Measuring device, power storage device, measuring system, and offset error measuring method

Abstract

A measuring device (50) for an electrochemical element (30) connected to a terminal portion (22P) connected to a load via a first switch (40), comprising: a current limiting portion (75) provided in a bypass path (BP) of the first switch (40); a current sensor (60) for measuring the current of the electrochemical element (30); and a processing portion (100), wherein the current limiting portion (75) is configured to measure the current of the electrochemical element (30) when a voltage difference ΔV between a voltage of the electrochemical element (30) and a voltage of the terminal portion (22P) is greater than a given value. The invention relates to a method for measuring an offset error ε of the current sensor (60) in a process of allowing power to be supplied to the load through the bypass path (BP), setting the bypass path (BP) to be current-free when the voltage difference ΔV is less than a given value, and performing a measurement process of measuring an offset error ε of the current sensor (60) after the first switch (40) is disconnected until the voltage difference ΔV becomes a given value due to a voltage change at the terminal portion (22P) caused by discharge of a charge-discharge element (170) connected in parallel with the load.

Description

Technical Field

[0001] The present invention relates to a technique for detecting an offset error of a current sensor. Background Art

[0002] As described in Patent Document 1 listed below, the SOC of a battery mounted on a vehicle is estimated by integrating the current detected by a current sensor.

[0003] Prior Art Literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-83256 Summary of the invention

[0006] Problems to be solved by the invention

[0007] Even when the true value of a current sensor is zero, there is an offset error that indicates a value other than zero. By detecting the measured value of the current sensor while the current is cut off, the offset error can be corrected. However, if the current is cut off to measure the offset error, the power supply to the load will be interrupted.

[0008] The present invention has been made based on the above-described situation, and an object of the present invention is to measure an offset error of a current sensor while maintaining power supply to a load.

[0009] Means for solving problems

[0010] A measuring device for measuring the current of an electrochemical element connected to a terminal portion connected to a load via a first switch comprises: a current limiting unit, which is arranged in a bypass path of the first switch; a current sensor, which measures the current of the electrochemical element; and a processing unit, wherein the current limiting unit allows power to be supplied to the load through the bypass path when the voltage difference between the voltage of the electrochemical element and the voltage of the terminal portion is greater than a given value, and sets the bypass path to no current when the voltage difference is less than a given value, and the processing unit performs a measurement process for measuring an offset error of the current sensor after the first switch is opened until the voltage difference becomes a given value due to a change in the voltage of the terminal portion caused by the discharge of a charge-discharge element connected in parallel with the load.

[0011] The above-mentioned technology can be applied to a power storage device, a measurement system, and a method for measuring an offset error, and can be realized in various forms such as a program for measuring an offset error and a storage medium storing the program.

[0012] Effects of the Invention

[0013] According to one aspect of the present invention, an offset error can be measured while maintaining power supply to a load. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a side view of the automobile in the first embodiment.

[0015] Figure 2 It is a three-dimensional diagram of a battery.

[0016] Figure 3 It is an exploded perspective view of a battery.

[0017] Figure 4 is a block diagram showing the electrical structure of a battery.

[0018] Figure 5 This is a diagram showing a current path to the vehicle ECU immediately after the first switch is turned off.

[0019] Figure 6 It is a diagram showing a current path to the vehicle ECU when the diode is turned on.

[0020] Figure 7 It is a diagram showing the current path to the vehicle ECU when the diode reaches the forward voltage.

[0021] Figure 8 is a graph showing a current waveform and a voltage waveform.

[0022] Fig. 9 It is magnified Figure 8 Part of the diagram.

[0023] Fig.10 This is a flowchart showing the flow of the offset error measurement process.

[0024] Fig.11 It is a block diagram showing another embodiment of a storage battery.

[0025] Fig.12 It is a block diagram showing another embodiment of a storage battery.

[0026] Fig.13 It is a block diagram showing another embodiment of a storage battery.

[0027] Fig.14 It is a block diagram showing another embodiment of a storage battery. DETAILED DESCRIPTION

[0028] A measuring device for measuring the current of an electrochemical element connected to a terminal portion connected to a load via a first switch comprises: a current limiting unit, which is arranged in a bypass path of the first switch; a current sensor, which measures the current of the electrochemical element; and a processing unit, wherein the current limiting unit allows power to be supplied to the load through the bypass path when the voltage difference between the voltage of the electrochemical element and the voltage of the terminal portion is greater than a given value, and sets the bypass path to be current-free when the voltage difference is less than a given value, and the processing unit performs a measurement process for measuring an offset error of the current sensor after the first switch is disconnected until the voltage difference becomes a given value due to a change in the voltage of the terminal portion caused by the discharge of a charge-discharge element connected in parallel with the load.

