JP2012257392A - Battery pack capacity adjuster - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery pack capacity adjuster that can properly equalize battery cells Ci (i=1 to n) constituting a battery pack 10.SOLUTION: A capacity adjuster for a battery pack 10 comprises a transformer Ti, a primary switch SW1i, a secondary switch SW2i, and so on. More specifically, in each battery cell Ci, a series connection body of a primary coil w1i and the primary switch SW1i is connected in parallel, and a series connection body of a secondary coil w2i and a diode Di is each connected in parallel via the secondary switch SW2i. In such a configuration, a selection is processed to pick a battery cell having a minimum internal resistance and a battery cell having a maximum internal resistance among the battery cells Ci. Then, an equalization processing of operating the primary switch SW1i and the secondary switch SW2i is performed so as to supply electric power from the battery cell having the minimum internal resistance to the battery cell having the maximum internal resistance via the transformer Ti.

Description

  The present invention relates to an assembled battery capacity adjusting device applied to an assembled battery as a serially connected unit battery that is one or a plurality of adjacent battery cells.

  As this type of circuit, as shown in Patent Document 1 below, a circuit that equalizes the voltages of a plurality of unit cells (unit cells) constituting an assembled battery is known. Specifically, this circuit includes an ON / OFF converter circuit in which the output voltage of the assembled battery is used as a primary side input, and the secondary side output is connected in a direction in which each unit battery is charged. Then, the unit battery having the lowest voltage is intensively charged by this converter circuit.

JP-A-11-176483

  By the way, the unit battery may be deteriorated due to, for example, a longer usage period of the unit battery. Here, when equalizing the voltages of the unit cells, it is desirable to supply charges from the unit cells having a low degree of deterioration to the unit cells having a high degree of deterioration. This is due to the following reason.

  When the degree of deterioration of the unit battery increases, the voltage (terminal voltage) of the unit battery tends to increase during the period when the unit battery is charged with the same current value. For this reason, in the situation where the assembled battery is charged, the voltage of the unit battery having a high degree of deterioration may be higher than the voltage of the unit battery having a low degree of deterioration.

  Under these circumstances, when a charge is supplied from a unit cell with a high degree of deterioration to a unit battery with a low degree of deterioration, immediately after that, the assembled battery is discharged, so that the unit battery with a high degree of deterioration and the degree of deterioration are reduced. A situation in which the magnitude relationship with the voltage of the small unit cell is reversed may occur. In this case, there is a concern that charges cannot be effectively exchanged between the unit batteries, and the capacity of the assembled battery cannot be adjusted appropriately.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide an assembled battery capacity adjusting device capable of appropriately adjusting the capacity of the assembled battery.

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

  The invention according to claim 1 is applied to an assembled battery as a series connection body of unit batteries which are one or a plurality of adjacent battery cells, and energy storage means for temporarily storing electric energy of the unit batteries; Based on connection means for selectively connecting some of the unit batteries to the energy storage means, and currents flowing through the unit batteries and voltages of the unit batteries, respective internal resistances of the unit batteries are calculated. And a process of selecting a unit battery having a low level of internal resistance and a unit cell having a high level of internal resistance from the unit cells based on the calculated internal resistance. Selection processing means; and operating means for performing processing for operating the connection means to supply electric charge from the low level unit cell to the high level unit cell. .

  When the degree of deterioration of the unit battery increases, the internal resistance of the unit battery generally tends to increase. In view of this point, in the above invention, the internal resistance of each unit cell is calculated by the internal resistance calculation means in the above-described manner. A unit cell having a low internal resistance is selected as a charge supply source from among unit cells, and a unit cell having a high internal resistance is selected as a charge supply destination. Then, the connecting means is operated to supply electric charge from the unit battery having a low internal resistance to the unit battery having a high internal resistance. Thereby, electric charge can be supplied from a unit battery having a low degree of deterioration to a unit battery having a high degree of deterioration, and the electric charge can be appropriately supplied between unit batteries constituting the assembled battery. Therefore, it is possible to appropriately adjust the capacity of the assembled battery, for example, it is possible to appropriately equalize the voltages of the unit batteries.

  According to a second aspect of the present invention, in the first aspect of the invention, the selection processing unit is a unit cell corresponding to the maximum value of the internal resistance calculated by the internal resistance calculation unit as the high-level unit cell. A selection process is performed.

  In the above invention, the unit battery having the greatest deterioration degree is selected as the charge supply destination among the unit batteries. For this reason, the capacity | capacitance of the unit battery with the largest deterioration degree can be increased rapidly, and equalization of each voltage of a unit battery can be performed more appropriately.

  According to a third aspect of the present invention, in the second aspect of the present invention, the selection processing unit is configured to select a unit cell corresponding to the minimum value of the internal resistance calculated by the internal resistance calculating unit as the low-level unit cell. A selection process is performed.

  In the above invention, the unit battery having the smallest deterioration degree is selected as the charge supply source among the unit batteries. For this reason, equalization of each voltage of a unit cell can be performed more appropriately.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the energy storage means is a transformer, and the connection means includes each of the unit batteries and the primary of the transformer. Primary side switching means capable of selectively opening and closing each of the electrical paths connecting the side coils, and selectively opening and closing each of the electrical paths connecting each of the unit batteries and the secondary coil of the transformer It is a possible secondary side opening / closing means.

  In the above invention, by adopting the above-described configuration including the transformer, the primary side opening / closing means and the secondary side opening / closing means, the unit battery as the charge supply source is changed from the unit battery as the charge supply destination via the transformer. An electric charge can be appropriately supplied.

