Electricity storage device and current measurement method

Abstract

To provide a power storage device that improves measuring accuracy of current by enabling suppressing measuring error due to Seebeck effect.SOLUTION: A power storage device 50 comprises: power storage cells 60; a first measuring part 54 for measuring current of the power storage cells 60; a second measuring part 58 whose measuring error of the current due to Seebeck effect is smaller than that of the first measuring part 54; and a control part 130. The control part 130 that calculates the measuring error of the first measuring part 54 due to Seebeck effect, based on measured values of the first measuring part 54 and the second measuring part 58 corrects and replaces the measured value of the first measuring part 54 by the measured value of the second measuring part 58 when the measuring error of the first measuring part 54 is larger than a threshold value.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present invention relates to a technique for measuring a current in a power storage cell. [Background technology]

[0002] One method for measuring the current of a storage cell is to use a shunt resistor. Since a shunt resistor generates a voltage according to the current, the current can be measured from the voltage across the shunt resistor.

[0003] When there is a temperature difference between both ends of a shunt resistor, a measurement error occurs due to the Seebeck effect. The following Patent Document 1 describes how the temperature at both ends of a resistor is detected to correct the current value. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2017-514115 Summary of the Invention [Problem to be solved by the invention]

[0005] The objective of the present invention is to improve the accuracy of current measurement by suppressing measurement errors due to the Seebeck effect. [Means for solving the problem]

[0006] The energy storage device includes a storage cell, a first measurement unit that measures a current of the storage cell, a second measurement unit that has a smaller measurement error of the current due to the Seebeck effect than the first measurement unit, and a control unit, wherein the control unit calculates a measurement error of the first measurement unit due to the Seebeck effect based on measurement values ​​of the first measurement unit and the second measurement unit, and if the measurement error of the first measurement unit is greater than a threshold value, corrects or replaces the measurement value of the first measurement unit with the measurement value of the second measurement unit.

[0007] The present technology can be applied to a current measurement method and a current measurement program for a power storage device. Effect of the Invention

[0008] It is possible to suppress measurement errors due to the Seebeck effect, and improve the accuracy of current measurement. [Brief description of the drawings]

[0009] [Figure 1] Car side view [Diagram 2] Exploded perspective view of the battery [Diagram 3] Plan view of secondary battery [Figure 4] Cross section of line AA in Figure 3 [Diagram 5] Block diagram showing the electrical configuration of the vehicle [Figure 6] Block diagram showing the electrical configuration of the battery [Figure 7] Perspective view of the first measurement unit [Figure 8] A graph showing the relationship between the temperature difference at both ends of the first measurement unit and the measurement error [Figure 9] Performance comparison results between the first and second measurement units [Figure 10] Current measurement waveform [Figure 11] Current measurement process flow chart [Figure 12] Block diagram showing the electrical configuration of the battery [Figure 13] Discharge circuit diagram [Figure 14] Current measurement process flow chart [Figure 15] Current measurement process flow chart [Figure 16] Current measurement waveform DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The outline of the power storage device will be described. The energy storage device includes a storage cell, a first measurement unit that measures a current of the storage cell, a second measurement unit that has a smaller measurement error of the current due to the Seebeck effect than the first measurement unit, and a control unit, wherein the control unit calculates a measurement error of the first measurement unit due to the Seebeck effect based on measurement values ​​of the first measurement unit and the second measurement unit, and if the measurement error of the first measurement unit is greater than a threshold value, corrects or replaces the measurement value of the first measurement unit with the measurement value of the second measurement unit.

[0011] This configuration calculates the measurement error of the first measurement unit due to the Seebeck effect based on the measurement values ​​of the first measurement unit and the second measurement unit. If the measurement error due to the Seebeck effect is greater than a threshold, the measurement value of the first measurement unit is corrected or replaced with the measurement value of the second measurement unit, which has a smaller current measurement error due to the Seebeck effect, thereby suppressing the current measurement error due to the Seebeck effect. By improving the current measurement accuracy, the SOC estimation accuracy can be improved.

[0012] The second measurement unit consumes more power than the first measurement unit, and when the control unit determines that the Seebeck effect is occurring in the first measurement unit, the control unit starts current measurement by the second measurement unit. Before the Seebeck effect occurs, the second measurement unit does not perform measurements, so it is possible to reduce power consumption of the power storage device. After the Seebeck effect occurs, the two measurement values ​​are compared to determine whether the measurement value needs to be corrected or replaced.

[0013] The control unit may stop the measurement of current by the second measurement unit when it is determined that the Seebeck effect has been eliminated after the start of measurement by the second measurement unit. By stopping the measurement of current by the second measurement unit after the Seebeck effect has been eliminated, it is possible to reduce power consumption of the power storage device. By reducing the power consumption of the power storage device, the long-term storage durability is improved. The long-term storage durability is the performance of the power storage device to suppress a decrease in capacity and maintain a remaining capacity when the power storage device is left unused for a long period of time or when the power storage device is left in an unused state for a long period of time without being charged.

