Current measuring device, power storage device

Abstract

To improve the measurement accuracy of a current.SOLUTION: A current measurement device 50 for measuring a current of a power storage element comprises: a measurement resistor 80 that is positioned on a current path and has a resistor 81; a pair of detection points Pa and Pb that are positioned on both sides of the resistor 81 on the current path; a current detection portion 160 that has a pair of voltage input portions 161A and 161B connected to the pair of detection points Pa and Pb, and detects the current of the power storage element from a voltage difference between the pair of detection points; and a ground connection point Pg that is connected to a common ground GND with the current detection portion 160. Resistance Rga of the current path X to the ground connection point Pg from the detection point Pa closer to the ground connection point Pg among the pair of detection points Pa and Pb is smaller than a value obtained by dividing a tolerance Vm of an input voltage of the current detection portion 160 by a predetermined current of the power storage element.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a device for measuring a current in an electric storage element. [Background technology]

[0002] One type of current measuring device for an energy storage element uses a measuring resistor such as a shunt resistor. Patent Document 1 listed below describes providing a ground terminal on the shunt resistor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2015-021815 Summary of the Invention [Problem to be solved by the invention]

[0004] A current measurement device has a current detection unit that detects the current from the voltage difference across a resistor. The input voltage of the current detection unit has an allowable limit. If the input voltage exceeds the allowable limit, it will saturate at the allowable limit, reducing the accuracy of current measurement.

[0005] An object of the present invention is to suppress saturation of the input voltage and improve the accuracy of current measurement. [Means for solving the problem]

[0006] A current measuring device for measuring the current of a storage element includes a measuring resistor located on a current path and having a resistor, a pair of detection points located on both sides of the resistor on the current path, a current detection unit having a pair of voltage input units connected to the pair of detection points and detecting the current of the storage element from the voltage difference between the pair of detection points, and a ground connection point connected to a common ground with the current detection unit, and the resistance of the current path from one of the pair of detection points that is closer to the ground connection point to the ground connection point is smaller than the allowable value of the input voltage of the current detection unit divided by a predetermined current of the storage element.

[0007] This technology can be applied to a power storage device. [Effects of the Invention]

[0008] The accuracy of current measurement can be improved. [Brief explanation of the drawings]

[0009] [Figure 1] Side view of an automobile applied to embodiment 1 [Figure 2] Block diagram showing the electrical configuration of the battery [Figure 3] Perspective view of a resistor [Figure 4] Perspective view of the battery [Figure 5] Exploded perspective view of the battery [Figure 6] Perspective view of inner lid [Figure 7] FIG. 1 is a perspective view showing a state in which a resistor is fitted into a connector of a circuit board. [Figure 8] Diagram showing the current path of current consumption [Figure 9] Block diagram showing the electrical configuration of the battery [Figure 10] 1 is a perspective view showing another embodiment of a resistor; [Figure 11] 1 is a block diagram illustrating another embodiment of a battery; [Figure 12] 1 is a block diagram illustrating another embodiment of a battery; [Figure 13]Diagram showing the connection structure of the ground wire and input wire for the measuring resistor [Figure 14] FIG. 10 is a plan view showing another embodiment of the measuring resistor; [Figure 15] FIG. 10 is a plan view showing another embodiment of the measuring resistor; DETAILED DESCRIPTION OF THE INVENTION

[0010] (Outline of current measuring device) As a result of studying ways to improve the current measurement accuracy and SOC estimation accuracy of the storage element, the inventors discovered that when the input voltage of the current detection unit exceeds the allowable value, the current detection unit becomes saturated and the measurement accuracy decreases.

[0011] A current measuring device for measuring the current of a storage element includes a measuring resistor located on a current path and having a resistor, a pair of detection points located on both sides of the resistor on the current path, a current detection unit having a pair of voltage input units connected to the pair of detection points and detecting the current of the storage element from the voltage difference between the pair of detection points, and a ground connection point connected to a common ground with the current detection unit, and the resistance of the current path from one of the pair of detection points that is closer to the ground connection point to the ground connection point is smaller than the allowable value of the input voltage of the current detection unit divided by a predetermined current of the storage element.