  The invention according to claim 5 is the invention according to claim 4, further comprising rectifying means for restricting a current flow of the secondary side coil in one direction, the transformer, the primary side opening / closing means, and the secondary side. Each of the side opening / closing means and the rectifying means is provided for each of the unit batteries, and the transformer includes the primary side coil and the secondary side coil. A serial connection body of the primary side coil and the primary side opening / closing means is connected in parallel, and each of the secondary side coil and the series connection body of the rectifying means is connected in parallel via the secondary side opening / closing means. The rectifying means has a function of flowing a current in a direction from the secondary coil toward the positive electrode side of the unit battery.

  In the above-described invention, the primary side opening / closing means corresponding to one or a plurality of unit batteries serving as the charge supply source is closed, so that the primary coil of the transformer corresponding to the unit battery serving as the charge supply source Electric energy is stored in Then, after the secondary side opening / closing means corresponding to the unit battery to which the electric charge is supplied is closed, the primary side opening / closing means is opened to cause an induced current in the secondary coil. Flows. Thereby, the unit battery used as the electric charge supply destination can be charged.

  According to a sixth aspect of the present invention, in the fourth aspect of the present invention, the transformer further includes a rectifying unit that restricts a current flow of the secondary coil in one direction, and the transformer includes the primary coil and the secondary coil. A plurality of pairs of side coils, and each of the primary side opening / closing means, the secondary side opening / closing means and the rectifying means is provided for each of the unit cells, and each of the unit cells includes the primary coil A secondary electric path including the secondary coil, the secondary opening / closing means and the rectifying means is connected in parallel with a serial connection of the side coil and the primary opening / closing means, and the secondary opening / closing means is The secondary side electrical path is opened and closed, and the rectifying means is provided so that a current flows through the secondary side electrical path toward the positive electrode side of the unit battery.

  In the above-described invention, the primary side opening / closing means corresponding to one or a plurality of unit batteries serving as the charge supply source is closed, so that the primary coil of the transformer corresponding to the unit battery serving as the charge supply source Electric energy is stored in Then, after the secondary side opening / closing means corresponding to one or a plurality of unit batteries to which the electric charge is supplied is closed, the primary side opening / closing means is opened to open the secondary side. An induced current flows through the coil. Thereby, the unit battery used as the electric charge supply destination can be charged.

  The invention according to claim 7 is the invention according to any one of claims 1 to 6, wherein each internal of the unit cell calculated by the internal resistance calculation means based on the temperature of each of the unit cells. The image processing apparatus further includes a correction unit that corrects the resistance, and the selection processing unit performs the selection process based on the corrected internal resistance.

  The internal resistance of the unit cell can vary depending on the temperature of the unit cell. Specifically, the higher the temperature of the unit cell, the lower the internal resistance of the unit cell. For this reason, if variations occur in the temperatures of the unit batteries constituting the assembled battery, the degree of deterioration between the unit batteries may not be properly grasped by the internal resistance of the unit batteries.

  In this regard, in the above-described invention, by performing the selection process based on the internal resistance corrected by the correction unit, it is avoided that the accuracy of grasping the degree of deterioration of the unit battery due to the difference in the temperature of the unit battery is reduced. it can. For this reason, it is possible to appropriately select a unit battery that is a supply source and a supply destination of charges.

  The invention according to an eighth aspect is the invention according to any one of the first to seventh aspects, wherein the capacity adjusting device includes a process of operating the connecting means by the operating means, and a voltage of each of the unit cells. And the process of detecting the squeezing alternately at a predetermined cycle.

  In order to exchange charges between unit cells by the operation means, it is necessary to perform voltage detection processing of each unit cell in order to grasp the internal resistance. However, when the voltage detection process is performed, the power consumption of the capacity adjusting device can be increased by this process. Here, in the said invention, the process which operates a connection means by an operation means and the said voltage detection process are alternately performed with a predetermined period. Thereby, it can suppress that the execution time of the said voltage detection process becomes long as much as possible, and can suppress that the power consumption of a capacity | capacitance adjustment apparatus increases with execution of a voltage detection process as much as possible.

1 is a system configuration diagram according to a first embodiment. FIG. The flowchart which shows the procedure of the equalization process concerning the embodiment. The figure which shows the outline | summary of the correction method of the internal resistance concerning the embodiment. The figure which shows the outline | summary of the correction method of the internal resistance concerning the embodiment. The figure which shows the selection aspect of the charging / discharging cell based on the internal resistance concerning the embodiment. The flowchart which shows the procedure of the charge process concerning the embodiment. The time chart which shows an example of the equalization process concerning the embodiment. The time chart which shows the effect of the equalization process concerning the embodiment. The system block diagram concerning 2nd Embodiment.

(First embodiment)
Hereinafter, a first embodiment in which an assembled battery capacity adjustment device according to the present invention is applied to a plug-in hybrid vehicle (PHV) including an internal combustion engine and a rotating machine (motor generator) as an in-vehicle main engine will be described with reference to the drawings. explain.

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

  As shown in the drawing, the assembled battery 10 constitutes a vehicle-mounted high-voltage system and serves as a power source for the motor generator. The assembled battery 10 is a series connection body of battery cells Ci (i = 1 to n: n is an integer of 2 or more), and the voltage (terminal voltage) becomes a predetermined high voltage (for example, several hundreds V). is there. In the present embodiment, a lithium ion secondary battery is assumed as the battery cell Ci, and a battery pack in which hundreds of dozens of battery cells are connected in series is assumed. Each battery cell Ci has a voltage of several volts.

  The assembled battery 10 is connected to the charger 12. A plug 14 can be connected to the charger 12. The assembled battery 10 is charged by connecting the plug 14 to a power supply device such as a commercial power supply outside the vehicle.