[0029] In this structure, if the first switch is switched from on to off, the main path becomes non-connected, and the current from the electrochemical element to the load is cut off. If the current from the electrochemical element is cut off, the charge and discharge element connected in parallel discharges, and current flows through the load. If the charge and discharge element discharges, the voltage of the terminal portion changes. During the period until the voltage difference between the terminal portion and the electrochemical element becomes a given value, the bypass path becomes current-free through the current limiting portion. Therefore, during the period when the bypass path becomes current-free, the offset error of the current sensor can be detected. If the voltage difference with the storage element reaches a given value, the current limiting portion allows the power supply to the load through the bypass path. Therefore, the supply of power from the electrochemical element to the load can be achieved through the bypass path.

[0030] In this structure, even if the first switch is switched from on to off to cut off the main path, the power supply path from the electrochemical element to the load is not cut off because the bypass path is provided. Moreover, during the measurement period of the offset error, the bypass path becomes currentless, so the charge-discharge element discharges to the load. Therefore, the offset error can be measured without power failure (power supply to the load is cut off).

[0031] The electrochemical element is a power storage element that supplies electric power to a vehicle load that does not allow power interruption, and the processing unit switches the first switch from on to off to execute the measurement process while the vehicle is stopped.

[0032] Vehicle loads that are highly related to vehicle safety, such as the engine starting device, the starting device of the drive system for EV, the electronic control device such as the vehicle ECU, and the auxiliary machines for operating the drive unit (engine, main drive motor for EV), require that the power should not be cut off not only during driving and parking, but also when parked. In other words, it is required that the power supply should not be cut off regardless of the state of the vehicle (that is, there should always be power supply). In this structure, for such vehicle loads that do not allow the power supply to be cut off, the offset error can be measured without the power being cut off, so that the requirement of ensuring safety can be met.

[0033] In this structure, the offset error is measured when the vehicle is parked, which is less likely to cause a dangerous incident than when the vehicle is traveling or parked. By measuring the offset error when the vehicle is parked, it is not necessary to measure the offset error when the vehicle is traveling or parked, so that high safety of the vehicle can be ensured. In addition, the current flowing through the vehicle load is smaller when the vehicle is parked than when the vehicle is traveling or parked. Therefore, a current limiting unit with a small rated capacity can be used.

[0034] A second switch may be provided in series with the current limiting unit in the bypass path. In this structure, the bypass path can be cut off by opening the second switch when the offset error is not measured. By cutting off the current when the offset error is not measured, the failure of the current limiting unit can be prevented, thereby improving the measurement accuracy of the offset error.

[0035] The current limiting unit is preferably a diode. If it is a diode, it can switch between energization and non-energization according to the voltage difference, so it is suitable as a current limiting element. By detecting the voltage difference between the two ends of the diode, it is possible to judge whether it is conductive or non-conductive, and by performing measurement processing during the non-conductive period, it is possible to measure the offset error with good accuracy.

[0036] <Implementation Method 1>

[0037] 1. Battery Description

[0038] Figure 1 is the side view of the car, Figure 2 This is a three-dimensional diagram of a battery. Figure 3 This is an exploded perspective view of the battery. Figure 4 is a block diagram showing the electrical structure of a battery.

[0039] The vehicle 1 as the upper system is an engine-driven vehicle equipped with an engine. Figure 1 As shown in FIG. 1 , the automobile 1 includes a battery 20 as an electric storage device. Figure 2As shown, the storage battery 20 has a block-shaped battery case 21, and a battery pack 30 composed of a plurality of secondary batteries B1 to B4 and a circuit board 28 are housed in the battery case 21. The battery case 21 corresponds to the "housing body" of the present invention.

[0040] like Figure 3 As shown, the battery case 21 is composed of: a box-shaped case body 23 opened at the top, a positioning member 24 for positioning the plurality of secondary batteries B1 to B4, a middle cover 25 mounted on the upper part of the case body 23, and an upper cover 26. Figure 3 As shown, in the case body 23, a plurality of single cell chambers 23A for individually accommodating the secondary batteries B1 to B4 are arranged side by side in the X direction.

[0041] like Figure 3 As shown, the positioning member 24 has a plurality of bus bars 27 arranged on the upper surface. The positioning member 24 is arranged above the plurality of secondary batteries B1 to B4 arranged in the case body 23 , so that the plurality of secondary batteries B1 to B4 are positioned and connected in series by the plurality of bus bars 27 .

[0042] like Figure 2 As shown, the middle cover 25 is substantially rectangular in a plan view. A pair of terminal portions 22P and 22N for connecting to a harness terminal (not shown) are provided at both ends in the X direction of the middle cover 25. The pair of terminal portions 22P and 22N are made of metal such as lead alloy, for example, and the terminal portion 22P is a positive terminal portion, and the terminal portion 22N is a negative terminal portion.

