JP2008125158A - Charging system, battery pack, and charging method thereof - Google Patents

Abstract

A charging system, a battery pack, and a battery pack capable of reducing the terminal voltage difference of each secondary battery and effectively utilizing the battery capacity of the assembled battery without promoting the deterioration of the secondary battery that has been deteriorated. And a charging method thereof.
An imbalance detection unit 214 that determines that an imbalance has occurred in the state of charge when terminal voltages α1, α2, and α3 of secondary batteries 141, 142, and 143 satisfy a predetermined determination condition; When the imbalance detection unit 214 determines that an imbalance has occurred, among the secondary batteries 141, 142, and 143, the supply of the charging current to the secondary battery having the maximum terminal voltage is stopped, and the terminal voltage And a supplementary charging control unit 215 that supplies a charging current to at least one of the other secondary batteries excluding the largest secondary battery.
[Selection] Figure 1

Description

  The present invention relates to a charging system, a battery pack, and a charging method thereof, and more particularly, to a charging method for cell balance collapse due to deterioration of a secondary battery in which a plurality of cells are connected in series.

  FIG. 8 is a graph for explaining a general charging voltage and current management method during charging of the secondary battery. FIG. 8 is a graph in the case of charging an assembled battery in which three secondary batteries, for example, lithium ion batteries are connected in series, and reference symbols α11, α12, and α13 indicate changes in voltage of each secondary battery, Reference symbol β11 indicates a change in charging current supplied to the secondary battery. Moreover, (gamma) 11 has shown the charging depth (SOC) of the assembled battery.

  First, with regard to the voltage, a trickle charge region is reached from the start of charging, a small constant current I1, for example, a charging current of 50 mA, is supplied, and the cell voltages of a plurality of secondary batteries are all the end voltage Vm of trickle charging, for example, This trickle charge continues until 2.3V is reached.

  When the cell voltage reaches the end voltage Vm, it switches to a constant current (CC) charging range, and the terminal voltage of the battery pack charging terminal is set to a predetermined end voltage Vf of 4.2 V per cell, and the number of series cells of the assembled battery Is applied to the charging terminal until the voltage is multiplied by (for example, 12.6 V in the case of three cells in series), and a predetermined constant current I2, for example, The nominal capacity value NC is discharged at a constant current, and a level that can be discharged in one hour is defined as 1 C. A charging current obtained by multiplying 70% by the number P of parallel cells is supplied, and constant current (CC) charging is performed.

  As a result, when the terminal voltage of the charging terminal becomes the termination voltage Vf × the number of series cells, the charging voltage value is reduced so as to switch to the constant voltage (CV) charging region and not exceed the termination voltage Vf × the number of series cells. Then, when the charging current value decreases to the current value I3 set by the temperature, it is determined that the battery is fully charged and the supply of the charging current is stopped. The charge control method as described above can be read from Patent Document 1, for example.

  By the way, since the internal resistance increases when the secondary battery deteriorates, when a plurality of secondary batteries are connected in series and a charging voltage is applied to both ends of the series circuit, a secondary battery having a high internal resistance, that is, deteriorates. Since the terminal voltage of the secondary battery is larger than that of other batteries that are not deteriorated, the charging voltage is not divided equally among the secondary batteries. Therefore, as described above, the terminal voltage of the charging terminal of the battery pack, that is, the terminal voltage of the assembled battery in which a plurality of secondary batteries are connected in series is the end voltage Vf × the number of series cells (12. 6V), the terminal voltage α11 of the deteriorated secondary battery exceeds 4.2V as shown in FIG. 8, and the terminal voltages α12, α13 of the non-degraded secondary battery are as shown in FIG. Becomes a voltage less than 4.2V.

  When such an unbalanced state of the secondary battery occurs, the deteriorated secondary battery has a problem that the deterioration is further promoted because a voltage exceeding 4.2 V is applied.

Therefore, in order to eliminate the unbalanced state of the secondary battery, the secondary battery having a high terminal voltage is discharged as shown in FIG. 8 to reduce the terminal voltage α11, thereby reducing the terminal voltage of the other secondary battery. A technique for reducing the difference between α12 and α13 and balancing the state of charge of the secondary battery is known (see, for example, Patent Document 2).
JP-A-6-78471 JP 2005-176520 A

  However, as described above, in the technique of discharging the secondary battery having a high terminal voltage and reducing the difference from the terminal voltage of other secondary batteries, the secondary battery having the smallest battery capacity due to deterioration. The battery will be further discharged. As a result, the number of discharges of the secondary battery that is most deteriorated increases and the number of charge / discharge cycles increases, resulting in further inconvenience of further deterioration of the secondary battery that is most deteriorated.

  In addition, even if the discharge for eliminating the imbalance is not performed, the secondary battery that is most deteriorated by the discharge due to use drops more quickly than other secondary batteries, and further deteriorates during charging Since the secondary battery will be discharged, the voltage drop of the secondary battery that is increasingly deteriorated will be faster than other secondary batteries, and the deterioration of the secondary battery will be further promoted. There was an inconvenience that the balance between the plurality of secondary batteries was lost.

  Further, in the constant voltage charging, charging is performed so that the voltage of the entire assembled battery becomes the end voltage Vf × the number of series cells (12.6 V in the case of three cells in series), so the terminal voltage of the deteriorated secondary battery When α11 exceeds 4.2V, the terminal voltages α12 and α13 of other secondary batteries that have not deteriorated do not reach 4.2V. Therefore, as shown in FIG. 8, at the end of constant voltage charging, the terminal voltage α12, α13 of the secondary battery that has not deteriorated is less than 4.2 V, so the SOC of the assembled battery does not reach 100%, For example, it is about 97%. Furthermore, since the deteriorated secondary battery is discharged to reduce the terminal voltage α11, the SOC of the assembled battery further decreases, for example, about 96%. As described above, the technique of reducing the difference from the terminal voltage of another secondary battery by discharging a secondary battery having a high terminal voltage has a disadvantage that the battery capacity of the assembled battery cannot be effectively used.

  The present invention has been made in view of such circumstances, and reduces the difference in the terminal voltage of each secondary battery without accelerating the deterioration of the secondary battery that has been deteriorated. It is an object of the present invention to provide a charging system, a battery pack, and a charging method that can effectively use battery capacity.

  A charging system according to the present invention includes an assembled battery in which a plurality of secondary batteries are connected in series, a charging current supply unit that supplies a charging current to the assembled battery, and a terminal voltage of the plurality of secondary batteries. A voltage detection unit for detecting each of the secondary batteries, and when the terminal voltages of the plurality of secondary batteries detected by the voltage detection unit satisfy a predetermined determination condition set in advance, the state of charge in the plurality of secondary batteries An imbalance detection unit that determines that an imbalance has occurred in the battery, and when the imbalance detection unit determines that the imbalance has occurred, the voltage detection unit detects the imbalance among the plurality of secondary batteries. Other secondary batteries excluding the secondary battery whose terminal voltage detected by the voltage detection unit is stopped and the supply of current by the charging current supply unit to the secondary battery having the maximum terminal voltage is stopped. At least one of Of, and a supplementary charging controller for causing the supply of current by the charging current supply unit.

