Equalizing Device

Abstract

To improve the equalization capability (current×time) of an equalization device.SOLUTION: An equalization device 91 equalizes the charge amounts of a plurality of cell batteries B included in a battery pack 95. A state determination unit 11 of the equalization device 91 includes at least one of a state in which the battery pack 95 is charged with constant current and a state in which the battery pack 95 is charged with constant power, and determines whether the battery pack 95 is in a predetermined charging state that does not include a state in which the battery pack is being charged at a constant voltage. A variation determination unit 12 of the equalization device 91 determines whether the variation voltage indicating the variation in the voltage of each of the cell batteries B is higher than a predetermined charging determination voltage. An equalization unit 13 of the equalization device 91 performs equalization on condition that the battery pack is determined to be in a predetermined charging state and that the variation voltage is higher than the charging determination voltage.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an equalization device provided for a battery pack. [Background technology]

[0002] The equalization device equalizes the charge amounts of the multiple cell batteries in the battery pack. An example of a document showing such a technique is Patent Document 1 below. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-125977 A Summary of the Invention [Problem to be solved by the invention]

[0004] When charging the battery pack, a charging current flows from the positive electrode to the negative electrode in each cell battery, causing the terminal voltage of each cell battery to rise by the amount of the internal resistance times the charging current. Hereinafter, this rise in terminal voltage is referred to as "charging polarization." The charging polarization in each cell battery does not immediately subside even after charging of the battery pack is terminated. This is because capacitive components such as parasitic capacitance exist in parallel with at least a portion of the internal resistance, and it takes time for the charge stored in these capacitive components to discharge.

[0005] On the other hand, when the battery pack is being used (discharging), a charging current flows from the negative electrode to the positive electrode in each cell battery, causing the terminal voltage of each cell battery to drop by an amount equal to the internal resistance times the current being used. Hereinafter, this drop in terminal voltage will be referred to as "use polarization." Furthermore, the use polarization in each cell battery does not immediately subside even when the use of the battery pack's power is terminated. This is because, just as after charging is terminated, it takes time for the charge stored in the capacitance component to discharge.

[0006] In the following, charging polarization and usage polarization are collectively referred to simply as "polarization." For the above reasons, the period for equalizing the charge amounts of each cell battery is generally limited to the period after the polarization is eliminated. This is because the voltage of each cell battery cannot be correctly grasped until the polarization is resolved.

[0007] However, the higher the capacity of a battery pack, the greater the self-discharge, and the greater the variation in charge amount, which increases the time required for equalization. In addition, depending on how the battery pack is used, such as when the battery pack's power is used for various purposes, the period during which the battery pack's power is used becomes longer and the period after the polarization is eliminated becomes shorter. Therefore, even in these cases, if the equalization period is limited to the period after the polarization is eliminated, the equalization capacity (current x time) of the equalizer may be insufficient.

[0008] The present invention has been made in consideration of the above circumstances, and has as its main object to improve the equalization capacity (current x time) of an equalizer. [Means for solving the problem]

[0009] The equalization device of the present invention is a device that performs equalization of the charge amounts of multiple cell batteries in a battery pack, and includes a state determination unit, a charging variation determination unit, and a charging equalization unit. The state determination unit determines whether the battery pack is in a predetermined charging state, which includes at least one of a state in which the battery pack is being charged at a constant current and a state in which the battery pack is being charged at a constant power, and does not include a state in which the battery pack is being charged at a constant voltage. The charging variation determination unit determines whether a variation voltage indicating a variation in the voltage of each of the cell batteries is greater than a predetermined charging determination voltage. The charging equalization unit performs the equalization on the condition that it is determined that the battery pack is in the predetermined charging state and that the variation voltage is greater than the charging determination voltage.

[0010] According to the present invention, equalization is performed not only after the battery packs have finished charging but also during charging, which extends the period during which equalization is possible and improves the equalization capability (current x time).

[0011] Moreover, the equalization is performed on the condition that it is determined that constant current charging or constant power charging is in progress. During constant current charging or constant power charging, charging is controlled based on current or power, so voltage measurement accuracy and frequency are not required to be as high as during constant voltage charging, in which charging is controlled based on voltage. Therefore, during constant current charging or constant power charging, even if the voltage measurement accuracy and frequency decrease due to equalization, this is not a problem compared to constant voltage charging.

[0012] As described above, according to the present invention, it is possible to extend the period during which equalization is possible and improve the equalization capability (current x time) while suppressing the adverse effects of reduced voltage measurement accuracy and measurement frequency due to equalization. [Brief description of the drawings]

[0013] [Figure 1] A circuit diagram showing an equalization device and its periphery according to a first embodiment. [Diagram 2] A graph showing the changes in voltage and current during and after charging of a battery pack [Diagram 3] A graph showing the changes in voltage and current while the main power is ON and after that [Figure 4] Block diagram showing the control unit and its surroundings [Diagram 5] Flowchart showing first to third equalization controls [Figure 6] A block diagram showing a control unit and its periphery in a second embodiment. [Figure 7] A block diagram showing a control unit and its periphery in a third embodiment. [Figure 8] FIG. 13 is a block diagram showing a control unit and its periphery according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiment, and can be appropriately modified and implemented without departing from the spirit and scope of the invention.

[0015] [First embodiment] 1 is a circuit diagram showing an equalization device 91 and its periphery according to this embodiment. In the following, being electrically connected is simply referred to as being "connected." The equalization device 91 is mounted on an electric vehicle 90 such as an electric vehicle or a plug-in hybrid vehicle. The equalization device 91 is connected to a battery pack 95 mounted on the electric vehicle 90.

[0016] First, the battery pack 95 will be described. The battery pack 95 has a series connection of cell batteries B, such as lithium ion batteries. Hereinafter, the voltage of the cell battery B with the highest terminal voltage in the battery pack 95 will be referred to as the "maximum cell voltage Vmax", and the voltage of the cell battery B with the lowest terminal voltage in the battery pack 95 will be referred to as the "minimum cell voltage Vmin". The voltage of the cell battery B when fully charged will be referred to as the "fully charged cell voltage Vf", and the voltage obtained by subtracting the maximum cell voltage Vmax from the fully charged cell voltage Vf will be referred to as the "free voltage (Vf-Vmax)". For each cell battery B, the voltage obtained by subtracting the minimum cell voltage Vmin from the voltage of that cell battery B will be referred to as the "variation voltage ΔV".

[0017] The battery pack 95 is connected to a general load 98 via a main power switch 98s such as an ignition switch, and is also connected to a dark current load 97 via a step-down circuit (not shown) or the like, without going through the main power switch 98s. Hereinafter, the ON state of the main power switch 98s is referred to as a "main power ON state," and the OFF state is referred to as a "main power OFF state." The period in which the main power is ON is referred to as a "main power ON period," and the period in which the main power is OFF is referred to as a "main power OFF period."

[0018] With the above configuration, the battery pack 95 can supply power only to the dark current load 97 out of the general load 98 and the dark current load 97 during a main power OFF period, and can supply power to both the general load 98 and the dark current load 97 during a main power ON period. However, instead of or in addition to the battery pack 95, another power source such as a low-voltage power source may be connected to the dark current load 97.

[0019] When charging the battery pack 95, an external power source 100 is connected to the battery pack 95. Hereinafter, the state in which the battery pack 95 is being charged by the external power source 100 will be referred to as a "charging state," and the state in which the battery pack 95 is not being charged will be referred to as a "non-charging state."