[0012] When the storage element current is below a predetermined value, the voltage at at least one of the detection points does not exceed the allowable input voltage of the current detection unit. Since the input voltage at at least one of the detection points does not saturate, current measurement errors can be reduced.

[0013] The resistance of the current path from one of the detection points to the ground connection point may be smaller than a value obtained by subtracting the voltage across the resistor at a predetermined current from the allowable value of the input voltage of the current detection unit, and dividing the result by the predetermined current.

[0014] When the current of the storage element is equal to or less than a predetermined value, the input voltage does not saturate at either of the pair of detection points, so that the accuracy of current measurement can be further improved.

[0015] The measuring resistor may have a pair of electrodes on both sides of the resistor, the pair of electrodes having a pair of the detection points, and one of the pair of electrodes may have the ground connection point in addition to the one detection point.

[0016] By providing one detection point and a ground connection point for one electrode, the distance from one detection point to the ground connection point is shortened, and the resistance from one detection point to the ground connection point can be reduced. By reducing the resistance, it is possible to suppress the voltage rise at the detection point and prevent the input voltage from saturating.

[0017] The ground connection point may be common to one of the detection points, and the resistance of the current path between the two common points may be zero. Since the resistance between the two points is zero, it is possible to suppress a voltage rise at the detection point relative to ground, and to prevent the input voltage from saturating.

[0018] The measuring resistor may have a pair of detection terminals corresponding to the pair of detection points and a ground terminal corresponding to the ground connection point, and the pair of detection terminals and the ground terminal may be fitted to a connector provided on the board. Because thermal resistance exists between each terminal and the connector, heat is less likely to be transmitted than when the measuring resistor and the board are connected by a harness, and even if the measuring resistor generates heat, the impact on the board can be reduced.

[0019] The predetermined current may be a maximum current. Even if the storage element has a maximum current, the input voltage can be prevented from saturating, and current measurement errors can be reduced.

[0020] <Embodiment 1> 1. Battery electrical configuration Fig. 1 is a side view of an automobile. The automobile 1 is an engine-driven vehicle and has an engine 5 as a drive device. Fig. 1 shows only the engine 5 and a battery 20, and omits other components that make up the automobile 1. The battery 20 is an example of an electricity storage device.

[0021] The electrical configuration of the battery 20 will be described with reference to Figure 2. The battery 20 is used to start the engine. A starter motor 15 and an IG switch 17 for starting the engine 5 mounted on the automobile 1 are connected to the battery 20.

[0022] When the IG switch 17 is turned on, current flows from the battery 20 to the starter motor 15, driving the starter motor 15. Driving the starter motor 15 allows the engine 5 to start.

[0023] In addition to the starter motor 15, a vehicle load (not shown) such as electrical equipment and an alternator (not shown) are connected to the battery 20. When the amount of power generated by the alternator is greater than the power consumption of the vehicle load, the battery 20 is charged by the alternator. When the amount of power generated by the alternator is less than the power consumption of the vehicle load, the battery 20 discharges to make up for the shortfall.

[0024] The battery 20 includes a battery pack 30, a measuring resistor 80, a current interruption device 120, a management unit 130, a signal processing circuit 150, and a circuit board 90. The battery pack 30 is composed of a plurality of secondary batteries 31 connected in series. The secondary batteries 31 are, for example, lithium-ion secondary batteries.

[0025] The battery pack 30, the current interruption device 120, and the measuring resistor 80 are connected in series via power lines 55P and 55N. The power lines 55P and 55N form a current path X of the battery pack 30.

[0026] The power line 55P is a power line that connects the positive external terminal 22P and the positive electrode of the battery pack 30. The power line 55N is a power line that connects the negative external terminal 22N and the negative electrode of the battery pack 30.

[0027] The current interruption device 120 is located on the positive electrode side of the battery pack 30 and is provided on the positive electrode side power line 55P.

[0028] The measuring resistor 80 is located at the negative electrode of the battery pack 30 and is provided on the negative-electrode power line 55N. As shown in FIG. 3, the measuring resistor 80 is a rectangular metal conductor that is long in one direction (the direction of the current path X). The measuring resistor 80 includes a pair of electrodes 83A, 83B and a resistive element 81.