[0014] The control unit may determine the occurrence of the Seebeck effect based on the current of the storage cell. In this configuration, it is possible to determine whether or not the Seebeck effect occurs during charging / discharging of the storage cell or after charging / discharging is stopped. When the Seebeck effect occurs, the measurement value of the first measurement unit is corrected or replaced with the measurement value of the second measurement unit, thereby reducing measurement errors of the current during charging / discharging or after charging / discharging is stopped.

[0015] The power storage device may further include a balancer that equalizes the voltages of the storage cells by resistive discharge, and the control unit may determine the occurrence of the Seebeck effect based on the operation time of the balancer. In this configuration, it is possible to determine whether the Seebeck effect occurs during operation of the balancer or after the operation has stopped. When the Seebeck effect occurs, the measurement value of the first measurement unit is corrected or replaced by the measurement value of the second measurement unit, thereby reducing current measurement errors during operation of the balancer or after the operation has stopped.

[0016] The control unit determines the occurrence of the Seebeck effect based on the presence or absence of a change in the vehicle state. With this configuration, it is possible to suppress measurement errors in the current due to the Seebeck effect caused by a temperature change in a heating element such as an engine when the vehicle transitions from driving to parking.

[0017] <Embodiment 1> 1. Battery Description Fig. 1 is a side view of an automobile, and Fig. 2 is an exploded perspective view of a battery. An automobile 10 is an engine-driven vehicle and is equipped with a battery 50. Fig. 1 shows only the automobile 10 and the battery 50, and omits other parts that configure the automobile 10.

[0018] The battery 50 includes a battery pack 60, a circuit board unit 65, and a container 71. The battery 50 is an example of a "power storage device."

[0019] As shown in Fig. 2, the container 71 includes a main body 73 and a cover 74 made of a synthetic resin material. The main body 73 is cylindrical with a bottom. The main body 73 includes a bottom portion 75 and four side portions 76. An upper opening 77 is formed at the upper end portion by the four side portions 76.

[0020] The container 71 houses the battery pack 60 and the circuit board unit 65. The battery pack 60 has 12 secondary battery cells 62. The 12 secondary battery cells 62 are connected in three parallel connections and four in series. The circuit board unit 65 is disposed on top of the battery pack 60. In the block diagram of FIG. 6, the three secondary battery cells 62 connected in parallel are represented by one battery symbol. The secondary battery cells 62 are an example of a "storage cell."

[0021] The lid body 74 closes an upper opening 77 of the main body 73. An outer peripheral wall 78 is provided around the lid body 74. The lid body 74 has a protruding portion 79 that is generally T-shaped in plan view. The positive electrode external terminal 51 is fixed to one corner of the front portion of the lid body 74, and the negative electrode external terminal 52 is fixed to the other corner.

[0022] 3 and 4, the secondary battery cell 62 is configured by housing an electrode assembly 83 together with a non-aqueous electrolyte in a rectangular parallelepiped case 82. The secondary battery cell 62 is, for example, a lithium ion secondary battery. The case 82 has a case body 84 and a lid 85 that closes the upper opening.

[0023] Although not shown in detail, the electrode body 83 is configured by disposing a separator made of a porous resin film between a negative electrode element made of a copper foil substrate coated with an active material and a positive electrode element made of an aluminum foil substrate coated with an active material. Both of these are strip-shaped, and are wound flatly so that they can be housed in the case body 84, with the negative electrode element and the positive electrode element offset from each other on opposite sides in the width direction relative to the separator.

[0024] A positive electrode terminal 87 is connected to the positive electrode element via a positive electrode current collector 86, and a negative electrode terminal 89 is connected to the negative electrode element via a negative electrode current collector 88. The positive electrode current collector 86 and the negative electrode current collector 88 each comprise a flat base portion 90 and legs 91 extending from the base portion 90. A through hole is formed in the base portion 90. The legs 91 are connected to the positive electrode element or the negative electrode element.

[0025] The positive electrode terminal 87 and the negative electrode terminal 89 each comprise a terminal body 92 and a shaft 93 that protrudes downward from the center of the lower surface of the terminal body 92. Of these, the terminal body 92 and shaft 93 of the positive electrode terminal 87 are integrally formed from aluminum (a single material). In the negative electrode terminal 89, the terminal body 92 is made of aluminum, and the shaft 93 is made of copper, and these are assembled together. The terminal body 92 of the positive electrode terminal 87 and the negative electrode terminal 89 are disposed on both ends of the lid 85 via gaskets 94 made of an insulating material, and are exposed to the outside from the gaskets 94.