[0020] Each cell battery B has a main body Bb that generates a voltage in an open circuit state that does not form a closed circuit, internal resistances Ra, Rb that exist in series with the main body Bb, and a capacitance component Cb such as a parasitic capacitance that exists in parallel with a portion (Rb) of the internal resistances Ra, Rb.

[0021] Next, the problem to be solved in this embodiment and the outline of the means for solving the problem will be described. When the battery pack 95 is charged, a charging current flows in the charging direction in each cell battery B, and the terminal voltage of the cell battery B increases by the amount of "internal resistance (Ra+Rb) x charging current". At this time, charge is stored in the capacitance component Cb until the terminal voltage of the capacitance component Cb becomes the same as the terminal voltage of the internal resistance Rb. Hereinafter, this increase in the terminal voltage of each cell battery B due to the charging current is referred to as "charging polarization". The charging polarization does not immediately subside even after charging of the battery pack 95 is terminated. This is because the charge of the capacitance component Cb gradually decreases as it flows from the high potential side of the capacitance component Cb through the internal resistance Rb to the low potential side.

[0022] On the other hand, when the main power supply is ON, a large amount of current flows in the discharging direction in each cell battery B, causing the terminal voltage of the cell battery B to drop by the amount of "internal resistance (Ra+Rb) x current used." At this time, charge is stored in the capacitance component Cb until the terminal voltage of the capacitance component Cb becomes the same as the terminal voltage of the internal resistance Rb. Hereinafter, this drop in the terminal voltage of each cell battery B due to the current used is referred to as "polarization of use." This polarization of use does not subside immediately even when the use of power from the battery pack 95 is terminated. As described above, the charge of the capacitance component Cb gradually decreases as it flows from the high potential side of the capacitance component Cb through the internal resistance Rb to the low potential side.

[0023] In the following, charging polarization and usage polarization are collectively referred to simply as "polarization." For the above reasons, the equalization period for reducing the voltage variation ΔV of each cell battery B is generally limited to the period after the polarization is eliminated. This is because the voltage variation ΔV cannot be correctly grasped until the polarization is resolved.

[0024] However, the higher the capacity of the battery pack 95, the greater the self-discharge, and the greater the variation in the charge amount, which increases the time required for equalization. Also, depending on how the battery pack 95 is used, such as using the power of the battery pack 95 for purposes other than driving the electric vehicle 90, the period during which the power of the battery pack 95 is used becomes longer and the period after the elimination of the polarization during use becomes shorter. Therefore, even in these cases, if the equalization period is limited to the period after the elimination of the polarization, the equalization capacity (current x time) of the equalizer 91 may be insufficient.

[0025] Therefore, the equalizer 91 performs equalization discharge to reduce the voltage variation ΔV of each cell battery B not only after polarization elimination but also during charging or while polarization is occurring, on the condition that certain requirements are met, more roughly than after polarization elimination. Furthermore, by changing the start timing of equalization discharge after polarization elimination according to the state of the battery pack 95, the start timing is made as early as possible.

[0026] Next, we will explain the circuit configuration of the equalization device 91. The equalization device 91 has a positive electrode side wiring Lp, a negative electrode side wiring Ln, a low-pass filter (Rf, Cf), and a discharge switch Sw for each cell battery B. However, the negative electrode side wiring Ln for each cell battery B is shared (shared) with the positive electrode side wiring Lp for the cell battery B that is one level lower in potential than that cell battery B.

[0027] The positive electrode side wiring Lp is connected to the positive electrode terminal of the cell battery B via the connection wiring M, and the negative electrode side wiring Ln is connected to the negative electrode terminal of the cell battery B via the connection wiring M. The positive electrode side wiring Lp is provided with a positive electrode side resistance Rp, and the negative electrode side wiring Ln is provided with a negative electrode side resistance Rn. However, the negative electrode side resistance Rn for each cell battery B is shared (shared) with the positive electrode side resistance Rp for the cell battery B that is one level lower in potential than that cell battery B.

[0028] The low-pass filter (Rf, Cf) is a series connection of a filter resistor Rf and a filter capacitor Cf. The low-pass filter (Rf, Cf) connects a portion of the positive wiring Lp that is closer to the cell battery B than the positive resistance Rp and a portion of the negative wiring Ln that is closer to the cell battery B than the negative resistance Rn.

[0029] The discharge switch Sw is a semiconductor switch such as a MOSFET or an IGBT. The positive terminal (source terminal in the figure) of the discharge switch Sw is connected to the opposite side of the positive resistance Rp of the positive wiring Lp from the cell battery B side. On the other hand, the negative terminal (drain terminal in the figure) of the discharge switch Sw is connected to the opposite side of the negative resistance Rn of the negative wiring Ln from the cell battery B side.

[0030] When each discharge switch Sw is turned ON, a current flows from the positive electrode side wiring Lp corresponding to that discharge switch Sw to the negative electrode side wiring Ln, thereby discharging the cell battery B corresponding to that discharge switch Sw. Hereinafter, the current that flows when the discharge switch Sw is turned ON is referred to as the "equalization current," and the discharge of the cell battery B by this equalization current is referred to as the "equalization discharge."

[0031] During equalization discharge of each cell battery B, an equalization current flows from the negative side to the positive side in the cell battery B, and the terminal voltage drops by the amount of the internal resistance (Ra+Rb) x the equalization current. At this time, charge is stored in the capacitance component Cb until the terminal voltage of the capacitance component Cb becomes the same as the terminal voltage of the internal resistance Rb. Hereinafter, this drop in the terminal voltage due to the equalization current is referred to as "equalization polarization". The equalization polarization does not immediately subside even after the equalization discharge is completed. As described above, the charge of the capacitance component Cb gradually decreases by flowing from the high potential side of the capacitance component Cb through the internal resistance Rb to the low potential side. Due to such equalization polarization, the equalization discharge α1 during charging is performed only during CC charging (constant current charging) and not during CV charging (constant voltage charging). Details will be described later.

[0032] Next, the control system of the equalizer 91 will be described. The equalizer 91 further includes a measurement unit 41, a plurality of switch drive circuits 49, and a control unit 50. The measurement unit 41, the plurality of switch drive circuits 49, and the control unit 50 constitute a part of a dark current load 97. The measurement unit 41 includes, for example, a multiplexer, and measures the terminal voltage of a series connection (Cf, Rn) of a filter capacitor Cf and a negative electrode resistor Rn as the voltage of the cell battery B corresponding to the series connection.

[0033] A switch drive circuit 49 is provided for each discharge switch Sw. Each switch drive circuit 49 is connected to the control terminal (gate terminal in the figure) of the corresponding discharge switch Sw, and controls the ON / OFF of the discharge switch Sw.

[0034] The control unit 50 is an electronic control unit (ECU) having a CPU, RAM, ROM, etc. The control unit 50 controls the equalization discharge by sending a command to the switch drive circuit 49 based on the voltage of each cell battery B measured by the measurement unit 41.

[0035] 2 is a graph showing the transition of voltage and current during and after the charging period of the battery pack 95. First, the charging period (T1a to T1c) of the battery pack 95 will be described. The external power source 100 performs CC charging while the available voltage (Vf-Vmax) is high, and switches to CV charging when the available voltage (Vf-Vmax) becomes small. For this reason, the external power source 100 performs CC charging from the charging start timing T1a to the charging switching timing T1b before the charging end timing T1c, and performs CV charging from the charging switching timing T1b to the charging end timing T1c.