  According to this configuration, the plurality of secondary batteries connected in series are charged by the charging current supplied from the charging current supply unit. And the terminal voltage of each secondary battery is each detected by the voltage detection part. Then, if there is a difference in the degree of deterioration of each secondary battery, an unbalanced state in which a difference occurs in the terminal voltage of each secondary battery as charging proceeds will occur. Therefore, whether or not the terminal voltage of each secondary battery detected by the voltage detection unit satisfies a predetermined determination condition set in advance by the imbalance detection unit, and if the determination condition is satisfied, It is determined that there is an imbalance in the state of charge in the plurality of secondary batteries. And when it determines with imbalance having arisen by the imbalance detection part, the secondary battery by which the terminal voltage detected by the voltage detection part among the several secondary batteries by the auxiliary charge control part is the largest, ie, At least one of the other secondary batteries except the secondary battery whose terminal voltage detected by the voltage detection unit is stopped and the terminal voltage detected by the voltage detection unit is stopped while the supply of current to the secondary battery considered to be most deteriorated is stopped. The terminal voltage is increased by charging the current supplied to the terminal. As a result, the terminal voltage of the secondary battery included in the assembled battery can be obtained without discharging the secondary battery that is considered to be most deteriorated, and thus without further promoting the deterioration of the secondary battery that has deteriorated. Can be reduced. In addition, since it is possible to further charge at least one of the other secondary batteries except the secondary battery having the maximum terminal voltage, that is, the secondary battery that is considered to have not yet fully charged, the battery of the assembled battery The capacity can be used effectively.

  The charging current supply unit further includes a constant current charging unit configured to perform constant current charging by supplying a predetermined constant current to the assembled battery, and the imbalance detection unit includes the constant current During the charge execution period, the determination is performed with the condition that the difference between the maximum value and the minimum value of the terminal voltage detected by the voltage detection unit is equal to or greater than a preset difference determination value, as the determination condition, The auxiliary charge control unit is configured to charge the secondary battery with the maximum terminal voltage when the imbalance detection unit determines that the imbalance has occurred during the constant current charging period. The supply of current by the current supply unit is stopped, and current is supplied by the charging current supply unit to the other secondary batteries except the secondary battery having the maximum terminal voltage until the terminal voltages of the plurality of secondary batteries match. To supply Preferred.

  According to this configuration, the constant current charging unit performs constant current charging by causing the assembled battery to supply a constant current from the charging current supply unit. Further, during the constant current charge execution period, if the difference between the maximum value and the minimum value of the terminal voltage detected by the voltage detection unit becomes equal to or greater than a preset difference determination value, the imbalance detection unit Is determined to have occurred. Then, if it is determined by the imbalance detection unit that an imbalance has occurred, the auxiliary charge control unit supplies the current to the secondary battery with the highest terminal voltage, that is, the secondary battery that is considered to have the most advanced deterioration. Is supplied to the other secondary batteries excluding the secondary battery having the maximum terminal voltage until the terminal voltages of the plurality of secondary batteries coincide with each other to charge the battery. The terminal voltage is increased. As a result, the assembled battery can be used during the constant current charging period without discharging the secondary battery that is considered to be most deteriorated, and thus without further promoting the deterioration of the secondary battery that has deteriorated. The difference in the terminal voltage of the secondary battery included in the battery can be reduced. Then, even when the constant current charging is in progress, if an imbalance occurs and the difference between the maximum value and the minimum value of the terminal voltage of each secondary battery exceeds the difference judgment value, the difference in the terminal voltage of the secondary battery Therefore, even if the user interrupts charging before charging of the assembled battery by constant current charging is completed, the imbalance of the secondary battery can be reduced.

  Further, the imbalance detection unit has a difference between a maximum value and a minimum value of the terminal voltage detected by the voltage detection unit during the constant current charging execution period is equal to or greater than a preset difference determination value. In this case, it is preferable that the determination is further performed with the condition that the maximum value of the terminal voltage is equal to or higher than a preset threshold voltage as the determination condition.

  When the charging depth is small, the secondary battery tends to increase the terminal voltage variation due to the capacity difference between the secondary batteries. Therefore, when the charging depth is shallow, it is determined that an imbalance has occurred only under the condition that the difference between the maximum value and the minimum value of the terminal voltage of each secondary battery is equal to or greater than a preset difference determination value. The terminal voltage variation due to the capacity difference between the secondary batteries may be erroneously determined as causing an imbalance. Therefore, the imbalance detection unit is configured such that the difference between the maximum value and the minimum value of the terminal voltage detected by the voltage detection unit is equal to or greater than a preset difference determination value during the constant current charging execution period. When the maximum value of the voltage is equal to or higher than a preset threshold voltage, that is, when the charging progresses to some extent and the variation of the terminal voltage due to the capacity difference of each secondary battery is reduced, an imbalance occurs. By determining, it is possible to reduce a possibility that the terminal voltage variation due to the capacity difference between the secondary batteries is erroneously determined to be imbalanced.

  The charging current supply unit further includes a constant current charging unit configured to perform constant current charging by supplying a predetermined constant current to the assembled battery, and the imbalance detection unit includes the constant current The condition that the maximum value of the terminal voltage detected by the voltage detection unit during the charging execution period exceeds the target voltage value that is the target value of the charging voltage per secondary battery is the determination condition. The auxiliary charging control unit determines that the imbalance is generated by the imbalance detection unit during the constant current charging period, and determines that the terminal voltage is the maximum. The supply of current by the charging current supply unit is stopped, and the terminal voltage of the other secondary battery reaches the target voltage value to other secondary batteries excluding the secondary battery having the maximum terminal voltage. Until the charging current supply It may be caused to supply a current by.

  According to this configuration, the constant current charging unit performs constant current charging by causing the assembled battery to supply a constant current from the charging current supply unit. In addition, imbalance detection is performed when the maximum value of the terminal voltage detected by the voltage detector exceeds the target voltage value that is the target value of the charging voltage per secondary battery during the constant current charging period. It is determined by the part that an imbalance has occurred. When it is determined by the imbalance detection unit that an imbalance has occurred, the auxiliary charge control unit stops supplying the charging current to the secondary battery having the maximum terminal voltage, and the terminal voltage is maximized. Current is supplied and charged to other secondary batteries except the secondary battery until the terminal voltage of the other secondary battery reaches the target voltage value. In this case, even if the difference in the terminal voltage of each secondary battery is small and the difference between the maximum value and the minimum value of the terminal voltage of each secondary battery is not equal to or greater than the difference determination value as described above. When the maximum value of the terminal voltage of each secondary battery exceeds the target voltage value, the current is only applied to the other secondary batteries except the secondary battery having the maximum terminal voltage until the terminal voltage reaches the target voltage value. As a result of being supplied and charged, even if the difference between the maximum value and the minimum value of the terminal voltage of each secondary battery is less than the difference judgment value, the difference in the terminal voltage of each secondary battery is reduced. Can do.

  In addition, a constant voltage charging unit that performs constant voltage charging by supplying the charging current by the charging current supply unit so that a predetermined preset end voltage is applied to each secondary battery. The imbalance detection unit further includes a difference between a maximum value and a minimum value of the terminal voltage detected by the voltage detection unit during the constant voltage charging is equal to or greater than a preset difference determination value. When the condition is determined as the determination condition, the auxiliary charge control unit determines that the imbalance is generated by the imbalance detection unit during the constant voltage charge execution period, Among the plurality of secondary batteries, the terminal voltage detected by the voltage detection unit stops supply of current by the charging current supply unit to a secondary battery that exceeds the end voltage, and the voltage detection Inspection by department Is the terminal voltage of the secondary battery is less than the termination voltage, the be continued the constant voltage charging by the constant voltage charging unit preferably.