[0026] The lid 85 has a pressure relief valve 95. As shown in Fig. 3, the pressure relief valve 95 is located between the positive electrode terminal 87 and the negative electrode terminal 89. The pressure relief valve 95 opens to reduce the internal pressure of the case 82 when the internal pressure of the case 82 exceeds a limit value.

[0027] FIG. 5 is a block diagram showing the electrical configuration of the automobile 10, and FIG. 6 is a block diagram showing the electrical configuration of the battery 50. As shown in FIG.

[0028] As shown in FIG. 5, the automobile 10 includes an engine 20 as a drive device, an engine control unit 21, an engine starting device 23, an alternator 25 as a vehicle generator, general electrical loads 27, a vehicle ECU (Electronic Control Unit) 30, a battery 50, etc.

[0029] The battery 50 is connected to the power line 37. The engine starting device 23, the alternator 25, and the general electric loads 27 are connected to the battery 50 via the power line 37.

[0030] The engine starting device 23 is a starter motor. When the ignition switch 24 is turned on, a cranking current flows from the battery 50, and the engine starting device 23 is driven. When the engine starting device 23 is driven, the crankshaft rotates, and the engine 20 can be started.

[0031] The general electric loads 27 are electric loads mounted on the automobile 10, excluding the engine starting device 23. The general electric loads 27 are rated at 12 V, and examples of the general electric loads 27 include an air conditioner, an audio system, a car navigation system, and auxiliary devices.

[0032] The alternator 25 is a vehicle generator that generates electricity using the power of the engine 20. When the amount of electricity generated by the alternator 25 exceeds the electrical load of the automobile 10, the battery 50 is charged by the alternator 25. When the amount of electricity generated by the alternator 25 is less than the electrical load of the automobile 10, the battery 50 discharges to make up for the shortage of electricity generated.

[0033] The vehicle ECU 30 is communicatively connected to the battery 50 via a communication line L1, and is communicatively connected to the alternator 25 via a communication line L2. The vehicle ECU 30 receives SOC information from the battery 50, and controls the amount of power generation of the alternator 25, thereby controlling the SOC of the battery 50.

[0034] The vehicle ECU 30 is communicatively connected to the engine control unit 21 via the communication line L3. The engine control unit 21 is mounted on the automobile 10, and monitors the operating state of the engine 20. The engine control unit 21 monitors the running state of the automobile 10 from the measured values ​​of instruments such as a speedometer. The vehicle ECU 30 can obtain, from the engine control unit 21, information on the on / off state of the ignition switch 24, information on the operating state of the engine 20, and information on the running state of the automobile 10 (driving, stopped, idling stop, etc.).

[0035] As shown in FIG. 6, the battery 50 includes a current interruption device 53, a battery pack 60, a first measurement unit 54, a second measurement unit 58, a management device 100, and a temperature sensor 115.

[0036] The current interruption device 53, the battery pack 60, the first measurement unit 54, and the second measurement unit 58 are connected in series via bus bars 63P and 63N. The bus bar 63P connects the positive external terminal 51 and the positive electrode of the battery pack 60. The bus bar 63N connects the negative external terminal 52 and the negative electrode of the battery pack 60.

[0037] The current interruption device 53 is located on the positive electrode side of the battery pack 60. The first measurement unit 54 and the second measurement unit 58 are located on the negative electrode side of the battery pack 60.

[0038] The current interrupter 53 can be configured with a contact switch (mechanical type) such as a relay, or a semiconductor switch such as an FET. The current interrupter 53 opens when an abnormality occurs in the battery 50, and is normally controlled to close. The temperature sensor 115 is of a contact type or a non-contact type and measures the temperature T [°C] of the battery pack 60.

[0039] The first measurement unit 54 detects the current I of the battery pack 60. The first measurement unit 54 may be a resistor (shunt resistor) made of a metal plate. As shown in Fig. 7, the first measurement unit 54 includes a resistor body 57 and a pair of electrodes 55A, 55B.

[0040] Resistor body 57 is an alloy with a small temperature coefficient of change in electrical resistance (for example, manganin, an alloy of copper, manganese, and nickel). Resistor body 57 generates a voltage Vr proportional to the value of the current flowing through first measuring unit .

[0041] The pair of electrodes 55A, 55B are located on both sides of resistor body 57 in direction A and are joined to resistor body 57. The pair of electrodes 55A, 55B are made of a metal such as copper. Bus bars 63N1, N2 made of a metal plate are connected to the pair of electrodes 55A, 55B by fasteners such as nuts.

[0042] The management device 100 can measure the current I of the battery pack 60 by detecting the voltage Vr generated across both ends of the resistor body 57 via the signal lines L4 and L5.

