JP2008182809A - Battery circuit, battery pack, and battery system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery circuit which can perform balance control during not only discharging but also charging, can always make adjustment with a small current before a certain voltage difference occurs to reduce imbalance between secondary batteries and can simplify the processing for the reduction of imbalance, and to provide a battery pack using the battery circuit. <P>SOLUTION: The battery circuit includes a cell unit 14 comprising a plurality of serially connected secondary batteries 141, 142, 143, and resistors R1, R2, R3 each connected in parallel with the plurality of secondary batteries 141, 142, 143. The resistors R1, R2, R3 each connected in parallel with the secondary batteries 141, 142, 143 are made to be substantially the same with each other in the resistance value. The resistance values of the resistors R1, R2, R3 are set so that the currents flowing into respective resistors R1, R2, R3 by, for example, the secondary batteries 141, 142, 143 are made not larger than 50 μA. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a battery circuit including a plurality of secondary batteries connected in series, and a battery pack and a battery system using the battery circuit.

  FIG. 4 shows each secondary battery, for example, each of three secondary batteries, when an assembled battery in which a plurality of secondary batteries are connected in series is charged and discharged by the secondary battery charging and discharging method according to the background art. It is a graph which shows the change of terminal voltage (alpha) 11, (alpha) 12, (alpha) 13.

  First, at timing T101, the terminal voltages α11, α12, and α13 of the secondary batteries are all equal to the discharge end voltage Vt (for example, 3.0 V), and the secondary batteries are in a balanced state. Here, when charging is performed by supplying a charging current to the assembled battery, the terminal voltages α11, α12, and α13 gradually increase.

  Further, when the secondary battery is charged until the terminal voltage exceeds a predetermined charge end voltage Vf, the secondary battery deteriorates. Therefore, when charging an assembled battery as described above, the voltage across the assembled battery is set to be the end-of-charge voltage Vf × the number of secondary batteries in series. The end-of-charge voltage Vf is generally 4.2 V when the secondary battery is, for example, a lithium ion battery. Therefore, in the case of an assembled battery in which three secondary batteries are connected in series, the voltage across the assembled battery Is charged to 4.2V × 3 = 12.6V.

  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. For example, the terminal voltage α11 of the secondary battery that is most degraded is the highest, and the terminal voltage α13 of the secondary battery that is least degraded is the lowest.

  Then, at the timing T102 when the charging is finished in FIG. 4, the terminal voltages α11, α12, α13 of the respective secondary batteries become different voltages, and an imbalance between the secondary batteries occurs. Next, when a load is connected to the assembled battery that has been charged in a state where such an imbalance has occurred and the battery is discharged, the terminal battery decreases more rapidly as the secondary battery is more deteriorated.

  When the secondary battery is discharged, if the secondary battery is overdischarged, the secondary battery deteriorates. Therefore, a voltage that does not deteriorate the secondary battery is set as the discharge end voltage Vt that is a voltage at which the discharge should be terminated. For example, in the case of a lithium ion battery, the discharge end voltage Vt is generally set to a voltage of about 3.0V. When the minimum voltage among the terminal voltages α11, α12, and α13 decreases to the discharge end voltage Vt = 3.0 V, the discharge is finished (timing T103).

  Then, at the timing T103, the terminal voltage α11 of the secondary battery that is most deteriorated is the lowest, the terminal voltage α13 of the secondary battery that is least degraded is the highest, and the terminal voltages α11, α12, and α13 are further increased. Unbalance will expand. Further, before the terminal voltages α12 and α13 of the secondary battery with little deterioration are reduced to the discharge end voltage Vt, the terminal voltage α11 of the secondary battery whose deterioration is most advanced is reduced to the discharge end voltage Vt. Since the current supply to the load is stopped after completion, there is a disadvantage that the battery capacity of the secondary battery with little deterioration cannot be effectively used, and the battery capacity of the entire assembled battery is reduced. When such charge and discharge operations are repeated, as shown at timings T104 and T105, the deterioration of the secondary battery, which is more advanced than the other secondary batteries, is further promoted, and the terminal voltages α11, α12, There is a disadvantage that the difference of α13 increases.

  Therefore, a series circuit of a discharging switching element and a resistor is connected in parallel with each secondary battery, and when charging is finished, the terminal voltage is connected in parallel with the secondary battery whose charge exceeds the end-of-charge voltage Vf. A technique is known in which a secondary battery is forcibly discharged by turning on the switching element (for example, see Patent Document 1). This technology discharges a secondary battery that exceeds the end-of-charge voltage Vf to lower the terminal voltage, thereby reducing a difference in terminal voltage among a plurality of secondary batteries, and forming a secondary battery. The imbalance between them is reduced.