[0043] The upper surface of the middle cover 25 is provided with a housing portion 25A. The circuit substrate 28 is housed inside the housing portion 25A of the middle cover 25, and the middle cover 25 is mounted on the case body 23 so that the secondary battery B and the circuit substrate 28 are connected. In addition, the upper cover 26 is mounted on the upper portion of the middle cover 25, and covers the upper surface of the housing portion 25A housing the circuit substrate 28.

[0044] Reference Figure 4 The electrical structure of the battery 20 will be described. The battery 20 is a 12V system for a vehicle, and includes a battery pack 30 , a first switch 40 , and a measuring device 50 .

[0045] The battery pack 30 is composed of four lithium ion secondary batteries B1 to B4 connected in series. The lithium ion secondary batteries B1 to B4 are an example of the "electrochemical element (electricity storage element)" of the present invention.

[0046] The positive electrode of the battery pack 30 is connected to the positive electrode side terminal portion 22P via the first switch 40. The negative electrode of the battery pack 30 is connected to the negative electrode side terminal portion 22N via the current detection resistor 61. Symbol 35P is a power-on circuit on the positive electrode side of the battery pack 30, and symbol 35N is a power-on circuit on the negative electrode side of the battery pack 30.

[0047] The first switch 40 is a switch for interrupting the current of the battery pack 30 , and can be formed of a relay, a FET, etc. The first switch 40 is disposed on the circuit board 28 and is accommodated in the battery case 21 .

[0048] The measuring device 50 is a whole device for measuring the current of the battery pack 30, and includes a current sensor 60, a parallel circuit 70, and a processing unit 100. The measuring device 50 is disposed on the circuit board 28 or in the vicinity of the circuit board 28 and is accommodated in the battery case 21.

[0049] The current sensor 60 is composed of a current detection resistor 61 and an AFE (Analog Front End) 65. The current detection resistor 61 is arranged in the current supply circuit 35N on the negative electrode side of the battery pack 30 inside the battery case 21. The current detection resistor 61 is arranged on the circuit board 28 or near the circuit board 28.

[0050] The AFE 65 detects the voltage across the current detection resistor 61 and changes the analog value into a digital value. The AFE 65 is connected to the processing unit 100 via a signal line. The AFE 60 is disposed on the circuit board 28 .

[0051] The parallel circuit 70 is located on the bypass path BP of the first switch 40 and is connected in parallel with the first switch 40. The parallel circuit 70 is composed of a second switch 71 and a diode 75. The FET 71 and the diode 75 are connected in series. The parallel circuit 70 is provided on the circuit board 28.

[0052] The second switch 71 is a P-channel field effect transistor, with its source connected to the positive electrode of the battery pack 30 and its drain connected to the anode of the diode 75. The diode 75 sets the discharge direction of the battery pack 30 to the forward direction, with its anode connected to the drain of the second switch 71 and its cathode connected to the positive terminal 22P. Figure 4 Reference numeral 90 is a driving circuit 90 for driving the second switch 71 .

[0053] The processing unit 100 includes a CPU (central processing unit) 101 having a calculation function, a memory 103 , a ROM 105 , a communication unit 107 , and the like, and is disposed on the circuit board 28 .

[0054] The CPU 101 sends commands to the first switch 40 and the second switch 71 to control the on and off of the first switch 40 and the second switch 71. "On" means closed (circuit closed), and "off" means open (circuit opened).

[0055] CPU 101 performs processing for detecting current I of lithium ion secondary batteries B1 to B4 based on the output of AFE 65 and processing for estimating SOC of lithium ion secondary batteries B1 to B4 based on the detected current I.

[0056] SOC (state of charge) is the ratio of the remaining capacity to the full capacity, and is expressed by the following formula (1). SOC can be estimated based on the integral value of the current I over time, as shown in the following formula (2). The sign of the current is set to positive during charging, and the sign of the current is set to negative during discharging.

[0057] SOC=Cr / Co×100 (1)

[0058] Co is the full charge capacity of the secondary battery, and Cr is the remaining capacity of the secondary battery.

[0059] SOC=SOCo+100×∫Idt / Co (2)

[0060] SOCo is the initial value of SOC, and I is the current.

[0061] The ROM 105 stores a program for estimating the SOC and a process for measuring the offset error ε. Fig.10 The program can be stored in a recording medium such as a CD-ROM and transferred, etc. The program can also be distributed using a telecommunication line.

[0062] The communication unit 107 is configured to communicate with a vehicle ECU (Electronic Control Unit) 150 mounted on the automobile 1. The vehicle ECU 150 is a vehicle load that does not allow power to be cut off regardless of the vehicle state such as driving, parking, or stopping. After being mounted on the vehicle, the communication unit 107 is connected to the vehicle ECU 150 through a signal line, and the processing unit 100 can receive information related to the vehicle such as the operating state (stop, drive) of the engine from the vehicle ECU 150.