[0043] The management device 100 is provided on the circuit board unit 65. The management device 100 includes a voltage detection circuit 110, a measurement IC 120, a control unit 130, and a communication unit 135. The voltage detection circuit 110 is connected to both ends of each secondary battery cell 62 by a signal line, and measures the cell voltage V [V] of each secondary battery cell 62 and the total voltage VB of the assembled battery 60. The total voltage VB [V] of the assembled battery 60 is the total voltage of the four secondary battery cells 62 connected in series.

[0044] The measurement IC 120 converts the output signal of the first measurement section 54 and the output signal of the second measurement section 58 into digital values ​​and outputs them to the control section 130.

[0045] The control unit 130 includes a CPU 131 having a calculation function and a memory 133. The control unit 130 monitors the current I, total voltage VB, and temperature T of the battery pack 60 based on the outputs of the first measurement unit 54, the voltage detection circuit 110, and the temperature sensor 115, and monitors for the presence or absence of an abnormality.

[0046] The memory 133 is a non-volatile storage medium such as a flash memory, an EEPROM, etc. The memory 133 stores a management program for the battery pack 60 and data required for executing the management program.

[0047] The management program includes a current measurement program (a program for executing a current measurement process) that measures the current I of the battery pack 60, and a monitoring program that monitors the state of the battery pack 60. The memory 133 stores each program and is also used as a working memory for the control unit 130.

[0048] The control unit 130 is connected to the vehicle ECU 30 via a communication unit 135 and a communication line L1, and can obtain information about the state of the automobile 10, such as whether the automobile 10 is parked or moving, from the vehicle ECU 30.

[0049] 2. SOC Estimation Using Current Integration Method The control unit 130 estimates the SOC of the battery pack 60. The SOC (state of charge) is the charging state of the battery 50. The SOC is the ratio of the remaining capacity to the full charge capacity (actual capacity), and can be defined by the following formula (1).

[0050] SOC[%]=(Cr / Co)×100 (1) Co is the full charge capacity of the secondary battery, and Cr is the remaining capacity of the secondary battery.

[0051] As shown in the following equation (2), the control unit 130 estimates the SOC of the battery 50 based on the integral value with respect to time of the current I measured by the first measurement unit 54. The sign of the current is positive during charging and negative during discharging.

[0052] SOC = SOCo + 100 × (∫Idt) / Co (2) SOCo is the initial value of SOC, and I is the current.

[0053] 3. Current measurement error due to the Seebeck effect The Seebeck effect is a phenomenon in which an electromotive force is generated at both ends of an object due to a temperature difference ΔT that occurs at both ends of the object. When a temperature difference ΔT occurs at both ends of the first measuring unit 54, a voltage ΔV is generated at both ends of the first measuring unit 54 due to the Seebeck effect, causing a measurement error in the measurement value of the current I.

[0054] For example, the bus bars 63N1 and N2 connected to both sides of the first measuring unit 54 generate heat due to Joule heat caused by charging and discharging the battery pack 60.

[0055] If the two bus bars 63N1 and 63N2 have different heat capacities, the one with the smaller heat capacity will experience a larger temperature change, resulting in a temperature difference between the two bus bars 63N1 and 63N2. Heat capacity [J / K] is the amount of heat Q [J] required to raise the temperature of an object by 1 [K].

[0056] Due to the temperature difference between the bus bars 63N1 and 63N2, a temperature difference ΔT occurs between both ends of the first measuring part 54, and a measurement error may occur due to the Seebeck effect.

[0057] The battery 50 includes a second measurement unit 58 in addition to the first measurement unit 54. The second measurement unit 58 is connected in series with the first measurement unit 54 as shown in Fig. 6. The second measurement unit 58 may be a magnetic sensor that measures the current I based on the strength of the magnetic field created by the current I. L6 is a signal line that inputs the measurement value Im of the second measurement unit 58 to the management device 100.

[0058] The second measurement unit 58 is started up by receiving power via the power line VCC and measures the current I. The control unit 130 controls the second measurement unit 58 by turning the power switch SW on and off. That is, by turning on the power switch SW, the second measurement unit 58 is started up and measurement is started, and by turning off the power switch SW, measurement is stopped. By turning off the power switch SW when measurement is not being performed, it is possible to reduce power consumption in the second measurement unit 58.

[0059] 9 shows the results of a performance comparison between the first measurement unit 54 and the second measurement unit 58. The first measurement unit 54 consumes less power than the second measurement unit 58. The shunt resistor consumes zero power. The first measurement unit 54 has a wider measurement range than the second measurement unit 58. The second measurement unit 58 has smaller measurement errors due to the Seebeck effect than the first measurement unit 54.

[0060] In this embodiment, the current I is measured by the first measurement unit 54, which consumes less power, and when the measurement error due to the Seebeck effect exceeds a threshold K, the measurement value of the first measurement unit 54 is replaced with the measurement value Im of the second measurement unit 58.

[0061] By replacing the measurement value of the first measurement unit 54 with the measurement value Im of the second measurement unit 58, which has a small measurement error due to the Seebeck effect, it is possible to suppress the measurement error of the current I due to the Seebeck effect.