[0029] The resistor 81 is made of an alloy (for example, manganin, an alloy of copper, manganese, and nickel) with a small temperature coefficient of change in electrical resistance. The resistor 81 generates a voltage Vr proportional to the current flowing through the measuring resistor 80.

[0030] The pair of electrodes 83A, 83B is made of a metal such as copper. The pair of electrodes 83A, 83B is located on both sides of the resistor 81 in the X direction and is joined to the resistor 81 by welding. The welding method may be electron beam welding, resistance welding, or the like.

[0031] The pair of electrodes 83A, 83B have screw holes 84 for attaching a bus bar. The electrode 83A is connected to the negative electrode of the battery pack 30 by a bus bar (not shown), and the electrode 83B is connected to the negative electrode of the battery pack 30 by a bus bar (not shown). ) is connected to the negative external terminal 22N.

[0032] The pair of electrodes 83A, 83B has a pair of detection points Pa, Pb, which are located on both sides of the resistor 81 on the current path X.

[0033] The pair of electrodes 83A, 83B have a pair of detection terminals 85A, 85B corresponding to the pair of detection points Pa, Pb. The pair of detection terminals 85A, 85B protrude parallel to the Y direction, which is perpendicular to the current path X, from the side surfaces of each electrode 83A, 83B. The detection terminal 85A of the electrode 83A is located at the position of the detection point Pa of the current path X, and the detection terminal 85B of the electrode 83B is located at the position of the detection point Pb of the current path X. The pair of detection points Pa, Pb are electrically connected to two input terminals 161A, 161B of the first signal processing unit 160 via the detection terminals 85A, 85B and the connector 100, respectively.

[0034] The measuring resistor 80 has a ground connection point Pg. The ground connection point Pg is located on the electrode 83A and adjacent to the detection point Pa. The ground connection point Pg is a distant point located further outward than the detection point Pa when viewed from the resistor 81. The ground connection point Pg is located on the current path X between the detection point Pa and the negative electrode of the battery pack 30 (see FIG. 2).

[0035] 3, electrode 83A has a ground terminal 87 corresponding to ground connection point Pg. Ground terminal 87 protrudes from a side surface of electrode 83A in the Y direction, which is perpendicular to current path X. Ground terminal 87 is parallel to detection terminals 85A and 85B. Ground terminal 87 of electrode 83A is located at the position of ground connection point Pg of current path X. Ground connection point Pg is electrically connected to the common ground GND of circuit board 90 via ground terminal 87 and connector 100.

[0036] The current interruption device 120 is a semiconductor switch such as a relay or an FET. By opening the current interruption device 120, it is possible to interrupt the current of the battery 20. The current interruption device 120 is normally controlled to be closed.

[0037] 2, the signal processing circuit 150 is mounted on a circuit board 90 and includes a first signal processing unit 160 and a second signal processing unit 170. The signal processing circuit 150 is connected to the positive power line 55P via a branch line 57, and receives power from the battery pack 30. The signal processing circuit 150 is electrically connected to the common ground GND of the circuit board 90.

[0038] The first signal processing unit 160 includes an amplifier 161 and an AD converter 163. The amplifier 161 has two input terminals 161A and 161B and one output terminal 161C.

[0039] The two input terminals 161A and 161B are electrically connected to two detection points Pa and Pb located on both sides of the resistor 81 via the connector 100 and detection terminals 85A and 85B, respectively.

[0040] The amplifier 161 amplifies the voltage difference between the two input terminals 161A and 161B, i.e., the voltage Vr across the resistor 81. The amplifier 161 is a detection unit that detects the voltage Vr across the resistor 81. The AD converter 163 is connected to the output terminal 161C of the amplifier 161, and converts the output value of the amplifier 161 from an analog signal to a digital signal and outputs it. The first signal processing unit 160 is an example of a current detection unit that detects the current I of the battery 20 from the voltage difference Vr between the two input terminals 161A and 161B.

[0041] The measuring resistor 80, the connector 100, and the first signal processing unit 160 are a part of the current measuring device 50. Here is an example.