  According to this configuration, the constant voltage charging unit executes constant voltage charging by applying a constant voltage so that a preset end voltage is applied to each secondary battery. In addition, when the difference between the maximum value and the minimum value of the terminal voltage detected by the voltage detection unit is equal to or greater than a preset difference determination value during the constant voltage charging period, the imbalance detection unit A charging current supply unit for a secondary battery in which a terminal voltage detected by the voltage detection unit of the plurality of secondary batteries exceeds the cut-off voltage among the plurality of secondary batteries by determining that an imbalance has occurred. Since the constant voltage charging by the constant voltage charging unit to the secondary battery whose terminal voltage detected by the voltage detection unit is equal to or lower than the end voltage is continued, the current supply by the voltage detection unit is stopped. However, if an imbalance occurs and the difference between the maximum value and the minimum value of the terminal voltage of each secondary battery exceeds the difference determination value, the difference in the terminal voltage of the secondary battery is reduced. Will stop charging the battery pack using constant current charging. Even when the interrupt the charging before, it is possible to reduce the imbalance of the secondary battery.

  Further, constant voltage charging is performed by performing constant voltage charging by supplying the charging current by the charging current supply unit so that a predetermined end voltage set in advance is applied to each of the secondary batteries. The imbalance detection unit is configured such that the maximum value of the terminal voltage detected by the voltage detection unit during the constant voltage charging period is a target value of the charging voltage per secondary battery. When the condition exceeding the target voltage value is determined as the determination condition, the auxiliary charge control unit is configured to generate the imbalance by the imbalance detection unit during the constant voltage charge execution period. If determined, the supply of current by the charging current supply unit to a secondary battery in which the terminal voltage detected by the voltage detection unit exceeds the end voltage among the plurality of secondary batteries is stopped. With Wherein the detected terminal voltage of the secondary battery is less than the end voltage by the voltage detection unit, it may be to continue the constant voltage charging by the constant voltage charging unit.

  According to this configuration, the constant voltage charging unit executes constant voltage charging by applying a constant voltage so that a preset end voltage is applied to each secondary battery. Also, imbalance detection is performed when the maximum value of the terminal voltage detected by the voltage detection unit exceeds the target voltage value that is the target value of the charging voltage per secondary battery during the constant voltage charging period. It is determined by the part that an imbalance has occurred. When the imbalance detection unit determines that an imbalance has occurred, the auxiliary charge control unit stops the supply of current to the secondary battery whose terminal voltage exceeds the end voltage, and charging is stopped. At the same time, the constant voltage charging to the secondary battery whose terminal voltage is equal to or lower than the end voltage is continued. In this case, even if the difference in the terminal voltage of each secondary battery is small and the difference between the maximum value and the minimum value of the terminal voltage of each secondary battery is not equal to or greater than the difference determination value as described above. When the maximum value of the terminal voltage of each secondary battery exceeds the target voltage value, constant voltage charging is continued only for the secondary battery whose terminal voltage is equal to or lower than the end voltage, resulting in the terminal voltage of each secondary battery. Even when the difference between the maximum value and the minimum value is less than the difference determination value, the difference in the terminal voltage of each secondary battery can be reduced.

  Further, the current detection unit further detects a current flowing through the assembled battery, the constant voltage charging unit, when the current detected by the current detection unit is equal to or less than a preset full charge determination current, The constant voltage charging by the constant voltage charging unit is stopped, and the auxiliary charging control unit further detects a terminal voltage detected by the voltage detecting unit among the plurality of secondary batteries after the constant voltage charging is stopped. It is preferable that the charging current supply unit supplies the charging current to a secondary battery that is less than the final voltage.

  According to this configuration, when the current flowing through the assembled battery becomes equal to or lower than the full charge determination current by the constant voltage charging unit, the constant voltage charging is stopped. Then, after the constant voltage charging is stopped, the auxiliary charging control unit supplies the charging current to the secondary battery whose terminal voltage is less than the end voltage among the plurality of secondary batteries by the charging current supply unit. As charging is performed, after the end of constant voltage charging, the terminal voltage is less than the end voltage, and therefore, the secondary battery that is considered not yet fully charged can be charged to increase the terminal voltage, The battery capacity of the assembled battery can be effectively utilized while reducing the difference in the terminal voltage of the secondary battery included in the assembled battery.

  The imbalance detection unit preferably determines that an imbalance has occurred in the state of charge in the plurality of secondary batteries when the determination condition is continuously satisfied for a preset period. . According to this configuration, the imbalance detection unit determines that there is an imbalance in the state of charge in the plurality of secondary batteries when the determination condition is continuously satisfied for a preset period. Therefore, it is possible to reduce the risk that it is erroneously determined that an imbalance has occurred due to fluctuations in the power supply environment or noise.

  Further, the battery pack according to the present invention includes an assembled battery in which a plurality of secondary batteries are connected in series, a connection terminal that receives current for charging the assembled battery, and the current received by the connection terminal. A control unit for charging by supplying to a plurality of secondary batteries, a voltage detection unit for detecting terminal voltages of the plurality of secondary batteries, and a plurality of the secondary batteries detected by the voltage detection unit. When the terminal voltage satisfies a predetermined determination condition set in advance, an imbalance detection unit that determines that an imbalance has occurred in the state of charge of the plurality of secondary batteries, and the imbalance detection unit detects the imbalance by the imbalance detection unit. When it is determined that an equilibrium has occurred, supply of current by the charge control unit to the secondary battery having the maximum terminal voltage detected by the voltage detection unit among the plurality of secondary batteries is stopped. Together with the above To at least one of the other secondary battery except the secondary battery detected terminal voltage is maximum by the pressure detecting unit, and a supplementary charging controller for causing the supply of current by the control unit.

  According to this configuration, the plurality of secondary batteries connected in series are charged by the current received by the connection terminal from the outside of the battery pack. And the terminal voltage of each secondary battery is each detected by the voltage detection part. Then, if there is a difference in the degree of deterioration of each secondary battery, an unbalanced state in which a difference occurs in the terminal voltage of each secondary battery as charging proceeds will occur. Therefore, whether or not the terminal voltage of each secondary battery detected by the voltage detection unit satisfies a predetermined determination condition set in advance by the imbalance detection unit, and if the determination condition is satisfied, It is determined that there is an imbalance in the state of charge in the plurality of secondary batteries. And when it determines with imbalance having arisen by the imbalance detection part, the secondary battery by which the terminal voltage detected by the voltage detection part among the several secondary batteries by the auxiliary charge control part is the largest, ie, At least one of the other secondary batteries except the secondary battery whose terminal voltage detected by the voltage detection unit is stopped and the terminal voltage detected by the voltage detection unit is stopped while the supply of current to the secondary battery considered to be most deteriorated is stopped. The terminal voltage is increased by charging the current supplied to the terminal. As a result, the terminal voltage of the secondary battery included in the assembled battery can be obtained without discharging the secondary battery that is considered to be most deteriorated, and thus without further promoting the deterioration of the secondary battery that has deteriorated. Can be reduced. In addition, since it is possible to further charge at least one of the other secondary batteries except the secondary battery having the maximum terminal voltage, that is, the secondary battery that is considered to have not yet fully charged, the battery of the assembled battery The capacity can be used effectively.

  Further, the charging method according to the present invention includes a charging step of supplying a charging current to an assembled battery in which a plurality of secondary batteries are connected in series and charging, and a terminal voltage of the plurality of secondary batteries, respectively. When the voltage detection step to detect and the terminal voltages of the plurality of secondary batteries satisfy a predetermined determination condition set in advance, it is determined that there is an imbalance in the state of charge in the plurality of secondary batteries. A secondary battery having a maximum terminal voltage detected in the voltage detection step among the plurality of secondary batteries when it is determined that the imbalance is generated in the imbalance detection step and the imbalance detection step; The charging current is stopped, and the charging current is supplied to at least one of the other secondary batteries excluding the secondary battery having the maximum terminal voltage detected in the voltage detection step. Auxiliary recharger supplying Provided with a door.