[0063] like Figure 4As shown, the vehicle ECU 150 is connected to the battery 20 via the power lines 135P and 135N, so that power is supplied from the battery 20 to the vehicle ECU 150. The vehicle ECU 150 is provided with a capacitor 170. The capacitor 170 is located between the power line 135P on the positive side and the power line 135N on the negative side, and is connected in parallel with the vehicle ECU 150. The capacitor 170 is provided to stabilize the power supply voltage of the vehicle ECU 150. The capacitor 170 plays a role of discharging power to the vehicle ECU 150 during the period of measuring the offset error ε of the current sensor 60. The capacitor 170 is equivalent to the "charge and discharge element" of the present invention.

[0064] The storage battery 20 includes lithium-ion secondary batteries B1 to B4, a battery case 21 accommodating the lithium-ion secondary batteries B1 to B4, a first switch 40, and a measuring device 50, and thus corresponds to the "electricity storage device" of the present invention. The battery pack 30 and the measuring device 50 in the storage battery 20 correspond to the "measuring system" of the present invention.

[0065] 2. Offset error ε of current sensor 60 and correction

[0066] Even when the true value of the current sensor 60 is zero, there is an offset error ε indicating a value other than zero. The offset error ε can be measured by detecting the measured value of the current sensor 60 (the output value of the AFE 65) in a state where the current I of the battery pack 30 is cut off. However, if the current I is cut off in order to measure the offset error ε, the power supply to the vehicle ECU 150 is interrupted.

[0067] In this configuration, after the first switch 40 is turned off, the capacitor 170 is discharged. As the voltage of the capacitor 170 decreases due to the discharge, the voltage V2 of the terminal 22P decreases. The period T until the voltage difference ΔV between the voltage V2 of the terminal 22P and the voltage V1 of the positive electrode of the battery pack 30 reaches the predetermined value Vx is 23 , the diode 75 is non-conductive. During the period T when the diode 75 is non-conductive 23 , paying attention to the situation where the current I of the battery pack 30 is cut off, the offset error ε of the current sensor 60 is measured.

[0068] Below, refer to Figures 4 to 9 First, the processing unit 100 controls the first switch 40 to be turned on and the second switch 71 to be turned off in normal times (when the offset error ε is not measured). Figure 4 As shown, current flows from the battery pack 30 to the vehicle ECU 150 through the main path L1 passing through the first switch 40 .

[0069] The capacitor 170 connected in parallel to the vehicle ECU 150 is charged, and the voltage V2 of the terminal portion 22P on the positive electrode side of the battery 20 becomes equal to the voltage V1 on the positive electrode side of the battery pack 30 ( V2 = V1 ).

[0070] When measuring the offset error ε, the processing unit 100 first switches the second switch 71 from off to on ( Figure 8 Then, the first switch 40 is switched from on to off ( Figure 8 The second switch 71 only needs to be turned on at least when the offset error ε is measured, and may be always turned on.

[0071] Figure 8 The “I 1 ” represents the current flowing through the main path L1, “I 2 ” represents the discharge current of capacitor 170, “I 3 " represents the current flowing through the current path L3. "I 13 ” is “I 1 ” and “I 3 The total current of ” is the discharge current from the battery pack 30 to the vehicle ECU 150.

[0072] At time t2, when the first switch 40 is switched from on to off, the main path L1 is disconnected and the capacitor 170 starts to discharge. Figure 5 The current path L2 shown in FIG. 1 is a path through which current flows from the capacitor 170. The voltage of the capacitor 170 decreases due to discharge, so after the first switch 40 is switched, as shown in FIG. Figure 8 , Fig. 9 As shown, the voltage V2 of the terminal portion 22P on the positive electrode side of the storage battery 20 drops, and a voltage difference Δ is generated between the voltage V2 and the voltage V1 on the positive electrode side of the battery pack 30 .

[0073] ΔV=V1-V2 (3)

[0074] exist Figure 8 , Fig. 9 At the time t3 shown, if the voltage difference Δ reaches a given value V X (As an example, 0.55V), the diode 75 is turned on. If the diode 75 is turned on, the power supply to the vehicle ECU 150 through the bypass path BP is allowed. Figure 6 As shown, in vehicle ECU 150 , current flows through current path L2 using capacitor 170 as a power source and current path L3 from battery pack 30 through parallel circuit 70 (bypass path BP).

[0075] After the diode 75 is turned on, as the voltage difference ΔV increases, the current flowing through the current path L3 increases, and the current L2 flowing through the current path L2 decreases. Figure 8 In the example of FIG. 1 , at time t4 when the voltage difference ΔV reaches the forward voltage Vf of the diode 75 (0.6 V as an example), the current in the current path L2 becomes zero. Thereafter, the power is supplied to the vehicle ECU 150 via the current path L3 passing through the diode 75 .

[0076] The period T from when the first switch 40 is switched off at time t2 to when the diode 75 is turned on at time t3 23 , the diode 75 is non-conductive, and no current is output from the battery pack 30. 23 By detecting the measured value of the current sensor 60 (the output of the AFE 65 ), the offset error ε of the current sensor 60 can be measured.

