Battery voltage equalization device

Abstract

The battery voltage equalization device (1) for an on-board battery (Bm) consisting of multiple batteries (B) connected in series includes: a voltage measuring unit (2) for measuring the battery voltage of each battery (B); a current measuring unit (4) for measuring the charging and discharging current (I) of the on-board battery (Bm); a cell balancing unit (7) for equalizing the battery voltage of each battery (B); and a control unit (8) for voltage equalization control via the cell balancing unit (7) based on the battery voltage measured by the voltage measuring unit (2). The control unit (8) starts voltage equalization control based on the condition that voltage equalization control is required based on the voltage of each battery and that the discharge current (Id) of the on-board battery (Bm) measured by the current measuring unit (4) is stable.

Description

Technical Field

[0001] This invention relates to a battery voltage equalization device. Background Technology

[0002] Electric vehicles and other mobile vehicles are equipped with battery packs, such as those composed of lithium-ion batteries, as a power source for driving. In such battery packs, multiple battery cells are connected in series to output a desired voltage. However, it is well known that if the individual battery voltages of the multiple series-connected battery cells are not uniform, problems such as limited chargeable and dischargeable energy will occur. Therefore, such battery packs mostly use cell balancing circuits, such as those disclosed in Patent Document 1, to equalize the battery voltage.

[0003] More specifically, Patent Document 1 discloses an active cell balancing circuit using a transformer, which controls the conduction of a transformer that can convert the output voltage of the battery pack and apply charging voltage to each battery cell in parallel, thereby charging the battery cells with relatively low battery voltage and thus equalizing the battery voltage.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 11-176483 Summary of the Invention

[0007] The technical problem that the invention aims to solve

[0008] However, the battery voltage of a vehicle battery pack is unstable during driving, thus requiring cell balancing control when the vehicle is stationary, such as when the ignition is off. Therefore, conventional cell balancing circuits have fewer opportunities to perform cell balancing control during extended periods of continuous vehicle operation, potentially leading to increased voltage deviations within the battery pack. Furthermore, existing cell balancing circuits often rely on receiving information about vehicle speed or ignition status from the vehicle side for control, necessitating complex control and structures involving signal transmission and reception with the vehicle.

[0009] The present invention was made in view of the above circumstances, and its object is to provide a battery voltage equalization device that does not transmit or receive signals with the vehicle side, and can ensure the opportunity to perform cell balance control of the vehicle battery pack even when the vehicle is in motion.

[0010] Technical solutions adopted to solve technical problems

[0011] To achieve the above objectives, the first battery voltage equalization device of the present invention is a battery voltage equalization device for an automotive battery composed of multiple batteries connected in series, comprising: a voltage measuring unit for measuring the battery voltage of each of the batteries; a current measuring unit for measuring the charging and discharging current of the automotive battery; a unit balancing unit for equalizing the battery voltage of each of the batteries; and a control unit for performing voltage equalization control via the unit balancing unit based on the battery voltage measured by the voltage measuring unit, wherein the control unit starts the voltage equalization control based on determining that voltage equalization control is required based on each battery voltage and determining that the discharging current of the automotive battery measured by the current measuring unit is stable.

[0012] Invention Effects

[0013] According to the present invention, a battery voltage equalization device is provided that does not transmit or receive signals with the vehicle side, and can ensure the opportunity for cell balance control of the vehicle battery pack even when the vehicle is in motion. Attached Figure Description

[0014] Figure 1 This is a circuit diagram showing the overall structure of the battery voltage equalization device.

[0015] Figure 2 This is a timing diagram of the balance control of the execution unit based on the current stability judgment condition in the first embodiment.

[0016] Figure 3 This is a timing diagram of the balance control of the execution unit based on the current stability judgment condition in the second embodiment.

[0017] Figure 4 This is a timing diagram of the balance control of the execution unit based on the current stability judgment condition in the third embodiment.