  According to this configuration, the plurality of secondary batteries connected in series are charged by the charging current. Then, if the terminal voltage of each secondary battery satisfies a predetermined determination condition set in advance, it is determined that there is an imbalance in the state of charge in the plurality of secondary batteries, and Among them, the secondary battery with the highest terminal voltage, that is, the secondary battery except the secondary battery with the highest terminal voltage is stopped while the supply of current to the secondary battery considered to be most deteriorated is stopped. The terminal voltage is raised by supplying current to at least one of them and charging them. As a result, the terminal voltage of the secondary battery included in the assembled battery can be obtained without discharging the secondary battery that is considered to be most deteriorated, and thus without further promoting the deterioration of the secondary battery that has deteriorated. Can be reduced. In addition, since it is possible to further charge at least one of the other secondary batteries except the secondary battery having the maximum terminal voltage, that is, the secondary battery that is considered to have not yet fully charged, the battery of the assembled battery The capacity can be used effectively.

  According to the charging system, the battery pack, and the charging method having such a configuration, the plurality of secondary batteries connected in series are charged by the charging current. Then, if the terminal voltage of each secondary battery satisfies a predetermined determination condition set in advance, it is determined that there is an imbalance in the state of charge in the plurality of secondary batteries, and Among them, the secondary battery with the highest terminal voltage, that is, the secondary battery except the secondary battery with the highest terminal voltage is stopped while the supply of current to the secondary battery considered to be most deteriorated is stopped. The terminal voltage is raised by supplying current to at least one of them and charging them. As a result, the terminal voltage of the secondary battery included in the assembled battery can be obtained without discharging the secondary battery that is considered to be most deteriorated, and thus without further promoting the deterioration of the secondary battery that has deteriorated. Can be reduced. In addition, since it is possible to further charge at least one of the other secondary batteries except the secondary battery having the maximum terminal voltage, that is, the secondary battery that is considered to have not yet fully charged, the battery of the assembled battery The capacity can be used effectively.

  Embodiments according to the present invention will be described below with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted. FIG. 1 is a block diagram illustrating an example of a configuration of a charging system that uses a charging method according to an embodiment of the present invention. Although this charging system is configured to include the battery pack 2 and the charger 3 that charges the battery pack 2, an electronic device system may be configured to further include a load device (not shown) that receives power from the battery pack 2. . In that case, although the battery pack 2 is charged from the charger 3 in FIG. 1, the battery pack 2 may be attached to the load device and charged through the load device. The battery pack 2 and the charger 3 are connected to each other by DC high-side terminals T11 and T21 that supply power, communication signal terminals T12 and T22, and GND terminals T13 and T23 for power supply and communication signals. . Similar terminals are also provided when the load device is provided.

  In the battery pack 2, FETs (Field Effect Transistors) 12 and 13 having different conductivity types for charging and discharging are interposed in the charging path 11 on the DC high side extending from the terminal T <b> 11. The charging path 11 is connected to the high-side terminal of the assembled battery 14. A low side terminal of the assembled battery 14 is connected to the GND terminal T13 via a DC low side charging path 15, and the charging path 15 includes a current detection resistor 16 that converts charging current and discharging current into voltage values. (Current detection unit) is interposed.

  The assembled battery 14 includes a plurality of secondary batteries 141, 142, and 143 connected in series. The temperature of each secondary battery is detected by a temperature sensor 17 and input to an analog / digital converter 19 in the control IC 18. Is done. The terminal voltages α1, α2, and α3 of the plurality of secondary batteries 141, 142, and 143 are read by the voltage detection circuit 20 (voltage detection unit) and input to the analog / digital converter 19 in the control IC 18. The Furthermore, the current value detected by the current detection resistor 16 is also input to the analog / digital converter 19 in the control IC 18. The analog / digital converter 19 converts each input value into a digital value and outputs the digital value to the control unit 21.

  FIG. 2 is a circuit diagram illustrating an example of a detailed configuration of the assembled battery 14. The assembled battery 14 shown in FIG. 2 includes an assembled circuit 41 in which a parallel switching element 412 is connected in parallel to a series circuit of the secondary battery 141 and the series switching element 411, a secondary battery 142, and the series switching element 421. A combination circuit 42 in which a parallel switching element 422 is connected in parallel to the series circuit of the second circuit, and a combination circuit 43 in which a parallel switching element 432 is connected in parallel to the series circuit of the secondary battery 143 and the series switching element 431. Are connected in series. As the series switching elements 411, 421, 431 and the parallel switching elements 412, 422, 432, for example, semiconductor switching elements such as FETs, relay switches, or the like can be used. The series switching elements 411, 421, and 431 are turned on, and the parallel switching elements 412, 422, and 432 are turned off, except when supplementary charging is performed by the auxiliary charging control unit 215.

  The control unit 21 includes, for example, a CPU (Central Processing Unit) that executes predetermined arithmetic processing, a ROM (Read Only Memory) that stores a predetermined control program, and a RAM (Random Access Memory) that temporarily stores data. And a peripheral circuit and the like, and by executing a control program stored in the ROM, the charge / discharge control unit 211, the constant current charging unit 212, the constant voltage charging unit 213, and the imbalance detection unit 214 , And the auxiliary charging control unit 215.

  In response to each input value from the analog / digital converter 19, the charge / discharge control unit 211 calculates a voltage value and a current value of a charging current that requires output from the charger 3. It transmits to the charger 3 via terminals T12, T22; T13, T23. In addition, the charge / discharge control unit 211 determines whether there is an abnormality outside the battery pack 2 such as a short circuit between the terminals T11 and T13 or an abnormal current from the charger 3 based on each input value from the analog / digital converter 19. A protection operation such as blocking the FETs 12 and 13 is performed against an abnormal temperature rise of the battery 14.

  The constant current charging unit 212 executes constant current charging by supplying a current β1 having a predetermined constant current value I2 from the charger 3. The constant voltage charging unit 213 executes constant voltage charging by causing the charger 3 to output a voltage obtained by multiplying a preset constant end voltage Vf (target voltage value) by 3 as the number of series cells.

  The imbalance detection unit 214 performs secondary operation when the terminal voltages α1, α2, and α3 of the secondary batteries 141, 142, and 143 input from the analog / digital converter 19 satisfy a predetermined determination condition set in advance. It is determined that there is an imbalance in the state of charge of batteries 141, 142, and 143.

  When it is determined by the imbalance detection unit 214 that an imbalance has occurred, the auxiliary charge control unit 215, among the plurality of secondary batteries 141, 142, 143, other secondary batteries excluding the one with the maximum terminal voltage. In the group circuit including the battery, the series switching element is turned on and the parallel switching element is turned off, and the series switching element of the group circuit not including the other secondary battery is turned off and the parallel switching element is turned off. By turning it on, at least one of the other secondary batteries except the one with the highest terminal voltage is charged.

  In the charger 3, the control IC 30 receives the request by the communication unit 32 that is a communication unit, and the charge control unit 31 that is a charge control unit receives a charge current supply circuit 33 (a charge current supply unit) that is a charge current supply unit. And the charging current is supplied with the voltage value, the current value, and the pulse width. The charging current supply circuit 33 is composed of an AC-DC converter, a DC-DC converter, etc., and converts an input voltage into a voltage value, a current value, and a pulse width instructed by the charging control unit 31, and a terminal T21, T11: Supply to charging paths 11 and 15 via T23 and T13.

  In addition, it is not restricted to the example provided with the control part 21 in the battery pack 2, You may make it provide the control part 21 in the charger 3. FIG. Further, the control unit 21 may be shared by the battery pack 2 and the charger 3.