[0077] The diode 75 is conductive when the voltage difference ΔV is greater than a given value Vx, allowing power to be supplied to the vehicle ECU 150 through the bypass path BP, and is non-conductive when the voltage difference ΔV is less than the given value Vx, making the bypass path BP currentless. Therefore, the diode 75 corresponds to the "current limiting unit" of the present invention.

[0078] Fig.10 1 is a diagram showing the flow of the measurement flow of the offset error ε. The measurement flow is composed of six steps S10 to S60. Before the measurement flow is executed, the CPU 101 controls the first switch 40 to be turned on and the second switch 71 to be turned off.

[0079] The CPU 101 first determines whether the vehicle 1 equipped with the battery 20 is parked (S10). The determination of being parked can be made based on the state of communication with the vehicle ECU 150. That is, when the vehicle 1 is traveling or parked, the vehicle ECU 150 and the processing unit 100 frequently communicate at a given cycle.

[0080] On the other hand, when the vehicle 1 is parked, the vehicle ECU 150 stops the communication. Therefore, when the communication with the vehicle ECU 100 is interrupted for a predetermined period of time, it can be determined that the vehicle 1 is parked.

[0081] If it is determined that the vehicle 1 is parked ( S10 : YES), the CPU 101 next performs a process of switching the second switch 71 from OFF to ON and then switching the first switch 40 from ON to OFF ( S20 , S30 ).

[0082] Next, the CPU 101 switches the first switch 40 off until the diode 75 is turned on during the period T 23, the offset error ε of the current sensor 60 is measured, and the measured offset error ε is stored in the memory 103 (S40). 23 The duration of φ can be obtained from the capacitance of capacitor 170, the discharge current of capacitor 170, and the voltage difference Vx when diode 75 is turned on. An experimental value can also be used.

[0083] Next, the CPU 101 performs a process of switching the first switch 40 from OFF to ON, and then performs a process of switching the second switch 71 from ON to OFF ( S50 , S60 ). The above-described process completes the measurement flow of the offset error ε.

[0084] As shown in the following formula (4), when measuring the current of the lithium-ion secondary batteries B1 to B4, the CPU 101 performs a correction process for correcting the measured value of the current sensor 60 using the offset error ε.

[0085] In this way, the measurement accuracy of the current I can be improved, and the SOC of the lithium-ion secondary batteries B1 to B4 can be estimated with high accuracy.

[0086] It=Io-ε (4)

[0087] It is the corrected current value, I o is the current value before correction, and ε is the offset error. In equation (4), the charging direction is set to positive and the discharging direction is set to negative for the signs of the current and the offset error.

[0088] Fig.10 In the embodiment, it is preferred that the measurement process of the offset error ε is repeatedly performed at given intervals such as once a week, and the offset error ε is updated to the latest value. In this way, even if the offset error ε changes due to temperature changes, the influence thereof can be reduced, and the measurement accuracy of the current I and the estimation accuracy of the SOC can be further improved.

[0089] The parallel circuit 70 can be used as a diagnostic circuit for a closure failure of the first switch 40. That is, if the first switch 40 is switched from on to off while the second switch 71 of the parallel circuit 70 is on, if the first switch 40 operates normally, the voltage ΔV (= V1-V2) across the first switch 40 becomes the forward voltage V of the diode 75. F On the other hand, when the first switch 40 is fixed to be closed, the voltage ΔV between both ends becomes zero. Therefore, by detecting the voltage ΔV between both ends of the first switch 40, it is possible to diagnose whether or not a closing failure has occurred in the first switch 40.

[0090] 4. Effect description

[0091] In this configuration, even if the first switch 40 is switched from on to off to cut off the main path L1, the bypass path BP is provided, so the power supply path from the battery pack 30 to the vehicle ECU 150 is not cut off. In addition, during the measurement period of the offset error ε, the diode 75 of the bypass path BP becomes non-conductive, and the current I of the battery pack 30 is temporarily cut off. However, the period T during which the current I is cut off is 23 , the capacitor 170 discharges to the vehicle ECU 150, and if the diode 75 is turned on, then the current I can be supplied from the battery pack 30 via the bypass path BP. Therefore, the offset error ε can be measured while maintaining the power supply to the vehicle ECU 150 that does not allow power to be cut off. In this structure, for such a vehicle load that does not allow power to be cut off, the offset error ε can be measured without power failure, so it can meet the need to ensure safety.

[0092] When the vehicle 1 is parked, which is less likely to cause a dangerous incident than when the vehicle 1 is traveling or parked, the processing unit 100 switches the first switch 40 from on to off, and measures the offset error ε of the current sensor 60. By measuring the offset error ε when the vehicle is parked, it is not necessary to measure the offset error ε when the vehicle is traveling or parked, so that high safety of the vehicle can be ensured. In addition, compared with when the vehicle is traveling or parked, the current consumed by the vehicle ECU 150 is small, and the current flowing through the diode 75 when it is turned on is small. Therefore, a diode 75 with a small rated capacity can be used.