[0018] Figure 5 This is a timing diagram of the balance control of the execution unit based on the current stability judgment condition in the fourth embodiment. Detailed Implementation

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, the present invention is not limited to the content described below, and any modifications can be made to implement it without changing its spirit. Additionally, the accompanying drawings used in the description of the embodiments schematically show structural components, and sometimes details are emphasized, enlarged, reduced, or omitted for the purpose of enhancing understanding, rather than accurately representing the scale, shape, etc., of the structural components.

[0020] <First Implementation Method>

[0021] Figure 1This is an overall circuit diagram showing the battery voltage equalization device 1. The battery voltage equalization device 1 is an active unit balancing circuit using a transformer, connected to an on-board battery Bm composed of multiple batteries B connected in series, to equalize the battery voltage of each battery B. The battery voltage equalization device 1 is installed in an electric vehicle and performs unit balancing control on the on-board battery Bm, which serves as the power source for the electric vehicle's operation, as needed.

[0022] Here, each battery B can be a rechargeable battery consisting of a single battery cell, or a rechargeable battery consisting of multiple battery cells connected in series to form a battery pack. Furthermore, in this embodiment, the vehicle battery Bm is described as having four connected batteries B, but the number of connected batteries B can be arbitrarily changed. Also, the battery voltage balancing device 1 is not limited to the form of cell balancing control; it can be either a transformer-based device or a passive cell balancing circuit.

[0023] The battery voltage equalization device 1 includes a voltage measuring unit 2, a current sensor 3, a current measuring unit 4, a temperature sensor 5, a temperature measuring unit 6, a cell balancing unit 7, and a control unit 8.

[0024] Voltage measurement unit 2 measures the individual battery voltages of the multiple batteries B and outputs them as digital values ​​to control unit 8 (described later). Current sensor 3 is installed on the conductive path connecting the vehicle battery Bm via the inverter and the vehicle's electric motor (not shown) to acquire the charging and discharging current I of the vehicle battery Bm. Current measurement unit 4 converts the analog value of the charging and discharging current I acquired by current sensor 3 into a digital value and outputs it to control unit 8.

[0025] Temperature sensor 5 is positioned close to the vehicle battery Bm to acquire the battery temperature of the vehicle battery Bm. Current measurement unit 6 converts the analog value of the battery temperature T acquired by current sensor 5 into a digital value and outputs it to control unit 8.

[0026] In this embodiment, the unit balancing unit 7 includes a transformer T, a switch SW, multiple diodes D and multiple capacitors C, and performs unit balancing control of the vehicle battery Bm based on control from the control unit 8 described later.

[0027] The transformer T includes a primary winding T1 that receives the output voltage from the vehicle battery Bm, and multiple secondary windings T2 corresponding to each battery B. The transformer T is energized via a switch SW located between it and the vehicle battery Bm, thereby converting the output voltage of the vehicle battery Bm into AC power and inputting it to the primary winding T1. Furthermore, the transformer T converts the voltage input to the primary winding T1 into a charging voltage for each battery B and outputs it to their respective secondary winding T2.

[0028] In this embodiment, the switch SW is an N-channel MOSFET (Metal-Oxide Semiconductor Field-Effect Transistor), with its drain connected to one end of the primary winding T1, its source connected to the negative side of the battery pack BP, and its gate connected to the control unit 8 described later. The switch SW is then continuously switched on and off by the control unit 8, thereby enabling energization control of the transformer T as described above.

[0029] Diode D and capacitor C are arranged as a rectifier / filter circuit on the conductive path from their respective secondary windings T2 to their respective batteries B, converting the AC voltage output from their respective secondary windings T2 into DC voltage to form a charging voltage for charging a single battery B.

[0030] The control unit 8 is, for example, composed of a known microcomputer control circuit including a timer (not shown). It determines whether voltage equalization is needed based on the battery voltage of each battery B. If voltage equalization is needed, as detailed below, it outputs a PWM signal to the switch SW of the unit balancing unit 7, based on the condition that the charging / discharging current I of the vehicle battery Bm is stable, and performs unit balancing control. Furthermore, if the control unit 8 determines that voltage equalization is not needed, or if the battery voltage deviation has been eliminated during the execution of unit balancing control, it stops outputting signals to the switch SW.