[0036] Therefore, from the charge start timing T1a to the charge switch timing T1b, the charge current is constant and the voltage applied between the terminals of the battery pack 95 gradually increases. On the other hand, from the charge switch timing T1b to the charge end timing T1c, the voltage applied between the terminals of the battery pack 95 is constant and the charge current gradually decreases.

[0037] Next, the reason why the above-mentioned equalization discharge α1 during charging is performed only during CC charging (T1a to T1b) and not during CV charging (T1b to T1c) will be explained. During CC charging, charging is controlled based on current. In contrast, during CV charging, charging is controlled based on voltage. Therefore, higher voltage measurement accuracy and measurement frequency are required during CV charging compared to CC charging. Nevertheless, when equalization polarization occurs, it becomes necessary to reduce at least one of the measurement accuracy and measurement frequency of the voltage of the battery pack 95.

[0038] That is, in order to maintain the measurement accuracy of the voltage of the battery pack 95, it is necessary to ensure a sufficiently long relaxation time of the equalization polarization, that is, a time from the end of the equalization discharge to the voltage measurement. Therefore, it is necessary to reduce the frequency of the voltage measurement. Therefore, it is not possible to ensure a sufficient frequency of the voltage measurement for performing CV charging. On the other hand, if the frequency of the voltage measurement is not reduced, it is not possible to ensure a sufficient relaxation time of the equalization polarization. Therefore, the measurement accuracy of the voltage decreases. Therefore, it is not possible to ensure a sufficient measurement accuracy of the voltage for performing CV charging.

[0039] Therefore, as described above, during charging (T1a to T1c), the control unit 50 performs the equalization discharge α1 only during CC charging (T1a to T1b). When performing the equalization discharge α1, the voltage of the battery pack 95 is measured with at least one of the voltage measurement accuracy and measurement frequency lowered compared to when the equalization discharge α1 is not performed during CC charging or during CV charging. However, in CC charging, the voltage measurement accuracy and measurement frequency are not as important as in CV charging, so this is acceptable.

[0040] Next, the period after charging of the battery pack 95 is completed (T1c~) will be described. Hereinafter, the time t that has elapsed since the timing T1c at which charging of the battery pack 95 is completed will be referred to as the "time t that has elapsed since charging was completed." While the time t that has elapsed since charging was completed is short, charging polarization has not yet fully settled. Therefore, the voltage of each cell battery B becomes higher by the amount of charging polarization than the voltage corresponding to the charge amount of that cell battery B. As a result, the voltage of the battery pack 95 becomes higher by the charge polarization integrated value Pc, which is the integrated value of the charging polarization in each cell battery B, than the voltage corresponding to the charge amount of that battery pack 95.

[0041] Therefore, the equalizing device 91 performs equalizing discharge α2 during polarization occurrence relatively roughly during the period before the elimination of such charging polarization. Specifically, this equalizing discharge α2 during polarization occurrence is performed during the period (Td to Te) from relaxation timing Td when the charging polarization is relaxed to a certain extent to elimination timing Te when the charging polarization can be regarded as having been eliminated. Then, after the elimination timing Te, equalizing discharge α3 after polarization elimination is performed with relatively high accuracy.

[0042] The relaxation speed of the charging polarization becomes slower as the temperature of the battery pack 95 becomes lower, as indicated by the dashed line in Fig. 3, and conversely, becomes faster as the temperature of the battery pack 95 becomes higher. Therefore, the relaxation timing Td and the elimination timing Te of the charging polarization become slower as the temperature of the battery pack 95 becomes lower, as indicated by the dashed arrows in Fig. 3, and conversely, become faster as the temperature of the battery pack 95 becomes higher.

[0043] 3 is a graph showing the transition of voltage and current during the main power ON period and the period thereafter. During the main power ON period (T2b to T2c), the electric vehicle 90 uses a lot of power from the battery pack 95. Therefore, the current used during the main power ON period (T2b to T2c) is larger than during the main power OFF period (up to T2b, T2c to).

[0044] In the following, the period after the end of the main power ON period (T2b to T2c) is referred to as "after the main power is turned off," and the time elapsed from the end of the main power ON period (T2b to T2c) is referred to as "elapsed time t after the main power is turned off." While the elapsed time t after the main power is turned off is small, the polarization of use has not yet subsided sufficiently. Therefore, the voltage of each cell battery B becomes lower by the amount of the polarization of use than the voltage corresponding to the charge level of that cell battery B. As a result, the voltage of the battery pack 95 becomes lower by the integrated polarization of use value Pu, which is the integrated value of the polarization of use in each cell battery B, than the voltage corresponding to the charge level of that battery pack 95.

[0045] Therefore, similarly to the case after the end of charging described above, the equalizer 91 performs equalization discharge α2 during polarization generation relatively roughly during the period before the elimination of the polarization in use. Specifically, this equalization discharge α2 during polarization generation is performed during the period (Td to Te) from relaxation timing Td, when the polarization in use is relaxed to a certain extent, to elimination timing Te, when the polarization in use can be considered to have been eliminated. Then, after the elimination timing Te, equalization discharge α3 after the polarization elimination is performed with relatively high accuracy.

[0046] 4 is a block diagram showing the equalization device 91 and its periphery. The control unit 50 has a first control unit 10 that controls the equalization discharge α1 during charging, a second control unit 20 that controls the equalization discharge α2 during polarization, and a third control unit 30 that controls the equalization discharge α3 after polarization is eliminated.

[0047] First, the first control unit 10 will be described. The first control unit 10 has a state determination unit 11, a variation determination unit 12, and an equalization unit 13. The variation determination unit 12 here is a "charge-time variation determination unit" that performs variation determination during charging, when distinguished from other variation determination units 22 and 32 described later. The equalization unit 13 here is a "charge-time equalization unit" that performs equalization discharge α1 during charging, when distinguished from other equalization units 23 and 33 described later.

[0048] The state determination unit 11 determines whether the available voltage (Vf-Vmax) is greater than a predetermined threshold available voltage Vth (Vf-Vmax>Vth) during the charging period of the battery pack 95. Then, if it is determined that the available voltage (Vf-Vmax) is greater than the threshold available voltage Vth (Vf-Vmax>Vth), it determines that CC charging is in progress.

[0049] The variation judgment unit 12 judges whether or not the variation voltage ΔV is larger than the judgment voltage V1 during charging for each cell battery B. The judgment voltage V1 during charging is a voltage that is a threshold voltage for determining whether or not equalization discharge α1 is performed during CC charging. The judgment voltage V1 during charging is set to a value larger than the error, assuming it as an error of the variation voltage ΔV due to equalization polarization. Therefore, if the measurement frequency is reduced without reducing the measurement accuracy of the voltage of the battery pack 95, it is not necessary to set the judgment voltage V1 during charging to be large. On the other hand, if the measurement accuracy is reduced without reducing the measurement frequency of the voltage, it is necessary to set the judgment voltage V1 during charging to be large by the amount of the reduction. The error of the variation voltage ΔV due to equalization polarization may be measured in advance, for example, by an experiment, or may be calculated by simulation analysis or the like.

[0050] The equalization unit 13 performs an equalization discharge α1 during charging on a cell battery B when the state determination unit 11 determines that CC charging is in progress and the variation determination unit 12 determines that the variation voltage ΔV for any cell battery B is greater than the determination voltage V1 during charging.