  In the battery pack 2, a trickle charging circuit 25 is provided in the DC high side charging path 11 in parallel with the normal (rapid) FET 12. The trickle charging circuit 25 is composed of a series circuit of a current limiting resistor 26 and an FET 27, and the charge / discharge control unit 211 turns off the FET 12 for rapid charging while keeping the FET 13 for discharging at the initial stage of charging, The trickle charge FET 27 is turned on to perform trickle charge. During normal charge and discharge, the FET 12 is turned on while the FET 13 is turned on, and the FET 27 is turned off to perform charge / discharge with a normal current.

  It should be noted that in the present embodiment, the auxiliary charging control unit 215 determines that the imbalance detection unit 214 determines that an imbalance has occurred, so that the secondary battery with the largest terminal voltage, that is, the most advanced deterioration is achieved. Without discharging the secondary battery, and charging at least one of the other secondary batteries except the one with the highest terminal voltage, without promoting the deterioration of the secondary battery that has deteriorated It is to reduce the difference in the terminal voltage of each secondary battery.

  Next, the operation of the charging system 1 configured as described above will be described. FIG. 3 is an explanatory diagram showing an example of the operation of the charging system 1 using the charging method according to the embodiment of the present invention. 4 and 5 are flowcharts showing an example of the operation of the charging system 1 using the charging method according to the embodiment of the present invention. When switching from trickle charging to constant current constant voltage (CC-CV) charging, in step S1, the constant current charging unit 212 supplies the charger 3 with a current having a current value I2 set in advance as a current for constant current charging. In response to a control signal from the charging control unit 31, the current β1 having a current value I2 is supplied from the charging current supply circuit 33 to the assembled battery 14, and constant current charging is started. (Timing T1).

  Then, the assembled battery 14 is charged with the current value I2, and the charging depth γ1 of the assembled battery 14 gradually increases. At this time, the degree of deterioration of the secondary batteries 141, 142, and 143 is different. For example, if the secondary battery 141 is most deteriorated, and then the secondary batteries 142 and 143 are sequentially deteriorated, the secondary battery 141, 143 is deteriorated. The terminal voltage α1 of the battery 141 becomes the highest, and then the terminal voltage increases in the order of the terminal voltages α2 and α3. As the charging progresses, the difference between the terminal voltages α1, α2, and α3 increases.

  Next, the imbalance detection unit 214 compares the maximum voltage among the terminal voltages α1, α2, and α3 obtained by the analog / digital converter 19 with a preset threshold voltage V1, and the terminal voltages α1, α2 , Α3, if the maximum voltage is equal to or higher than the threshold voltage V1, the process proceeds to step S3 to determine whether there is an imbalance based on the difference between the maximum voltage and the minimum voltage (YES in step S2). If the voltage does not satisfy the threshold voltage V1 (NO in step S2), the process proceeds to step S4 without determining an imbalance based on the difference between the maximum voltage and the minimum voltage.

  The terminal voltages α1, α2, and α3 have a large variation in voltage due to the capacity difference at the end of discharge of the battery, that is, in a low voltage state. Therefore, the charging proceeds to some extent and the variation in the terminal voltages α1, α2, and α3 due to the capacitance difference occurs. A voltage value that can be reduced to some extent is set as the threshold voltage V1, and is set to, for example, 3.8V. As a result, in step S2, the maximum voltage among the terminal voltages α1, α2, and α3 is equal to or higher than the threshold voltage V1, and the process proceeds to step S3 only when variations in the terminal voltages α1, α2, and α3 due to the capacitance difference are suppressed to some extent. Since it is determined whether or not there is an imbalance, it is possible to reduce the possibility of erroneously detecting the terminal voltage variation due to the capacity difference in step S3 as the battery being out of balance.

  Next, the difference between the maximum voltage and the minimum voltage among the terminal voltages α1, α2, and α3 obtained by the analog / digital converter 19 by the imbalance detection unit 214 is determined as a preset difference determination value Vdiff. (Step S3). The difference determination value Vdiff is set to a voltage of about 40 mV, for example. In this case, since the terminal voltages α1, α2, and α3 vary depending on the current values flowing through the secondary batteries 141, 142, and 143, the difference determination value Vdiff is appropriately set according to the current value I2.

  If the difference between the maximum voltage and the minimum voltage among the terminal voltages α1, α2, and α3 does not satisfy the difference determination value Vdiff (NO in step S3), an imbalance is determined based on the maximum value of the terminal voltage. Therefore, the process proceeds to step S4, and if the difference between the maximum voltage and the minimum voltage is equal to or greater than the difference determination value Vdiff (YES in step S3, timing T2), it is determined that an imbalance has occurred and the process proceeds to step S5. To do.

  Note that the imbalance determination process in step S3 determines that an imbalance has occurred continuously, for example, 5 times every 2 seconds when it is determined that an imbalance has occurred for about 10 seconds, for example. When it is done, it may be made to shift to Step S5 and perform supplementary charging processing. Thereby, it is possible to reduce the possibility of erroneously detecting an imbalance of the secondary battery due to a difference in response speed or a measurement speed with respect to a current variation during charging. The cause of current fluctuation during charging is that the power supplied by the AC adapter is consumed by the main body load, for example, when the charging system 1 is built in a personal computer to which power is supplied by the AC adapter. There are cases where the battery pack 2 cannot be charged at full current, or so-called float charging.

  Next, in step S5, the auxiliary charging control unit 215 turns off the series switching element 411 and turns on the parallel switching element 412 to stop the supply of current to the secondary battery 141 having the maximum terminal voltage. At the same time, the series switching elements 421 and 431 are turned on, the parallel switching elements 422 and 432 are turned off, and current is supplied to the secondary batteries 142 and 143 until the terminal voltages α2 and α3 coincide with the terminal voltage α1. Secondary batteries 142 and 143 are charged.

  Then, by charging the secondary batteries 142 and 143 without discharging the secondary battery 141 that is most deteriorated, the secondary batteries 141 and 142 and 143 can be charged without promoting the deterioration of the secondary battery 141. The difference in terminal voltage can be reduced. In addition, since the difference in the terminal voltages of the secondary batteries 141, 142, and 143 is reduced during the constant current charging, the difference in the terminal voltages of the secondary batteries 141, 142, and 143 at the end of charging is reduced. As a result of the variation in the charging depth of each secondary battery being reduced, the battery capacity of the assembled battery can be effectively utilized. Furthermore, if the secondary batteries 141, 142, and 143 are imbalanced during the constant current charging, the auxiliary charging control unit 215 reduces the difference in the terminal voltages of the secondary batteries 141, 142, and 143. For example, even when the user stops charging the battery pack 2 in the middle of constant current charging without waiting for the charging of the battery pack 2 to end, the terminal voltage difference between the secondary batteries 141, 142, and 143 is reduced. be able to.

  Hereinafter, the charging operation for charging at least a part of the other secondary batteries excluding the secondary battery that is most deteriorated will be referred to as auxiliary charging.

  Next, the auxiliary charging control unit 215 turns on the series switching elements 411, 421, 431 and turns off the parallel switching elements 412, 422, 432, and constant current charging to the secondary batteries 141, 142, 143 is performed. The process is resumed (step S6, timing T3).

  Next, in step S4, the auxiliary charging control unit 215 compares the maximum voltage among the terminal voltages α1, α2, and α3 obtained by the analog / digital converter 19 with the end voltage Vf (step S4). . If the maximum voltage among the terminal voltages α1, α2, and α3 is equal to or lower than the end voltage Vf (NO in step S4), it is determined that no imbalance has occurred, and the process proceeds to step S7. If the maximum voltage of α2 and α3 exceeds the end voltage Vf, for example, 4.21 V or more (YES in step S4, timing T4), it is determined that an imbalance has occurred, and the process proceeds to step S8.