[0031] Here, it is possible to determine whether voltage equalization is needed by the deviation of each battery voltage. For example, it can be determined by the difference between the maximum and minimum values ​​of each battery voltage, or whether the standard deviation of each battery voltage is above a specified threshold.

[0032] Furthermore, if the battery temperature measured by the temperature measurement unit 6 is above a predetermined temperature threshold, the control unit 8 will disable voltage balancing control regardless of whether cell balancing control is being performed. That is, if the battery temperature reaches or exceeds the temperature threshold during the execution of cell balancing control, the control unit 8 will stop cell balancing control. Here, the predetermined temperature threshold is a pre-set battery temperature threshold arbitrarily set to monitor the temperature and prevent it from reaching a high temperature that would cause battery B to deteriorate.

[0033] Next, the execution conditions for cell balancing control will be explained. As described above, the control unit 8 performs cell balancing control even when the vehicle's ignition is not off, based on the condition that voltage equalization is required according to the battery voltage and that the charging / discharging current I of the vehicle battery Bm is stable. Here, the case where voltage equalization is required when the ignition is on but is not completed during the execution of cell balancing control will be explained.

[0034] Figure 2 This is a timing diagram of the balance control of the execution unit based on the current stability judgment condition according to the first embodiment. More specifically, Figure 2 This refers to the timing of the execution of the balance control unit for the change in the discharge current Id of the vehicle battery Bm during vehicle operation, ΔId. Furthermore, the control unit 8 can determine whether the charging / discharging current I is the discharge current Id or the charging current Ic based on the direction of the current flowing through the current sensor 3.

[0035] In this embodiment, if the change in the discharge current Id of the vehicle battery Bm, ΔId, remains smaller than a predetermined first change threshold ΔIth1 for a predetermined first period T1, the control unit 8 determines that the discharge current Id is stable and begins voltage equalization control. Furthermore, during the execution of voltage equalization control, the control unit 8 terminates voltage equalization control if the change in the discharge current Id, ΔId, exceeds a predetermined second change threshold ΔIth2.

[0036] Here, the defined first change threshold △Ith1 is a pre-set threshold used to determine whether the change △Id of the discharge current Id sampled at regular intervals has a significant change compared to the previous change △Id. Furthermore, the defined first period T1 is a pre-set threshold used to determine whether the change △Id of the discharge current Id remains unchanged.

[0037] The specified second change threshold △Ith2 is a pre-set threshold used to determine when the change in discharge current Id △Id changes significantly again during the execution of voltage equalization control and to stop voltage equalization control.

[0038] Furthermore, although the second change threshold △Ith2 is exemplified as being the same as the first change threshold △Ith1 in this embodiment, by setting it to a value larger than the first change threshold △Ith1, the execution period of voltage equalization control can be more effectively ensured.

[0039] If based on the above conditions Figure 2 The operation in the situation is explained as follows: just after timer t1 has passed, because the change in discharge current Id ΔId exceeds the range of the first change threshold ΔIth1 during each sampling, the timer of control unit 8 does not start counting for the first period T1, and the unit balance control does not start either.

[0040] In contrast, at time t2, the change in discharge current Id, ΔId, is compared with the previously sampled value and is within the range of the first change threshold, ΔIth1. Therefore, the timer of the control unit 8 starts counting for the first period T1.

[0041] Then, during the first period T1 from time t2 to time t3, when the change in discharge current Id ΔId does not exceed the range of the first change threshold ΔIth1, the control unit 8 determines that the discharge current Id of the vehicle battery Bm is stable and begins to perform cell balance control on the vehicle battery Bm.

[0042] Furthermore, at time t4, if the change in discharge current Id, ΔId, exceeds the second change threshold ΔIth2 when compared with the previously sampled value, the control unit 8 terminates the cell balancing control for the vehicle battery Bm and resets the timer. Alternatively, assuming voltage equalization was completed before time t4, cell balancing control terminates at that time.