[0042] The second signal processing unit 170 includes a multiplexer 171 and an AD converter 173. The multiplexer 171 has five input terminals 171A to 171E and one output terminal 171F. The five input terminals 171A to 171E are electrically connected to the electrodes of the secondary batteries 31, respectively.

[0043] The multiplexer 171 switches between the secondary batteries 31 to be measured, and sequentially detects and outputs the voltage of each secondary battery 31. The AD converter 173 is connected to the output terminal 171F of the multiplexer 171, and converts the output value of the multiplexer 171 from an analog signal to a digital signal and outputs it.

[0044] The first signal processing unit 160 and the second signal processing unit 170 are connected to the management unit via a bus 180, and the outputs (measured values) of both the signal processing units 160 and 170 are input to the management unit .

[0045] 2, the management unit 130 is mounted on a circuit board 90. The management unit 130 includes a CPU 131 and a memory 133. The management unit 130 is connected to the positive power line 55P via a branch line 58, and receives power from the battery pack 30 as a power source. The management unit 130 is connected to the common ground GND of the circuit board 90.

[0046] The CPU 131 monitors the current I of the battery 20 based on the output of the first signal processing unit 160. The CPU 131 monitors the voltage of each secondary battery 31 and the total voltage of the battery pack 30 based on the output of the second signal processing unit 170.

[0047] If there is an abnormality in the voltage, current, or temperature of the secondary battery 31, the CPU 131 sends a command to the current interruption device 120 to interrupt the current I, thereby protecting the battery 20.

[0048] The SOC (state of charge) is the state of charge of the battery 20. The SOC is the ratio of the remaining capacity to the fully charged capacity (actual capacity), and can be defined by the following equation (1).

[0049] 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.

[0050] The CPU 131 estimates the SOC of the battery 20 based on the integral value of the current I measured by the measuring resistor 80 with respect to time, as shown in the following equation (2).

[0051] SOC = SOCo + 100 × (∫Idt) / Co (2) SOCo is the initial value of SOC, and I is the current.

[0052] 2. Battery 20 structure explanation Fig. 4 is a perspective view of the battery, and Fig. 5 is an exploded perspective view of the battery. As shown in Fig. 4, the battery 20 has a block-shaped battery case 21. The battery case 21 contains an assembled battery 30 consisting of a plurality of secondary batteries 31, a measuring resistor 80, a current interruption device 120, a circuit board 90, and the like.

[0053] As shown in Fig. 5, the battery case 21 includes a box-shaped case body 23 that opens upward, a positioning member 24 that positions multiple secondary batteries 31, an inner lid 25 attached to the top of the case body 23, and an upper lid 29 attached to the top of the inner lid 25. Multiple cell chambers 23A are arranged in the X direction inside the case body 23. Each cell chamber 23A contains a secondary battery 31. 31 will be housed individually.

[0054] The positioning member 24 positions each secondary battery 31 housed in each cell chamber 23A. As shown in Fig. 5, a plurality of bus bars 24A are arranged on the upper surface of the positioning member 24. The plurality of bus bars 24 connect the secondary batteries 31 housed in each cell chamber 23A in series.

[0055] The inner lid 25 has a generally rectangular shape in a plan view, as shown in Fig. 5. The inner lid 25 has a pair of external terminals 22P, 22N at both ends in the X direction. The pair of external terminals 22P, 22N are made of a metal such as a lead alloy, with 22P being a positive external terminal and 22N being a negative external terminal. The external terminals 22P, 22N are terminals for connecting the battery 20 to an electrical load such as the starter motor 15.

[0056] As shown in Fig. 5, a first housing section 25A and a second housing section 25B are provided on the top surface of inner lid 25. These two housing sections 25A and 25B are surrounded by an outer wall 26. As shown in Fig. 6, a circuit board 90 is housed in first housing section 25A and fixed thereto by screws. In Fig. 6, only a portion of circuit board 90, such as connector 100 and signal processing circuit 150, is shown, and other components are omitted.

[0057] The circuit board 90 is roughly rectangular, and has a connector 100 disposed on its upper surface. The connector 100 is disposed in a position facing the measuring resistor 80. The connector 100 is fixed to the upper surface of the circuit board 90 by a fixing portion 115 such as a claw.