[0062] 10 is a graph showing the relationship between the temperature difference ΔT of the first measuring unit 54 and the measurement values ​​Is and Im. “Is” is the measurement value of the first measuring unit 54, and “Im” is the measurement value of the second measuring unit 58.

[0063] In this example, the discharge current I of the battery pack 60 is “I1” during the period from time t0 to tb, and at time tb, the discharge current I decreases from “I1” to “I2.” “X” is a judgment value for judging the magnitude of the current I.

[0064] After time t0, the bus bars 63N1, 63N2 generate heat due to Joule heat caused by the discharge of the battery pack 60. When the bus bars 63N1, 63N2 generate heat, a temperature difference occurs between the two bus bars 63N1, 63N2 due to the difference in thermal capacity, and as a result, the temperature difference ΔT between both ends of the first measurement unit 54 increases.

[0065] After time tb when the discharge current I decreases to "I2", the amount of heat generated by the bus bars 63N1, 63N2 decreases. As the amount of heat generated decreases, the temperature difference between the two bus bars 63N1, 63N2 also decreases thereafter, and as a result, the temperature difference ΔT between both ends of the first measurement unit 54 decreases.

[0066] The measurement error of the first measuring unit 54 increases as the temperature difference ΔT between both ends of the first measuring unit 54 increases, and for example, exceeds the threshold value K during the period TK from ta to tc in FIG.

[0067] In this embodiment, the second measuring section 58 starts measurement at time t1 when a predetermined time TP has elapsed from the measurement start time t0.

[0068] After that, during the period from time tb to time tc, the measurement value Is of the first measurement unit 54 is replaced with the measurement value Im of the second measurement unit 58, which has a smaller measurement error due to the Seebeck effect.

[0069] By replacing the measured value, it is possible to suppress measurement errors in the current I due to the Seebeck effect during the period from time tb to tc.

[0070] The reason why the replacement of the measurement value is limited to the period from tb to tc among the entire period from ta to tc during which the measurement error exceeds the threshold value K is as follows.

[0071] The measurement error of the current I due to the Seebeck effect depends on the temperature difference ΔT between both ends of the first measuring unit 54, and is generally about 1 [A] at most. When comparing under the same measurement error conditions, the smaller the current I is, the larger the proportion of the measurement error to the current I is, and the greater the influence of the Seebeck effect is.

[0072] 11 is a flowchart of the current measurement process. The current measurement process is started, for example, by being triggered by the start of the management device 100. At the start of the current measurement process, the power switch SW is off and the second measurement unit 58 is stopped.

[0073] When the management device 100 is started up at time t0, the control unit 130 starts measuring the current I, and sets the measurement value Is of the first measurement unit 54 as the measurement value of the current I of the battery pack 60 (S10, S20).

[0074] I=Is (3)

[0075] The control unit 130 compares the measured value Is with a predetermined value X to determine whether the current I of the battery pack 60 is equal to or greater than the predetermined value X.

[0076] The control unit 130 counts the time during which a current I equal to or greater than a predetermined value X continues to flow (hereinafter, referred to as a duration TI), and determines whether the duration TI has reached a predetermined time TP (S30).

[0077] S30 is a process for determining whether the Seebeck effect occurs due to heat generation accompanying charging and discharging of the battery pack 60.

[0078] If the duration TI is less than the predetermined time TP (S30: NO), it can be determined that the Seebeck effect has not occurred or, even if it has occurred, its influence is small, and the control unit 130 continues measuring the current I by the first measuring unit 54 (from time t0 to time t1).

[0079] At time t1, if the duration TI reaches the predetermined time TP (S30: YES), the control unit 130 determines that the Seebeck effect is occurring, and proceeds to S40.

[0080] When the process proceeds to S40, the control unit 130 switches the power switch SW from off to on. As a result, power is supplied through the power line VCC, and the second measurement unit 58 is started up and starts measuring the current I. After this, the current I is measured by both the first measurement unit 54 and the second measurement unit 58.

[0081] Thereafter, the process proceeds to S50, where the control unit 130 determines whether the current I is smaller than a predetermined value X. During the period from time t1 to tb, the current I exceeds the predetermined value X, so that the determination in S50 is NO.

[0082] At time tb, the current I decreases from "I1" to "I2" and becomes smaller than the determination value X, so that the determination in S50 is YES and the process proceeds to S60.

[0083] When the process proceeds to S60, the control unit 130 calculates the measurement error of the first measuring unit 54 based on the two measurement values ​​Is and Im. Specifically, the control unit 130 calculates the measurement error from the difference between the two measurement values ​​Is and Im, and compares the absolute value of the calculated measurement error with a threshold value K.