[0043] Then, following the same steps, at time 5, when the change in discharge current Id ΔId is compared with the previously sampled value and falls within the range of the first change threshold ΔIth1, the timer starts counting. However, at time t6, the change in discharge current Id ΔId exceeds the range of the first change threshold ΔIth1 before the first period T1 has elapsed. Therefore, at time t6, the timer resets its count.

[0044] As described above, the battery voltage equalization device 1 according to the first embodiment can determine the stability of the discharge current Id based on the change ΔId of the discharge current Id of the vehicle battery Bm by presetting a first change threshold ΔIth1, a second change threshold ΔIth2, and a first period T1.

[0045] Therefore, even when the vehicle is not ignited or at a speed of zero (not idling), the battery voltage equalization device 1 can perform cell balancing control on the vehicle battery Bm while the discharge current Id is stable. In other words, even during prolonged periods of constant speed driving, such as on highways, the battery voltage equalization device 1 will not miss the opportunity to perform cell balancing control, thus maintaining the vehicle battery Bm in a good condition.

[0046] Furthermore, the battery voltage equalization device 1 determines whether to perform voltage equalization control based on the change in discharge current Id of the vehicle battery Bm obtained by the current sensor 3, ΔId. Therefore, it does not require complex control and structure for signal transmission and reception with the vehicle.

[0047] Therefore, according to the battery voltage equalization device 1 of the first embodiment, there is no need to transmit or receive signals with the vehicle side, and even when the vehicle is in motion, the opportunity to perform cell balance control for the vehicle battery pack can be ensured.

[0048] <Second Implementation Method>

[0049] Next, the battery voltage equalization device 1 according to the second embodiment will be described. The difference between the battery voltage equalization device 1 according to the second embodiment and the battery voltage equalization device 1 of the first embodiment described above lies in the current stability judgment condition. Hereinafter, the parts that are different from those in the first embodiment will be described, and the same reference numerals will be used for the components that are common to the first embodiment, and detailed descriptions will be omitted.

[0050] Figure 3 This is a timing diagram of the balance control of the execution unit based on the current stability judgment condition according to the second embodiment. More specifically, Figure 3 This indicates the timing of the execution of the balance control of the discharge current Id of the on-board battery Bm when the vehicle is in motion.

[0051] In this embodiment, if the discharge current of the vehicle battery Bm remains lower than a predetermined first current threshold Ith1 for a predetermined second period T2, the control unit 8 determines that the discharge current Id is stable and begins voltage equalization control. Furthermore, during the execution of voltage equalization control, the control unit 8 terminates voltage equalization control if the discharge current Id exceeds a predetermined second current threshold Ith2.

[0052] Here, the first current threshold Ith1 is a pre-set threshold used to determine states where the vehicle's battery power is minimally consumed, such as idling while waiting at traffic lights or driving downhill, based on the discharge current Id sampled at regular intervals. Furthermore, the second period T2 is a pre-set threshold used to determine whether the discharge current Id remains relatively low.

[0053] The specified second current threshold Ith2 is a pre-set threshold used to determine when the discharge current Id increases again and to stop the voltage equalization control during the execution of voltage equalization control.

[0054] Furthermore, although the second current threshold Ith2 is exemplified as being the same as the first current threshold Ith1 in this embodiment, by setting it to a value larger than the first current threshold Ith1, the execution period of voltage equalization control can be more effectively ensured.

[0055] If based on the above conditions Figure 3 To explain the operation in the situation, as soon as timer t7 passes, the discharge current Id is above the first current threshold Ith1. Therefore, the timer of control unit 8 does not start counting for the second period T2, nor does it start unit balance control.

[0056] In contrast, at time t8, the discharge current Id is smaller than the first current threshold Ith1, and the timer of the control unit 8 starts counting for the second period T2.

[0057] Then, during the second period T2 from time t8 to time t9, when the discharge current Id is below the first current threshold Ith1, the control unit 8 determines that the discharge current Id of the vehicle battery Bm is stable and starts cell balancing control for the vehicle battery Bm.

[0058] Furthermore, at time t10, the discharge current Id exceeds the second current threshold Ith2, therefore, the control unit 8 terminates the cell balancing control for the vehicle battery Bm and resets the timer. Alternatively, assuming that voltage equalization was completed before time t10, the cell balancing control terminates at that time.