  The signal line Li is connected to the positive terminal of each battery cell Ci, and the signal line L (i + 1) is connected to the negative terminal of each battery cell Ci. That is, except for the signal lines L1, L (n + 1), the signal line on the negative terminal side of the battery cell on the high potential side and the positive terminal side of the battery cell on the low potential side of the pair of adjacent battery cells Ci. It is shared with the signal line.

  For each of the battery cells Ci, a transformer Ti including a pair of primary side coil w1i and secondary side coil w2i, an electrical path connecting the battery cell Ci and the primary side coil w1i are turned on / off. A primary side switch SW1i to be turned off and a secondary side switch SW2i to turn on / off an electrical path connecting the battery cell Ci and the secondary side coil w2i are provided. Here, the turn ratio N of the primary side coil w1i and the secondary side coil w2i of each transformer Ti is set to a value larger than 1. The turn ratio N is given by “N2 / N1” where N1 is the number of turns of the primary coil w1i and N2 is the number of turns of the secondary coil w2i.

  Incidentally, in the present embodiment, an N-channel MOSFET is assumed as the primary side switch SW1i. Further, the secondary side switch SW2i is constituted by a pair of switches (a first secondary side switch SW2ip and a second secondary side switch SW2in).

  Each battery cell Ci is connected in parallel with a series connection of a primary coil w1i and a primary switch SW1i. Specifically, the drain side of the primary side switch SW1i is connected in series to the primary side coil w1i, and this series connection body is connected between the signal lines Li and L (i + 1). Note that the drain side of the primary side switch SW1i is connected to the primary side coil w1i to avoid a situation where the battery cell Ci is short-circuited via the body diode of the primary side switch SW1i (N-channel MOSFET). Because.

  In addition, each of the battery cells Ci is connected in parallel with a series connection body of the secondary coil w2i and the diode Di via the secondary switch SW2i. Specifically, a series connection of a first secondary switch SW2ip, a secondary coil w2i, a diode Di, and a second secondary switch SW2in is connected in parallel to each battery cell Ci. Of both ends of the series connection body, the first secondary switch SW2ip side is connected to the signal line Li, and the second secondary switch SW2in side is connected to the negative terminal of the battery cell Ci. Yes.

  More specifically, the positive terminal side of the battery cell Ci in the secondary coil w2i is the side where the polarity of the voltage generated in the secondary coil w2i is positive. The anode side of the diode Di is connected to the second secondary side switch SW2in.

  For each battery cell Ci, the electrical path including the primary coil w1i connected in parallel to the battery cell Ci and the electrical path including the secondary coil w2i connected in parallel to the battery cell Ci are Share some. Specifically, among the signal lines Li, an electric path (shared path) that connects the first secondary switch SW2ip and the battery cell Ci is shared. The shared path is provided with a coil current detector Ai that detects a current flowing through the path. This is because the current flowing in each of the primary coil w1i and the secondary coil w2i is detected by a single current detector to simplify the circuit. In the present embodiment, a shunt resistor is assumed as the coil current detector Ai.

  A connection point between the first secondary switch SW2ip and the secondary coil w2i is connected by a first electrical path La, and a connection point between the anode side of the diode Di and the second secondary switch SW2in. The two are connected by a second electrical path Lb.

  Incidentally, in the present embodiment, a serial connection body of the sources of a pair of N-channel MOSFETs is used as the secondary side switch SW2i. This is because a predetermined electric path (for example, the signal line L1, the body diode of the first secondary switch SW21p, the first electric path La, the first electric path, even though the secondary switch SW2i is turned off) Via the body diode of the secondary side switch SW23p and the signal line L3, the high potential via the positive terminal of the battery cell C1 on the high potential side and the negative terminal of the battery cell C2 on the low potential side). This is to prevent a current from flowing from the battery cell on the side (for example, battery cell C1) to the battery cell on the low potential side (for example, battery cell C2).

  A temperature sensor TVi that detects the temperature of the battery cell Ci is provided near each of the battery cells Ci.

  The voltage across the shunt resistor as the coil current detector Ai, the voltage across the load current detector 16 (shunt resistor) that detects the current flowing through the assembled battery 10, and the output signal of the temperature sensor TVi are the control circuit 18 Is taken in.

  The control circuit 18 is mainly composed of a microcomputer, and turns on / off the primary side switch SW1i and the secondary side switch SW2i via the drive circuit DUi corresponding to each battery cell Ci.

  Further, the control circuit 18 detects the current flowing through the primary coil w1i or the secondary coil w2i based on the voltage drop amount in the coil current detector Ai, or based on the voltage drop amount in the load current detector 16 The current flowing through the assembled battery 10 is detected, or the voltage Vi of each battery cell Ci is detected based on the voltage of the battery cell Ci acquired via the signal lines Ci, C (i + 1). Further, the temperature of the battery cell Ci is detected based on the output signal of the temperature sensor TVi.

  Incidentally, the control circuit 18 has information SPD about whether or not the vehicle is traveling from the outside (vehicle-mounted low-pressure system) and charging information about whether or not the assembled battery 10 is being charged from the charger 12. Entered. Here, information relating to the traveling of the vehicle is input to the control circuit 18 via an insulating means such as a photocoupler. In addition, power is supplied to the control circuit 18 from the assembled battery 10 via a step-down converter or the like.

  In particular, the control circuit 18 performs an equalization process for eliminating variations in the voltage Vi of the battery cell Ci. In this process, the voltage of some battery cells is excessively lowered to reduce the reliability of the battery cells, or the power of battery cells other than some of the battery cells whose voltage is excessively low is appropriately used. This is a process for avoiding that the performance of the assembled battery 10 cannot be lower than originally assumed.