  FIG. 5 shows that when charging is completed, the switching element connected in parallel with the secondary battery whose terminal voltage exceeds the charging end voltage Vf is turned on to forcibly discharge and decrease the terminal voltage. FIG. 6 is a graph showing changes in terminal voltages α11, α12, and α13 when a difference in terminal voltages among a plurality of secondary batteries is reduced.

As shown in FIG. 5, when charging is completed (timing T202), the switching element connected in parallel with the secondary battery (terminal voltage α11) whose terminal voltage exceeds the charging end voltage Vf is turned on and balanced. By forcibly discharging for adjustment and reducing the terminal voltage α11, the difference between the terminal voltages α11, α12, and α13 in each secondary battery is reduced (timing T203).
JP 2005-176520 A

  However, in the technique described in Patent Document 1, a switching element connected in parallel to a secondary battery whose terminal voltage exceeds the end-of-charge voltage Vf is turned on, and the secondary battery is short-circuited via a resistor. Since discharging is performed in a state, the driving capacity is substantially reduced if it is performed during discharging. Further, in order to reduce the unbalance between the secondary batteries, it is necessary to detect the terminal voltage of each secondary battery and selectively discharge the secondary battery exceeding the charge end voltage Vf. There is an inconvenience that processing for reduction becomes complicated.

  The present invention was devised in view of such circumstances, and balance control is possible during charging as well as during charging, and each secondary is adjusted by always adjusting with a small current before a certain voltage difference occurs. An object of the present invention is to provide a battery circuit capable of reducing unbalance between batteries and simplifying processing for reducing unbalance, and a battery pack using the battery circuit.

  The battery circuit according to the present invention includes an assembled battery in which a plurality of secondary batteries are connected in series, and outputs a voltage at both ends of the assembled battery as a load driving voltage and receives a charging voltage to receive the assembled battery. And a plurality of unbalance reduction resistors connected in parallel to each of the plurality of secondary batteries, and the resistance values of the unbalance reduction resistors are substantially the same as each other. It is.

  According to this configuration, the assembled battery is discharged by using the voltage at both ends of the assembled battery in which a plurality of secondary batteries are connected in series as the voltage for driving the load, and the charging voltage is applied to both ends of the assembled battery. As a result, the assembled battery is charged, so that an unbalance between the secondary batteries tends to occur as it is. However, since resistors having substantially the same resistance value are connected in parallel to the plurality of secondary batteries, the current flowing through each resistor increases as the terminal voltage of the secondary batteries connected in parallel increases. As the voltage increases, the discharge current of the secondary battery increases and the terminal voltage decrease rate increases. As a result, the difference in the terminal voltage of each secondary battery is reduced and the unbalance between the secondary batteries is reduced. . In this case, as in the technique described in the background art, the terminal voltage of each secondary battery is detected, and the switching element connected in parallel with the secondary battery having a high terminal voltage is selectively turned on and discharged. Since there is no need to perform processing, processing for reducing imbalance can be simplified. In addition, as in the technology described in the background art, in order to discharge a part of the series-connected secondary batteries in a short-circuited state through a resistor, the output voltage of the assembled battery is lowered and driven to the load. The balance can be controlled during charging as well as during discharging, without being unable to supply voltage, and by always adjusting with a small current before a certain voltage difference occurs, the unbalance between each secondary battery is reduced. can do.

  In addition, it is preferable that the resistance value of each of the unbalance reduction resistors is set so that the current flowing through the secondary battery is 50 μA or less.

  According to this configuration, the current discharged by each resistor is 50 μA or less, which is about the same as the current consumption in the standby state of the battery-equipped device. The risk of excessively shortening the drive time of the secondary battery is reduced.

  Moreover, it is preferable that a capacitor is connected in parallel to each of the plurality of secondary batteries. According to this configuration, since the load current fluctuation is absorbed by the capacitor, it is easy to balance the terminal voltage of each capacitor by the resistance for unbalance reduction while improving the response to the steep load fluctuation. .

  The battery pack according to the present invention includes the battery circuit described above. According to this configuration, the imbalance between the secondary batteries can be reduced inside the battery pack.

