Equalizing Device

Abstract

To improve the equalization capacity (current×time) of an equalization device.SOLUTION: An equalization device 91 performs equalization of the charge amounts of multiple cell batteries B of a battery pack 95. A mitigation determination unit 21 determines whether an elapsed time t from the charging end timing T1c of the battery pack is greater than a predetermined mitigation determination time t2. A polarization equalization unit 23 performs equalization on a condition that the elapsed time is determined to be greater than the mitigation determination time and the voltage variation is determined to be greater than the polarization determination voltage. A post-resolution equalization unit 33 performs equalization on the condition that the elapsed time is determined to be greater than the resolution determination time and the voltage variation is determined to be greater than the post-resolution 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] Japanese Patent Application Publication No. 2018-125977 Summary of the Invention [Problem to be solved by the invention]

[0004] When charging a battery pack, a charging current flows from the positive electrode to the negative electrode within each cell battery, causing the terminal voltage of each cell battery to rise by the amount of the internal resistance multiplied by the charging current. Hereinafter, this rise in terminal voltage will be 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 (discharged), a charging current flows from the negative electrode to the positive electrode within each cell battery, causing a drop in the terminal voltage of each cell battery by the amount of the internal resistance multiplied by the current used. Hereinafter, this drop in terminal voltage will be referred to as "use polarization." Furthermore, use polarization in each cell battery does not immediately subside even after the battery pack's use of power has ended. This is because, just as after charging has ended, it takes time for the charge stored in the capacitance component to discharge.

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

[0007] However, the higher the capacity of a battery pack, the greater the self-discharge, which tends to lead to greater variations in charge amount and therefore the longer the time required for equalization. Furthermore, depending on how the battery pack is used, such as when the battery pack's power is used for various purposes, the battery pack's power usage period may be longer and the period after the polarization is eliminated may be 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 view 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 first means is an equalization device (91-94) that equalizes the charge amounts of the plurality of cell batteries (B) included in the battery pack (95), a relaxation determination unit (21) that determines 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) equipped with the battery pack is turned OFF is longer than a predetermined relaxation determination time (t2); a polarization variation determination unit (22) that determines 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 (23) during polarization that performs the equalization on the condition that it is determined that the elapsed time is longer than the relaxation determination time and that the voltage variation is larger 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 the condition that it is determined that the elapsed time is longer than the elimination determination time and that the voltage variation is larger than the post-elimination determination voltage; It has. [Brief explanation of the drawings]

[0010] [Figure 1] A circuit diagram showing the equalization device and its periphery according to the first embodiment. [Figure 2] Graph showing the changes in voltage and current during and after charging of the battery pack [Figure 3] Graph showing the voltage and current changes during the period when the main power is ON and the period thereafter [Figure 4] Block diagram showing the control unit and its surroundings [Figure 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] A block diagram showing a control unit and its periphery in a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] 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 of the invention.

[0012] [First embodiment] 1 is a circuit diagram showing an equalization device 91 and its periphery according to this embodiment. Hereinafter, being electrically connected will simply be 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.

[0013] 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 inter-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 inter-terminal voltage in the battery pack 95 will be referred to as the "minimum cell voltage Vmin." The voltage of a cell battery B when fully charged will be referred to as the "fully charged cell voltage Vf," and the fully charged cell voltage Vf minus the maximum cell voltage Vmax will be referred to as the "free voltage (Vf-Vmax)." For each cell battery B, the voltage of that cell battery B minus the minimum cell voltage Vmin will be referred to as the "variation voltage ΔV."

[0014] 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 will be referred to as the "main power ON state," and the OFF state will be referred to as the "main power OFF state." The period in which the main power is ON will be referred to as the "main power ON period," and the period in which the main power is OFF will be referred to as the "main power OFF period."

[0015] 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 period when the main power supply is OFF, and can supply power to both the general load 98 and the dark current load 97 during a period when the main power supply is ON. 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.

[0016] 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 the "charging state," and the state in which the battery pack 95 is not being charged will be referred to as the "non-charging state."

[0017] 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 and 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 and Rb.

[0018] Next, we will explain the problem to be solved by this embodiment and an outline of the means for solving it. When the battery pack 95 is being charged, a charging current flows in each cell battery B in the charging direction, causing the terminal voltage of the cell battery B to increase by an amount equal to the internal resistance (Ra + Rb) × 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 will be referred to as "charging polarization." This charging polarization does not immediately subside even after charging of the battery pack 95 is completed. 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.