  Next, in step S8, the auxiliary charging control unit 215 supplies current to the secondary battery 141 in which the series switching element 411 is turned off and the parallel switching element 412 is turned on and the terminal voltage α1 reaches the final voltage Vf. Is stopped, the series switching elements 421 and 431 are turned on, the parallel switching elements 422 and 432 are turned off, and the current supply to the secondary batteries 142 and 143 until the terminal voltages α2 and α3 reach the final voltage Vf. The secondary batteries 142 and 143 are charged with a constant current.

  As a result, the secondary batteries 141 and 143 are charged at a constant current without discharging the secondary battery 141 that has been most deteriorated, so that the secondary batteries 141 and 142 and 143 do not accelerate the deterioration of the secondary battery 141. The difference in the terminal voltage of 143 can be reduced. Further, even if the difference between the maximum voltage and the minimum voltage among the terminal voltages α1, α2, and α3 is not equal to or greater than a preset difference determination value Vdiff, the constant current charging is terminated and the constant voltage charging is performed. Since the difference between the terminal voltages of the secondary batteries 141, 142, and 143 can be reduced immediately before the transition to, the difference between the terminal voltages of the secondary batteries 141, 142, and 143 at the end of charging is reduced. As a result of the variation in the charging depth of the secondary battery being reduced, the battery capacity of the assembled battery can be effectively utilized. Furthermore, the difference between the terminal voltages of the secondary batteries 141, 142, and 143 is reduced by the auxiliary charging control unit 215 immediately before the constant current charging is finished and the constant voltage charging is started. Even when the charging of the battery pack 2 is stopped in the middle of constant voltage charging without waiting for the end of charging, the difference in the terminal voltages of the secondary batteries 141, 142, and 143 can be reduced.

  Next, in step S7, the constant current charging unit 212 compares the termination voltage Vf with the terminal voltages α1, α2, and α3, and if any of the terminal voltages α1, α2, and α3 has not reached the termination voltage Vf ( Step S7: NO) Steps S1 to S8 are repeated again, and if the terminal voltages α1, α2, α3 are all equal to or higher than the end voltage Vf, the flow proceeds to step S9 to shift to constant voltage charging.

  Next, in step S9, the constant voltage charging unit 213 requests the charger 3 to output a voltage obtained by multiplying the final voltage Vf by the number of secondary batteries, and the control from the charging control unit 31 is performed. In response to the signal, a voltage of the final voltage Vf × 3 is output from the charging current supply circuit 33, and constant voltage charging is started (timing T5).

  Then, the end voltage Vf × 3 is applied to both ends of the assembled battery 14, and the charging depth γ1 of the assembled battery 14 gradually increases while the charging current β1 gradually decreases. At this time, the degree of deterioration of the secondary batteries 141, 142, and 143 is different. For example, if the secondary battery 141 is most deteriorated, and then the secondary batteries 142 and 143 are sequentially deteriorated, the secondary battery 141, 143 is deteriorated. The terminal voltage α1 of the battery 141 becomes the highest, and then the terminal voltage increases in the order of the terminal voltages α2 and α3. As a result, a difference occurs again between the terminal voltages α1, α2 and α3. In this case, since the total voltage of the terminal voltages α1, α2, and α3 is equal to the end voltage Vf, for example, if the degree of deterioration of the secondary batteries 142 and 143 is approximately the same, only the terminal voltage α1 exceeds the end voltage Vf. The voltages α2 and α3 are lower than the end voltage Vf. As the charging progresses, the difference between the terminal voltages α1, α2, and α3 increases.

  Next, the difference between the maximum voltage and the minimum voltage among the terminal voltages α1, α2, and α3 obtained by the analog / digital converter 19 by the imbalance detection unit 214 is determined as a preset difference determination value Vdiff. (Step S10). If the difference between the maximum voltage and the minimum voltage among the terminal voltages α1, α2, and α3 is less than the difference determination value Vdiff (NO in step S10), step S11 is performed to confirm the constant voltage charging end condition. If the difference between the maximum voltage and the minimum voltage is equal to or greater than the difference determination value Vdiff (YES in step S10), it is determined that an imbalance has occurred, and the process proceeds to step S12.

  Note that the imbalance determination process in step S10 is, for example, about 10 seconds, as in step S2, for example, when it is determined that an imbalance has occurred continuously, for example, 5 times every 2 seconds. When it is determined that an imbalance has occurred, the process may proceed to step S12 to perform the auxiliary charging process.

  Further, in step S10 or between step S10 and step S11, as in step S4, if the maximum voltage among the terminal voltages α1, α2, and α3 is equal to or lower than the end voltage Vf, an imbalance has occurred. If not, the process proceeds to step S11, and if the maximum voltage of the terminal voltages α1, α2, α3 exceeds the end voltage Vf, for example, 4.21 V or more, it is determined that an imbalance has occurred. You may make it transfer to S12.

  In step S11, the constant current charging unit 212 compares the current β1 obtained by the analog / digital converter 19 with the current value I3. If the current β1 exceeds the current value I3 (NO in step S11), step S11 is performed. While returning to S9 and constant voltage charging is continued, if the current β1 is equal to or smaller than the current value I3 (YES in step S11), the process proceeds to step S14 to end the constant voltage charging and shift to the auxiliary charging region ( Timing T7).

  On the other hand, in step S12, the auxiliary charging control unit 215 supplies current to the secondary battery 141 in which the series switching element 411 is turned off and the parallel switching element 412 is turned on and the terminal voltage exceeds the final voltage Vf. At the same time, the series switching elements 421 and 431 are turned on and the parallel switching elements 422 and 432 are turned off, so that the voltage is supplied to the secondary batteries 142 and 143 whose terminal voltage is less than the final voltage Vf. In this case, if the output voltage of the charging current supply circuit 33 remains the final voltage Vf × 3, the applied voltage to the secondary batteries 142 and 143 exceeds the final voltage Vf. The charger 3 is requested to output a voltage of the final voltage Vf × 2, and the voltage of the final voltage Vf × 2 is output from the charging current supply circuit 33 in response to a control signal from the charge control unit 31. Thus, constant voltage charging of the secondary batteries 142 and 143 is performed (timing T6).

  In addition, it is not restricted to the example which changes the output voltage from the charging current supply circuit 33 and performs constant voltage charging in step S12, for example, charging current supply is performed using the assembled battery 14a shown in FIG. The output voltage from the circuit 33 may be maintained as the final voltage Vf × 3. Specifically, the assembled battery 14a shown in FIG. 6 includes a bypass circuit in which a switching element SW1 and a resistor R1 are connected in series, a combined circuit 41a in which a secondary battery 141 is connected in parallel, a switching element SW2, A bypass circuit in which a resistor R2 is connected in series and a secondary battery 142 are connected in parallel, and a combined circuit 42a in which a switching element SW3 and a resistor R3 are connected in series and a secondary battery 143 are provided. A combination circuit 43a connected in parallel is connected in series.

  Then, the auxiliary charging control unit 215 turns on the switching element SW1 of the assembled circuit 41a including the secondary battery 141 whose terminal voltage exceeds the end voltage Vf, and switches the assembled circuits 42a and 43a not including the secondary battery 141. By turning off the elements SW2 and SW3, the output voltage from the charging current supply circuit 33 remains at the final voltage Vf × 3 due to the divided voltage of the resistor R1 and the secondary batteries 142 and 143, respectively, to the secondary batteries 142 and 143, respectively. The end voltage Vf may be applied. In this case, by appropriately setting the resistance values of the resistors R1, R2, and R3, even if the switching device connected in series with the resistors R1, R2, and R3 is turned on, the secondary battery of the assembled circuit in which the switching device is turned on In addition, the termination voltage Vf is applied by a voltage drop of a resistor connected in parallel with the secondary battery, and the secondary battery is discharged and deterioration is accelerated.