  The battery system according to the present invention includes the battery circuit described above and a charging circuit that charges the assembled battery by supplying the charging voltage to the conductive portion. According to this configuration, the charging voltage supplied by the charging circuit is applied to both ends of the assembled battery by the conductive portion, and an unbalance between the secondary batteries tends to occur as it is. However, since resistors having substantially the same resistance value are connected in parallel to the plurality of secondary batteries, the current flowing through each resistor increases as the terminal voltage of the secondary batteries connected in parallel increases. As the voltage increases, the discharge current of the secondary battery increases and the terminal voltage decrease rate increases. As a result, the difference in the terminal voltage of each secondary battery is reduced and the unbalance between the secondary batteries is reduced. .

  In the battery circuit, the battery pack, and the battery system having such a configuration, the current flowing through each resistor increases as the terminal voltage of the secondary battery connected in parallel increases, so that the discharge of the secondary battery increases as the terminal voltage increases. As a result of increasing the current and increasing the terminal voltage decrease rate, the difference in the terminal voltage of each secondary battery is reduced and the imbalance between the secondary batteries is reduced. In this case, as in the technique described in the background art, the terminal voltage of each secondary battery is detected, and the switching element connected in parallel with the secondary battery having a high terminal voltage is turned on and discharged. Since there is no need, it is possible to simplify the process for reducing imbalance. In addition, as in the technology described in the background art, in order to discharge a part of the series-connected secondary batteries in a short-circuited state through a resistor, the output voltage of the assembled battery is lowered and driven to the load. The balance can be controlled during charging as well as during discharging, without being unable to supply voltage, and by always adjusting with a small current before a certain voltage difference occurs, the unbalance between each secondary battery is reduced. can do.

  Embodiments according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating an example of a configuration of a battery system 1 that charges a battery pack 2 that uses a battery circuit 5 according to an embodiment of the present invention. The battery system 1 includes a battery pack 2 and a charging device 3 that charges the battery pack 2. The battery pack 2 and the charging device 3 do not have to be separated, and the battery pack 2 and the charging device 3 shown in FIG. 1 may be configured as an integrated battery system. Further, the battery system may be configured as an electric equipment system including the battery circuit 5 including the load circuit 4 that is fed from the battery pack 2. Further, although the battery pack 2 is charged from the charging device 3 in FIG. 1, the battery pack 2 may be attached to the load circuit 4 and charged through the load circuit 4. The battery pack 2 and the charging device 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 battery pack 2 is attached to the load circuit 4.

  The terminals T21 and T23 of the charging device 3 are connected to the load circuit 4, and the current supplied from the assembled battery 14 is supplied to the load circuit 4 via the switching element 12, the charging path 11, and the terminals T11 and T21. It has become so. The load circuit 4 is a load circuit of an electric device driven by power supplied from the battery pack 2. For example, when a power switch of an electric device (not shown) is turned on, the load circuit is transferred from the battery pack 2 to the load circuit 4. 4 drive current is supplied.

  The battery pack 2 includes a switching element 12, a battery circuit 5, a current detection resistor 16, a temperature sensor 17, a control IC (Integrated Circuit) 18, a voltage detection circuit 20, and terminals T11, T12, and T13. ing. As the switching element 12, a semiconductor switching element such as an FET (Field Effect Transistor) or a switching element such as a relay switch is used. The control IC 18 includes an analog / digital converter 19, a control unit 21, and a communication unit 22.

  In the battery pack 2, the switching element 12 is interposed in the DC high-side charging path 11 (conductive portion) extending from the terminal T <b> 11, and the charging path 11 is connected to the secondary batteries 141, 142, and 143. Connected to the high-side terminal of the assembled battery 14. The low-side terminal of the assembled battery 14 is connected to the GND terminal T13 via the DC low-side charging path 15 (conductive portion). The charging path 15 has a current detection for converting charging current and discharging current into voltage values. A resistor 16 is interposed.

  The battery circuit 5 includes a plurality of secondary batteries 141, 142, and 143 connected in series, and resistors R1, R2, and R3 connected in parallel to the secondary batteries 141, 142, and 143, respectively. The resistance values of the resistors R1, R2, and R3 are substantially the same. Moreover, the secondary batteries 141, 142, and 143 are, for example, lithium ion batteries, and the assembled battery 14 is configured by a series circuit of the secondary batteries 141, 142, and 143.

  Note that “substantially the same” means that the same range includes a range of manufacturing variations and errors. Further, the secondary batteries 141, 142, and 143 are not necessarily limited to a single secondary battery, and for example, a plurality of secondary batteries may be connected in parallel.