[0019] On the other hand, when the main power supply is ON, a large amount of current flows in each cell battery B in the discharging direction, causing the terminal voltage of the cell battery B to decrease by an amount equal to the internal resistance (Ra + Rb) × 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 decrease in terminal voltage of each cell battery B due to the current used will be referred to as "usage polarization." This usage polarization does not immediately subside even after the battery pack 95 has stopped using power. As mentioned above, the charge in 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.

[0020] In the following, charging polarization and operating polarization will be collectively referred to simply as "polarization." For these reasons, the equalization period for reducing the voltage variation ΔV of each cell battery B is generally limited to the period after polarization is eliminated. This is because the voltage variation ΔV cannot be accurately determined until the polarization is resolved.

[0021] However, the higher the capacity of the battery pack 95, the greater the self-discharge, which tends to increase the variation in charge amount and the longer the time required for equalization. Also, depending on how the battery pack 95 is used, such as when the power of the battery pack 95 is used for purposes other than driving the electric vehicle 90, the period during which the power of the battery pack 95 is used may be longer and the period after the elimination of polarization during use may be shorter. Therefore, even in these cases, if the equalization period is limited to the period after the elimination of polarization, the equalization capacity (current x time) of the equalizer 91 may be insufficient.

[0022] 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 and polarization occurrence, provided that certain requirements are met, more roughly than after polarization elimination. Furthermore, by changing the start timing of equalization discharge after polarization elimination depending on the state of the battery pack 95, the start timing is made as early as possible.

[0023] Next, we will explain the circuit configuration of the equalizer 91. The equalizer 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.

[0024] The positive side wiring Lp is connected to the positive terminal of the cell battery B via the connection wiring M, and the negative side wiring Ln is connected to the negative terminal of the cell battery B via the connection wiring M. The positive side wiring Lp is provided with a positive side resistance Rp, and the negative side wiring Ln is provided with a negative side resistance Rn. However, the negative side resistance Rn for each cell battery B is shared (shared) with the positive side resistance Rp for the cell battery B that is one level lower in potential than that cell battery B.

[0025] 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 the part of the positive wiring Lp closer to the cell battery B than the positive resistance Rp and the part of the negative wiring Ln closer to the cell battery B than the negative resistance Rn.

[0026] The discharge switch Sw is a semiconductor switch such as a MOSFET or IGBT. The positive terminal (source terminal in the figure) of the discharge switch Sw is connected to the positive wiring Lp on the side opposite the cell battery B side from the positive resistance Rp. On the other hand, the negative terminal (drain terminal in the figure) of the discharge switch Sw is connected to the negative wiring Ln on the side opposite the cell battery B side from the negative resistance Rn.

[0027] 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 this discharge switch Sw is turned ON will be referred to as the "equalization current," and the discharge of the cell battery B by this equalization current will be referred to as the "equalization discharge."

[0028] During equalization discharge of each cell battery B, an equalization current flows from the negative electrode to the positive electrode of the cell battery B, causing a drop in the terminal voltage by the amount of the internal resistance (Ra + Rb) × the equalization current. At this time, charge is stored in the capacitance component Cb until the terminal voltage of the capacitance component Cb becomes equal to the terminal voltage of the internal resistance Rb. Hereinafter, this drop in terminal voltage due to the equalization current is referred to as "equalization polarization." This equalization polarization does not immediately subside even after the equalization discharge is completed. As mentioned above, the charge in 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. Due to this equalization polarization, equalization discharge α1 during charging is performed only during constant current charging (CC charging) and not during constant voltage charging (CV charging). Details of this will be described later.

[0029] Next, the control system of the equalizer 91 will be described. The equalizer 91 further includes a measurement unit 41, multiple switch drive circuits 49, and a control unit 50. The measurement unit 41, multiple switch drive circuits 49, and 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 side resistor Rn as the voltage of the cell battery B corresponding to the series connection.

[0030] 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 that discharge switch Sw.

[0031] 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.

[0032] 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 supply 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. Therefore, the external power supply 100 performs CC charging from the charging start timing T1a to the charge switching timing T1b before the charging end timing T1c, and performs CV charging from the charge switching timing T1b to the charging end timing T1c.

[0033] 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.

[0034] Next, the reason why the aforementioned 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 frequency are required during CV charging compared to CC charging. Nevertheless, if equalization polarization occurs, it becomes necessary to reduce at least one of the measurement accuracy and frequency of the voltage of the battery pack 95.