[0051] Next, the second control unit 20 will be described. The second control unit 20 has a mitigation determination unit 21, a variation determination unit 22, and an equalization unit 23. The variation determination unit 22 here is a "polarization variation determination unit" that performs variation determination during polarization, when distinguished from the other variation determination units 12 and 32. The equalization unit 23 here is a "polarization equalization unit" that performs variation determination during polarization, when distinguished from the other equalization units 13 and 33. Hereinafter, the elapsed time t after the end of charging and the elapsed time t after the main power is turned off are collectively referred to simply as "elapsed time t".

[0052] The mitigation judgment unit 21 judges whether the elapsed time t is greater than the mitigation judgment time t2 after charging is completed and after the main power is turned off. The mitigation judgment time t2 is a threshold time for judging whether the charging polarization or usage polarization of the cell battery B has been mitigated to a predetermined standard or more. The mitigation judgment unit 21 sets the mitigation judgment time t2 based on the state of the cell battery B at the timing T1c when charging of the battery pack 95 is completed or the timing T2c when the main power switch 98s is turned OFF. The details are described below.

[0053] In the following, a case where the temperature is higher than a predetermined value will be referred to simply as a "higher case" compared to a case where the temperature is lower than the predetermined value. A case where the temperature is higher than a predetermined value will be referred to simply as a "larger case" compared to a case where the temperature is smaller than the predetermined value. A case where the temperature is lower than the predetermined value will be referred to simply as a "smaller case" compared to a case where the temperature is higher than the predetermined value.

[0054] The mitigation determination unit 21 first sets the mitigation determination time t2 based on the temperature of the cell battery B. Specifically, the mitigation determination unit 21 sets the mitigation determination time t2 to be shorter when the battery pack 95 has a higher temperature because the polarization is mitigated more quickly. Furthermore, the mitigation determination unit 21 sets the mitigation determination time t2 based on the SOHpw (State Of Health power). The SOHpw is a variable that indicates that the internal resistances Ra, Rb are smaller as the value increases. Therefore, the mitigation determination unit 21 sets the mitigation determination time t2 to be shorter when the SOHpw of the battery pack 95 is larger because the internal resistances Ra, Rb are smaller and the polarization is mitigated more quickly.

[0055] Furthermore, the mitigation determination unit 21 changes the mitigation determination time t2 based on the SOC (State Of Charge) indicating the charging state of the battery pack 95. Specifically, for example, in this embodiment, when charging is completed, if the SOC of the battery pack 95 at the charging completion timing T1c is small, that is, when the charged amount is small, the charging polarization is more likely to be small, so the mitigation determination time t2 is set to be short. On the other hand, after the main power is turned off, if the SOC of the battery pack 95 at the turn-off timing T2c is large, that is, when the power usage is small, the usage polarization is more likely to be small, so the mitigation determination time t2 is set to be short.

[0056] The variation determination unit 22 determines whether the variation voltage ΔV is greater than the determination voltage V2 during polarization. This determination voltage V2 during polarization is a voltage that is a threshold for determining whether or not to perform equalization discharge α2 during polarization. This determination voltage V2 during polarization is set assuming the following error. That is, equalization discharge α2 during polarization is performed without waiting for the polarization to be eliminated in each cell battery B. Therefore, the measured value of the voltage of each cell battery B includes an error due to polarization. Therefore, the variation determination unit 22 sets a voltage value at least greater than the error due to polarization as the determination voltage V2 during polarization so that the error due to polarization can be absorbed. The error due to polarization may be measured in advance, for example, by an experiment, or may be calculated by simulation analysis or the like.

[0057] As in the case of the relaxation judgment time t2, the judgment voltage V2 during the occurrence of polarization is set based on the state of the cell battery B at the timing T1c when charging of the battery pack 95 ends or the timing T2c when the main power switch 98s is turned OFF.

[0058] Specifically, the variation determination unit 22 sets the determination voltage V2 during polarization occurrence to be smaller when the temperature of the battery pack 95 is higher because the polarization is alleviated faster. Furthermore, the variation determination unit 22 sets the determination voltage V2 during polarization occurrence to be smaller when the SOHpw of the battery pack 95 is larger because the internal resistances Ra, Rb are smaller and the polarization is alleviated faster.

[0059] Furthermore, the variation determination unit 22 changes the determination voltage V2 based on the SOC of the battery pack 95. Specifically, for example, in this embodiment, when charging is completed, if the SOC of the battery pack 95 at the charging completion timing T1c is small, that is, when the charge amount is small, the charging polarization is more likely to be small, so the determination voltage V2 during polarization is set to be small. On the other hand, after the main power is turned off, if the SOC of the battery pack 95 at the turn-off timing T2c is large, that is, when the power usage amount is small, the usage polarization is more likely to be small, so the determination voltage V2 during polarization is set to be small.

[0060] When the mitigation judgment unit 21 judges that the elapsed time t is greater than the mitigation judgment time t2, the equalization unit 23 performs an equalization discharge α2 on the cell battery B during polarization occurrence, on the condition that the variation judgment unit 22 judges that the variation voltage ΔV of any of the cell batteries B is greater than the judgment voltage V2 during polarization occurrence.

[0061] Next, the third control unit 30 will be described. The third control unit 30 has a elimination judgment unit 31, a variation judgment unit 32, an equalization unit 33, and a next setting unit 34. The variation judgment unit 32 referred to here is a "post-elimination variation judgment unit" that performs variation judgment after elimination of polarization, when distinguished from the other variation judgment units 12 and 22. The equalization unit 33 referred to here is a "post-elimination equalization unit" that performs equalization discharge α3 after elimination of polarization, when distinguished from the other equalization units 13 and 23.

[0062] The cancellation judgment unit 31 judges whether the elapsed time t is longer than the cancellation judgment time t3, which is longer than the mitigation judgment time t2 described above, after charging is completed and after the main power is turned off. The cancellation judgment time t3 is a threshold time for judging whether the polarization of the cell battery B has been resolved. As with the mitigation judgment time t2, the cancellation judgment time t3 is set based on the state of the cell battery B at the charging completion timing T1c or the turn-OFF timing T2c.

[0063] That is, the resolution determination unit 31 sets the resolution determination time t3 to be shorter when the temperature of the battery pack 95 is higher because the polarization is resolved more quickly. Furthermore, the resolution determination unit 31 sets the resolution determination time t3 to be shorter when the SOHpw of the battery pack 95 is larger because the internal resistances Ra, Rb are smaller and the polarization, Pu, are resolved more quickly.

[0064] Furthermore, the resolution determination unit 31 changes the resolution determination time t3 based on the SOC of the battery pack 95. Specifically, for example, in this embodiment, after charging the battery pack 95, if the SOC of the battery pack 95 at the charging end timing T1c is small, that is, the charged amount is small, the charging polarization is more likely to be small, so the resolution determination time t3 is set to be small. On the other hand, after the main power is turned off, if the SOC of the battery pack 95 at the turn-off timing T2c is large, that is, the power used is small, the usage polarization is more likely to be small, so the resolution determination time t3 is set to be small.

[0065] The variation determination unit 32 determines whether the variation voltage ΔV is greater than the determination voltage V3 after polarization elimination for each cell battery B. The determination voltage V3 after polarization elimination is a voltage that is a threshold for determining whether or not to perform equalization discharge α3 after polarization elimination. This determination voltage V3 after polarization elimination is smaller than both the determination voltage V1 during charging and the determination voltage V2 while polarization is occurring. Therefore, this equalization discharge α3 after polarization elimination is performed with higher accuracy than both the equalization discharge α1 during charging and the equalization discharge α2 while polarization is occurring.