  In the present embodiment, the equalization processing is processing for calculating the internal resistance of the battery cell Ci and supplying power from the battery cell having the minimum internal resistance to the battery cell having the maximum internal resistance. This is because the equalization process is effectively performed. Hereinafter, this process will be described.

  The battery cell Ci may be deteriorated due to repeated charging / discharging of the battery cell Ci during traveling of the vehicle, exposure of the battery cell Ci to a high temperature environment, or the like. When the battery cell Ci deteriorates, the internal resistance of the battery cell Ci usually increases. Specifically, the degree of increase in internal resistance of the battery cell Ci tends to increase as the degree of deterioration of the battery cell Ci increases. When the internal resistance of the battery cell Ci increases, the voltage (terminal voltage) of the battery cell Ci during the period in which the battery cell Ci is charged with the same current value tends to increase, and the battery has the same current value. There is a tendency that the voltage of the battery cell Ci decreases during the period in which the cell Ci is discharged.

  For this reason, the voltage of the battery cell with a high degree of deterioration may be higher than the voltage of the battery cell with a low degree of deterioration under a situation where the assembled battery 10 is charged by regenerative power generation using a motor generator, for example.

  Under such circumstances, for example, power is supplied from the battery cell having the maximum value (maximum voltage) of the voltages Vi of each battery cell Ci to the battery cell having the minimum value (minimum voltage) of the voltages Vi. When the equalization process is performed, power may be supplied from a battery cell having a high degree of deterioration to a battery cell having a low degree of deterioration. In this case, immediately after that, the discharge process of the assembled battery 10 is performed, so that a situation in which the magnitude relationship between the voltage of the battery cell having a large deterioration degree and the voltage of the battery cell having a low deterioration degree is reversed occurs, and the equalization process is effective. There is a risk that it will not be possible to perform it automatically. Moreover, there is a possibility that the charging rate (percentage of the current charge amount with respect to the full charge amount: SOC) of the battery cell having a high degree of deterioration becomes excessively small. In these cases, the time until the voltage Vi of the battery cell Ci falls below the predetermined voltage is shortened, and the travel distance of the vehicle may be shortened.

  In order to avoid such a situation, the equalization process is effectively performed by performing the equalization process based on the internal resistance.

  FIG. 2 shows a procedure of equalization processing according to the present embodiment. This process is repeatedly executed by the control circuit 18.

  In this series of processing, first, in step S10, the voltage Vi, the temperature Thi, and the load current value Ir of each battery cell Ci are detected. Here, the load current value Ir is detected by the load current detector 16. In the present embodiment, the load current value Ir when the assembled battery 10 is discharged is defined as positive.

  In the subsequent step S12, the internal resistance ri of the battery cell Ci is calculated based on the voltage Vi of the battery cell Ci, the temperature Thi, the load current value Ir, and the charge rate SOCi of the battery cell Ci. Hereinafter, a method for calculating the internal resistance ri will be described in detail.

  First, the internal resistance ri of the battery cell Ci is calculated based on the load current value Ir and the voltage Vi of the battery cell Ci. For example, this is because the load current value Ir and the voltage Vi of the battery cell Ci when the load current value Ir changes in a situation where power is transferred between the motor generator and the assembled battery 10 or the like. Can be obtained by multiple regression analysis based on a plurality of detected values. In calculating the internal resistance, for example, a series connection body of a power source and a resistor that generate an electromotive force may be used as an equivalent circuit model of the battery cell Ci.

  Next, the calculated internal resistance ri is corrected based on the temperature Thi and SOCi of the battery cell Ci. This correction is performed in order to improve the accuracy of grasping the degree of deterioration of the battery cell Ci. That is, since the internal resistance ri of the battery cell Ci varies depending on the temperature Thi and SOCi of the battery cell Ci, if the temperature Thi and SOCi of the battery cell Ci vary due to the temperature distribution in the assembled battery 10 or the like, the battery There is a concern that the degree of deterioration of the battery cell Ci cannot be properly grasped by the internal resistance ri of the cell Ci.

  The correction method will be described in detail. As shown in FIG. 3A, in view of the fact that the internal resistance ri tends to decrease as the temperature Thi of the battery cell Ci increases, the reference temperature Tα and the actual temperature Thi The temperature correction coefficient Kt is set based on the temperature difference ΔTi. More specifically, the temperature difference ΔTi is a value obtained by subtracting the actual temperature Thi from the reference temperature Tα, and the temperature correction coefficient Kt decreases as the temperature difference ΔTi increases as shown in FIG. Set. Here, the temperature correction coefficient Kt becomes 0 when the temperature difference ΔTi becomes 0. The reference temperature Tα can be set to, for example, any actual temperature of the battery cell Ci (detected value of the temperature sensor TVi) or a predetermined temperature.

  On the other hand, as shown in FIG. 4A, in view of the tendency that the internal resistance ri tends to decrease as the SOCi of the battery cell Ci increases, the SOC is determined based on ΔSOCi that is the difference between the reference SOC and the actual SOCi. A correction coefficient Ks is set. More specifically, ΔSOCi is a value obtained by subtracting the actual SOCi from the reference SOC. As shown in FIG. 5B, the larger the ΔSOCi, the smaller the SOC correction coefficient Ks is set. Here, the SOC correction coefficient Ks becomes 0 when ΔSOCi becomes 0. The reference SOC can be, for example, any actual SOCi of the battery cell Ci, or a predetermined SOC, similarly to the reference temperature Tα.