[0035] In other words, in order to maintain the accuracy of measuring the voltage of the battery pack 95, it is necessary to ensure a sufficiently long relaxation time for equalization polarization, i.e., a sufficiently long time from the end of equalization discharge to voltage measurement. Therefore, it is necessary to reduce the frequency of voltage measurement. As a result, it is not possible to ensure a sufficient frequency of voltage measurement for performing CV charging. On the other hand, if the frequency of voltage measurement is not reduced, it is not possible to ensure a sufficient relaxation time for equalization polarization. As a result, the accuracy of voltage measurement decreases. As a result, it is not possible to ensure a sufficient accuracy of voltage measurement for performing CV charging.

[0036] Therefore, as described above, the control unit 50 performs the equalization discharge α1 only during CC charging (T1a to T1b) when charging (T1a to T1c). 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 when CV charging. However, this is acceptable because the voltage measurement accuracy and measurement frequency are not as important during CC charging as they are during CV charging.

[0037] Next, the period after charging of the battery pack 95 is completed (T1c~) will be described. Hereinafter, the time t elapsed since the timing T1c at which charging of the battery pack 95 is completed will be referred to as the "time t elapsed after charging is completed." While the time t elapsed since charging is completed is short, charge polarization has not yet fully subsided. Therefore, the voltage of each cell battery B becomes higher by the amount of charge polarization than the voltage corresponding to the charge level 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 charge polarization of each cell battery B, than the voltage corresponding to the charge level of that battery pack 95.

[0038] Therefore, the equalizing device 91 performs a relatively rough equalizing discharge α2 during polarization generation during the period before the elimination of such charge polarization. Specifically, this equalizing discharge α2 during polarization generation is performed during the period from relaxation timing Td, when the charge polarization is relaxed to a certain extent, to elimination timing Te, when the charge polarization can be considered to have been eliminated (Td to Te). Then, after elimination timing Te, an equalizing discharge α3 after polarization elimination is performed with relatively high accuracy.

[0039] As indicated by the dashed line in Fig. 3, the relaxation rate of the charge polarization becomes slower as the temperature of the battery pack 95 decreases, and conversely, becomes faster as the temperature of the battery pack 95 increases. Therefore, the relaxation timing Td and elimination timing Te of the charge polarization become slower as the temperature of the battery pack 95 decreases, and conversely, become faster as the temperature of the battery pack 95 increases, as indicated by the dashed arrow in Fig. 3.

[0040] 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, during the main power ON period (T2b to T2c), the current used is larger than during the main power OFF period (up to T2b, T2c).

[0041] Hereinafter, the period after the end of the main power ON period (T2b to T2c) will be referred to as "after the main power OFF," and the time elapsed from the end of the main power ON period (T2b to T2c) will be referred to as "the elapsed time t after the main power OFF." While the elapsed time t after the main power OFF is short, the polarization has not yet fully subsided. Therefore, the voltage of each cell battery B becomes lower by 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 Pu, which is the integrated value of the polarization of use of each cell battery B, than the voltage corresponding to the charge level of that battery pack 95.

[0042] Therefore, as in the case after the end of charging described above, the equalizer 91 performs a relatively rough equalization discharge α2 during polarization generation during the period before the elimination of the polarization in use. Specifically, this equalization discharge α2 during polarization generation is performed during the period from the relaxation timing Td, when the polarization in use is relaxed to a certain extent, to the elimination timing Te, when the polarization in use can be considered to have been eliminated (Td to Te). Then, after the elimination timing Te, an equalization discharge α3 after the polarization elimination is performed with relatively high accuracy.

[0043] 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 generation, and a third control unit 30 that controls the equalization discharge α3 after polarization is eliminated.

[0044] 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. Note that the variation determination unit 12 referred to 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. Furthermore, the equalization unit 13 referred to 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.

[0045] 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.

[0046] The variation determination unit 12 determines whether the voltage variation ΔV of each cell battery B is greater than the determination voltage V1 during charging. The determination voltage V1 during charging is a threshold voltage for determining whether or not to perform equalization discharge α1 during CC charging. The determination voltage V1 during charging is set to a value greater than the error in the voltage variation ΔV due to equalization polarization, assuming the error. Therefore, if the measurement frequency of the voltage of the battery pack 95 is reduced without reducing the measurement accuracy, it is not necessary to set the determination voltage V1 during charging higher. On the other hand, if the measurement accuracy is reduced without reducing the voltage measurement frequency, it is necessary to set the determination voltage V1 during charging higher by the amount of the reduction. The error in the voltage variation ΔV due to equalization polarization may be measured in advance, for example, by experiment or may be calculated by simulation analysis.

[0047] The equalization unit 13 performs equalization discharge α1 during charging on the 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.