[0093] In this structure, when the offset error ε is not measured (T 23 The CPU 101 controls the second switch 71 to be turned off during the period other than the period of time when the battery pack 30 is in the state of overdischarge, by turning off the second switch 71, the bypass path BP can be cut off. By cutting off the current when the measurement is not in progress, the failure of the diode 75 as the current limiting unit can be prevented, thereby improving the measurement accuracy of the offset error ε. In addition, when the battery pack 30 has an abnormality such as overdischarge, the current flowing through the bypass path BP can be cut off by turning off the second switch 71.

[0094] <Other Implementation Methods>

[0095] The present invention is not limited to the embodiments described in the above description and drawings, and for example, the following embodiments are also included in the technical scope of the present invention.

[0096] (1) In Embodiment 1, a measuring device 50 for measuring the current of lithium-ion secondary batteries B1 to B4 is illustrated. The present technology can be widely applied to electrochemical elements other than lithium-ion secondary batteries B1 to B4 as long as it is a measuring device for measuring current. Electrochemical elements include secondary batteries, electric double layer capacitors and other storage elements, primary batteries that only discharge, fuel cells, solar cells, etc. In Embodiment 1, a method of connecting multiple lithium-ion secondary batteries B1 to B4 in series is illustrated, but it can also be a single cell structure.

[0097] (2) In Embodiment 1, an example is shown in which a battery 20 as a power storage device is mounted on an engine-driven vehicle. The use of the battery 20 is not limited to engine-driven vehicles. It can also be mounted on electric vehicles and hybrid electric vehicles. In addition to vehicles, the present technology can also be applied to power storage devices for aircraft, ships, and railways. In particular, it is preferably used for loads that do not allow power to be cut off, but it can also be used for some loads that allow power to be cut off.

[0098] (3) In the first embodiment, the battery pack 30 supplies power to the vehicle ECU 150, but the power supply target (vehicle load) is not limited to the vehicle ECU 150. Other vehicle loads that do not allow power to be cut off, such as the starter motor for driving the engine and auxiliary machines of the engine, may also be used.

[0099] (4) In the first embodiment, an example is shown in which the first switch 40 and the parallel circuit 70 are provided on the positive electrode side of the battery pack 30, and the current sensor 60 is provided on the negative electrode side of the battery pack 30. The structure may be reversed, and the first switch 40 and the parallel circuit 70 may be provided on the negative electrode side of the battery pack 30, and the current sensor 60 may be provided on the positive electrode side of the battery pack 30. In the case where the first switch 40 and the parallel circuit 70 are provided on the negative electrode, when the first switch 40 is turned off, the voltage of the terminal 22N changes due to the discharge of the capacitor 170, and a voltage difference ΔV is generated between the terminal 22N on the negative electrode side and the negative electrode of the battery pack 30. During the period until the generated voltage difference ΔV reaches the predetermined value Vx, the diode 75 becomes non-conductive, and thus the offset error ε of the current sensor 60 can be measured during this period. When the first switch 40 and the parallel circuit 70 are arranged on the negative electrode side, the voltage of the terminal 22N becomes higher than the negative electrode of the battery pack 30 due to the discharge of the capacitor 170. Therefore, the anode of the diode 75 is connected to the terminal 22N and the cathode is connected to the negative electrode of the battery pack 30, so that the discharge direction becomes the forward direction.

[0100] (5) In Embodiment 1, the capacitor 170 is provided outside the battery. The capacitor 170 may be disposed inside the battery. Fig.11The battery 200 shown in the figure has a capacitor 270 disposed inside the battery case 21. One end of the capacitor 270 is connected to the terminal portion 22P on the positive side, and the other end is connected to the terminal portion 22N on the negative side. The capacitor 270 is charged by the battery pack 30. When the first switch 40 is turned off to cut off the main path L1, the capacitor 270 is discharged and supplies power to the vehicle ECU 150. Due to the discharge of the capacitor 270, the period T until the voltage difference ΔV between the positive electrode voltage V1 of the battery pack 30 and the positive electrode terminal portion V2 reaches a given value Vx 23 , the diode 75 is non-energized, and the bypass path BP becomes currentless. Therefore, during the period T 23 , the processing unit 100 can measure the offset error ε of the current sensor 60. In this configuration, since the capacitor 270 is built into the battery 20, even if the capacitor 170 is not provided on the vehicle 1 side, the offset error ε of the current sensor 60 can be measured while continuing to supply power to the vehicle load 150. The capacitor 270 built into the battery 20 is on for a period T during which the processing unit 100 performs the measurement process of the offset error ε. 23 This plays the role of discharging the vehicle load 150 .