[0084] |Is-Im|>K (4) Is is the measurement value of the first measurement unit (shunt resistor), and Im is the measurement value of the second measurement unit (magnetic sensor).

[0085] If |Is-Im|>K, that is, if the absolute value of the measurement error is greater than the threshold value K, the control unit 130 determines that the measurement error of the first measuring unit 54 is outside the allowable range (S60: YES).

[0086] If it is determined that the measurement error is outside the allowable range, the control unit 130 replaces the measurement value Is of the first measurement unit 54 with the measurement value Im of the second measurement unit 58, and sets this as the measurement value of the current I.

[0087] I=Im (5)

[0088] Between times tb and tc, |Is-Im|>K, and the measurement value Im of the second measuring unit 58 is adopted as the measurement value of the current I (S70).

[0089] At time tc, when |Is-Im|≦K, the control unit 130 determines that the Seebeck effect has disappeared (NO judgment in S60). If it is determined that the Seebeck effect has disappeared, the process proceeds to S80. In S80, the control unit 130 returns the measurement value of the current I to the measurement value Is of the first measurement unit 54.

[0090] Thereafter, the control unit 130 turns off the power switch SW to stop the power supply to the second measurement unit 58 (S90). With the second measurement unit 58 stopped, the state returns to S10.

[0091] 3.Effects In this configuration, by using the first measurement unit 54 which consumes little power and has a wide measurement range, it is possible to measure a wide range of current I, such as the dark current to the electrical load 27 to the cranking current, while suppressing the power consumption of the battery 50.

[0092] When a measurement error occurs due to the Seebeck effect, the measurement value of the first measurement unit 54 is replaced with the measurement value of the second measurement unit 58, which has a smaller measurement error due to the Seebeck effect. By replacing the measurement value, the measurement error due to the Seebeck effect can be suppressed, and the measurement accuracy of the current I is improved. The improvement in the measurement accuracy of the current I allows the SOC of the battery 50 to be estimated with high accuracy.

[0093] In this configuration, by replacing the measured value, it is possible to improve the current measurement accuracy in the small current region where the current I is equal to or less than a predetermined value, and to suppress malfunction of the management device 100 in the small current region. For example, when switching the operation mode of the management device 100 according to the magnitude of the current I, it is possible to suppress erroneous switching of the operation mode due to erroneous recognition of the magnitude of the current I.

[0094] In this configuration, the second measuring unit 58 is used only for a predetermined period (t1 to tc) from the occurrence of the Seebeck effect, and is stopped from being used for other periods (t0 to t1, after tc). By limiting the period during which the second measuring unit 58, which consumes a large current, is used, it is possible to reduce the power consumption of the battery 50.

[0095] <Embodiment 2> 12 is a block diagram of the battery 150. The battery 150 differs from the battery 50 of the first embodiment in that the battery 150 includes a balancer 160.

[0096] As shown in FIG. 13, the balancer 160 is composed of a discharge resistor 161 and a discharge switch 163, and is provided for each secondary battery cell 62.

[0097] The cell voltages or capacities of the secondary battery cells 62 can be equalized by discharging the secondary battery cells 62 with the balancer 160. For example, the cell voltages of the secondary battery cells 62 can be equalized by setting the secondary battery cell 62 with the lowest voltage among the four secondary battery cells 62 as a reference and discharging the other three secondary battery cells 62 with higher voltages to make the voltages uniform.

[0098] During operation of the balancer 160, the balancer 160 generates heat due to Joule heat of the discharge resistor 161. The heat of the balancer 160 is transferred to the first measurement unit 54 via the circuit board unit 65, causing a temperature difference ΔT between both ends of the first measurement unit 54, which may result in a measurement error due to the Seebeck effect.

[0099] Fig. 14 is a flowchart of the current measurement process. The current measurement process in Fig. 14 differs from the current measurement process in Fig. 10 in that S30 is changed to S33.

[0100] S33 is a process for determining whether or not the operation time TB of the balancer 160 has reached a predetermined time TP. S33 is a process for determining whether or not the Seebeck effect caused by heat generation of the balancer 160 has occurred.

[0101] When the operation time TB of the balancer 160 reaches the predetermined time TP, the control unit 130 determines that the Seebeck effect is occurring, and starts measurement by the second measurement unit 58 (S40).

[0102] After the second measuring unit 58 starts measuring, if |Is-Im|>K (S60: YES), the measurement value of the current I is replaced with the measurement value Im of the second measuring unit 58, thereby making it possible to suppress measurement errors of the current I due to the Seebeck effect.

[0103] In the second embodiment, it is possible to suppress measurement errors in the current I during operation of the balancer 160 and after the operation has stopped.

[0104] <Embodiment 3> Fig. 15 is a flowchart of the current measurement process in embodiment 3. The current measurement process in Fig. 15 differs from the current measurement process in Fig. 10 in that S30 is changed to S35.