[0048] 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, as distinguished from the other variation determination units 12 and 32, is a "polarization variation determination unit" that performs variation determination while polarization is occurring. The equalization unit 23, as distinguished from the other equalization units 13 and 33, is a "polarization equalization unit" that performs variation determination while polarization is occurring. Hereinafter, the elapsed time t after charging is completed and the elapsed time t after the main power is turned off will be collectively referred to simply as "elapsed time t."

[0049] The mitigation determination unit 21 determines whether the elapsed time t is greater than the mitigation determination time t2 after charging is completed and after the main power is turned off. The mitigation determination time t2 is a threshold time used to determine whether the charging polarization or usage polarization of the cell battery B has been mitigated to a predetermined standard or more. The mitigation determination unit 21 sets the mitigation determination 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. Details of this are explained below.

[0050] Hereinafter, a case where the temperature is higher than a predetermined temperature will be simply referred to as a "high case" compared to a case where the temperature is lower than the predetermined temperature. A case where the temperature is higher than a predetermined value will be simply referred to as a "large case." A case where the temperature is lower than a predetermined value will be simply referred to as a "small case" compared to a case where the temperature is higher than the predetermined value.

[0051] 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 a shorter mitigation determination time t2 when the battery pack 95 has a higher temperature because polarization is mitigated more quickly. Furthermore, the mitigation determination unit 21 sets the mitigation determination time t2 also based on SOHpw (State Of Health power). The SOHpw is a variable that indicates that the larger the value, the smaller the internal resistances Ra and Rb. Therefore, the mitigation determination unit 21 sets a shorter mitigation determination time t2 when the SOHpw of the battery pack 95 is larger because the internal resistances Ra and Rb are smaller and polarization is mitigated more quickly.

[0052] Furthermore, the mitigation determination unit 21 changes the mitigation determination time t2 based on the SOC (State Of Charge) that indicates the state of charge of the battery pack 95. Specifically, for example, in this embodiment, after charging is completed, if the SOC of the battery pack 95 at the charging completion timing T1c is small, that is, if the charged amount is small, the charging polarization is more likely to be small, and therefore 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, if the power usage is small, the usage polarization is more likely to be small, and therefore the mitigation determination time t2 is set to be short.

[0053] 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 serves as a threshold for determining whether or not to perform equalization discharge α2 during polarization. This determination voltage V2 during polarization is set taking into account the following error. That is, equalization discharge α2 during polarization is performed without waiting for the polarization to be resolved in each cell battery B. Therefore, an error due to polarization is included in the measured voltage of each cell battery B. Therefore, the variation determination unit 22 sets a voltage value that is 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. Note that the error due to polarization may be measured in advance, for example, by experiment, or calculated by simulation analysis, etc.

[0054] As with the relaxed judgment time t2, the judgment voltage V2 during this polarization occurrence 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.

[0055] Specifically, the variation determination unit 22 sets the determination voltage V2 during polarization to a smaller value when the temperature of the battery pack 95 is high because polarization is alleviated more quickly. Furthermore, the variation determination unit 22 sets the determination voltage V2 during polarization to a smaller value when the SOHpw of the battery pack 95 is high because the internal resistances Ra and Rb are smaller and polarization is alleviated more quickly.

[0056] 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, after charging is completed, if the SOC of the battery pack 95 at the charge completion timing T1c is small, that is, if the charge amount is small, the charging polarization is more likely to be small, and therefore the determination voltage V2 during polarization occurrence 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, if the power usage amount is small, the usage polarization is more likely to be small, and therefore the determination voltage V2 during polarization occurrence is set to be small.

[0057] 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 equalization discharge α2 on the cell battery B during polarization occurrence, provided 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.

[0058] Next, the third control unit 30 will be described. The third control unit 30 has a elimination determination unit 31, a variation determination unit 32, an equalization unit 33, and a next setting unit 34. The variation determination unit 32, when distinguished from the other variation determination units 12 and 22, is a "post-elimination variation determination unit" that performs variation determination after polarization elimination. The equalization unit 33, when distinguished from the other equalization units 13 and 23, is a "post-elimination equalization unit" that performs equalization discharge α3 after polarization elimination.

[0059] The cancellation determination unit 31 determines whether the elapsed time t after charging is completed and after the main power is turned off is longer than a cancellation determination time t3, which is longer than the aforementioned mitigation determination time t2. The cancellation determination time t3 is a threshold time for determining whether the polarization of the cell battery B has been resolved. As with the mitigation determination time t2, the cancellation determination 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.