  The resistance values of the resistors R1, R2, and R3 are set so that the currents flowing by the secondary batteries 141, 142, and 143 are, for example, 50 μA or less, for example, resistance values of about 100 kΩ to 1 MΩ are set. Has been. If the resistance values of the resistors R1, R2, and R3 are in the range of 100 kΩ to 1 MΩ, when the output voltages Vb1, Vb2, and Vb3 of the secondary batteries 141, 142, and 143 are 4.2 V, for example, the resistors R1, The current flowing through R2 and R3 is 42 μA to 4.2 μA, and is 50 μA or less.

  In the case of an electronic device driven by a battery, even when the user is not using the electronic device, a consumption of about several tens of μA is required to perform a standby operation such as operating a clock or performing a liquid crystal display. Often, current is discharged from the battery. Then, if the current flowing through the resistors R1, R2, and R3 is 50 μA or less, the current consumption is the same as the current consumption in the standby operation of the electronic device, so the time that the electronic device can be driven by the secondary batteries 141, 142, and 143 is shortened. It is thought that there is almost no influence such as being done.

  The temperatures of the secondary batteries 141, 142, and 143 are detected by the temperature sensor 17 and input to the analog / digital converter 19 in the control IC 18. The terminal voltages Vb1, Vb2, and Vb3 of the secondary batteries 141, 142, and 143 are read by the voltage detection circuit 20 and input to the analog / digital converter 19 in the control IC 18. 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.

  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 these peripheral circuits and the like.

  Then, the control unit 21 executes the control program stored in the ROM, thereby responding to each input value from the analog / digital converter 19 to the charging current that instructs the charging device 3 to output. The voltage value and the current value are calculated, and the calculation results are transmitted from the communication unit 22 to the charging device 3 via the terminals T12 and T22; T13 and T23, whereby the assembled battery 14 is charged by the charging device 3.

  Further, the control unit 21 detects an abnormality outside the battery pack 2 such as a short circuit between the terminals T <b> 11 and T <b> 13 or an abnormal current from the charging device 3 based on each input value from the analog / digital converter 19, An abnormal temperature rise or the like is detected, and a protective operation such as turning off the switching element 12 is performed.

  In the charging device 3, the instruction is received by the communication unit 32 that is a communication unit in the control IC 30, and the charging control unit 31 controls the charging current supply circuit 33 (charging unit) so that the voltage value, current The charging current is supplied with the value and the pulse width. The charging current supply circuit 33 includes an AC-DC converter, a DC-DC converter, and the like, converts an input voltage into a voltage value, a current value, and a pulse width that are instructed from the charging control unit 31, and is connected to terminals T21 and T11. Supply to charging paths 11 and 15 via T23 and T13.

  Note that the control unit 21 is not limited to the example provided in the battery pack 2, and the charging device 3 may include the control unit 21. Further, the control unit 21 may be shared by the battery pack 2 and the charging device 3.

  Next, the operation of the battery pack 2 using the battery circuit 5 configured as described above and the battery system 1 for charging the battery pack 2 will be described. FIG. 2 is an explanatory diagram showing an example of the operation of the battery system 1 shown in FIG. First, for example, when the battery pack 2 is connected to the charging device 3, the switching unit 12 is turned on by the control unit 21, and an instruction to start charging with a predetermined current and voltage is received from the control unit 21. The data is transmitted to the charging control unit 31 via the unit 22, the terminals T12 and T22, and the communication unit 32, and charging is started (timing T1).

  Then, according to the control signal from the charging control unit 31, the current and voltage according to the instruction from the control unit 21, from the charging current supply circuit 33 through the terminals T 21 and T 11, the charging path 11, and the switching element 12. A charging current is supplied to the assembled battery 14. As the secondary batteries 141, 142, and 143 are charged, the terminal voltages Vb1, Vb2, and Vb3 increase.

  At the timing T1, the terminal voltages Vb1, Vb2, and Vb3 are all equal to, for example, the discharge end voltage Vt (for example, 3.0 V), and the secondary batteries 141, 142, and 143 are in a balanced state. It has become.