[0058] The connector 100 has three internal terminals (not shown). Two of the internal terminals correspond to the two detection terminals 85A and 85B provided on the measurement resistor 80, and one internal terminal corresponds to the ground terminal 87. Each internal terminal is joined to a conductor pattern provided on the upper surface of the circuit board 90 by, for example, soldering.

[0059] As shown in Fig. 6, the second housing portion 25B houses a measuring resistor 80. The measuring resistor 80 is housed in a state where two electrodes 83A, 83B are screwed in, while two detection terminals 85A, 85B and a ground terminal 87 are fitted into the connector 100 (see Fig. 7).

[0060] When the detection terminals 85A, 85B are fitted into the connector 100, the detection terminals 85A, 85B elastically contact the internal terminals, and the detection terminals 85A, 85B can be electrically connected to the first signal processing unit 160 mounted on the circuit board 90.

[0061] When the ground terminal 87 is fitted into the connector 100 , the ground terminal 87 elastically contacts the internal terminal, and the ground terminal 87 of the measuring resistor 80 can be electrically connected to the common ground GND of the circuit board 90 .

[0062] Because thermal resistance exists between each terminal 85A, 85B, 87 and the connector 100, heat is less likely to be transmitted than when the measuring resistor 80 and the circuit board 90 are connected by a harness, and even if the measuring resistor 80 generates heat, the impact on the circuit board 90 can be reduced.

[0063] 3. Input voltage and current measurement error of the first signal processing unit 160 There is a limit to the magnitude of the input voltage to the amplifier 161. If a voltage exceeding the allowable value Vm is input to the amplifier 161, the amplifier 161 will saturate, causing a measurement error in the measurement value of the first signal processing unit 160.

[0064] The input voltage tolerance Vm is, for example, ±300 mV. + indicates discharge and - indicates charge. If the voltage at detection point Pa is +310 mV and the voltage at detection point Pb is +330 mV, the input voltage to amplifier 161 will saturate at +300 mV for both detection points Pa and Pb, resulting in a measurement error. In other words, the potential difference between the two detection points Pa and Pb is measured as zero, even though it is actually +20 mV.

[0065] The ground connection point Pg of the measuring resistor 80 is connected to the common ground GND of the circuit board 90 and is at the same potential as the common ground GND of the circuit board 90 .

[0066] By making the ground connection point Pg the same potential as the common ground GND, the reference potential difference between the measurement resistor 80 and the circuit board 90 can be reduced, and the voltages of the detection points Pa and Pb relative to the common ground GND can be lowered.

[0067] 8, when the ground terminal 87 is provided separately from the detection terminals 85A and 85B, the consumption current Ir of the management unit 130 and the signal processing circuit 150 passes through the ground terminal 87 and returns to the battery pack 30. Therefore, the consumption current Ir does not flow through the detection terminals 85A and 85B, and it is possible to suppress a decrease in the accuracy of current measurement.

[0068] If the ground connection point Pg and the detection point Pa are provided separately for the electrode 83A, when a current flows through the measuring resistor 80, a voltage is generated between the ground connection point Pg and the detection point Pa. The reason for this voltage is that the electrodes 83A and 83B are made of copper, and the material itself has electrical resistance. In other words, the resistance from the ground connection point Pg to the detection point Pa causes a voltage to be generated between the two points Pg and Pa.

[0069] The electrical resistivity of the electrode 83A is ρ [Ωm], and the cross-sectional area of ​​the electrode 83A is S [m 2 ], and the length along the current path X from the ground connection point Pg to the detection point Pa is L [m], the resistance Rga [Ω] of the current path X from the ground connection point Pg to the detection point Pa is obtained by the following equation (3). Rga=ρ×L / S (3)

[0070] The resistance Rga of the current path X from the ground connection point Pg to the detection point Pa satisfies the following formula (4) and is equal to or less than the value obtained by dividing the allowable value Vm of the input voltage of the first signal processing unit 160 by the maximum current Imax of the battery 20.