[0060] That is, the elimination determination unit 31 sets the elimination determination time t3 to be shorter when the temperature of the battery pack 95 is higher because polarization is eliminated more quickly. Furthermore, the elimination determination unit 31 sets the elimination determination time t3 to be shorter when the SOHpw of the battery pack 95 is larger because the internal resistances Ra and Rb are smaller and the polarization Pu is eliminated more quickly.

[0061] 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 low, that is, if the charge amount is small, the charging polarization is more likely to be small, and therefore the resolution determination time t3 is set to be short. On the other hand, after turning off the main power, if the SOC of the battery pack 95 at the turn-off timing T2c is high, that is, if the power usage is small, the usage polarization is more likely to be small, and therefore the resolution determination time t3 is set to be short.

[0062] The variation determination unit 32 determines whether the variation voltage ΔV for each cell battery B is greater than the post-polarization elimination determination voltage V3. The post-polarization elimination determination voltage V3 is a threshold voltage for determining whether or not to perform equalization discharge α3 after polarization elimination. This post-polarization elimination determination voltage V3 is smaller than both the determination voltage V1 during charging and the determination voltage V2 during polarization. Therefore, this post-polarization elimination equalization discharge α3 is performed with higher accuracy than both the equalization discharge α1 during charging and the equalization discharge α2 during polarization.

[0063] When performing this equalization discharge α3 after polarization elimination, unlike when performing equalization discharge α2 during polarization, polarization does not appear in the voltage measurement values ​​of each cell battery B. Therefore, it is sufficient for the variation determination unit 32 to set a voltage value that is at least greater than the measurement error of the voltage of the cell battery B by the measurement unit 41 as the determination voltage V3 after polarization elimination so that the measurement error can be absorbed.

[0064] 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 equalization discharge α3 after polarization elimination on the cell battery B, provided 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.

[0065] Next, the next setting unit 34 of the third control unit 30 will be described. Hereinafter, the timing at which the elimination determination unit 31, the variation determination unit 32, and the equalization unit 33 determine whether or not to perform equalization discharge α3 after polarization elimination will be 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.

[0066] Specifically, the next setting unit 34 first sets the time until the next determination timing based on the voltage variation ΔV of the cell batteries B at the current determination timing. In other words, the next setting unit 34 sets the time until the next determination timing longer when the voltage variation ΔV of the cell battery B with the smallest voltage variation ΔV among the cell batteries B to undergo equalization discharge α3 is large, because the time required for 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 to undergo equalization discharge α3 is set as the time until the next determination timing.

[0067] 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.

[0068] The equalization current may be measured using an ammeter or calculated. Specifically, the equalization current may be calculated by dividing the voltage of cell battery B by the magnitude of the resistance of the entire discharge path in equalization discharge α3 of cell battery B. Alternatively, instead of the above calculation method, the equalization current may be calculated by dividing the voltage between the terminals of a predetermined resistor (e.g., positive electrode resistor Rp) through which the equalization current flows by the magnitude of the resistor.

[0069] Next, the startup state of the control unit 50 will be described. When the control unit 50 is in an ON state (not in sleep mode), it controls the equalization discharge α1 during charging and the equalization discharge α2 during polarization. After polarization elimination, the control unit 50 temporarily enters a sleep state or an OFF state. When the determination timing arrives, the control unit 50 wakes up from the sleep state or the OFF state, and 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 control the equalization discharge α3. The next setting unit 34 in the third control unit 30 then sets the time until the next determination timing. Thereafter, the control unit 50 enters a sleep state or an OFF state again until the next determination timing arrives. By repeating the above process, the equalization discharge α3 after polarization elimination is controlled while saving as much power as possible.

[0070] 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 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 process 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 a power-off state (S101: YES), it is determined in the following S102 whether the battery is in a charging state. If it is determined that the battery is in a charging state (S102: YES), the process proceeds to S111 to determine whether to perform equalizing discharge α1 during charging.

[0071] 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 then 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, where it is determined whether to continue with the equalizing discharge α1 during charging.

[0072] In S115, the voltage variation ΔV for each cell battery B is detected, and the charging determination voltage V1 is calculated. In the following S116, it is determined whether the voltage variation ΔV for each cell battery B is greater than the charging determination voltage V1. If it is determined that it is greater than the charging determination voltage V1 (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 smaller than the charging determination voltage V1 (S116: NO), the discharge switch Sw corresponding to that cell battery B is turned OFF, and the flow ends.

[0073] 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 turned 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.

[0074] In S121, the elapsed time t, the mitigation determination time t2, and the resolution determination time t3 are calculated. In the following S122, it is determined whether the elapsed time t is greater than the mitigation determination time t2 and less than the resolution determination time t3. If it is determined that the requirements are met (S122: YES), the process proceeds to S125 to determine whether to perform equalization discharge α2 during polarization occurrence.