[0066] When performing this equalization discharge α3 after polarization elimination, unlike when performing equalization discharge α2 during polarization, polarization is not present in the voltage measurement value of each cell battery B. Therefore, it is sufficient for the variation determination unit 32 to set a voltage value at least greater than the measurement error by the measurement unit 41 as the determination voltage V3 after polarization elimination so that the measurement error of the voltage of the cell battery B by the measurement unit 41 can be absorbed.

[0067] When the elimination determination unit 31 determines that the elapsed time t is greater than the elimination determination time t3, the equalization unit 33 performs an equalization discharge α3 after polarization elimination on the cell battery B, on the condition that the variation determination unit 32 determines that the variation voltage ΔV of any of the cell batteries B is greater than the determination voltage V3 after polarization elimination.

[0068] Next, the next setting unit 34 of the third control unit 30 will be described. Hereinafter, the timing at which the resolution determination unit 31, the variation determination unit 32, and the equalization unit 33 determine whether or not to perform equalization discharge α3 after polarization resolution is referred to as the "determination timing." The next setting unit 34 sets the time until the next determination timing based on the state of the cell battery B.

[0069] Specifically, the next setting unit 34 first sets the time until the next judgment timing based on the voltage variation ΔV of the cell battery B at the current judgment timing. In other words, the next setting unit 34 sets the time until the next judgment timing to be longer when the voltage variation ΔV of the cell battery B with the smallest voltage variation ΔV among the cell batteries B undergoing the equalization discharge α3 is large, because the time required for the equalization discharge α3 is longer. As a result, specifically, the time required for equalization of the cell battery B with the smallest voltage variation ΔV among the cell batteries B undergoing the equalization discharge α3 is set as the time until the next judgment timing.

[0070] Furthermore, the next setting unit 34 sets the time until the next judgment timing based on the magnitude of the equalization current of the cell battery B at the current judgment timing. That is, the next setting unit 34 measures the magnitude of the equalization current. Then, when the equalization current is small, the time required for equalization discharge α3 becomes longer, so the time until the next judgment timing is set longer.

[0071] The equalization current may be measured by an ammeter or calculated. Specifically, for example, the equalization current can be calculated by dividing the voltage of the cell battery B by the magnitude of the resistance of the entire discharge path in the equalization discharge α3 of the cell battery B. Alternatively, instead of the above calculation method, the equalization current may be calculated by dividing the terminal voltage of a specific resistor (e.g., the positive electrode resistor Rp) through which the equalization current flows by the magnitude of the resistor.

[0072] Next, the start-up state of the control unit 50 will be described. In the ON state, not in sleep, the control unit 50 controls the equalization discharge α1 during charging and the equalization discharge α2 during polarization. After the polarization is eliminated, the control unit 50 temporarily enters a sleep state or an OFF state. When the determination timing is reached, the control unit 50 wakes up from the sleep state or the OFF state, and the equalization discharge α3 is controlled by the elimination determination unit 31, the variation determination unit 32, and the equalization unit 33 of the third control unit 30 in the control unit 50. The next setting unit 34 in the third control unit 30 sets the time until the next determination timing. After that, the control unit 50 enters a sleep state or an OFF state again until the next determination timing. By repeating the above, the equalization discharge α3 after the polarization elimination is controlled while saving as much power as possible.

[0073] FIG. 5 is a flowchart showing the control of each of the equalizing discharges α1 to α3 by the control unit 50 described above. First, in S101, it is determined whether or not the battery is in a charging state or in a main power OFF state. If the requirements of S101 are not met, that is, if the battery is in a non-charging state and the main power is ON (S101: NO), the flow proceeds to S109, where each discharge switch Sw is turned OFF, and the flow ends. On the other hand, if it is determined in S101 that the battery is in a charging state or in a power OFF state (S101: YES), it is determined in the following S102 whether or not the battery is in a charging state. If it is determined that the battery is in a charging state (S102: YES), the flow proceeds to S111 to determine whether or not to perform equalizing discharge α1 during charging.

[0074] In S111, the empty voltage (Vf-Vmax) is detected. Then, in the following S112, it is determined whether the empty voltage (Vf-Vmax) is greater than a predetermined threshold empty voltage Vth. If it is determined that the empty voltage is less than the threshold empty voltage Vth (S112: NO), it is determined that CV charging is in progress, and the flow proceeds to S109, where each discharge switch Sw is turned OFF, and the flow ends. On the other hand, if it is determined in S112 that the empty voltage (Vf-Vmax) is greater than the threshold empty voltage Vth (S112: YES), it is determined that CC charging is in progress, and the flow proceeds to S115 to determine whether or not to continue with equalizing discharge α1 during charging.

[0075] In S115, the voltage variation ΔV for each cell battery B is detected, and the judgment voltage V1 during charging is calculated. In the following S116, it is determined whether the voltage variation ΔV for each cell battery B is greater than the judgment voltage V1 during charging. If it is determined that it is greater than the judgment voltage V1 during charging (S116: YES), the discharge switch Sw corresponding to that cell battery B is turned ON, and the flow ends. On the other hand, if it is determined in S116 that the voltage variation ΔV is less than the judgment voltage V1 during charging (S116: NO), the discharge switch Sw corresponding to that cell battery B is turned OFF, and the flow ends.

[0076] On the other hand, if it is determined in S102 that the battery is not in a charging state (S102: NO), this means that the battery is in a non-charging state and that the main power has been OFF since S101, so the process proceeds to S121 to determine whether to perform equalization discharge α2 during polarization or equalization discharge α3 after polarization is eliminated.

[0077] In S121, the elapsed time t, the mitigation judgment time t2, and the resolution judgment time t3 are calculated. In the following S122, it is determined whether the elapsed time t is longer than the mitigation judgment time t2 and shorter than the resolution judgment time t3. If it is determined that the requirements are met (S122: YES), the process proceeds to S125 to determine whether or not to perform equalization discharge α2 during polarization occurrence.

[0078] In S125, the voltage variation ΔV for each cell battery B is calculated, and the judgment voltage V2 during polarization is calculated. In the following S126, it is determined whether the voltage variation ΔV for each cell battery B is greater than the judgment voltage V2 during polarization. If it is determined that it is greater than the judgment voltage V2 during polarization (S126: YES), the discharge switch Sw corresponding to that cell battery B is turned ON, and the flow ends. On the other hand, if it is determined in S126 that the voltage variation ΔV is smaller than the judgment voltage V2 during polarization (S126: NO), the discharge switch Sw corresponding to that cell battery B is turned OFF, and the flow ends.

[0079] On the other hand, in the backward S122, when it is determined that the requirement (t2 < t < t3) is not satisfied (S122: NO), it means that the elapsed time t is smaller than the relaxation determination time t2 or larger than the elimination determination time t3. Therefore, in order to determine whether to perform the equalization discharge α3 after polarization elimination, the process proceeds to S132.

[0080] In S132, it is determined whether the elapsed time t is larger than the elimination determination time t3. When it is determined that the elapsed time t is smaller than the elimination determination time t3 (S132: NO), since it means that the elapsed time t is smaller than the relaxation determination time t2 from the previous S122, the process proceeds to S138, turns off each discharge switch Sw, and then ends the flow. On the other hand, when it is determined in S132 that the elapsed time t is larger than the elimination determination time t3 (S132: YES), the process proceeds to S135 in order to determine whether to continue to perform the equalization discharge α3 after polarization elimination.