  Then, the internal resistance ri is corrected by multiplying the internal resistance ri by the temperature correction coefficient Kt and the SOC correction coefficient Ks. Hereinafter, the corrected internal resistance ri is simply referred to as an internal resistance ri.

  Incidentally, SOCi may be calculated based on the open circuit voltage (OCV) of the battery cell Ci. This is based on the fact that the relationship between OCV and SOCi hardly changes regardless of the degree of deterioration of the battery cell Ci. Here, the OCV uses the fact that the voltage Vi of the battery cell Ci is the sum of the voltage drop due to the OCV and the internal resistance ri, and the voltage Vi of the battery cell Ci, the internal resistance ri, and the load current value Ir It may be calculated based on

  Further, in view of the fact that the deterioration of the battery cell Ci does not proceed in a short period of time, the processing of this step is performed at a sufficiently long predetermined cycle, for example, every time the travel distance of the vehicle becomes a specified distance or every time a predetermined time elapses. You may go on.

  Returning to the description of FIG. 2, in the subsequent step S <b> 14, it is determined whether or not the vehicle is traveling. Here, whether or not the vehicle is traveling may be determined based on the information SPD input from the low-pressure system side.

  When an affirmative determination is made in step S14, the process proceeds to step S16, and it is determined whether or not the minimum value (minimum voltage Vmin) of the voltages Vi of each battery cell Ci exceeds the lower limit voltage Vth1 (for example, 3V). In the present embodiment, the lower limit voltage Vth1 is set as the lower limit value of the voltage that can maintain the reliability of the battery cell Ci. In this process, it is determined whether or not the voltage Vi of the battery cell Ci is excessively lowered and the reliability of the battery cell Ci is lowered under the situation where the power of the assembled battery 10 is consumed by driving the motor generator. Is to do.

  If an affirmative determination is made in step S16, the process proceeds to step S18, where the primary coil w1i is based on the voltage difference ΔV between the maximum value (maximum voltage Vmax) and the minimum voltage Vmin among the voltages Vi of each battery cell Ci. Is set to the peak value of the current (equalized current value Ib). Specifically, the equalization current value Ib is set higher as the absolute value of the voltage difference ΔV is larger. This is a setting for optimizing the charge amount of the battery cell Ci within the execution period of the equalization process. Specifically, the voltage difference ΔV may be calculated by subtracting the minimum voltage Vmin from the maximum voltage Vmax.

  In the subsequent step S20, the secondary side switch SW2i corresponding to the battery cell having the maximum internal resistance rmax (shown as a charge cell in FIG. 5) among the battery cells Ci is turned on. Specifically, both the first and second secondary switches SW2ip and SW2in are simultaneously turned on.

  In subsequent step S22, is the elapsed time (secondary side on time T) from when the secondary side switch SW2i of the battery cell having the maximum internal resistance rmax turned on is less than a specified time T2on (for example, 0.8 seconds)? Judge whether or not. This process is for determining whether or not the execution period of the equalization process has elapsed.

  Here, the specified time T2on is, for example, that the power consumption of the battery cell is not increased due to the execution of the equalization process, and the power is supplied from the power supply source battery cell to the power supply destination battery cell by the equalization process. This time is set from the standpoint of ensuring a sufficient time to do so. In other words, when the equalization process is performed, the power of the battery cell is wasted due to the power loss associated with the transmission / reception of power through the transformer Ti and the increase in the power consumption of the control circuit 18 associated with the voltage detection process. The Rukoto. In addition, if the specified time T2on is short, the voltage change of the battery cell due to the equalization process becomes small, so that sufficient power cannot be supplied from the power supply source to the power supply destination, and it cannot be appropriately equalized. There are concerns.

  In practice, the voltage detection process in step S10 and the equalization process in steps S22 to S32 are alternately performed at a predetermined cycle under the situation in which an affirmative determination is made in steps S14 and S16. More specifically, for example, after the voltage detection process is performed for 0.2 seconds, a cycle in which the equalization process is performed for 0.8 seconds is repeated.

  If it is determined in step S22 that the secondary-side on-time T is less than the specified time T2on, the process proceeds to step S24 and corresponds to a battery cell having the minimum internal resistance rmin (denoted as a discharge cell in FIG. 5). The primary side switch SW1i is turned on.

  In subsequent step S26, the process waits until the current value (primary current value I1) flowing through the primary coil w1i detected by the coil current detector Ai reaches the equalization current value Ib. This process is a process for temporarily storing the electric energy of the battery cell serving as the power supply source in the primary coil w1i.

  When it is determined that the primary current value I1 has reached the equalized current value Ib, the process proceeds to step S28, and the primary switch SW1i corresponding to the battery cell having the minimum internal resistance rmin is turned off. As a result, a voltage with the diode Di side being negative is applied to the secondary coil w2i corresponding to the battery cell having the maximum internal resistance rmax, and the battery cell having the maximum internal resistance rmax is charged from the secondary coil w2i. Current will flow.

  In the subsequent step S30, it is determined whether or not the current value (charging current value I2) flowing from the secondary coil w2i to the battery cell having the maximum internal resistance rmax becomes 0A. This process is for avoiding a situation where the charging current value I2 becomes excessively large.

  That is, for example, the primary side switch SW1i of the primary side coil w1i in which the electric energy of the battery cell having the minimum internal resistance rmin is stored before the charging current value I2 becomes 0A, that is, during the period when the charging current flows. When switching from on to off, in addition to the current charging current, there is a concern that the charging current resulting from the voltage generated this time will flow in the secondary coil w2i and the reliability of the charging path will be reduced. For this reason, by providing the processing of this step, the occurrence of a situation where the reliability of the charging path is reduced is avoided. The charging current value I2 is detected by the coil current detector Ai.