[0075] In S125, the voltage variation ΔV for each cell battery B is calculated, and the reference 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 reference voltage V2 during polarization. If it is determined that the voltage variation ΔV is greater than the reference 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 reference voltage V2 during polarization (S126: NO), the discharge switch Sw corresponding to that cell battery B is turned OFF, and the flow ends.

[0076] On the other hand, in the backward S122, if it is determined that the requirement (t2 < t < t3) is not satisfied (S122: NO), it means that the elapsed time t is less than the relaxation determination time t2 or greater than the dissipation determination time t3. Therefore, in order to determine whether to perform the equalization discharge α3 after polarization dissipation, the process proceeds to S132.

[0077] In S132, it is determined whether the elapsed time t is greater than the dissipation determination time t3. If it is determined that the elapsed time t is less than the dissipation determination time t3 (S132: NO), since it means that the elapsed time t is less 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, if it is determined in S132 that the elapsed time t is greater than the dissipation determination time t3 (S132: YES), the process proceeds to S135 in order to determine whether to continue performing the equalization discharge α3 after polarization dissipation.

[0078] In S135, the variation voltage ΔV for each cell battery B is calculated, and the determination voltage V3 after polarization dissipation is calculated. In the subsequent S136, for each cell battery B, it is determined whether the variation voltage ΔV is greater than the determination voltage V3 after polarization dissipation. If it is determined that the variation voltage ΔV is greater than the determination voltage V3 after polarization dissipation (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, if it is determined in S136 that the variation voltage ΔV is less than the determination voltage V3 after polarization dissipation (S136: NO), the process proceeds to S138, turns off the discharge switch Sw corresponding to that cell battery B, and then ends the flow.

[0079] 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, SOHpw, and SOC of the battery pack 95, 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.

[0080] 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 (from T1c) but also during charging (from T1a to T1c). This extends the period during which equalization is possible, thereby improving the equalization capability (current x time).

[0081] Furthermore, this equalization is performed only when 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 as highly as during CV charging, which controls charging based on voltage. Therefore, even if voltage measurement accuracy and frequency decrease due to equalization during CC charging, this is not a problem compared to CV charging.

[0082] 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 a decrease in voltage measurement accuracy and measurement frequency due to equalization.

[0083] Furthermore, the state determination unit 11 determines that the battery pack 95 is being CC charged on the condition that the available voltage (Vf-Vmax) is determined to be 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).

[0084] Furthermore, the variation determination unit 12 sets a voltage value 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 risk of the voltage error causing unnecessary discharge of the voltage of the cell battery B, which does not need to be subjected to the equalization discharge α1.

[0085] Furthermore, when it is determined that the elapsed time t is longer than the relaxation determination time t2, the equalizer 23 of the second control unit 20 performs equalization discharge α2 during polarization occurrence, provided 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 when polarization is occurring, equalization can be performed 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. Therefore, in this respect as well, the period during which equalization is possible can be extended, and the equalization capability (current × time) can be improved.

[0086] Furthermore, the elimination determination unit 31 of the third control unit 30 sets the elimination determination time t3 based on the state of the battery pack 95. This makes it easier to set the elimination determination time t3 just right, and avoids setting an unnecessarily long elimination determination time t3. This makes it easier to transition to the post-polarization equalization discharge α3, which is performed with relatively high accuracy, as early as possible. Therefore, this also improves the equalization capability (current x time).

[0087] Furthermore, the next setting unit 34 sets the time until the next determination timing longer when the voltage variation ΔV at the current determination timing is large. Therefore, in a situation where the voltage variation ΔV is large and the equalizing discharge α3 takes a long time, the time until the next determination timing can be set longer. Therefore, the number of determinations can be reduced as much as possible to suppress dark current.

[0088] Furthermore, the next setting unit 34 sets the time until the next determination 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 determination timing can be set longer. Therefore, in this respect, the number of determinations can be reduced as much as possible to suppress dark current.

[0089] In this way, the next setting unit 34 sets the time until the next determination timing based on the time required for the equalization discharge α3. Therefore, unlike when the time until the determination timing is simply set to be long, there is no risk of the equalization discharge α3 overshooting due to the discharge switch Sw being kept ON until the next determination timing.

[0090] [Second embodiment] Next, a second embodiment will be described. In the following embodiments, the same reference numerals will be used to designate components that are the same as or correspond to those in the previous embodiments. However, different reference numerals will be used for the equalization device itself in each embodiment. This embodiment will be described based on the first embodiment, focusing on differences from the first embodiment, and descriptions of components that are the same as or similar to the first embodiment will be omitted as appropriate.