[0081] In S135, the variation voltage ΔV for each cell battery B is calculated, and the determination voltage V3 after polarization elimination is calculated. In the subsequent S136, for each cell battery B, it is determined whether the variation voltage ΔV is larger than the determination voltage V3 after polarization elimination. When it is determined that the variation voltage ΔV is larger than the determination voltage V3 after polarization elimination (S136: YES), the process proceeds to S137, turns on the discharge switch Sw corresponding to that cell battery B, and then proceeds to S139. On the other hand, in S136, when it is determined that the variation voltage ΔV is smaller than the determination voltage V3 after polarization elimination (S136: NO), the process proceeds to S138, turns off the discharge switch Sw corresponding to that cell battery B, and then ends the flow.

[0082] In S139, the next setting unit 34 sets the time until the next determination timing based on the state of the battery pack 95, that is, the temperature of the battery pack 95, SOHpw, and SOC, and then ends the flow. Then, at the next determination timing, the flow is restarted from START. However, if it does not pass through S139 and the next determination timing is not set, the flow is restarted from START after a predetermined period.

[0083] According to this embodiment, the following effects can be obtained. The equalizer 91 performs equalization discharge α1 not only after charging of the battery pack 95 is completed (T1c or later), but also during charging (T1a to T1c). Therefore, the period during which equalization is possible is lengthened accordingly, and the equalization capability (current x time) can be improved.

[0084] Moreover, the equalization is performed on the condition that it is determined that CC charging is in progress. During CC charging, charging is controlled based on current, so voltage measurement accuracy and frequency are not required to be as high as during CV charging, in which charging is controlled based on voltage. Therefore, during CC charging, even if the voltage measurement accuracy and frequency drop due to equalization, it is not a problem compared to CV charging.

[0085] Therefore, according to this embodiment, it is possible to extend the period during which equalization is possible and improve the equalization capability (current x time) while suppressing the adverse effects of reduced voltage measurement accuracy and measurement frequency due to equalization.

[0086] Furthermore, the state determination unit 11 determines that the battery pack 95 is being CC charged on condition that it determines that the available voltage (Vf-Vmax) is greater than the threshold available voltage Vth while the battery pack 95 is being charged. Therefore, it is possible to efficiently determine whether the battery pack 95 is being CC charged based on the available voltage (Vf-Vmax).

[0087] In addition, the variation determination unit 12 sets a voltage value that is greater than at least the voltage error of the cell battery B caused by the equalization discharge α1 as the determination voltage V1 during charging. Therefore, there is no need to worry about the voltage error resulting from the wasteful discharge of the cell battery B, which does not require the equalization discharge α1.

[0088] Furthermore, when it is determined that the elapsed time t is longer than the relaxation determination time t2, the equalization unit 23 of the second control unit 20 performs the equalization discharge α2 during polarization occurrence, on the condition that it is determined that the voltage variation ΔV is greater than the determination voltage V2 during polarization occurrence, which is greater than the determination voltage V3 at the time of polarization elimination. Therefore, even if polarization is occurring, if the voltage variation ΔV is greater than the determination voltage V2 during polarization occurrence, which is greater than the determination voltage V3 at the time of polarization elimination, equalization can be performed. Therefore, in this respect as well, the period during which equalization is possible can be extended, and the equalization ability (current x time) can be improved.

[0089] In addition, the cancellation determination unit 31 of the third control unit 30 sets the cancellation determination time t3 based on the state of the battery pack 95. This makes it easier to set the cancellation determination time t3 without being too long or too short, and makes it possible to avoid setting an unnecessarily long cancellation determination time t3. This makes it easier to transition to the equalization discharge α3 after polarization cancellation, which is performed with relatively high accuracy, as early as possible. Therefore, in this respect as well, the equalization ability (current x time) can be improved.

[0090] Furthermore, the next setting unit 34 sets the time until the next judgment timing longer when the voltage variation ΔV at the current judgment timing is large. Therefore, in a situation where the voltage variation ΔV is large and the equalization discharge α3 takes a long time, the time until the next judgment timing can be set longer. Therefore, the number of judgments can be reduced as much as possible to suppress the dark current.

[0091] In addition, the next setting unit 34 sets the time until the next judgment timing longer when the equalization current is small. Therefore, in a situation where the equalization current is small and the equalization discharge α3 takes a long time, the time until the next judgment timing can be set longer. Therefore, in this respect, the number of judgments can be reduced as much as possible to suppress the dark current.

[0092] In this way, the next setting unit 34 sets the time until the next judgment timing based on the time required for the equalization discharge α3. Therefore, unlike a case where the time until the judgment timing is simply set to be long, there is no need to worry about the equalization discharge α3 overshooting due to the discharge switch Sw being kept ON until the next judgment timing.

[0093] [Second embodiment] Next, a second embodiment will be described. In the following embodiments, the same reference numerals will be used for the same or corresponding members as those in the previous embodiments. However, the equalizer itself will be given a different reference numeral for each embodiment. This embodiment will be described based on the first embodiment, focusing on the differences from the first embodiment, and descriptions of the same or similar parts to the first embodiment will be omitted as appropriate.

[0094] 6 is a block diagram showing an equalization device 92 and its periphery in this embodiment. The equalization device 92 has a measurement unit 41 for each cell battery B, instead of the measurement unit 41 having a multiplexer or the like in the first embodiment. Each measurement unit 41 has a measurement circuit 42 that measures the voltage of the corresponding cell battery B, and a microcomputer 43 that controls the measurement circuit 42. A control unit 50 collects the voltages measured by each measurement unit 41.

[0095] The first control unit 10 and the second control unit 20 are provided in the control unit 50, as in the first embodiment. On the other hand, the third control unit 30 is provided in the microcomputer 43 of each measurement unit 41.

[0096] The equalization discharge α1 during charging and the equalization discharge α2 during polarization are controlled by the first control unit 10 and the second control unit 20 in the control unit 50 when both the microcomputer 43 and the control unit 50 are in the ON state and not in the sleep state. After the polarization is eliminated, both the control unit 50 and the microcomputer 43 temporarily go into the sleep state or the OFF state.

[0097] Then, when the judgment timing arrives, while the control unit 50 is in a sleep state or OFF state, the microcomputer 43 wakes up and the third control unit 30 in the microcomputer 43 controls the equalization discharge α3. Then, the next setting unit 34 of the third control unit 30 sets the time until the next judgment timing. The time until the next judgment timing is different for each microcomputer 43. After that, the microcomputer 43 goes into a sleep state or OFF state again until the next judgment timing. By repeating the above, the equalization discharge α3 after polarization elimination is controlled while saving as much power as possible.

[0098] As described above, according to this embodiment, after the polarization is eliminated, while the control unit 50 is in a sleep state or in an OFF state, the microcomputer 43 controls the equalizing discharge α3 and can set the time until the next determination timing. Therefore, the dark current can be further suppressed compared to the state of the first embodiment.

[0099] Furthermore, the microcomputer 43 for each cell battery B sets a different determination timing for each microcomputer 43, and wakes up at a different timing for each microcomputer 43. Therefore, the number of times each microcomputer 43 wakes up can be minimized for each microcomputer 43. Therefore, dark current can be suppressed in this respect as well.