  If it is determined in step S22 that the secondary-side on-time T is equal to or greater than the specified time T2on, the process proceeds to step S32, and the secondary-side switch SW2i corresponding to the battery cell having the maximum internal resistance rmax is turned off.

  On the other hand, if a negative determination is made in step S14, the process proceeds to step S34 to determine whether or not the assembled battery 10 is being charged. Here, whether or not the assembled battery 10 is being charged may be determined based on, for example, charging information from the charger 12.

  When an affirmative determination is made in step S34, the process proceeds to step S36, and the assembled battery 10 is charged. This process is a process for raising the voltage of all the battery cells Ci to the vicinity of the upper limit voltage Vth2 (for example, 4.1 V) by the electric power supplied from the power supply device in preparation for the next traveling of the vehicle. . For example, the upper limit voltage Vth2 may be set as an upper limit value of a voltage that can maintain the reliability of the battery cell Ci.

  If a negative determination is made in steps S16 and S34, or if the processes in steps S32 and S36 are completed, this series of processes is temporarily terminated.

  Next, FIG. 6 shows the procedure of the charging process according to the present embodiment. This process is repeatedly executed by the control circuit 18.

  In this series of processes, first, in step S40, it is determined whether or not the maximum voltage Vmax is equal to or higher than the upper limit voltage Vth2. This process is a process for determining whether any of the battery cells Ci is in a fully charged state.

  When an affirmative determination is made in step S40, the process proceeds to step S42, and it is determined whether or not the minimum voltage Vmin is smaller than a value obtained by subtracting the specified value Δβ (> 0) from the upper limit voltage Vth2. This process is a process for determining whether or not all the battery cells Ci are fully charged and the charging process of the assembled battery 10 is completed.

  If an affirmative determination is made in step S42, it is determined that the charging process has not yet been completed, and the process proceeds to step S44. In step S44, power is supplied from the battery cell having the maximum voltage Vmax to the battery cell having the minimum voltage Vmin. Specifically, first, the secondary side switch SW2i corresponding to the battery cell having the minimum voltage Vmin is turned on. Then, the primary side switch SW1i corresponding to the battery cell Ci having the maximum voltage Vmax is turned on, and the primary side switch SW1i is turned off after a predetermined time has elapsed. As a result, a charging current flows from the secondary coil w2i corresponding to the battery cell having the minimum voltage Vmin to the battery cell having the minimum voltage Vmin.

  If a negative determination is made in steps S40 and S42 described above, or if the process of step S44 is completed, this series of processes is temporarily terminated.

  FIG. 7 shows an example of equalization processing according to the present embodiment. Specifically, the equalization process when the battery cell C1 is selected as the battery cell having the minimum internal resistance rmin and the battery cell C3 is selected as the battery cell having the maximum internal resistance rmax will be described using FIG. To do. 3A shows the transition of the operating state of the primary side switch SW11, FIG. 3B shows the transition of the operating state of the secondary side switch SW23, and FIG. The transition of the secondary current value I1 is shown, and FIG. 3D shows the transition of the charging current value I2.

  In the illustrated example, voltage detection processing of the battery cell Ci is performed in a period of time t1 to t2 (for example, 0.2 seconds), and the battery cells C1 and C3 having the minimum internal resistance rmin and the maximum internal resistance rmax are specified. .

  At time t2, the secondary side switch SW23 is turned on and the primary side switch SW11 is turned on to start the equalization process. When the primary side switch SW11 is turned on, a closed loop circuit including the positive terminal of the battery cell C1, the signal line L1, the primary side coil w11, the primary side switch SW11, the signal line L2, and the negative terminal of the battery cell C1. Is formed, and the primary current value I1 flowing through the primary coil w11 starts to increase gradually. Further, when the secondary side switch SW23 is turned on, the secondary side coil w21, the first electric path La, the first secondary side switch SW23p, the signal line L3, the battery cell C3, the second secondary side switch A closed loop circuit composed of the SW 23n, the second electric path Lb, and the diode D1 is formed.

  At time t3 when the primary side current value I1 reaches the equalized current value Ib, the primary side switch SW11 is turned off. As a result, a voltage that makes the diode Di side negative is applied to the secondary coil w21 by electromagnetic induction, and a charging current flows through the battery cell C3. Then, at time t4 when the charging current value I2 becomes 0A, the primary side switch SW11 is turned on.

  Thereafter, the above-described switching operation of the primary side switch SW11 and the secondary side switch SW23 is repeated until the time t5 when the secondary side on-time T becomes the specified time T2on. The reason why the secondary side switch SW23 is kept on for the specified time T2on is to reduce the switching loss when the secondary side switch SW23 is turned on and off.

  Next, FIG. 8 shows the effect of the equalization processing according to the present embodiment. Specifically, FIG. 8 shows the transition of the voltage of a specific battery cell when equalization processing is performed in a predetermined vehicle traveling pattern (for example, JC08 mode).

  First, the solid line in the figure shows the case where the equalization process based on the internal resistance is performed under the situation where the assembled battery 10 is discharged by driving the motor generator.

  In the illustrated example, the capacity variation between the battery cells can be reduced as quickly as possible, and the time tB until the voltage of the battery cell becomes a predetermined low voltage (for example, 2.5 V) is extended.

  On the other hand, when performing the equalization process of selecting the power supply destination and the supply source based on the voltage of the battery cell, it is possible to suppress the variation in capacity between the battery cells as shown by the broken line in the figure. Therefore, the time tA until the voltage of the battery cell becomes a predetermined low voltage is shortened.