  By the way, when the degree of deterioration of the secondary batteries 141, 142, and 143 is different, the secondary battery that is more deteriorated has a larger internal resistance and a higher terminal voltage. Therefore, if the resistors R1, R2, and R3 are not present, the terminal voltages Vb1, Vb2, and the secondary batteries 141, 142, and 143 depend on the degree of deterioration of the secondary batteries 141, 142, and 143 as the secondary batteries 141, 142, and 143 are charged. If there is a difference in Vb3 and, for example, the deterioration is progressing in the order of the secondary batteries 141, 142, and 143, the terminal voltage Vb1 of the secondary battery 141 that is most deteriorated has the highest voltage and the least deterioration. The terminal voltage Vb3 of the secondary battery 143 has the lowest voltage.

  However, in the battery circuit 5 shown in FIG. 1, resistors R1, R2, and R3 having substantially the same resistance value are connected in parallel with the secondary batteries 141, 142, and 143, respectively. As a result, the currents flowing through the resistors R1, R2, and R3 increase as the terminal voltages Vb1, Vb2, and Vb3 of the secondary batteries 141, 142, and 143 connected in parallel respectively increase. Therefore, as the terminal voltage increases, the current of the secondary battery increases. As a result of the increase in the discharge current and the decrease in the terminal voltage increase rate due to charging, the terminal voltages Vb1, Vb2, and Vb3 remain substantially equal, that is, there is an unbalance between the secondary batteries 141, 142, and 143. Charging is performed in a reduced state.

  In this case, since the unbalance between the secondary batteries 141, 142, and 143 is automatically reduced by the resistors R1, R2, and R3, the process for reducing the unbalance can be simplified.

  In FIG. 2, the change in the terminal voltages Vb1, Vb2, and Vb3 in the case of constant current (CC) charging for supplying a constant current to the assembled battery 14 is described as an example, but the charging method is not limited. , Constant voltage (CV) charging for charging at a constant voltage, constant current constant voltage (CCCV) charging for switching from constant current (CC) charging to constant voltage (CV) charging, pulse charging for supplying charging current in pulses, Various charging methods such as trickle charging for charging with a minute current can be used. Alternatively, the battery pack 14 may be charged while supplying a load current to the load circuit 4.

  For example, the terminal voltage Vb of the assembled battery 14 detected by the voltage detection circuit 20 and obtained by the analog / digital converter 19 is a voltage obtained by multiplying the end-of-charge voltage Vf by the series number of secondary batteries, for example, 4.2 V. When x3 = 12.6V, the control unit 21 transmits an instruction to stop supplying the charging current to the charging control unit 31 via the communication unit 22, the terminals T12 and T22, and the communication unit 32. The charging control unit 31 sets the output current of the charging current supply circuit 33 to zero, and charging ends (timing T2).

  It should be noted that the charging is terminated only when the terminal voltage Vb of the assembled battery 14 reaches a voltage (for example, 4.2 V × 3 = 12.6 V) obtained by multiplying the charging end voltage Vf by the number of secondary batteries in series. Therefore, when the maximum voltage among the terminal voltages Vb1, Vb2, and Vb3 reaches the charge end voltage Vf (for example, 4.2V), the charging is terminated, thereby reducing the deterioration of the secondary batteries 141, 142, and 143. You may do it.

  At the timing T2, the unbalance of the secondary batteries 141, 142, and 143 is automatically reduced by the resistors R1, R2, and R3, so that there is almost no difference between the terminal voltages Vb1, Vb2, and Vb3. The unbalance of the batteries 141, 142, 143 is reduced.

  Next, for example, when a power switch (not shown) of the load circuit 4 is turned on, the current supplied from the assembled battery 14 is supplied to the load circuit 4 via the switching element 12, the charging path 11, and the terminals T11 and T21. The assembled battery 14, that is, the secondary batteries 141, 142, and 143 are discharged. Then, the terminal voltages Vb1, Vb2, and Vb3 are gradually decreased according to the discharge of the secondary batteries 141, 142, and 143.

  In the process of discharging the secondary batteries 141, 142, and 143, the voltage of the secondary battery whose deterioration has progressed decreases more quickly. Therefore, if there is no resistance R1, R2, R3, the terminal voltage becomes lower as the secondary battery is more deteriorated, and an imbalance occurs between the secondary batteries 141, 142, and 143.