[0105] S35 judges whether the automobile 10, which is moving or stopped, has switched to parking. When the automobile 10, which is moving or stopped, switches to parking, the engine 20 and other heat generating elements stop, the temperature drops, and a temperature change occurs around the heat generating elements.

[0106] If the battery 50 is arranged around a heating element, after parking, the difference in how the bus bars 63N1 and 63N2 cool will cause a temperature difference ΔT between both ends of the first measuring unit 54, which may result in a measurement error due to the Seebeck effect.

[0107] The control unit 130 acquires information regarding the state of the automobile 10 from the vehicle ECU 30, and when the automobile 10 transitions from a driving or stopped state to a parked state, it determines that the Seebeck effect is occurring and starts measurement by the second measurement unit 58 (S40).

[0108] After the second measuring unit 58 starts measuring, if |Is-Im|>K (S60: YES), the measurement value of the current I is replaced with the measurement value Im of the second measuring unit 58, thereby making it possible to suppress measurement errors of the current I due to the Seebeck effect.

[0109] In the third embodiment, if the Seebeck effect occurs immediately after parking, the measurement value of the first measurement unit 54 is replaced with the measurement value of the second measurement unit 58, thereby making it possible to suppress measurement errors in the current I. After the Seebeck effect is eliminated, the second measurement unit 58 is stopped, thereby making it possible to suppress power consumption of the battery 50. By suppressing power consumption of the battery 50, the SOC of the battery 50 can be maintained while the vehicle is parked. If the battery 50 is for cranking (for starting the engine), it is possible to ensure the battery capacity required for cranking.

[0110] <Embodiment 4> In the first embodiment, the measurement value of the first measuring unit 54 is replaced with the measurement value of the second measuring unit 58 only during the period tb-tc during which the current I is equal to or less than the predetermined value X, among the period ta-tc during which the measurement error exceeds the threshold. The measurement value may also be replaced during the period during which the current I is equal to or more than the predetermined value X.

[0111] As shown in FIG. 16, the measurement value of the first measuring unit 54 may be replaced with the measurement value of the second measuring unit 58 also during the period from t1 to tb (the period during which the current I is equal to or greater than the predetermined value X) in addition to the period from tb to tc.

[0112] <Other embodiments> The present invention is not limited to the embodiments described above and illustrated in the drawings, and the following embodiments, for example, are also included within the technical scope of the present invention.

[0113] (1) In the above embodiment, the secondary battery cell 62 is illustrated as an example of the power storage cell. The power storage cell is not limited to the secondary battery cell 62, but may be a capacitor. The secondary battery cell 62 is not limited to a lithium ion secondary battery, but may be another non-aqueous electrolyte secondary battery. A lead storage battery or the like may also be used. The power storage cells are not limited to being connected in series or parallel, but may be connected in series or configured as a single cell.

[0114] (2) In the above embodiment, a "shunt resistor" is exemplified as the first measuring unit 54, and a "magnetic sensor" is exemplified as the second measuring unit 58. The combination of the first measuring unit 54 and the second measuring unit 58 is not limited to the combination of a "shunt resistor" and a "magnetic sensor". The first measuring unit 54 may be a measuring unit other than a shunt resistor. The second measuring unit may be a measuring unit other than a magnetic sensor as long as it has a smaller current measurement error due to the Seebeck effect than the first measuring unit. The second measuring unit may use the same detection principle as the first measuring unit as long as it has a smaller current measurement error due to the Seebeck effect than the first measuring unit.

[0115] (3) In the above embodiment, the management device 100 is provided inside the battery 50. The battery 50 only needs to have at least the assembled battery 60 and measurements, and the management device 100 may be provided outside the battery 50. In the embodiment, the first measurement unit 54 and the second measurement unit 58 are provided on the negative electrode side of the assembled battery 60, but they may be provided on the positive electrode side. The first measurement unit 54 and the second measurement unit 58 may be provided separately on the positive electrode and the negative electrode.

[0116] (4) In the above embodiment, the battery 50 is for a vehicle. The use of the battery 50 is not limited to a specific use. The battery 50 can be used for various purposes, such as for moving objects (vehicles, ships, AGVs, etc.) and stationary uses (electricity storage devices for uninterruptible power supply systems and solar power generation systems). The same applies to the battery 150.

[0117] (5) It is also considered that measurement errors due to the Seebeck effect may occur due to changes in the outside air temperature of the battery 50, 150. Instead of "S30", "S33", and "S35", the occurrence of the Seebeck effect may be determined based on whether the outside air temperature of the battery 50, 150 has changed by a predetermined temperature or more. The outside air temperature may be detected by providing a dedicated temperature sensor, or, if a temperature sensor is installed inside the vehicle, temperature information may be obtained from the vehicle ECU 30.