  In addition, according to the equalization process according to the present embodiment, the travel time of the vehicle is increased from 71.7 minutes to 74.3 minutes compared to the equalization process of selecting the battery cells based on the voltage (the travel distance of the vehicle). Has increased by 4.7%).

  As described above, in the present embodiment, the battery cell Ci is appropriately configured by performing the equalization process for supplying power from the battery cell having the minimum internal resistance rmin to the battery cell having the maximum internal resistance rmax via the transformer Ti. Can be equalized.

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

  (1) The battery cell having the minimum internal resistance rmin and the battery cell having the maximum internal resistance rmax were selected from the battery cells Ci. And the equalization process which supplies electric power via the transformer Ti from the battery cell which has the minimum internal resistance rmin to the battery cell which has the maximum internal resistance rmax was performed. Thereby, equalization of the battery cell Ci can be performed appropriately and the usable time of the assembled battery 10 can be lengthened. Thereby, the travel distance of the vehicle can be increased.

  (2) The internal resistance ri calculated based on the voltage Vi and the load current value Ir of the battery cell Ci was corrected based on the SOCi and temperature Thi of the battery cell Ci. Thereby, the influence which the temperature of battery cell Ci has on internal resistance ri can be excluded as much as possible, and the grasping | ascertainment precision of the deterioration degree of battery cell Ci can be improved.

  (3) The equalization process and the voltage detection process were alternately performed at a predetermined cycle. As a result, it is possible to balance that the power consumption accompanying the equalization process does not increase and that sufficient time for supplying power from the battery cell having the minimum internal resistance rmin to the battery cell having the maximum internal resistance rmax is secured. Etc.

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

  FIG. 9 shows a system configuration according to the present embodiment.

  The circuit shown in the figure is provided with one transformer TW. The transformer TW has the same number of primary side coils w1i and secondary side coils w2i as the number of battery cells Ci.

  Each battery cell Ci is connected in parallel with a series connection of a primary coil w1i and a primary switch SW1i. Specifically, the series connection body is connected between the signal lines Li and L (i + 1).

  Each battery cell Ci is further connected in parallel with a series connection of a secondary coil w2i, a diode Di, and a secondary switch SW2i. Specifically, in the secondary coil w2i, the positive terminal side of the battery cell Ci is the side where the polarity of the voltage generated in the secondary coil w2i is positive. The anode side of the diode Di is connected to the secondary switch SW2i side.

  According to such a configuration, a plurality of battery cells as power supply destinations can be selected, and power can be supplied and charged to these battery cells.

  Specifically, the battery cell C1 having the maximum internal resistance rmax and the battery cell C2 having the next lowest internal resistance rmax are selected as the battery cells to which power is supplied, and the battery cell of the power supply source is selected. As an example, when the battery cell C3 having the minimum internal resistance rmin is selected, first, when the primary side switch SW13 corresponding to the battery cell C3 is turned on, electric energy is stored in the primary side coil w13. It is done.

  Then, after the secondary side switches SW21 and SW22 corresponding to the battery cells C1 and C2 are turned on, the primary side switch SW13 is turned off to supply power from the battery cell C3 to the battery cells C1 and C2. Is done.

  In contrast to the circuit configuration according to the present embodiment, in the circuit configuration according to the first embodiment, it is difficult to select a plurality of battery cells as the power supply destination battery cells and perform the equalization process.

  That is, when two battery cells C1 and Cn that are separated from each other are selected as the battery cells to which power is supplied, secondary switches SW21 and SW2n corresponding to these battery cells C1 and Cn are turned on. Since the positive terminal and the negative terminal of the series connection body of the battery cells C2 to Cn are short-circuited, power is transferred without passing through the transformer Ti, and the equalization process cannot be performed appropriately.

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

  The method for correcting the internal resistance ri of the battery cell Ci is not limited to the one exemplified in the first embodiment. For example, the larger the temperature difference ΔTi is, the smaller the temperature correction amount is set. The larger the ΔSOCi is, the smaller the SOC correction amount is set, and the internal resistance calculated based on the voltage Vi and the load current value Ir of the battery cell Ci. The internal resistance ri may be corrected by adding the temperature correction amount and the SOC correction amount to ri. Here, the temperature correction amount becomes 0 when the temperature difference ΔTi becomes 0, and the SOC correction amount becomes 0 when the ΔSOCi becomes 0.

  The method for selecting the battery cell of the power supply source is not limited to the method exemplified in the first embodiment. For example, the average value (average internal resistance rbar) of the internal resistance ri of all the battery cells Ci is calculated, and one or a plurality of battery cells having an internal resistance lower than the average internal resistance rbar are calculated as the battery cell of the power supply source. You may choose. In this case, the equalization current value Ib may be set to be smaller as the number of battery cells having an internal resistance lower than the average internal resistance rbar is increased, for example.

  When a plurality of battery cells that are power supply sources are selected, the equalization current values Ib corresponding to the plurality of battery cells that are power supply sources may be different from each other in the equalization process.

  Further, the equalization process may be performed without delaying the ON timing of the primary side switch SW1i corresponding to a plurality of battery cells. Thereby, since the peak value of the charging current value I2 can be lowered, it is possible to suppress an increase in circuit scale.

  The circuit configuration for performing the equalization process is not limited to those illustrated in the above embodiments. For example, a flying capacitor (energy storage means), a multiplexer (connecting means) that selectively connects some of the battery cells to the flying capacitor, and a battery cell that is a power supply destination supplies charges to the flying capacitor. It is good also as a circuit structure provided with the control circuit (operation means) which operates a multiplexer in order to supply the stored electric charge to the battery cell of an electric power supply destination (refer FIG. 2 of Unexamined-Japanese-Patent No. 2010-183766). However, in this case, when the voltage of the power supply destination battery cell is higher than the voltage of the power supply source battery cell, power cannot be supplied from the power supply source battery cell to the power supply destination battery cell. For this reason, for example, it is desirable to perform the equalization process in a situation where the battery pack is discharged. As described above, under the situation where the battery pack is discharged, the voltage of the battery cell having a large internal resistance as the power supply destination is lower than the voltage of the battery cell having a low internal resistance as the power supply source. This is in view of the high probability of becoming.

