rechargeable electric vehicle such as a forklift has a so-called timer charging function and may have a calendar function for recognizing the current date and day of the week. By utilizing the calendar function, the storage unit 2 stores the usage status such as the start / stop date / time of the electric vehicle, the charging execution date / time, etc. Can be used.

  FIG. 11 shows an example of a usage pattern of an electric vehicle or the like. In general, an electric vehicle such as a forklift often repeats a regular pattern depending on the day of the week and the time of day when the vehicle is stopped, operating, or being charged. Therefore, the usage pattern of the electric vehicle (that is, the battery) is learned based on the usage history of the user's electric vehicle, and the usage pattern is stored in the storage unit 2. Alternatively, the usage pattern may be input from the outside and registered in the storage unit 2 without depending on learning.

  The offset voltage determined according to the first to third embodiments is used as it is until learning of the use pattern is completed or when the use pattern is not registered from the outside. After the learning of the usage pattern is completed, or after acquiring the usage pattern information by external registration, the time for which the electric vehicle is left is predicted based on the usage pattern information. And it correct | amends as follows according to the estimated leaving time with respect to the offset voltage determined by Embodiment 1-3.

  FIG. 12 shows an example of functional blocks and polarization correction coefficients of the voltage equalization apparatus according to the fourth embodiment. As shown in FIG. 12A, the voltage equalization apparatus of the fourth embodiment includes a usage pattern time table 121, an offset voltage correction unit 122, a calendar function unit 123, a cross control execution date and time acquisition unit 124, and a vehicle state determination unit 125. Is provided.

  The usage pattern time table 121 is learned based on the above-described user's usage history of the electric vehicle, or is registered from the outside, and the electric vehicle (battery) according to the day of the week / time zone is stopped, operating or charged. It is the time table which stored the inside usage pattern.

  The cross control execution date and time acquisition unit 124 refers to the current date and time information from the calendar function unit 123, and performs the cross control execution date and time of the cross control cell balance process (from the cross control execution start time at time t1 in FIG. 3 or from the time t1). Information of the cross control execution time until time t2) is acquired, and the information is notified to the offset voltage correction unit 122. The offset voltage correction unit 122 refers to the use pattern time table 121 based on the information on the execution date and time of the cross control, and determines whether or not the offset voltage needs to be corrected.

  Whether the offset voltage needs to be corrected is determined based on whether the period from the execution time of the cross control to the operation time of the next electric vehicle is completely canceled when the electric vehicle is stopped. Judgment is made based on whether or not the time is T or more.

  That is, when the period from the execution time of the cross control to the operation time of the next electric vehicle is equal to or longer than the complete polarization elimination time T, it is determined that the correction of the offset voltage is unnecessary. On the other hand, when the period from the execution time of the cross control to the operation time of the next electric vehicle is equal to or shorter than the complete polarization elimination time T, it is determined that the offset voltage needs to be corrected.

  When it is determined that the offset voltage needs to be corrected, the offset voltage Vofs calculated in the first to third embodiments is multiplied by the polarization correction coefficient A (t / T) corresponding to the voltage change due to the polarization elimination. Thus, the offset voltage Vofs is corrected. FIG. 12B shows an example of the polarization correction coefficient A (t / T). The polarization correction coefficient A (t / T) will be described below with reference to FIG.

  FIG. 13 shows an example of battery voltage change when the charge-side battery that performs cross-control cell balance processing is depolarized. In FIG. 13, the horizontal axis represents elapsed time, and the vertical axis represents battery voltage. FIG. 13 shows a state of voltage change by depolarization after the cross-control cell balance process is performed and the cross-control cell balance process of the battery is stopped at time t10 in a state where the polarization of the battery is saturated. .

  As shown in FIG. 13, when the cross-control cell balance process is stopped at time t10, the battery voltage gradually decreases with the elapse of time due to the depolarization, and the charging is stopped until the complete polarization elimination time T at which the polarization is completely eliminated. The voltage keeps decreasing from the voltage of the hour. This voltage change is measured in advance by experiments or the like. The voltage that changes with this complete polarization elimination time T will be referred to as the total polarization voltage Vp. The discharge side is a change obtained by inverting the voltage change in FIG.