[0100] [Third embodiment] Next, a third embodiment will be described. The third embodiment will be described based on the second embodiment, focusing on the differences, and descriptions of parts that are the same as or similar to the second embodiment will be omitted as appropriate.

[0101] 7 is a block diagram showing an equalization device 93 and its periphery according to this embodiment. Each measurement circuit 42 has a calculation circuit 42c in addition to the microcomputer 43. The third control unit 30 is provided in the calculation circuit 42c.

[0102] The equalization discharge α1 during charging and the equalization discharge α2 during polarization are controlled by the first control unit 10 and the second control unit 20 in the control unit 50 when the arithmetic circuit 42c, the microcomputer 43, and the control unit 50 are in an ON state and not in a sleep state. After the polarization is eliminated, the control unit 50, the microcomputer 43, and the arithmetic circuit 42c temporarily go into a sleep state or an OFF state.

[0103] Then, when the determination timing after the polarization elimination arrives, while the control unit 50 and the microcomputer 43 are in a sleep state or OFF state, the calculation circuit 42c wakes up and the equalization discharge α3 is controlled by the third control unit 30 in the calculation circuit 42c. Then, the next setting unit 34 of the third control unit 30 sets the time until the next determination timing. Thereafter, the calculation circuit 42c goes into a sleep state or OFF state again until the next determination timing. By repeating the above, the equalization discharge α3 after the polarization elimination is controlled while saving as much power as possible.

[0104] As described above, according to this embodiment, in the sleep state of not only the control unit 50 but also the microcomputer 43, the equalizing discharge α3 can be controlled by the arithmetic circuit 42c and the time until the next judgment timing can be set. Therefore, the dark current can be suppressed more than in the second embodiment.

[0105] [Fourth embodiment] Next, a fourth embodiment will be described. The fourth embodiment will be described based on the third embodiment, focusing on the differences, and descriptions of parts that are the same as or similar to the second embodiment will be omitted as appropriate.

[0106] FIG. 8 is a block diagram showing the equalization device 94 and its periphery in this embodiment. The control unit 50 has a third control unit 30. That is, the third control unit 30 is provided in both the control unit 50 and the arithmetic circuit 42c. After the polarization is eliminated, the control unit 50, the microcomputer 43, and the arithmetic circuit 42c maintain a non-sleep ON state until the control of the equalization discharge α3 after the first division elimination is performed. Then, the control of the equalization discharge α3 after the first division elimination is performed by the third control unit 30 in the control unit 50. Then, the next time setting unit 34 in the control unit 50 calculates the time until the next judgment timing for each cell battery B, and transmits it to the third control unit 30 in the corresponding arithmetic circuit 42c.

[0107] Thereafter, similarly to the third embodiment, the control unit 50, the microcomputer 43, and the arithmetic circuit 42c temporarily go into a sleep state or an OFF state. Then, when the determination timing after the second or subsequent polarization cancellation arrives, while the control unit 50 and the microcomputer 43 are in a sleep state or an OFF state, the arithmetic circuit 42c wakes up and controls the equalization discharge α3 by the third control unit 30 in the arithmetic circuit 42c.

[0108] According to this embodiment, the control of the equalizing discharge α3 after the first polarization elimination and the calculation of the next judgment timing can be quickly performed using the CPU, ROM, RAM, etc. of the control unit 50. On the other hand, the control of the equalizing discharge α3 after the second and subsequent polarization eliminations and the calculation of the next judgment timing can suppress dark current as in the third embodiment.

[0109] Although this embodiment is implemented based on the third embodiment, it may be implemented based on the second embodiment instead. In other words, in that case, the control of the equalization discharge α3 after the first polarization elimination and the calculation of the next judgment timing are performed by the third control unit 30 in the control unit 50, and the control of the equalization discharge α3 after the second polarization elimination and the calculation of the next judgment timing are performed by the third control unit 30 in the microcomputer 43.

[0110] [Other embodiments] The embodiment described above can be modified as follows, for example.

[0111] In the first to fourth embodiments, all three of the equalization discharge α1 during charging, the equalization discharge α2 during polarization, and the setting of the cancellation determination time t3 based on the state of the cell battery B are performed. Alternatively, only one or two of these three may be performed.

[0112] In the first to fourth embodiments, for each cell battery B, the voltage of that cell battery B minus the lowest cell voltage Vmin is taken as the "variation voltage ΔV" of that cell battery B. Alternatively, the variation voltage ΔV may be corrected based on the SOC or SOH (State of Health). Specifically, for example, for each cell battery B, the voltage equivalent to the SOC of that cell battery B minus the SOC of the cell battery B with the lowest SOC may be taken as the "variation voltage ΔV" of that cell battery B.

[0113] In the first to fourth embodiments, the external power source 100 performs CC charging and CV charging on the battery pack 95, but CP charging (constant power charging) may be performed instead of or in addition to CC charging. The state determination unit 11 may determine whether CP charging is in progress or not, or whether CC charging or CP charging is in progress, instead of whether CC charging is in progress. The equalization unit 13 may perform equalization on the condition that it is determined that CC charging is in progress, or on the condition that it is determined that CC charging is in progress or CP charging is in progress, instead of performing equalization on the condition that it is determined that CP charging is in progress, or on the condition that CC charging or CP charging is in progress.

[0114] In the first to fourth embodiments, the mitigation judgment unit 21 sets the mitigation judgment time t2 based on all three of the temperature, SOHpw, and SOC of the battery pack 95. Alternatively, the mitigation judgment time t2 may be set based on only one or two of these three, or the mitigation judgment time t2 may be a fixed value.

[0115] In the first to fourth embodiments, the variation determination unit 22 sets the determination voltage V2 during polarization based on all three of the temperature, SOHpw, and SOC of the battery pack 95. Alternatively, the determination voltage V2 during polarization may be set based on only one or two of these three, or the determination voltage V2 during polarization may be set to a fixed value.

[0116] In the first to fourth embodiments, the resolution determination unit 31 sets the resolution determination time t3 based on all three of the temperature, SOHpw, and SOC of the battery pack 95. Alternatively, the resolution determination time t3 may be set based on only one or two of these three, or the resolution determination time t3 may be a fixed value.

[0117] In the first to fourth embodiments, the next setting unit 34 sets the time until the next determination timing based on the voltage variation ΔV and the equalization current at the current determination timing. Alternatively, the time until the next determination timing may be fixed.

[0118] In the first to fourth embodiments, the next setting unit 34 sets the time until the next determination timing based on the voltage variation ΔV and the equalization current. Instead of the equalization current, the next setting unit 34 may set the time until the next determination timing simply based on the resistance of the discharge path in the equalization discharge α3 of the cell battery B. In other words, in this case, when the resistance of the discharge path is large, the time required for the equalization discharge α3 becomes longer, so the time until the next determination timing is set longer.

[0119] In the first to fourth embodiments, the equalization discharges α1 to α3 are used to equalize the charge amounts of the cell batteries B. Alternatively, the charge amounts of the cell batteries B may be equalized by charging a cell battery B with a hypothetical lower charge amount with a cell battery B with a relatively higher charge amount.

[0120] In the first to fourth embodiments, the equalizing current is a typical DC current, but instead, the equalizing current may be a current having a waveform different from a typical DC current, such as a waveform in which a typical DC current is mixed with an AC current.