  However, in the battery circuit 5 shown in FIG. 1, resistors R1, R2, and R3 having substantially the same resistance value are connected in parallel with the secondary batteries 141, 142, and 143, respectively. As a result, the currents flowing through the resistors R1, R2, and R3 increase as the terminal voltages Vb1, Vb2, and Vb3 of the secondary batteries 141, 142, and 143 connected in parallel respectively increase. Therefore, as the terminal voltage increases, the current of the secondary battery increases. As a result of the increase in the discharge current and the decrease in the terminal voltage, the terminal voltages Vb1, Vb2, and Vb3 remain substantially equal, that is, the unbalance between the secondary batteries 141, 142, and 143 is reduced. In the state, discharge, that is, supply of the drive voltage to the load circuit 4 is performed. In this case, since the unbalance between the secondary batteries 141, 142, and 143 is automatically reduced by the resistors R1, R2, and R3, the process for reducing the unbalance can be simplified.

  Further, since the resistors R1, R2, and R3 are always connected to the secondary batteries 141, 142, and 143, the unbalance between the secondary batteries 141, 142, and 143 can be reduced while supplying the drive voltage to the load. Can do.

  When the lowest terminal voltage among the terminal voltages Vb1, Vb2, and Vb3 obtained by the analog / digital converter 19 reaches the discharge end voltage Vt, the controller 21 prevents overdischarge of the assembled battery 14. Accordingly, the switching element 12 is turned off and the discharge is stopped (timing T3). The terminal voltage Vb1, Vb2, Vb3 is not limited to the example in which the discharge is stopped when the lowest terminal voltage reaches the discharge end voltage Vt. For example, the terminal voltage Vb of the assembled battery 14 is not discharged. Discharging may be stopped when the voltage Vt is equal to or lower than the value obtained by multiplying the number of secondary batteries in series.

  At the timing T3, the unbalance of the secondary batteries 141, 142, and 143 is automatically reduced by the resistors R1, R2, and R3. Therefore, the difference between the terminal voltages Vb1, Vb2, and Vb3 hardly occurs, and the secondary battery The unbalance of the batteries 141, 142, 143 is reduced.

  And even when the same charging / discharging process as timing T1-T3 is repeated (timing T3-T5), the imbalance of the secondary batteries 141, 142, 143 is always automatically performed by the resistors R1, R2, R3. Therefore, as in the background art shown in FIGS. 4 and 5, it is possible to reduce the cumulative increase in the terminal voltage difference between the secondary batteries by repeatedly charging and discharging the assembled battery.

  In recent years, attention has been focused on a system that improves the response to sudden load fluctuations by connecting a capacitor such as an electric double layer capacitor having a large capacitance in parallel with each secondary battery constituting the assembled battery. ing. Therefore, for example, as in the battery circuit 5a shown in FIG. 3, the capacitors C1, C2, C3 and the resistors R1, R2, R3 may be connected in parallel to the secondary batteries 141, 142, 143, respectively. According to the battery circuit 5a shown in FIG. 5, the difference between the terminal voltages of the secondary batteries 141, 142, and 143 can be constantly reduced by the resistors R1, R2, and R3. The terminal voltages of the capacitors C1, C2, and C3 connected in parallel to each other can be easily balanced at all times.

  INDUSTRIAL APPLICABILITY The present invention is suitably used as a battery circuit used in battery-mounted devices such as electronic devices such as portable personal computers, digital cameras, and video cameras, vehicles such as electric cars and hybrid cars, and battery packs using the battery circuits. be able to.

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

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery system 2 Battery pack 3 Charging device 4 Load circuit 5, 5a Battery circuit 14 Battery assembly 21 Control part 22 Communication part 31 Charge control part 32 Communication part 33 Charging current supply circuit 141,142,143 Secondary battery 18,30 Control IC
R1, R2, R3 resistance Vb, Vb1, Vb2, Vb3 terminal voltage

Claims (5)

An assembled battery in which a plurality of secondary batteries are connected in series;
A conductive portion that outputs a voltage at both ends of the assembled battery as a voltage for driving a load and receives a charging voltage to be applied to both ends of the assembled battery;
A plurality of unbalance reduction resistors connected in parallel to each of the plurality of secondary batteries,
The battery circuit characterized in that resistance values of the respective unbalance reducing resistors are substantially the same. 2. The battery circuit according to claim 1, wherein a resistance value of each of the unbalance reducing resistors is set such that a current flowing through the secondary battery is 50 μA or less. The battery circuit according to claim 1, wherein a capacitor is connected in parallel to each of the plurality of secondary batteries.   The battery pack provided with the battery circuit of any one of Claims 1-3. The battery circuit according to any one of claims 1 to 3,
A battery system comprising: a charging circuit that charges the assembled battery by supplying the charging voltage to the conductive portion.

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