[0118] (6) In the above embodiment, a case has been described in which a temperature difference ΔT occurs on both sides of the first measurement unit 54 due to a difference in heat capacity between the bus bars 63N1 and N2. The cause of the temperature difference ΔT is not limited to the difference in heat capacity between the bus bars 63N1 and N2. For example, a temperature difference ΔT occurs on both sides of the first measurement unit 54 when one bus bar 63N1 is more susceptible to temperature rise than the other bus bar 63N2 due to a positional relationship with a heat generating element such as the balancer 160 or the battery pack 60. This technology can also be applied to such a case.

[0119] (7) In the embodiment, the difference (Is-Im) between the measurement value Is of the first measurement unit 54 and the measurement value Im of the second measurement unit 58 is defined as the measurement error of the first measurement unit 54 (S60). The measurement error may be calculated using any other method based on the two measurement values ​​Is and Im.

[0120] (8) In the above embodiment, when the measurement error of the first measurement unit 54 is larger than the threshold value K, the measurement value Is of the first measurement unit 54 is replaced with the measurement value Im of the second measurement unit 58. The measurement value Is of the first measurement unit 54 may be corrected with the measurement value Im of the second measurement unit 58. For example, the measurement value Is of the first measurement unit 54 may be corrected by multiplying the difference (Is-Im) between the two measurement values ​​Is and Im by a correction coefficient. By setting the correction coefficient to 1 or less, it is possible to reduce the change in the measurement value due to correction compared to replacement of the measurement value.

[0121] (9) In the third embodiment, measurement errors caused by the Seebeck effect that occur after the automobile 10, which is moving or stopped, transitions to parking are suppressed. Measurement errors caused by the Seebeck effect that occur after the automobile 10, which is parked, transitions to moving may also be suppressed. In other words, the occurrence of the Seebeck effect may be determined based on the presence or absence of a change in the state of the vehicle, and if the Seebeck effect is occurring, measurement errors caused by the Seebeck effect may be suppressed. The change in the state of the vehicle may be the engine being started or stopped.

[0122] (10) Measurement errors due to the Seebeck effect occur when a temperature difference occurs at both ends of the first measuring unit 54, and disappear when the temperature difference disappears. Therefore, by comparing the two measurement values ​​Is and Im, it is possible to determine whether the first measuring unit 54 or the second measuring unit 58 is malfunctioning. For example, if a difference occurs between the two measurement values ​​Is, Im due to the Seebeck effect, and if the two measurement values ​​Is, Im do not match and a difference still occurs even after a predetermined period of time has passed since the cause of the Seebeck effect has disappeared (after the temperature difference has been eliminated due to temperature equilibrium), it can be determined that either the first measurement unit 54 or the second measurement unit 58 is malfunctioning. [Explanation of symbols]

[0123] 10. Automobiles 50, 150 Battery (energy storage device) 54 First Measurement Section 58 Second Measurement Section 60 Battery pack 62 Secondary battery cell (storage cell) 100 Management device 130 Control section 160 Balancer

Claims

1. A power storage device, A storage cell; A first measurement unit that measures a current of the storage cell; a second measurement unit having a smaller current measurement error due to the Seebeck effect than the first measurement unit; A control unit, The control unit is A power storage device that calculates a measurement error of the first measurement unit due to the Seebeck effect based on the measurement values ​​of the first measurement unit and the second measurement unit, and corrects or replaces the measurement value of the first measurement unit with the measurement value of the second measurement unit if the measurement error of the first measurement unit is greater than a threshold value.

2. The power storage device according to claim 1 , the second measurement unit consumes more power than the first measurement unit, When the control unit determines that the Seebeck effect is occurring in the first measurement unit, the control unit starts measuring the current by the second measurement unit.

3. The power storage device according to claim 2, When the control unit determines that the Seebeck effect has disappeared after the second measurement unit starts measurement, the control unit stops the measurement of the current by the second measurement unit.

4. The power storage device according to claim 2 or 3, The control unit determines the occurrence of the Seebeck effect based on the current of the storage cell.

5. The power storage device according to claim 2 or 3, A balancer is provided to equalize the voltages of the storage cells by resistive discharge, The control unit determines the occurrence of the Seebeck effect based on an operation time of the balancer.

6. The vehicle-mounted power storage device according to claim 2 or 3, The control unit determines whether the Seebeck effect occurs based on the presence or absence of a change in a state of the vehicle.

7. A current measurement method, comprising: A current of the power storage cell is measured by two measurement units, a first measurement unit and a second measurement unit having a smaller measurement error due to the Seebeck effect than the first measurement unit; calculating a measurement error of the first measurement unit due to the Seebeck effect based on the measurement values ​​of the first measurement unit and the second measurement unit; A current measurement method, comprising: correcting or replacing the measurement value of the first measurement unit with the measurement value of the second measurement unit when the measurement error of the first measurement unit is greater than a threshold value.

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