[0121] In the first to fourth embodiments, the battery pack 95 and the equalization devices 91 to 93 are mounted on the electric vehicle 90. Alternatively, the battery pack 95 and the equalization devices 91 to 93 may be mounted on other devices such as a drone. [Explanation of symbols]

[0122] 11...state determination unit, 12...variation determination unit, 13...equalization unit, 91-94...equalization device, 95...battery pack, ΔV...variation voltage, V1...determined voltage during charging, α1...equalization discharge during charging, α2...equalization discharge during polarization occurrence, α3...equalization discharge after polarization is eliminated.

Claims

1. An equalization device (91-94) for equalizing the charge amounts of a plurality of cell batteries (B) included in a battery pack (95), a state determination unit (11) that determines whether the battery pack is in a predetermined charging state, including at least one of a state in which the battery pack is being charged at a constant current and a state in which the battery pack is being charged at a constant power, and does not include a state in which the battery pack is being charged at a constant voltage; a charge-time variation judgment unit (12) that judges whether a variation voltage (ΔV) indicating the variation in the voltage of each of the cell batteries is greater than a predetermined charge-time judgment voltage (V1); an equalization unit during charging (13) that performs the equalization on condition that the predetermined state of charge is determined and that the voltage variation is determined to be greater than the charging-time determination voltage; An equalization device having

2. The equalization device of claim 1, wherein the state determination unit, when charging the battery pack, determines whether the available voltage (Vf-Vmax), which is the voltage (Vf) of the cell battery when fully charged minus the voltage (Vmax) of the cell battery having the highest voltage in the battery pack, is greater than a predetermined threshold available voltage (Vth), and determines that the battery pack is in the specified charging state if it is determined that the available voltage is greater than the threshold available voltage.

3. 3. The equalization device according to claim 1, wherein the charging variation determination unit sets a voltage value greater than at least a voltage error of the cell batteries caused by the equalization as the charging determination voltage.

4. a relaxation judgment unit (21) that judges whether or not an elapsed time (t) from a charging end timing (T1c) of the battery pack or an elapsed time (t) from a timing (T2c) when a main power switch (98s) of a device (90) in which the battery pack is mounted is switched to OFF is longer than a predetermined relaxation judgment time (t2); a polarization variation determination unit (22) for determining whether a variation voltage (ΔV) indicating the variation in the voltage of each of the cell batteries is greater than a predetermined polarization determination voltage (V2); an equalization unit during polarization (23) that performs the equalization on condition that it is determined that the elapsed time is longer than the relaxation determination time and that the voltage variation is greater than the polarization-time determination voltage; a resolution determination unit (31) that determines whether the elapsed time is longer than a resolution determination time (t3) that is longer than the mitigation determination time; a post-elimination variation determination unit (32) that determines whether the variation voltage is greater than a post-elimination determination voltage (V3) that is smaller than the polarization-time determination voltage; a post-elimination equalization unit (33) that performs the equalization on condition that it is determined that the elapsed time is greater than the elimination judgment time and that the voltage variation is greater than the post-elimination judgment voltage; The equalizer according to any one of claims 1 to 3, comprising:

5. The mitigation determination unit sets the mitigation determination time based on at least a temperature of the battery pack, and sets the mitigation determination time to be smaller when the temperature of the battery pack is higher than a predetermined temperature than when the temperature of the battery pack is lower than the predetermined temperature; or a variable SOHpw indicating that the internal resistance (Ra, Rb) is smaller as the value is larger, and the mitigation determination unit sets the mitigation determination time based on at least the SOHpw of the battery pack, and sets the mitigation determination time to be smaller when the SOHpw of the battery pack is larger than a predetermined value than when the SOHpw is smaller than the predetermined value.

5. The equalizer of claim 4.

6. the polarization variation determination unit sets the polarization determination voltage based on at least a temperature of the battery pack, and sets the polarization determination voltage to be smaller when the temperature of the battery pack is higher than a predetermined temperature than when the temperature of the battery pack is the predetermined temperature; or a variable SOHpw indicating that the internal resistance (Ra, Rb) is smaller as the value is larger, and the polarization variation determination unit sets the polarization determination voltage based on at least the SOHpw of the battery pack, and sets the polarization determination voltage to be smaller when the SOHpw of the battery pack is larger than a predetermined value than when the SOHpw is smaller than the predetermined value; 6. An equalization device according to claim 4 or 5.

7. 7. The equalization device according to claim 4, wherein the resolution determination unit sets the resolution determination time based on a state of the battery pack.

8. The resolution determination unit sets the resolution determination time based on at least a temperature of the battery pack, and sets the resolution determination time to be shorter when the temperature of the battery pack is higher than a predetermined temperature than when the temperature of the battery pack is lower than the predetermined temperature; or a variable SOHpw indicating that the internal resistance (Ra, Rb) is smaller as the value is larger, and the resolution determination unit sets the resolution determination time based on at least the SOHpw of the battery pack, and sets the resolution determination time to be shorter when the SOHpw of the battery pack is larger than a predetermined value compared to when the SOHpw is smaller than the predetermined value.

8. The equalizer of claim 7.

9. The timing at which the resolution determination unit, the post-resolution variation determination unit, and the post-resolution equalization unit determine whether or not to perform the equalization is set as a determination timing, A next setting unit (34) for setting a time until the next determination timing, the next setting unit sets the time until the next determination timing based on at least the voltage variation at the current determination timing, and sets the time until the next determination timing longer when the voltage variation at the current determination timing is greater than a predetermined value than when the voltage variation at the current determination timing is smaller than the predetermined value. An equalizing device according to any one of claims 4 to 8.

10. the next setting unit sets the time until the next determination timing based on the magnitude of resistance of the discharge path of the cell battery, and sets the time until the next determination timing longer when the magnitude of resistance of the discharge path is greater than a predetermined value than when the magnitude of resistance is smaller than the predetermined value.

10. The equalizer of claim 9.

11. the next setting unit measures an equalization current from the voltage of the cell battery and the magnitude of resistance of the discharge path of the cell battery, or from the terminal voltage of a resistor through which a current flows due to the equalization and the magnitude of the resistor, and sets the time until the next determination timing based on the equalization current, and sets the time until the next determination timing longer when the equalization current is smaller than a predetermined value compared to when the equalization current is greater than the predetermined value; An equalization device according to claim 9 or 10.

12. The battery cell includes a measuring unit (41) for measuring the voltage of each of the cell batteries, and a control unit (50) for collecting the voltages measured by each of the measuring units, the measurement unit is provided with the resolution determination unit, the post-resolution variation determination unit, the post-resolution equalization unit, and the next setting unit, At the determination timing, when the control unit is in a sleep state or an OFF state, the resolution determination unit, the post-resolution variation determination unit, and the post-resolution equalization unit in the measurement unit control the equalization, and the next setting unit in the measurement unit sets a time until the next determination timing. An equalizer according to any one of claims 9 to 11.

13. The measurement unit has a measurement circuit (42) that measures the voltage of the cell battery and a microcomputer (43) that controls the measurement circuit, The measurement circuit has an arithmetic circuit (42c) separate from the microcomputer, the arithmetic circuit is provided with the resolution determination unit, the post-resolution variation determination unit, the post-resolution equalization unit, and the next setting unit, At the determination timing, when the microcomputer is in a sleep state or an OFF state, the resolution determination unit, the post-resolution variation determination unit, and the post-resolution equalization unit in the arithmetic circuit control the equalization, and the next setting unit in the arithmetic circuit sets a time until the next determination timing.

13. The equalizer of claim 12.

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