  In step S12, the secondary batteries 142 and 143 may be charged by constant current charging with a minute current.

  Next, in step S13, the constant current charging unit 212 compares the current β1 obtained by the analog / digital converter 19 with the current value I4, and if the current β1 exceeds the current value I4 (in step S13). NO) Returning to step S12, the constant voltage charging of the secondary batteries 142, 143 is continued, while if the current β1 is equal to or less than the current value I4 (YES in step S13), the constant voltage charging is terminated and the auxiliary charging region The process proceeds to step S14 to shift to (timing T7).

  In step S13, since only two secondary batteries are charged, the current β1 is reduced as compared with the case where three are charged at a constant voltage. Therefore, the current value I4 is set to a value smaller than the current value I3.

  Here, in step S12, since the voltage of the final voltage Vf × 2 is applied to the series circuit of the secondary batteries 142 and 143, if the degree of deterioration is different between the secondary battery 142 and the secondary battery 143, the battery is deteriorated. For example, the terminal voltage α2 of the secondary battery 142 exceeds the end voltage Vf, and the terminal voltage α3 of the secondary battery 143 is lower than the end voltage Vf. Then, when the constant voltage charging is finished (timing T7), the terminal voltage α3 of the secondary battery 143 is lower than the end voltage Vf.

  Therefore, in step S14, the secondary charging batteries 141 and 142 in which the auxiliary switching controller 215 turns off the series switching elements 411 and 421 and turns on the parallel switching elements 412 and 422 and the terminal voltage exceeds the end voltage Vf. Is stopped, the series switching element 431 is turned on, and the parallel switching element 432 is turned off, so that the voltage is supplied to the secondary battery 143 whose terminal voltage is less than the final voltage Vf. In this case, if the output voltage of the charging current supply circuit 33 remains the final voltage Vf × 2, the voltage applied to the secondary batteries 142 and 143 exceeds the final voltage Vf. The charger 3 is requested to output the voltage of the end voltage Vf, and the voltage of the end voltage Vf is output from the charging current supply circuit 33 in response to the control signal from the charge control unit 31, so that the secondary voltage The battery 143 is charged with a constant voltage.

  Next, in step S15, the constant current charging unit 212 compares the current β1 obtained by the analog / digital converter 19 with the current value I5, and if the current β1 exceeds the current value I5 (in step S15). NO) Returning to step S14, the constant voltage charging of the secondary battery 143 is continued. On the other hand, if the current β1 is equal to or less than the current value I5 (YES in step S15), the process proceeds to step S16 to end the charging. In step S15, since only one secondary battery is charged, the current β1 is reduced as compared with the case where two are charged at a constant voltage. Therefore, the current value I5 is set to a value smaller than the current value I4.

  Next, in step S16, the constant voltage charging unit 213 outputs a request for making the charging current zero, to the charger 3, and the charging control unit 31 sets the output current of the charging current supply circuit 33 to zero to perform charging. End (timing T8).

  As described above, since the difference between the maximum voltage and the minimum voltage among the terminal voltages α1, α2, and α3 is less than the difference determination value Vdiff by the processing in steps S14 and S15, the secondary battery is determined in steps S3 and S10. Even if the imbalance is not detected and the supplementary charging in steps S5 and S12 is not executed, only the secondary battery whose terminal voltage is less than the final voltage Vf and therefore not fully charged is further supplemented. By doing so, all secondary batteries can be fully charged while reducing the terminal voltage difference of each secondary battery without accelerating the deterioration of secondary batteries that have been deteriorated. The battery capacity of the battery can be used effectively.

  In step S14, as in step S12, the present invention is not limited to the example in which the output voltage from the charging current supply circuit 33 is changed and constant voltage charging is performed. For example, instead of the assembled battery 14, the assembled battery 14a shown in FIG. The output voltage from the charging current supply circuit 33 may be used to maintain the final voltage Vf × 3. In this case, the auxiliary charging control unit 215 turns on the switching elements SW1 and SW2 of the assembled circuits 41a and 42a including the secondary batteries 141 and 142 whose terminal voltage exceeds the end voltage Vf, and turns on the secondary batteries 141 and 142. By turning off the switching element SW3 of the assembly circuit 43a that is not included, the output voltage from the charging current supply circuit 33 remains at the final voltage Vf × 3 by the voltage division of the resistors R1 and R2 and the secondary battery 143, and the secondary battery The end voltage Vf may be applied to 143. In this case, by appropriately setting the resistance values of the resistors R1, R2, and R3, even if the switching device connected in series with the resistors R1, R2, and R3 is turned on, the secondary battery of the assembled circuit in which the switching device is turned on The end voltage Vf can be applied to the secondary battery to discharge the secondary battery and promote deterioration. In step S14, the secondary battery 143 may be supplemented by performing constant current charging with a minute current.

  As described above, the secondary battery 142 and 143 are charged without discharging the secondary battery 141 that has been most deteriorated by the processes of steps S1 to S16, and thus the secondary battery 141 is not deteriorated. The terminal voltage difference between the secondary batteries 141, 142, and 143 can be reduced. In addition, since the difference in the terminal voltages of the secondary batteries 141, 142, and 143 at the end of charging is reduced, the variation in the charging depth of each secondary battery is reduced, so that the battery capacity of the assembled battery can be effectively utilized. it can.

  In addition, after timing T6, when α2 reaches the end voltage Vf, a method of switching from Vf × 2 charging to only α3 charging and charging until α3 reaches the end voltage Vf may be used.

  Furthermore, if the difference between α2 and α3 is equal to or greater than the threshold before completion of constant voltage charging (timing T7) after timing T6, charging of α2 having a high voltage is stopped at that time, and the voltage A method may be used in which charging is switched to low α3 only and charging is performed until α3 reaches the final voltage Vf.

  For example, a configuration in which the processes in steps S2, S3, S5, and S6 are not performed may be performed, and a configuration in which the processes in steps S4 and S8 are not performed may be performed.

  Further, as shown in FIG. 7, for example, the processes of steps S2 to S6, S8, S10, S12, and S13 are not executed, that is, the auxiliary charging is not performed in the constant current charging region and the constant voltage charging region, and constant voltage charging is not performed. It is good also as a structure which performs supplementary charge by the process of step S14, S15 after completion | finish, and reduces the terminal voltage difference of each secondary battery.

  The present invention relates to a battery pack used as a power source for a battery-mounted device such as an electronic device such as a portable personal computer or a digital camera, a vehicle such as an electric vehicle or a hybrid car, and a battery system for charging such a battery pack. It can utilize suitably for a charging method.