[0101] (6) The capacitors 170 and 270 only need to discharge when the first switch 40 is turned off, and can be replaced by a charging and discharging element such as a secondary battery, for example.

[0102] (7) Embodiment 1 shows a diode 75 as an example of a current limiting unit. The current limiting unit only needs to allow power to be supplied to the load through the bypass path BP when the voltage difference ΔV between the voltage V1 of the battery pack 30 and the voltage V2 of the terminal portion 22P is greater than a given value Vx, and when the voltage difference ΔV is less than the given value, the bypass path BP is set to no current. The current limiting unit may also be a component other than a diode. Fig.12 In the battery 300 shown, a current limiting unit is formed by a diode-connected FET 310. The diode connection is a connection in which the gate and the source are short-circuited. The diode-connected FET 310 is similar to the diode 75. It is turned on when the voltage difference becomes greater than a given value, and is non-conductive otherwise. Therefore, it can replace the diode 75. Fig.12 The battery 300 disables the second switch 71.

[0103] (8) Fig.13The storage battery 400 shown in the figure is constituted by a current limiting unit 410 including a third switch 420 and a comparator 430. The comparator 430 detects a voltage difference ΔV between a voltage V1 of the positive electrode of the battery pack 30 and a voltage V2 of the terminal portion 22P on the positive electrode side. The comparator 430 outputs a signal to turn on the third switch 420 when the voltage difference ΔV is greater than a given value, and outputs a signal to turn off the third switch 420 when the voltage difference ΔV is less than the given value. Even when the current limiting unit 410 is constituted by the third switch 420 and the comparator 430, the third switch 420 is turned off during the period from when the first switch 40 is turned off until the voltage difference ΔV becomes a given value, so that the bypass path BP becomes currentless, and therefore the offset error ε of the current sensor 60 can be measured during this period. When the current limiting unit 410 is constituted by the third switch 420 and the comparator 430 , there is an advantage that a threshold (voltage difference) for switching the bypass path BP from a non-conductive state (third switch: off) to a conductive state (third switch: on) can be arbitrarily set.

[0104] (9) Fig.14 The battery 500 shown uses a buck regulator 510 as a current limiting unit. The buck regulator 510 steps down the input voltage (the voltage V1 of the battery pack) and outputs it. When the voltage V2 of the terminal portion 22P on the positive side is higher than the output voltage V3 of the buck regulator 510, the bypass path BP becomes non-current. Therefore, after the first switch 40 is turned off, the offset error ε of the current sensor 60 can be measured until the voltage V2 of the terminal portion on the positive side drops from the voltage V1 of the positive electrode of the battery pack 30 to the output voltage V3 of the buck regulator 510 due to the discharge of the capacitor 170. If the voltage V2 of the terminal portion 22P drops to the output voltage V3, the voltage V2 of the terminal portion 22P is maintained at the output voltage V3 of the buck regulator 510, and power can be supplied to the vehicle load 150 via the bypass path BP.

[0105] (10) In the first embodiment, the period T from when the first switch 40 is switched off until the diode 75 is turned on is calculated based on the capacitance of the capacitor 170, the discharge current of the capacitor 170, and the voltage difference Vx when the diode 75 is turned on. 23. The diode 75 is non-conductive when the voltage difference ΔV between the voltage V2 of the terminal portion 22P and the voltage V1 of the positive electrode of the battery pack 30 is less than a given value Vx, and is conductive when it reaches the given value Vx. Therefore, after the first switch 40 is switched off, the voltage V2 of the terminal portion 22P and the voltage V1 of the positive electrode of the battery pack 30 are detected and the voltage difference ΔV is calculated, and the offset error ε is measured during the period until the calculated voltage difference ΔV reaches the given value Vx. In this way, the measurement can be performed during the period when the diode 75 is not energized, so the measurement accuracy of the offset error ε is improved. In addition, even when the buck regulator 510 is used as a current limiting unit, the current-free period of the bypass path BP can be determined by detecting the voltage V2 of the terminal portion 22P and comparing it with the output voltage V3 of the buck regulator.

[0106] (11) In the first embodiment, whether the vehicle 1 is parked is determined based on the state of communication with the vehicle ECU 150, but it may also be determined based on the magnitude of the current I of the battery pack 30. In other words, it may be determined that the vehicle is parked when the current I is below a given value for a certain period of time. Alternatively, it may be determined based on the presence or absence of vibration for a given period of time or longer. The vibration may also be detected by a sensor.

[0107] (12) In the first embodiment, the correction process of correcting the current I of the lithium-ion secondary batteries B1 to B4 based on the offset error ε is performed. In addition, the SOC may be corrected without correcting the current I. Specifically, the SOC error (the SOC error caused by the offset error ε of the current sensor 60) may be corrected based on the accumulated time of the current I for calculating the SOC and the offset error ε.

