Device and method for testing internal resistance of ultra-low internal resistance power battery

Abstract

The application discloses a kind of ultra-low internal resistance power battery's internal resistance testing device and testing method, belong to waste battery processing technical field, testing device includes test piece and two can be connected with measuring equipment patch, two patches are close to the two ends of the battery to be measured or test piece, two patches are respectively arranged on fixed pole plate and mobile pole plate connected with power component, fixed pole plate is fixed on base, mobile pole plate is slidably connected with base;The battery to be measured is the power battery of ultra-low internal resistance, patch is conductive material, fixed pole plate, mobile pole plate and base are all insulating materials;The testing method of internal resistance of power battery is as follows: the internal resistance of test piece testing device is used, and then the internal resistance of ultra-low internal resistance power battery is measured by device internal resistance. The application can reduce the error caused by the error of testing device, can improve the internal resistance measurement accuracy of power battery, especially suitable for measuring the internal resistance of power battery with ultra-low internal resistance.

Description

Technical Field

[0001] This invention belongs to the field of battery internal resistance testing technology, and particularly relates to an internal resistance testing device and method for ultra-low internal resistance power batteries. Background Technology

[0002] Traditionally, a Wheatstone bridge is used to measure the internal resistance of a battery. This involves using a loop circuit consisting of four resistors to measure the resistance of an unknown resistor using the known values ​​of three of the resistors. However, this method has two problems for testing power batteries:

[0003] (1) The detection process is greatly affected by the detection principle and the external environment, and its accuracy needs to be improved. Although the Wheatstone bridge can accurately detect unknown resistances, it is mainly used to measure medium-value resistances (10). 1 ~10 6 (Ω). For power batteries, especially ultra-low internal resistance power batteries, due to the special manufacturing process, the internal resistance is often extremely small, even possibly below 1mΩ, requiring extremely high precision in the manufacturing of the three fixed resistors. This not only significantly increases the cost of the components but also makes the resistance more sensitive to the environment. When the measured resistance is extremely small, slight environmental disturbances can easily cause a serious decrease in the accuracy of the measured resistance, affecting the measurement accuracy.

[0004] (2) The testing process is greatly affected by the external clamping condition, and the resistance of the measurement system often has a significant impact on the measurement results of the internal resistance of the tested battery. Conventional measurements require wire connections. According to theoretical electrical calculations, if a 50cm long, 1mm diameter pure copper wire is used to connect the measuring equipment in the measurement system, its resistance will reach 1.5mΩ. If aluminum wire is used instead, the resistance will approach 3mΩ. This is only the wire resistance; in reality, since most clamping devices are currently spring-type structures, the contact force varies greatly with the battery size, leading to changes in contact resistance. Furthermore, to ensure current output capability, the internal resistance of some power batteries has reached the 10mΩ level, or even the 1mΩ level. The system error already largely covers the differences in the internal resistance of the tested battery, thus introducing measurement errors. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing an internal resistance testing device and method for ultra-low internal resistance power batteries, which can reduce the errors caused by the system error of the testing device and improve the accuracy of power battery resistance detection.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] An internal resistance testing device for an ultra-low internal resistance power battery includes a test piece for measurement and two patches for connecting to a measuring device. The two patches can contact both ends of the battery or test piece under test. The two patches are respectively disposed on a fixed electrode plate and a movable electrode plate. The fixed electrode plate is fixed on a base, and the movable electrode plate is slidably engaged with the base. The movable electrode plate is connected to a power component for driving the movable electrode plate to move relative to the fixed electrode plate. The patches are made of conductive material, and the fixed electrode plate, movable electrode plate, and base are all made of insulating material.

[0008] Preferably, the movable electrode plate is slidably engaged with a sliding groove on the base via a sliding seat. The sliding seat is connected to the power component via a force sensor, and the force value measured by the force sensor is used to control the power component to drive the sliding seat to start and stop.