It is a block diagram which shows an example of a structure of the charging system using the charging method which concerns on one Embodiment of this invention. It is a circuit diagram which shows an example of a detailed structure of the assembled battery shown in FIG. It is explanatory drawing which shows an example of operation | movement of the charging system using the charging method which concerns on one Embodiment of this invention. It is a flowchart which shows an example of operation | movement of the charging system using the charging method which concerns on one Embodiment of this invention. It is a flowchart which shows an example of operation | movement of the charging system using the charging method which concerns on one Embodiment of this invention. It is a circuit diagram which shows another example of the assembled battery shown in FIG. It is explanatory drawing which shows an example of operation | movement of the charging system using the charging method which concerns on one Embodiment of this invention. It is explanatory drawing for demonstrating the charging method which concerns on background art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Charging system 2 Battery pack 3 Charger 14, 14a Battery assembly 16 Current detection resistor 17 Temperature sensor 19 Analog / digital converter 20 Voltage detection circuit 21 Control unit 31 Charge control unit 33 Charging current supply circuit 41, 41a, 42, 42a , 43, 43a Assembly circuit 141, 142, 143 Secondary battery 211 Charging / discharging control unit 212 Constant current charging unit 213 Constant voltage charging unit 214 Unbalance detection unit 215 Supplementary charging control unit 411, 421, 431 Series switching element 412 422, 432 Parallel switching element T11, T12, T13, T21, T22, T23 Terminal V1 Threshold voltage Vdiff Difference judgment value Vf End voltage α1, α2, α3 Terminal voltage β1 Current γ1 Charging depth

Claims (10)

An assembled battery in which a plurality of secondary batteries are connected in series;
A charging current supply unit for supplying a charging current to the assembled battery;
A voltage detector for detecting terminal voltages of the plurality of secondary batteries, respectively;
When the terminal voltages of the plurality of secondary batteries detected by the voltage detection unit satisfy a predetermined determination condition set in advance, it is determined that there is an imbalance in the state of charge in the plurality of secondary batteries. An imbalance detector to
When it is determined by the imbalance detection unit that the imbalance has occurred, among the plurality of secondary batteries, the charging current to the secondary battery with the maximum terminal voltage detected by the voltage detection unit The supply of current by the supply unit is stopped, and the current supplied by the charging current supply unit to at least one of the other secondary batteries excluding the secondary battery having the maximum terminal voltage detected by the voltage detection unit. A charging system comprising: an auxiliary charging control unit that performs supply. The charging current supply unit further includes a constant current charging unit that performs constant current charging by supplying a predetermined constant current to the assembled battery.
The imbalance detection unit has a condition that a difference between a maximum value and a minimum value of the terminal voltage detected by the voltage detection unit is equal to or greater than a preset difference determination value during the constant current charging execution period. , Performing the determination as the determination condition,
The auxiliary charge control unit is configured to charge the secondary battery with the maximum terminal voltage when the imbalance detection unit determines that the imbalance has occurred during the constant current charging period. The supply of current by the current supply unit is stopped, and current is supplied by the charging current supply unit to the other secondary batteries except the secondary battery having the maximum terminal voltage until the terminal voltages of the plurality of secondary batteries match. The charging system according to claim 1, wherein the charging system is supplied. When the difference between the maximum value and the minimum value of the terminal voltage detected by the voltage detection unit is equal to or larger than a preset difference determination value during the constant current charging execution period The charging system according to claim 2, wherein the determination is further performed with the condition that the maximum value of the terminal voltage is equal to or higher than a preset threshold voltage as the determination condition. The charging current supply unit further includes a constant current charging unit that performs constant current charging by supplying a predetermined constant current to the assembled battery.
The imbalance detection unit is a target voltage value in which the maximum value of the terminal voltage detected by the voltage detection unit during the execution of the constant current charging is a target value of the charging voltage per secondary battery. The determination is performed with the condition exceeding
The auxiliary charge control unit is configured to charge the secondary battery with the maximum terminal voltage when the imbalance detection unit determines that the imbalance has occurred during the constant current charging period. While stopping the supply of current by the current supply unit, to the other secondary battery except the secondary battery having the maximum terminal voltage, the charging current until the terminal voltage of the other secondary battery reaches the target voltage value The charging system according to claim 1, wherein a current is supplied by the supply unit. A constant voltage charging unit that performs constant voltage charging by supplying the charging current by the charging current supply unit such that a predetermined end voltage set in advance is applied to each secondary battery; Prepared,
The imbalance detection unit has a condition that a difference between a maximum value and a minimum value of the terminal voltage detected by the voltage detection unit is equal to or greater than a preset difference determination value during the constant voltage charging execution period. , Performing the determination as the determination condition,
When the imbalance detection unit determines that the imbalance has occurred during the constant voltage charging execution period, the auxiliary charge control unit uses the voltage detection unit among the plurality of secondary batteries. The supply of current by the charging current supply unit to the secondary battery whose detected terminal voltage exceeds the end voltage is stopped, and the terminal voltage detected by the voltage detection unit is equal to or lower than the end voltage. The charging system according to any one of claims 1 to 4, wherein the constant voltage charging by the constant voltage charging unit to the secondary battery is continued. A constant voltage charging unit that performs constant voltage charging by causing the charging current supply unit to supply the charging current so that a predetermined end voltage set in advance is applied to each of the secondary batteries. In addition,
The imbalance detection unit is a target voltage value in which the maximum value of the terminal voltage detected by the voltage detection unit during the execution of the constant voltage charging is a target value of the charging voltage per secondary battery. The determination is performed with the condition exceeding
When the imbalance detection unit determines that the imbalance has occurred during the constant voltage charging execution period, the auxiliary charge control unit uses the voltage detection unit among the plurality of secondary batteries. The supply of current by the charging current supply unit to the secondary battery whose detected terminal voltage exceeds the end voltage is stopped, and the terminal voltage detected by the voltage detection unit is equal to or lower than the end voltage. The charging system according to any one of claims 1 to 4, wherein the constant voltage charging by the constant voltage charging unit to the secondary battery is continued. A current detection unit for detecting a current flowing in the assembled battery;
The constant voltage charging unit, when the current detected by the current detection unit is equal to or less than a preset full charge determination current, stops the constant voltage charging by the constant voltage charging unit,
The auxiliary charge control unit is further configured such that after the constant voltage charging is stopped, a terminal voltage detected by the voltage detection unit among the plurality of secondary batteries is less than the end voltage, The charging system according to claim 5, wherein the charging current is supplied by a charging current supply unit. The imbalance detection unit determines that an imbalance has occurred in the state of charge in the plurality of secondary batteries when the determination condition is continuously satisfied for a preset period. The charging system according to any one of claims 1 to 7. An assembled battery in which a plurality of secondary batteries are connected in series;
A connection terminal for receiving a current for charging the assembled battery;
A control unit for charging by supplying the current received by the connection terminal to the plurality of secondary batteries; and
A voltage detector for detecting terminal voltages of the plurality of secondary batteries, respectively;
When the terminal voltages of the plurality of secondary batteries detected by the voltage detection unit satisfy a predetermined determination condition set in advance, it is determined that there is an imbalance in the state of charge in the plurality of secondary batteries. An imbalance detector to
When it is determined by the imbalance detection unit that the imbalance has occurred, among the plurality of secondary batteries, the charge control to the secondary battery having the maximum terminal voltage detected by the voltage detection unit And the controller supplies the current to at least one of the other secondary batteries excluding the secondary battery having the maximum terminal voltage detected by the voltage detector. A battery pack, comprising: an auxiliary charge control unit. A charging step of supplying a charging current to a battery pack in which a plurality of secondary batteries are connected in series to charge the battery;
A voltage detection step of detecting terminal voltages of the plurality of secondary batteries,
An imbalance detection step of determining that an imbalance has occurred in the state of charge in the plurality of secondary batteries when the terminal voltages of the plurality of secondary batteries satisfy a predetermined determination condition set in advance;
When it is determined in the imbalance detection step that the imbalance has occurred, among the plurality of secondary batteries, the secondary battery having the maximum terminal voltage detected in the voltage detection step is used for charging. And the auxiliary charging step of supplying the charging current to at least one of the other secondary batteries excluding the secondary battery having the maximum terminal voltage detected in the voltage detecting step. A charging method comprising: and.

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