[0059] The same steps are then followed, starting the timer count at time t11 when the discharge current Id is smaller than the first current threshold Ith1. However, at time t12, the discharge current Id has already exceeded the first current threshold Ith2 before the second period T2 has elapsed. Therefore, at time t12, the timer resets its count.

[0060] As described above, according to the battery voltage equalization device 1 of the second embodiment, by pre-setting a first current threshold Ith1, a second current threshold Ith2, and a second period T2, the stability of the discharge current Id of the vehicle battery Bm can be determined. Therefore, the battery voltage equalization device 1 of the second embodiment, like the battery voltage equalization device 1 of the first embodiment, does not require signal transmission and reception with the vehicle side, and can ensure the opportunity for cell balancing control of the vehicle battery pack even when the vehicle is in motion.

[0061] <Third Implementation Method>

[0062] Next, the battery voltage equalization device 1 according to the third embodiment will be described. The battery voltage equalization device 1 according to the third embodiment differs from the battery voltage equalization device 1 of the first or second embodiment described above in that, when the vehicle battery Bm can be charged using regenerative power from the vehicle side, cell balance control is performed during a period of stable regenerative current during charging. Hereinafter, the parts that differ from the first embodiment will be described, and the same reference numerals will be used for components common to the first or second embodiment, with detailed descriptions omitted.

[0063] Figure 4 This is a timing diagram of the balance control of the execution unit based on the current stability judgment condition according to the third embodiment. More specifically, Figure 4This indicates the timing of the execution of the balance control of the unit when the vehicle is regenerating the on-board battery Bm on a relatively long downhill road, and the change in the charging current Ic of the on-board battery Bm is ΔIc.

[0064] In this embodiment, if the change in the charging current Ic of the vehicle battery Bm, ΔIc, remains smaller than a predetermined third change threshold, ΔIth3, for a predetermined third period T3, the control unit 8 determines that the charging current Ic is stable and begins voltage equalization control. Furthermore, during the execution of voltage equalization control, the control unit 8 terminates voltage equalization control if the change in the charging current Ic, ΔIc, exceeds a predetermined fourth change threshold, ΔIth4.

[0065] Here, the specified third change threshold △Ith3 is a pre-set threshold used to determine whether the change △Ic of the charging current Ic sampled at regular intervals has a significant change compared to the previous change △Ic. Furthermore, the specified third period T3 is a pre-set threshold used to determine whether the change △Ic of the charging current Ic remains unchanged.

[0066] The specified fourth change threshold △Ith4 is a pre-set threshold used to determine if the change in charging current Ic △Ic changes significantly again during the execution of voltage equalization control and to stop voltage equalization control.

[0067] Furthermore, although the fourth change threshold △Ith4 is exemplified in this embodiment as being the same value as the third change threshold △Ith3, by setting it to a value larger than the third change threshold △Ith3, the execution period of voltage equalization control can be more ensured.

[0068] If based on the above conditions Figure 4 The operation in the situation is explained as follows: just after timer t13, since the change in charging current Ic ΔIc exceeds the range of the third change threshold ΔIth3 at each sampling, the timer of control unit 8 does not start counting in the third period T3, nor does it start unit balance control.

[0069] In contrast, at time t14, the change in charging current Ic, ΔIc, is compared with the previously sampled value and falls within the range of the third change threshold, ΔIth3. Therefore, the timer of the control unit 8 begins counting in the third period T3.

[0070] Then, during the third period T3 from time t14 to time t15, when the change in charging current Ic ΔIc does not exceed the range of the third change threshold ΔIth3, the control unit 8 determines that the charging current Ic of the vehicle battery Bm is stable and begins to perform cell balancing control for the vehicle battery Bm.

[0071] Furthermore, at time t16, if the change in charging current Ic, ΔIc, exceeds the fourth change threshold ΔIth4 when compared with the previously sampled value, the control unit 8 terminates the cell balancing control for the vehicle battery Bm and resets the timer count. Alternatively, assuming voltage equalization is completed before time t16, cell balancing control terminates at that time.