[0071] Rga≦Vm / Imax (4) Vm is the allowable value of the input voltage of the first signal processing unit (amplifier), and Imax is the maximum current of the battery 20. The maximum current Imax is the maximum value of the current that the battery 20 can discharge or charge in a short period of time. The maximum current Imax is a value determined by the characteristics of the battery 20 (electromotive force, internal resistance, etc.), and a design value or an experimental value can be used.

[0072] When the input voltage tolerance Vm of the first signal processing unit 160 is ±300 [mV] and the maximum current ±Imax of the battery 20 is 6000 [A], Rga≦50 [μΩ]. + indicates discharging and − indicates charging.

[0073] As shown in equation (3), the resistance Rga is proportional to the length L along the current path X from the ground connection point Pg to the detection point Pa, and is inversely proportional to the cross-sectional area S of the electrode 83A. Therefore, the measurement resistor 80 determines the length L along the current path X from the ground terminal 87 to the detection terminal 85A and the cross-sectional area S of the electrode 83A so that the resistance Rga satisfies equation (4).

[0074] When the resistance Rga satisfies the above formula (4), the voltage at the detection terminal 85A does not exceed the input voltage tolerance Vm of the first signal processing unit 160, even when the battery 20 is at its maximum current Imax. Therefore, the input voltage does not saturate at the detection point Pa, which is closer to the ground connection point Pg, among the two detection points Pa and Pb. If the input voltages at both detection points Pa and Pb are not saturated, there is almost no current measurement error due to saturation, and current measurement accuracy can be improved. Furthermore, even if the input voltage saturates at detection point Pb, the voltage difference between the two detection points Pa and Pb will not become zero because detection point Pa is not saturated. Therefore, current measurement errors due to saturation can be reduced at both detection points Pa and Pb compared to when the input voltage is saturated.

[0075] 3. Explanation of effects The battery 20 can suppress measurement errors of the current I due to an excess input voltage to the first signal processing unit 160, and can improve the measurement accuracy of the current I. Furthermore, the improvement in the measurement accuracy of the current I also improves the estimation accuracy of the SOC.

[0076] <Embodiment 2> The second embodiment differs from the first embodiment in the value of the resistance Rga of the current path X from the ground connection point Pg to the detection point Pa.

[0077] The resistance Rga satisfies the following equation (5) and is less than the value obtained by subtracting the maximum value Vrmax of the voltage Vr across the resistor 81 from the allowable value Vm of the input voltage of the first signal processing unit 160, and dividing the result by the maximum current Imax of the battery 20.

[0078] Rga≦(Vm-Vrmax) / Imax (5) Vm is the allowable value of the input voltage of the first signal processing unit, Vrmax is the maximum voltage of the resistor 81, and Imax is the maximum current of the battery 20. Vrmax is the product of the resistance value of the resistor 81 and the maximum current Imax of the battery 20.

[0079] When the input voltage tolerance Vm of the first signal processing unit 160 is ±300 [mV], the maximum voltage Vrmax of the resistor 81 is ±150 [mV], and the maximum current Imax of the battery 20 is ±6000 [A], Rga≦25 [μΩ].

[0080] When the resistance Rga satisfies the above formula (5), even if the battery 20 is at the maximum current Imax, the voltage at the detection terminal 85A as well as the detection terminal 85B will not exceed the allowable value Vm of the input voltage of the first signal processing unit 160. Since the input voltage does not saturate at either of the two detection points Pa and Pb, the accuracy of current measurement can be improved.

[0081] <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.

[0082] (1) In the above first and second embodiments, the energy storage element is a secondary battery 31. The secondary battery 31 is not limited to a lithium-ion secondary battery, and may be another non-aqueous electrolyte secondary battery. A lead-acid battery or the like may also be used. The energy storage element is not limited to the secondary battery 31, and may be a capacitor. The energy storage element is not limited to a case where a plurality of energy storage elements are connected in series or parallel, and may be connected in series or configured as a single cell.

[0083] (2) In the above-described first and second embodiments, the battery 20 is for use in a vehicle. The use of the battery 20 is not limited to a specific use. The battery 20 can be used for various purposes, such as for mobile bodies (vehicles, ships, AGVs, etc.) and stationary uses (power storage devices for uninterruptible power supply systems and solar power generation systems).