[0108] (13) The measuring device 50 only needs to include the current sensor 60, the parallel circuit 70, and the processing unit 100, and these components 60, 70, 80 do not necessarily have to be arranged inside the battery. In the first embodiment, a structure in which the first switch 40 and the parallel circuit 70 are arranged inside the battery 20 is illustrated. The first switch 40 and the parallel circuit 70 only need to be mounted on the vehicle, or they can be arranged outside the battery 20. In addition, the current sensor 60 and the processing unit 100 also only need to be mounted on the vehicle, or they can be arranged outside the battery 20. That is, the battery 20 may be configured as a structure having only lithium-ion secondary batteries B1 to B4, and the processing unit 100 arranged outside the battery may obtain the current value during the period T from the current sensor 60 arranged outside the battery. 23 The offset error ε is measured using the measured value data.

[0109] (14) The measuring system may be any system as long as it includes the electrochemical element such as the battery pack 30 and the measuring device 50, and the measuring device 50 measures the current of the electrochemical element 30. The physical structure such as where the electrochemical element 30 and the measuring device 50 are arranged may be any structure.

[0110] (15) The technology disclosed in the first embodiment can be realized in various forms such as a program for measuring an offset error of a current sensor and a recording medium recording the program.

[0111] The first measurement program is a measurement program for measuring the offset error ε of the current sensor 60, which causes the computer 40 to perform the following measurement processing (S40): after the first switch 40 connecting the terminal portion 22P and the electrochemical element 30 is disconnected, until the current limiting element 75 provided in the bypass path BP of the first switch 40 sets the bypass path BP to a period T without current. 23 , and measure the offset error ε of the current sensor 60.

[0112] Explanation of symbols

[0113] 1 vehicle;

[0114] 20. Battery (equivalent to the "power storage device" of the present invention);

[0115] 30 battery packs;

[0116] 40 1st switch;

[0117] 60 current sensor;

[0118] 61 Current detection resistor;

[0119] 65 AFE;

[0120] 70 Parallel circuits;

[0121] 71 2nd switch;

[0122] 75 diode (equivalent to the “current limiting unit” of the present invention);

[0123] 100 Processing Department;

[0124] 101 CPU;

[0125] 150 vehicle ECU (equivalent to “vehicle load” of the present invention);

[0126] 170 capacitor (equivalent to the “charge and discharge element” of the present invention);

[0127] B1 to B4 Lithium ion secondary batteries (corresponding to the "electrochemical element (electricity storage element)" of the present invention).

Claims

1. A measuring device for measuring a current of an electrochemical element connected to a terminal portion connected to a load via a first switch, wherein: The measuring device comprises: a current limiting unit provided in a bypass path of the first switch; A current sensor for measuring the current of the electrochemical element; and Processing Department, The current limiting unit allows power to be supplied to the load through the bypass path when the voltage difference between the voltage of the electrochemical element and the voltage of the terminal is greater than a given value, and sets the bypass path to no current when the voltage difference is less than the given value. The processing unit performs a measurement process of measuring an offset error of the current sensor until the voltage difference reaches a given value due to a change in the voltage of the terminal unit caused by discharge of a charge-discharge element connected in parallel to the load after the first switch is turned off.

2. The measuring device according to claim 1, wherein: The electrochemical element is a storage element that supplies electric power to a vehicle load that does not allow power to be cut off. The processing unit switches the first switch from on to off to execute the measurement process while the vehicle is stopped.

3. The measuring device according to claim 1 or 2, wherein: The measuring device includes a second switch provided in the bypass path and connected in series with the current limiting unit.

4. The measuring device according to claim 1 or 2, wherein: The current limiting unit is a diode.

5. A power storage device, wherein: have: As an electric storage element of an electrochemical element; A container for accommodating the power storage element; A terminal portion, disposed on the housing body and connected to a load; a first switch, housed in the housing and disposed between the power storage element and the terminal portion; and The measuring device according to any one of claims 1 to 4 is accommodated in the housing.

6. The power storage device according to claim 5, wherein: The power storage device includes a charge and discharge element accommodated in the housing and connected to the terminal portion.

7. The power storage device according to claim 6, wherein: The power storage device is used in a vehicle, The charge-discharge element discharges the vehicle load that does not allow power interruption while the processing unit is performing the measurement processing.

8. A measuring system, wherein: have: electrochemical element; and The measuring device according to any one of claims 1 to 4.

9. A method for measuring an offset error, which is a method for measuring an offset error of a current sensor, wherein: After the first switch connecting the terminal portion and the electrochemical element is opened, discharge is performed from the charge-discharge element connected in parallel with the load connected to the terminal portion to the load, The current limiting unit provided in the bypass path of the first switch makes the bypass path currentless until the voltage difference between the voltage of the electrochemical element and the voltage of the terminal portion reaches a given value, thereby measuring an offset error of the current sensor.

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