[0072] Following the same steps, at time 17, when the change in charging current Ic, ΔIc, is compared to the previously sampled value and falls within the third change threshold ΔIth3, the timer starts counting. However, at time t18, the change in charging current Ic, ΔIc, exceeds the third change threshold ΔIth3 before the third period T3 has elapsed. Therefore, at time t18, the timer resets its count.

[0073] As described above, according to the battery voltage equalization device 1 of the third embodiment, by presetting the third change threshold △Ith3, the fourth change threshold △Ith4, and the third period T3, the stability of the charging current Ic can be determined based on the change △Ic of the charging current Ic of the vehicle battery Bm.

[0074] Therefore, even when the vehicle is not ignited or at a zero speed (not idling), the battery voltage equalization device 1 can perform cell balancing control on the vehicle battery Bm while the regenerative charging current Ic is stable. In other words, even during prolonged downhill driving at a constant speed, such as on a highway, the battery voltage equalization device 1 will not miss the opportunity to perform cell balancing control, thus maintaining the vehicle battery Bm in a good condition.

[0075] Furthermore, the battery voltage equalization device 1 determines whether voltage equalization control can be performed based on the change ΔIc of the charging current Ic of the vehicle battery Bm obtained by the current sensor 3, thus eliminating the need for complex control and structure that requires signal transmission and reception with the vehicle.

[0076] Therefore, according to the battery voltage equalization device 1 of the third embodiment, there is no need to transmit or receive signals with the vehicle side, and even when the vehicle is in motion, the opportunity to perform cell balance control for the vehicle battery pack can be ensured.

[0077] Furthermore, when the vehicle is parked at a charging station and the on-board battery Bm is being charged, the charging current Ic provided by the charging station will hardly change. Therefore, according to the structure of the battery voltage balancing device 1 according to this embodiment, cell balance control can be performed during charging.

[0078] <Fourth Implementation Method>

[0079] Next, the battery voltage equalization device 1 according to the fourth embodiment will be described. The battery voltage equalization device 1 according to the fourth embodiment differs from the battery voltage equalization device 1 of the third embodiment in the current stability judgment condition. Hereinafter, the parts that are different from those in the third embodiment will be described, and the same reference numerals will be given to the constituent elements common to the third embodiment, and detailed descriptions will be omitted.

[0080] Figure 5 This is a timing diagram of the balance control of the execution unit based on the current stability judgment condition according to the fourth embodiment. More specifically, Figure 5 This indicates the timing of the balance control of the charging current Ic of the on-board battery Bm when the vehicle is regenerating and charging the on-board battery Bm on a relatively long downhill road.

[0081] In this embodiment, if the charging current of the vehicle battery Bm exceeds a predetermined third current threshold Ith3 for a predetermined fourth period T4, the control unit 8 determines that the charging current Ic is stable and begins voltage equalization control. Furthermore, during the execution of voltage equalization control, the control unit 8 terminates voltage equalization control if the charging current Ic exceeds a predetermined fourth current threshold Ith4.

[0082] Here, the defined third current threshold Ith3 is a pre-set threshold arbitrarily used to determine whether the charging current Ic sampled at regular intervals is sufficiently large. Since the regenerative current has an upper limit, when the charging current Ic is sufficiently large, it stabilizes near that upper limit. Furthermore, the defined fourth period T4 is a pre-set threshold arbitrarily used to determine whether the charging current Ic remains in a stable state.

[0083] The specified fourth current threshold Ith4 is a pre-set threshold used to determine when the charging current Ic drops again and to stop the voltage equalization control during the execution of voltage equalization control.

[0084] Furthermore, although the fourth current threshold Ith4 is exemplified as being the same as the third current threshold Ith3 in this embodiment, by setting it to a value smaller than the third current threshold Ith3, the execution period of voltage equalization control can be more effectively ensured.

[0085] If based on the above conditions Figure 5 To explain the operation in the following situation, just after timer t19 has passed, the charging current Ic is below the third current threshold Ith3, so the timer of control unit 8 does not start counting in the fourth period T4, nor does it start unit balance control.