[0084] (3) In the above-described first and second embodiments, the first signal processing unit 160 is configured with the amplifier 161 and the AD converter 163. The first signal processing unit 160 may have any configuration as long as it has two voltage input terminals and detects the current of the battery 20 from the voltage difference between the two voltage input terminals. For example, it may be configured with an amplifier and a comparator. It may also be configured to detect the magnitude of the current from the output value of the amplifier using a comparator.

[0085] (4) In the first embodiment, the resistance Rga is defined by the maximum current Imax of the battery 20. The resistance Rga may be defined by the rated current of the battery 20. In other words, the resistance Rga may be set to a value smaller than the value obtained by dividing the allowable value Vm of the input voltage of the first signal processing unit 160 by the rated current of the battery 20 (the maximum current at which the battery 20 can be used safely). The resistance Rga may be defined by a predetermined current of the battery 20. The predetermined current is the maximum current or rated current of the battery. The same applies to equation (5) in the second embodiment.

[0086] (5) In the above-described first and second embodiments, the management unit 130 is provided inside the battery 20. The battery 20 only needs to have at least the assembled battery 30 and the signal processing circuit 150, and the management unit 130 may be provided outside the battery 20.

[0087] (6) In the above-described first and second embodiments, the ground connection point Pg of the measurement resistor 80 is connected to the common ground GND via the ground terminal 87. The ground connection point Pg of the measurement resistor 80 may be connected to the common ground GND using a harness. In this case, it is preferable to provide a screw hole in the measurement resistor 80 for fixing a harness terminal to the ground connection point Pg.

[0088] (7) In the first and second embodiments, the measuring resistor 80 is provided with the ground connection point Pg. The ground connection point may be located anywhere on the current path X of the battery pack 30. It may also be located at a location other than the measuring resistor 80.

[0089] (8) In the above-described first and second embodiments, the ground connection point Pg is provided between the negative electrode of the battery pack 30 and the resistor 81. The ground connection point Pg may be provided between the resistor 81 and the negative external terminal 22N. The battery 200 shown in FIG. 9 includes a current measurement device 250. The current measurement device 250 includes a measurement resistor 280, a connector 100, and a first signal processing unit 160. The measurement resistor 280 provides the ground connection point Pg between the resistor 81 and the negative external terminal 22N. In this case, it is preferable that the resistance Rgb of the current path X from the ground connection point Pg to the detection point Pb satisfies the formula (4) of the first embodiment or the formula (5) of the second embodiment.

[0090] (9) In the first and second embodiments, the measurement resistor 80 is provided with the ground terminal 87 alongside the detection terminals 85A and 85B. The ground terminal 87 may be provided anywhere on the measurement resistor 80 as long as Rga≦Vm / Imax is satisfied. The measurement resistor 380 shown in FIG. 10 differs from the measurement resistor 80 shown in FIG. 3 in the position of the ground terminal 87. The ground terminal 87 is provided on one of the two long sides of the measurement resistor 380, opposite the long side on which the detection terminals 85A and 85B are provided. The ground terminal 87 may also be provided on a short side of the measurement resistor 380.

[0091] (10) In the first and second embodiments, the measuring resistor 80 is disposed on the negative electrode side of the battery pack 30. However, it may be disposed on the positive electrode side as long as it is on the current path of the battery pack 30.

[0092] (11) Figure 11 is a circuit diagram of battery 400A. Battery 400A differs from battery 20 in the way the measuring resistor 480 is grounded. Specifically, measuring resistor 480 shares a ground connection point Pg with one of the detection points Pa.

[0093] When the ground connection point Pg and the detection point Pa are common, the two common points Pg and Pa are at the same potential, and the resistance of the current path X between the two points Pg and Pa is zero. Therefore, it is possible to suppress a voltage rise at the detection points Pa and Pb relative to the common ground GND, and therefore it is possible to prevent the input voltage of the amplifier 161 from saturating.

[0094] (12) Fig. 12 is a circuit diagram of battery 400B. Battery 400B is similar in that it shares ground connection point Pg with detection point Pa, but differs in that ground line 410G of measurement resistor 480 is provided separately from input line 410A to amplifier 161.