[0091] 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 and 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.

[0092] 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.

[0093] 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 sleep mode. After polarization is eliminated, both the control unit 50 and the microcomputer 43 temporarily enter the sleep state or the OFF state.

[0094] Then, when the determination 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 determination timing. The time until the next determination timing is different for each microcomputer 43. After that, the microcomputer 43 again enters a sleep state or OFF state until the next determination timing arrives. By repeating the above process, the equalization discharge α3 after polarization elimination is controlled while saving as much power as possible.

[0095] As described above, according to this embodiment, after the polarization is eliminated, the equalizing discharge α3 is controlled by the microcomputer 43 while the control unit 50 is in the sleep state or OFF state, and the time until the next determination timing can be set. Therefore, the dark current can be further suppressed compared to the state of the first embodiment.

[0096] Furthermore, the microcomputer 43 for each cell battery B is set to a different determination timing 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.

[0097] [Third embodiment] Next, a third embodiment will be described. This 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.

[0098] 7 is a block diagram showing the equalization device 93 and its periphery according to this embodiment. Each measurement circuit 42 has a calculation circuit 42c separate from the microcomputer 43. The third control unit 30 is provided within the calculation circuit 42c.

[0099] 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 sleep mode. After polarization is eliminated, the control unit 50, the microcomputer 43, and the arithmetic circuit 42c temporarily enter a sleep state or an OFF state.

[0100] Then, when the time comes to make a judgment after the polarization has been eliminated, while the control unit 50 and the microcomputer 43 are in a sleep or OFF state, the arithmetic circuit 42c wakes up and the third control unit 30 in the arithmetic circuit 42c controls the equalization discharge α3. Then, the next setting unit 34 of the third control unit 30 sets the time until the next judgment time. Thereafter, the arithmetic circuit 42c again goes into a sleep or OFF state until the next judgment time. By repeating the above process, the equalization discharge α3 after the polarization has been eliminated is controlled while saving as much power as possible.

[0101] As described above, according to this embodiment, the equalizing discharge α3 can be controlled by the arithmetic circuit 42c and the time until the next determination timing can be set while not only the control unit 50 but also the microcomputer 43 is in a sleep state. Therefore, the dark current can be suppressed more than in the second embodiment.

[0102] [Fourth embodiment] Next, a fourth embodiment will be described. This 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.

[0103] 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 both in the control unit 50 and in the arithmetic circuit 42c. After polarization elimination, the control unit 50, the microcomputer 43, and the arithmetic circuit 42c maintain an ON state (not in sleep mode) until control of the equalization discharge α3 after the first division elimination is performed. Then, 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 setting unit 34 in the control unit 50 calculates the time until the next judgment timing separately for each cell battery B and transmits it to the third control unit 30 in the corresponding arithmetic circuit 42c.

[0104] Thereafter, as in the third embodiment, the control unit 50, the microcomputer 43, and the arithmetic circuit 42c temporarily enter a sleep state or an OFF state. Then, when the determination timing after the second or subsequent polarization elimination arrives, the arithmetic circuit 42c wakes up while the control unit 50 and the microcomputer 43 are in a sleep state or an OFF state, and the third control unit 30 in the arithmetic circuit 42c controls the equalization discharge α3.

[0105] According to this embodiment, the control of the equalization discharge α3 after the first polarization elimination and the calculation of the next determination timing can be quickly performed using the CPU, ROM, RAM, etc. of the control unit 50. On the other hand, the control of the equalization discharge α3 after the second and subsequent polarization eliminations and the calculation of the next determination timing can suppress dark current as in the third embodiment.

[0106] Although this embodiment is implemented based on the third embodiment, it may alternatively be implemented based on the second embodiment. In other words, in that case, the control of the equalizing discharge α3 after the first polarization elimination and the calculation of the next determination timing are performed by the third control unit 30 in the control unit 50, and the control of the equalizing discharge α3 after the second polarization elimination and the calculation of the next determination timing are performed by the third control unit 30 in the microcomputer 43.

[0107] [Other embodiments] The embodiment described above can be modified as follows, for example.

[0108] In the first to fourth embodiments, all three of the equalization discharge α1 during charging, the equalization discharge α2 during polarization occurrence, 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.

[0109] 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.