[0009] Preferably, the patch is connected to the fixed electrode plate and the movable electrode plate respectively by elastic claws. The elastic claws are composed of multiple arc-shaped spring pieces, with adjacent spring pieces set at an acute angle. One end of the spring piece is connected to the back of the patch, and the other end of the spring piece engages with the track groove on the surface of the fixed electrode plate or the movable electrode plate.

[0010] Preferably, the spring sheet is a pure copper sheet with a width of 1mm, a length of 10mm, and a thickness of 0.5mm; the patch is connected to the measuring device via a copper wire with a thickness of 2mm, a width of 5mm, and a length of 10mm.

[0011] Preferably, when the force sensor outputs a force value of 2N, it sends a stop command to the power component.

[0012] Preferably, the specimen is made of ultra-low carbon Inconel 625 alloy and includes two columnar specimens, namely type I specimen and type II specimen. The length L of type I specimen is 65±0.5mm and the diameter D is 18±0.2mm. The length L of type II specimen is 70±0.5mm and the diameter D is 21±0.2mm.

[0013] Preferably, the chemical composition of the ultra-low carbon Inconel 625 alloy, by weight percentage, meets the following requirements:

[0014] C: ≤0.02%, Cr: 20-23%, Nb+Ta: 3.15-4.15%, Fe: ≤5%, Mn: ≤0.5%, Mo: 8-10%, Si: ≤0.05%, S: ≤0.015%, P: ≤0.015%, Al: ≤0.4%, Ti: ≤0.4%, Co: ≤1.0%, Ni: ≥58%.

[0015] Preferably, the specimen is a forging, which is subjected to solution heat treatment before processing: vacuum heating to 10650-1100℃, constant temperature for 2 hours, water cooling, and then cut to the design size after the test.

[0016] Preferably, both ends of the specimen are encapsulated with a low-resistivity material and vacuum plasma sprayed to a thickness of 0.2 mm. The low-resistivity material is aluminum, the same material used for the battery casing.

[0017] This invention also provides a method for testing the internal resistance of an ultra-low internal resistance power battery. The method uses the aforementioned internal resistance testing device for ultra-low internal resistance power batteries to test the internal resistance of the batteries, and includes the following steps:

[0018] S1: Internal resistance r of the test device

[0019] When the type I specimen is loaded between the two patches and an external voltage is applied, the internal resistance r of the device satisfies the following formula:

[0020]

[0021] In the formula: the unit of resistance r in the device is Ω; ρ is resistivity, the unit is Ω·m; V ocr This refers to the applied voltage, measured in volts (V). I Voltage on Type I specimen, in volts (V).

[0022] When the Type II specimen is loaded between the two patches and an external voltage is applied, the internal resistance r of the device satisfies the following formula:

[0023]

[0024] In the formula: r, ρ, and V ocr All are the same as in Formula 1; V II Voltage on type II specimen, in volts (V);

[0025] If the resistivity ρ is given, the resistance r of the device can be obtained by formula 1 or formula 2;

[0026] Otherwise, by measuring the current I in the type I specimen... I Then, substituting the values ​​into the calculation formula for the Type II specimen, the resistance r of the device is obtained as shown in Formula 3:

[0027]

[0028] I I The current in the Type I specimen is expressed in A. The symbols in the remaining formulas are defined in the same way as in Formula 1 and Formula 2.

[0029] S2: Measuring the internal resistance of ultra-low internal resistance power batteries:

[0030] Subtracting the device's internal resistance from the measured internal resistance of the power battery gives the pure battery internal resistance, as shown in Formula 4:

[0031] r b =r t -r Formula 4

[0032] In the formula: r b The internal resistance of the ultra-low internal resistance power battery, in Ω; r t r is the measured internal resistance of the power battery, in Ω; r is the internal resistance of the device, in Ω.