On the other hand, the change voltage due to the depolarization at the time when the time t has elapsed from the time t10 when the cross-control cell balance processing is stopped (that is, when the elapsed time t at the time of depolarization of the battery has elapsed) is the polarization change voltage V ( t). The above-described polarization correction coefficient A (t / T) is calculated by the following (Equation 1).
(Equation 1) Polarization correction coefficient A (t / T) = polarization change voltage V (t) ÷ total polarization voltage Vp
A map in which the polarization correction coefficient A (t / T) calculated by (Equation 1) is associated with the elapsed time t at the time of depolarization is stored in the storage unit 2 in advance as a polarization correction coefficient table. An example of the polarization correction coefficient table is shown in FIG.

  The offset voltage correction unit 122 in FIG. 12A obtains a period from the execution time of the cross control to the operation time of the next electric vehicle with reference to the use pattern time table 121 as a predicted stoppage time. Further, the offset voltage correction unit 122 acquires information indicating whether the current electric vehicle is actually being charged, stopped, or operating from the vehicle state determination unit 125, and the information The offset voltage is corrected accordingly. As an example, the correction of the offset voltage is performed only when the electric vehicle is stopped.

When the offset voltage correction unit 122 determines that the offset voltage needs to be corrected, the above-described polarization correction coefficient A (() is added to the offset voltage Vofs calculated in the first to third embodiments as shown in (Expression 2) below. The offset voltage Vofs is corrected by multiplying by t / T).
(Expression 2) Correction offset voltage Vofs = offset voltage Vofs × polarization correction coefficient A
FIG. 14 shows an example of the operation flow of the fourth embodiment. The processes shown in steps S1401 to S1408 of FIG. 14 are the same as the processes of steps S401 to S408 of FIG.

  In step S1409, the stop time (predicted stop time t) is predicted based on the execution date and time of the cross control and the information in the usage pattern time table 121. In the next step S1410, the predicted stoppage time t is estimated as the elapsed time t when the polarization is eliminated, and the polarization correction coefficient A (t / T) corresponding to the elapsed time t when the polarization is eliminated is calculated as the offset voltage Vofs. To correct the offset voltage Vofs.

  The processing from the next step S1411 to step S1413 is the same as the processing from step S409 to step S411 described with reference to FIG. 4 except that the corrected offset voltage Vofs is used. In the operation flow of the fourth embodiment shown in FIG. 14, the stop time (predicted stop time t) is estimated based only on the time when the execution of cross control is started (time t1 in FIG. 3), and the predicted stop is performed. A polarization correction coefficient A (t / T) corresponding to the intermediate time t was obtained to correct the offset voltage Vofs.

  In this operation example, the time during execution of the cross control is included in the predicted stop time t, and the predicted stop time t includes an error with respect to the actual stop time. However, for a battery that requires a long time for depolarization, the time during execution of the cross control is negligible compared to the depolarization time, and can be ignored.

  As described above, by correcting the offset voltage and executing the cross control, for example, for an electric vehicle that is operated immediately after the cell balance process is completed, the cell balance process is completed and the vehicle is operated. The offset voltage is determined so that the voltages of the batteries are equal to each other. On the other hand, the offset voltage is determined so that the voltage of each battery is aligned after a long time (for example, 12 hours) for an electric vehicle that is left for a long time, for example, at midnight or on a holiday after the cross control cell balance process is completed. Is done.

  By reflecting the usage pattern of the electric vehicle etc. in the execution timing of the cross control cell balance process and the calculation of the offset voltage of the cross control, the battery voltage is accurately equalized when the electric vehicle etc. is in operation. It is possible to increase the actual usage amount of a battery such as an electric vehicle, and to extend the operation time.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the above-mentioned embodiment, A various improvement and change are possible within the range which does not deviate from the summary of this invention.