  In the first embodiment, the ON time T1on (see FIG. 7) of the primary side switch SW1i is adjusted by adjusting the equalization current value Ib. However, in the process of step S18 of FIG. The on-time T1on may be variably set.

  In the first embodiment, the control logic that always turns on the secondary side switch SW2i during the execution of the equalization process is adopted, but the present invention is not limited to this. For example, a control logic that turns on the secondary side switch SW2i only during a period in which the charging current flows may be employed.

  The setting method of the lower limit voltage Vth1 is not limited to the one exemplified in the above embodiments. For example, even if the lower limit voltage Vth1 is set to a value higher than the lower limit value of the voltage capable of maintaining the reliability of the battery cell in order to notify the low voltage system side that the capacity of the assembled battery 10 is small. Good.

  In each of the above embodiments, the equalization process is performed using one battery cell Ci as a unit battery, but the present invention is not limited to this. For example, the equalization process may be performed using a series connection body (1 block) of a plurality of battery cells adjacent to each other as a unit battery.

  -As a battery cell, not only a lithium secondary battery but a nickel-hydrogen secondary battery etc. may be sufficient. In short, any battery cell having a tendency that the internal resistance tends to increase as the degree of deterioration of the battery cell increases.

  The rectifying means is not limited to a diode, and may be a thyristor, for example.

  In each of the above embodiments, the present invention is applied to a plug-in hybrid vehicle. However, the present invention is not limited to this, and the present invention may be applied to an electric vehicle (EV) that does not have an internal combustion engine mounted thereon.

  DESCRIPTION OF SYMBOLS 10 ... Battery pack, Ci ... Battery cell, 18 ... Control circuit, Ti ... Transformer, SW1i ... Primary side switch, SW2i ... Secondary side switch, Di ... Diode.

Claims (8)

Applied to an assembled battery as a serially connected unit battery, which is one or a plurality of adjacent battery cells,
Energy storage means for temporarily storing electric energy of the unit cell;
Connection means for selectively connecting some of the unit cells to the energy storage means;
Internal resistance calculating means for calculating the internal resistance of each of the unit cells based on the current flowing through each of the unit cells and the voltage of each of the unit cells;
Based on the calculated internal resistance, a selection processing means for performing a process of selecting a unit battery having a low level of internal resistance and a unit battery having a high level of internal resistance from the unit batteries;
An assembled battery capacity adjustment device comprising: an operation unit that performs a process of operating the connection unit to supply electric charge from the low-level unit cell to the high-level unit cell.   2. The set according to claim 1, wherein the selection processing unit performs a process of selecting a unit cell corresponding to the maximum value of the internal resistance calculated by the internal resistance calculation unit as the high-level unit battery. Battery capacity adjustment device.   3. The set according to claim 2, wherein the selection processing unit performs a process of selecting a unit cell corresponding to the minimum value of the internal resistance calculated by the internal resistance calculation unit as the low-level unit battery. Battery capacity adjustment device. The energy storage means is a transformer,
The connection means includes primary side opening / closing means capable of selectively opening and closing each of the electrical paths connecting each of the unit batteries and the primary coil of the transformer, and each of the unit batteries and the transformer 2. 4. The assembled battery capacity adjusting device according to claim 1, wherein the battery pack capacity adjusting device is a secondary side opening / closing means capable of selectively opening and closing each of the electrical paths connecting the secondary side coil. 5. Rectifying means for restricting the current flow of the secondary coil in one direction;
Each of the transformer, the primary side opening / closing means, the secondary side opening / closing means, and the rectifying means is provided for each of the unit cells,
The transformer includes the primary side coil and the secondary side coil,
In each of the unit cells, a serial connection body of the primary side coil and the primary side opening / closing means is connected in parallel, and the secondary side coil and the rectifying means are connected via the secondary side opening / closing means. Each series connection is connected in parallel,
5. The capacity adjustment device for an assembled battery according to claim 4, wherein the rectifying means has a function of flowing a current in a direction from the secondary coil toward the positive electrode side of the unit battery. Rectifying means for restricting the current flow of the secondary coil in one direction;
The transformer includes a plurality of pairs of the primary side coil and the secondary side coil,
Each of the primary side opening / closing means, the secondary side opening / closing means and the rectifying means is provided for each of the unit cells,
Each of the unit batteries has a secondary electrical path including the secondary coil, the secondary switching means, and the rectifying means, as well as a serial connection of the primary coil and the primary switching means. Connected in parallel,
The secondary side opening / closing means opens and closes the secondary side electric path,
5. The capacity adjustment device for an assembled battery according to claim 4, wherein the rectifying means is provided such that a current flows through the secondary-side electric path toward the positive electrode side of the unit battery. And a correction means for correcting the internal resistance of each of the unit cells calculated by the internal resistance calculation means based on the temperature of each of the unit batteries,
The assembled battery capacity adjustment apparatus according to claim 1, wherein the selection processing unit performs the selection process based on the corrected internal resistance.   8. The capacity adjustment device according to claim 1, wherein the operation means operates the connection means and the processing for detecting each voltage of the unit battery alternately in a predetermined cycle. The capacity adjustment apparatus of the assembled battery of Claim 1.

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