[0095] By providing the ground line 410G separately from the input line 410A, the current consumption Ir of the management unit 130 and the signal processing circuit 150 returns to the battery pack 30 through the ground line 410G and does not pass through the input line 410A. Therefore, there is no current measurement error due to the current consumption Ir, which has the advantage of high current measurement accuracy.

[0096] 13, the two lines 410G and 410A may be commonly connected to a connection hole 485A provided at the detection point Pa. For example, the common connection may be made by a fastener such as a screw 486. 411A is a terminal of the input line 410A, and 411G is a terminal of the ground line 410G.

[0097] (13) FIG. 14 is a plan view of the measuring resistor 480. The measuring resistor 480 has a connection hole 485A at the detection point Pa and a connection hole 485B at the detection point Pb. The two connection holes 485A and 485B are for connecting the input lines 410A and 410B to the amplifier 161. The two connection holes 485A and 485B may be symmetrical with respect to the center line Lc of the resistor 81. By symmetrically arranging the two connection holes 485A and 485B, the voltage across the resistor 81 can be accurately detected, improving current measurement accuracy. The ground line 410G may be commonly connected to the connection hole 485A, or a dedicated connection hole 485G may be provided and connected separately from the input line 410A. Furthermore, the measuring resistor 480 has screw holes 84 at both ends, but these may be eliminated by sharing the holes with the connection holes 485A and 485B.

[0098] (14) Figure 15 is a plan view of a measurement resistor 580. The measurement resistor 580 has an L-shaped outer shape and differs from the measurement resistor 480 in that the current path X is not linear. When the current path X is not linear, the two connection holes 485A and 485B can be arranged symmetrically with respect to the center line Lc by tilting the center line Lc of the resistor 81 with respect to the current path X. The same applies to the screw holes 84 for attaching the bus bar. [Explanation of symbols]

[0099] 20 Battery (an example of an energy storage device) 31 Secondary battery (an example of a storage element) 50 Current measuring device 80 Measuring resistor 81 Resistor 83A, 83B electrode 85A, 85B detection terminals 87 Ground terminal 90 Circuit Board 100 Connectors 130 Management Department 160 First signal processing unit (current detection unit) 170 Second signal processing section Pa, Pb detection points Pg Ground connection point

Claims

1. A current measurement device that measures a current of a storage element included in a storage device, a measuring resistor having a resistive element; a current detection unit, The measuring resistor is a pair of detection points located on both sides of the resistor, and a ground connection point connected to the ground of the current detection unit, the current detection unit has a pair of voltage input units connected to the pair of detection points, and detects the current of the storage element from a voltage difference between the pair of detection points; an electrical resistance of a current path from one of the pair of detection points that is closer to the ground connection point to the ground connection point is smaller than a value obtained by dividing an allowable value of an input voltage of the current detection unit by a predetermined current of the storage element; the measuring resistor is located on the negative external terminal side of the power storage device, the ground connection point is located between the negative electrode external terminal of the power storage device and the resistor, A current measuring device in which, during discharge at the specified current, a negative voltage generated between the other detection point farther from the ground connection point and one detection point closer to the ground connection point does not exceed the allowable value of the input voltage of the current detection unit.

2. 2. The current measuring device according to claim 1, a current measuring device in which a current path from one of the pair of detection points that is closer to the ground connection point to the ground connection point has an electrical resistance that is smaller than an allowable resistance value obtained by subtracting the voltage across the resistor at a predetermined current from the allowable value of the input voltage of the current detection unit and dividing the result by the predetermined current of the storage element.

3. 3. The current measuring device according to claim 1, The predetermined current is a maximum current of the storage element.

4. 4. The current measuring device according to claim 1, The measuring resistor is A pair of electrodes is provided on both sides of the resistor, The pair of electrodes has a pair of the detection points, a current measuring device, wherein the electrode of the pair of electrodes connected to the external terminal of the negative electrode of the power storage device has the ground connection point in addition to one of the detection points;

5. 5. The current measuring device according to claim 1, A current measuring device, wherein the ground connection point is common to one of the detection points, and the resistance of the current path between the two common points is zero.

6. A storage element; A power storage device comprising the current measuring device according to any one of claims 1 to 5.

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