DESCRIPTION OF SYMBOLS 1 Control part 2 Memory | storage part 3a, 3b, 3c, 3d Battery 4a, 4b, 4c, 4d Voltage measurement part 5a, 5b, 5c, 5d Current measurement part 501 Offset voltage information table 701 Charge offset voltage information table 801 Discharge offset Voltage information table L1, L2, L3 Coil SW1, SW2, SW3, SW4, SW5, SW6, SW7 Switch 121 Usage pattern time table 122 Offset voltage correction unit 123 Calendar function unit 124 Cross control execution date and time acquisition unit 125 Vehicle state determination unit

Claims (2)

A voltage measuring unit for measuring the voltages of the first and second batteries;
A current is passed from one of the first and second batteries to the other so as to equalize the voltages of the first and second batteries, and a voltage change due to polarization of the first and second batteries is estimated. Even after the voltages of the first and second batteries are equalized, the current flows from one of the first and second batteries to the other until an offset voltage corresponding to the voltage change due to the polarization is reached. A control unit that executes a cross-control cell balance process,
A time measuring unit for measuring an elapsed time from the start of the cross-control cell balance process;
A storage unit,
The storage unit
Offset voltage information in which a cross time, which is an elapsed time until the voltage difference between the first and second batteries is within a predetermined voltage range by the cross control cell balance process, and the offset voltage are stored in association with each other. Table,
About the first and second batteries, a usage pattern time table showing a time table of a usage pattern including a status of suspension of use;
The ratio of the voltage at the time of depolarization of the first or second battery to the total polarization voltage, which is a voltage that changes with the complete depolarization time of the first or second battery, is the first or second as a polarization correction coefficient. Storing a polarization correction coefficient table stored in association with an elapsed time at the time of depolarization of the second battery,
The controller is
During the execution of the cross control cell balance process, the voltage difference between the voltages of the first and second batteries is obtained, the cross time until the voltage difference is within a predetermined voltage range is obtained, and the cross time is supported. Obtained offset voltage with reference to the offset voltage information table,
Predicting the time during which the first and second batteries are used for power feeding after the cross time with reference to the usage pattern time table,
The estimated time during which the use is suspended is estimated as an elapsed time when the polarization of the first or second battery is released, and a polarization correction coefficient corresponding to the elapsed time when the polarization of the first or second battery is released With reference to the polarization correction coefficient table,
An offset voltage obtained by multiplying the polarization correction coefficient by the offset voltage is calculated as an offset voltage in the cross control cell balance process. A voltage equalizing apparatus for equalizing the voltages of a plurality of batteries. A current is passed from one of the first and second batteries to the other so as to equalize the voltages of the first and second batteries, and a change in voltage due to the polarization of the first and second batteries is estimated. Thus, even after the voltages of the first and second batteries become equal, current is passed from one of the first and second batteries to the other until an offset voltage corresponding to the voltage change due to the polarization is reached. A voltage equalization method by cross control cell balance processing,
Offset voltage information in which a cross time, which is an elapsed time until the voltage difference between the first and second batteries is within a predetermined voltage range by the cross control cell balance process, and the offset voltage are stored in association with each other. Store the table in the storage unit,
For the first and second batteries, a usage pattern time table indicating a usage status pattern time table including a usage suspended status is stored in the storage unit;
The ratio of the voltage at the time of depolarization of the first or second battery to the total polarization voltage, which is a voltage that changes with the complete depolarization time of the first or second battery, is the first or second as a polarization correction coefficient. The polarization correction coefficient table stored in association with the elapsed time at the time of depolarization of the second battery is stored in the storage unit,
During the execution of the cross control cell balance process, the voltage difference between the voltages of the first and second batteries is obtained, the cross time until the voltage difference is within a predetermined voltage range is obtained, and the cross time is supported. Obtained offset voltage with reference to the offset voltage information table,
Predicting the time during which the first and second batteries are used for power feeding after the cross time with reference to the usage pattern time table,
The estimated time during which the use is suspended is estimated as an elapsed time when the polarization of the first or second battery is released, and a polarization correction coefficient corresponding to the elapsed time when the polarization of the first or second battery is released With reference to the polarization correction coefficient table,
An offset voltage corrected by multiplying the polarization correction coefficient by the offset voltage is calculated as an offset voltage in the cross control cell balance process.
A voltage equalizing method for equalizing the voltages of a plurality of batteries.

Images