[0110] In the first to fourth embodiments, the external power supply 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 whether CC charging or CP charging is in progress, instead of determining whether CC charging is in progress. The equalization unit 13 may perform equalization on the condition that CP charging is in progress, or on the condition that CC charging or CP charging is in progress, instead of performing equalization on the condition that CC charging is in progress.

[0111] In the first to fourth embodiments, the mitigation determination unit 21 sets the mitigation determination time t2 based on all three of the temperature, SOHpw, and SOC of the battery pack 95. Alternatively, the mitigation determination time t2 may be set based on only one or two of these three, or the mitigation determination time t2 may be a fixed value.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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 magnitude of the resistance of the discharge path in the equalization discharge α3 of the cell battery B. In other words, in this case, the time required for the equalization discharge α3 becomes longer when the resistance of the discharge path is large, so the time until the next determination timing is set longer.

[0116] 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 using a cell battery B with a relatively higher charge amount.

[0117] In the first to fourth embodiments, the equalizing current is a general DC current, but instead, it may be a current with a waveform different from that of a general DC current, such as a waveform in which an AC waveform is mixed with a general DC current.

[0118] 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]

[0119] 11...state determination unit, 12...variation determination unit, 13...equalization unit, 91 to 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 elimination.

Claims

1. An equalization device (91-94) that equalizes the charge amounts of a plurality of cell batteries (B) included in a battery pack (95), a relaxation determination unit (21) that determines 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) equipped with the battery pack is switched OFF is longer than a predetermined relaxation determination time (t2); a polarization variation determination unit (22) that determines 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 (23) during polarization that performs the equalization on the condition that it is determined that the elapsed time is longer than the relaxation determination time and that the voltage variation is larger 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 the condition that it is determined that the elapsed time is longer than the elimination determination time and that the voltage variation is larger than the post-elimination determination voltage; An equalization device having:

2. the mitigation determination unit sets the mitigation determination time based on at least the temperature of the battery pack, and sets the mitigation 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 The mitigation determination unit sets the mitigation determination time based on at least the SOHpw of the battery pack, with the SOHpw being a variable indicating that the internal resistance (Ra, Rb) is smaller as the value increases, and sets the mitigation determination time to be shorter when the SOHpw of the battery pack is larger than a predetermined value than when the SOHpw is smaller than the predetermined value.

2. The equalizer of claim 1.

3. the polarization variation determination unit sets the polarization determination voltage based on at least the 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 higher than the predetermined temperature; or The polarization variation determination unit sets the polarization determination voltage based on at least the SOHpw of the battery pack, with the SOHpw being a variable indicating that the internal resistance (Ra, Rb) decreases as the value increases, 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.

3. An equalization device according to claim 1 or 2.

4. 4. The equalization device according to claim 1, wherein the resolution determination unit sets the resolution determination time based on a state of the battery pack.

5. 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 The SOHpw is a variable that indicates that the internal resistance (Ra, Rb) is smaller as the value thereof increases, 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 than when the SOHpw is smaller than the predetermined value.

5. The equalizer of claim 4.

6. An equalization device (91-94) that equalizes the charge amounts of multiple cell batteries (B) in a battery pack (95), a resolution determination unit (31) that determines 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) equipped with the battery pack is switched OFF is longer than a predetermined resolution determination time (t3); a post-elimination variation determination unit (32) that determines whether a variation voltage (ΔV) indicating the variation in the voltage of each of the cell batteries is greater than a predetermined post-elimination determination voltage (V3); a post-elimination equalization unit (33) that performs the equalization on the condition that it is determined that the elapsed time is longer than the elimination determination time and that the voltage variation is larger than the post-elimination determination voltage, the resolution determination unit sets the resolution determination time based on a state of the battery pack, 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 The SOHpw is a variable that indicates that the larger the value, the smaller the internal resistance (Ra, Rb), 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 greater than a predetermined value than when it is smaller than the predetermined value.

7. 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 the 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. The equalizer according to any one of claims 1 to 6.

8. 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; 8. The equalizer of claim 7.

9. The next setting unit measures the equalization current from the voltage of the cell battery and the magnitude of the resistance of the discharge path of the cell battery, or from the voltage between the terminals of a resistor through which a current flows due to the equalization and the magnitude of the resistance, and sets the time until the next judgment timing based on the equalization current, and sets the time until the next judgment timing longer when the equalization current is smaller than a predetermined value than when it is larger than the predetermined value.

9. An equalization device according to claim 7 or 8.

10. The system has a measuring unit (41) for measuring the voltage of each cell battery, and a control unit (50) for collecting the voltages measured by each measuring unit, 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 7 to 9.

11. 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 the time until the next determination timing.

11. The equalizer of claim 10.

Images