[0086] In contrast, at time t20, the charging current Ic is greater than the third current threshold Ith3, and the timer of the control unit 8 starts counting during the fourth period T4.

[0087] Then, during the fourth period T4 from time t20 to time t21, when the charging current Ic exceeds the third current threshold Ith3, the control unit 8 determines that the charging current Ic of the vehicle battery Bm is stable and starts cell balancing control for the vehicle battery Bm.

[0088] Furthermore, at time t22, the charging current Ic drops below the fourth current threshold Ith4, therefore, the control unit 8 terminates the cell balancing control for the vehicle battery Bm and the timer resets the count. Alternatively, assuming voltage equalization is completed before time t22, the cell balancing control terminates at that time.

[0089] Then, following the same steps, the timer starts counting at time t23 when the charging current Ic reaches a state higher than the third current threshold Ith3. However, at time t24, the charging current Ic drops below the third current threshold Ith3 before the fourth period T4. Therefore, at time t24, the timer resets its count.

[0090] As described above, according to the battery voltage equalization device 1 of the fourth embodiment, by pre-setting the third current threshold Ith3, the fourth current threshold Ith4, and the fourth period T4, the stability of the charging current Ic of the vehicle battery Bm can be determined. Therefore, the battery voltage equalization device 1 of the fourth embodiment, like the battery voltage equalization device 1 of the third embodiment, does not require signal transmission and reception with the vehicle side, and can ensure the opportunity for cell balancing control of the vehicle battery pack even when the vehicle is in motion.

[0091] The above provides a description of each embodiment, but the technology is not limited to the embodiments described above. For example, in the embodiments described above, although voltage equalization control is illustrated based on the stability of current values ​​or their changes sampled at regular intervals, these current values ​​and changes can also be calculated by averaging the average of multiple measurements taken within a previous time period, i.e., a so-called moving average. In this case, the battery voltage equalization device 1 averages the measured values, thereby suppressing the influence of noise and suppressing malfunctions.

[0092] <Embodiments of the Invention>

[0093] The first aspect of the present invention is a battery voltage equalization device, which is a battery voltage equalization device for an automotive battery consisting of multiple batteries connected in series. It includes: a voltage measuring unit for measuring the voltage of each battery; a current measuring unit for measuring the charging and discharging current of the automotive battery; a unit for equalizing the voltage of each battery; and a control unit for performing voltage equalization control via the unit balancing unit based on the battery voltage measured by the voltage measuring unit. The control unit initiates the voltage equalization control based on a condition that voltage equalization control is required for each battery voltage and that the discharging current of the automotive battery measured by the current measuring unit is stable.

[0094] The second aspect of the present invention is a battery voltage equalization device. In the first aspect of the present invention described above, the control unit determines that the discharge current is stable when the change in the discharge current is smaller than a predetermined first change threshold for a predetermined first period of time.

[0095] The third aspect of the present invention is a battery voltage equalization device. In the second aspect of the present invention described above, the control unit terminates the voltage equalization control during the execution of the voltage equalization control if the change in the discharge current exceeds a predetermined second change threshold.

[0096] The fourth aspect of the present invention is a battery voltage equalization device. In the first aspect of the present invention described above, the control unit determines that the discharge current is stable when the state in which the discharge current is less than a predetermined first current threshold has continued for a predetermined second period.

[0097] The fifth aspect of the present invention is a battery voltage equalization device. In the fourth aspect of the present invention described above, the control unit terminates the voltage equalization control during the execution of the voltage equalization control when the discharge current exceeds a predetermined second current threshold.

[0098] The sixth aspect of the present invention is a battery voltage equalization device. In any of the first to fifth aspects of the present invention described above, the control unit starts the voltage equalization control based on the condition that the charging current of the vehicle battery measured by the current measurement unit is stable.

[0099] The seventh aspect of the present invention is a battery voltage equalization device. In the sixth aspect of the present invention described above, the control unit determines that the charging current is stable when the change in the charging current is smaller than a predetermined third change threshold for a predetermined third period.

[0100] The eighth aspect of the present invention is a battery voltage equalization device. In the seventh aspect of the present invention described above, the control unit terminates the voltage equalization control when the change in the charging current exceeds a predetermined fourth change threshold during the voltage equalization control process.

[0101] The ninth aspect of the present invention is a battery voltage equalization device. In the sixth aspect of the present invention described above, the control unit determines that the charging current is stable when the state in which the charging current is greater than a predetermined third current threshold has continued for a predetermined fourth period.

[0102] The tenth aspect of the present invention is a battery voltage equalization device. In the ninth aspect of the present invention described above, the control unit terminates the voltage equalization control when the charging current is lower than a predetermined fourth current threshold during the voltage equalization control process.

[0103] The eleventh aspect of the present invention is a battery voltage equalization device. In any of the first to tenth aspects of the present invention described above, a temperature measuring unit is included to measure the battery temperature of the vehicle battery. When the battery temperature measured by the temperature measuring unit is above a predetermined temperature threshold, the control unit prohibits the voltage equalization control.

[0104] Label Explanation

[0105] 1. Battery voltage equalization device

[0106] 2. Voltage Measurement Section

[0107] 4 Current Measurement Section

[0108] 7-unit balance section

[0109] 8. Control Department

[0110] B battery

[0111] Bm vehicle batteries

[0112] I. Charging and discharging current

[0113] Id discharge current

[0114] Ic is the charging current.

Claims

1. A battery voltage equalization device, which is a battery voltage equalization device for a vehicle battery composed of multiple batteries connected in series, characterized in that, include: A voltage measuring unit that measures the voltage of each of the batteries; A current measuring unit for measuring the charging and discharging current of the vehicle-mounted battery; A unit balancing section that equalizes the voltage of each of the batteries; as well as The control unit performs voltage equalization control via the cell balancing unit based on the battery voltage measured by the voltage measuring unit. The control unit starts the voltage equalization control based on the condition that it determines that voltage equalization control is required based on each battery voltage and that the discharge current of the vehicle battery measured by the current measurement unit is stable.

2. The battery voltage equalization device as described in claim 1, characterized in that, If the change in the discharge current is less than a predetermined first change threshold for a predetermined first period of time, the control unit determines that the discharge current is stable.

3. The battery voltage equalization device as described in claim 2, characterized in that, During the execution of the voltage equalization control, the control unit terminates the voltage equalization control if the change in the discharge current exceeds a predetermined second change threshold.

4. The battery voltage equalization device as described in claim 1, characterized in that, If the discharge current is less than a predetermined first current threshold for a predetermined second period, the control unit determines that the discharge current is stable.

5. The battery voltage equalization device as described in claim 4, characterized in that, During the execution of the voltage equalization control, the control unit terminates the voltage equalization control if the discharge current exceeds a predetermined second current threshold.

6. The battery voltage equalization device as described in claim 1 or 2, characterized in that, The control unit starts the voltage equalization control based on the condition that the charging current of the vehicle battery measured by the current measurement unit is stable.

7. The battery voltage equalization device as described in claim 6, characterized in that, If the change in the charging current is less than a predetermined third change threshold for a predetermined third period, the control unit determines that the charging current is stable.

8. The battery voltage equalization device as described in claim 7, characterized in that, During the voltage equalization control process, the control unit terminates the voltage equalization control if the change in the charging current exceeds a predetermined fourth change threshold.

9. The battery voltage equalization device as described in claim 6, characterized in that, If the control unit determines that the charging current is stable for a predetermined fourth period when the state in which the charging current is greater than a predetermined third current threshold has continued for a predetermined fourth period.

10. The battery voltage equalization device as described in claim 9, characterized in that, During the voltage equalization control process of charging, the control unit terminates the voltage equalization control when the charging current is lower than a predetermined fourth current threshold.

11. The battery voltage equalization device as described in claim 1 or 2, characterized in that, Includes a temperature measuring unit for measuring the battery temperature of vehicle-mounted batteries. If the battery temperature measured by the temperature measuring unit is above a specified temperature threshold, the control unit disables the voltage equalization control.

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