[0033] The beneficial effects of adopting the above technical solution are as follows: Compared with the prior art, the present invention drives the movable electrode plate to move relative to the fixed electrode plate through a power component, which can bring the two ends of the test piece or the power battery under test into contact with the patch. The internal resistance of the device is measured using the test piece and measuring equipment, and then the internal resistance of the ultra-low internal resistance power battery is measured through the internal resistance of the device. The present invention uses conductive springs and insulating materials to assemble a measuring device with a fixed electrode plate, a movable electrode plate, and a base, which can reduce the error caused by the error of the testing device. At the same time, the above measurement method eliminates the difference in the measured resistance, further improving the measurement accuracy of the internal resistance of the power battery. The present invention is mainly for testing cylindrical batteries with planar tabless at both ends, and is especially suitable for measuring the internal resistance of power batteries with ultra-low internal resistance. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the internal resistance testing device for an ultra-low internal resistance power battery provided in an embodiment of the present invention.

[0035] Figure 2 This is a schematic diagram of the structure of the fixed electrode plate in an embodiment of the present invention;

[0036] Figure 3 yes Figure 2 Left view of the fixed electrode plate in the middle;

[0037] Figure 4 This is a schematic diagram of the structure of the specimen in an embodiment of the present invention;

[0038] In the figure: 00-test piece; 1-spring piece; 2-fixed electrode plate; 3-moving electrode plate; 4-base; 5-power component; 6-slide block; 7-force sensor; 8-elastic claw; 80-spring piece; 9-track groove; 10-copper wire. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0040] like Figure 1-3 As shown, this invention provides an internal resistance testing device for an ultra-low internal resistance power battery. The internal resistance testing device includes a test piece 00 for measurement and two patches 1 for connecting to a measuring device (not shown in the figure). The two patches 1 can contact both ends of the battery under test or the test piece 00. The two patches 1 are respectively bolted to two measuring plates, which are a fixed plate 2 and a movable plate 3. The fixed plate 2 is fixed to a base 4, and the movable plate 3 is slidably engaged with the base 4. The movable plate 3 is connected to a power component 5 for driving the movable plate 3 to move relative to the fixed plate 2. The patches 1 are made of conductive material, while the fixed plate 2, the movable plate 3, and the base 4 are all made of insulating material. The movable plate 3 slides with a sliding groove on the base 4 via a slide block 6, which reduces the resistance encountered by the movable plate during movement. The slide block 6 is connected to the power component 5 via a force sensor 7, and the force measured by the force sensor 7 controls the starting and stopping action of the power component 5 in pushing the slide block 6. The force sensor uses a pressure sensor, which can directly test the clamping force of the specimen or power battery; the power component is driven by a motor.

[0041] During normal testing, the power battery is clamped between the fixed electrode plate 2 and the movable electrode plate 3, with the battery horizontally placed on the base and the positive and negative terminals aligned with the two contact patches. When the motor pushes the slide to move, the movable electrode plate moves together with the slide, allowing the two contact patches to attach to the positive and negative electrodes of the power battery. This completes the clamping of the power battery and establishes circuitry for the measuring equipment, enabling testing. Considering the wide variation in the size of the power batteries to be tested, the movable electrode plate and the slide are connected by bolts. This allows for multi-purpose use by replacing the measuring electrode plates of different sizes when testing power batteries of different dimensions.

[0042] In one specific embodiment of the present invention, such as Figure 2 , 3 As shown, the patch 1 is connected to the fixed electrode plate 2 and the movable electrode plate 3 respectively through elastic claws 8. The elastic claws 8 are composed of multiple arc-shaped spring plates 80. Two adjacent spring plates 80 are set at an acute angle. One end of the spring plate 80 is connected to the back of the patch 1, and the other end of the spring plate 8 is engaged with the track groove 9 on the surface of the fixed electrode plate 2 or the movable electrode plate 3, so that the spring claw moves along the track groove when subjected to force, which can prevent the spring plate from shifting or flying out.

[0043] In specific manufacturing, the spring sheet 80 is a pure copper sheet with a width of 1mm, a length of 10mm, and a thickness of 0.5mm. A copper wire 10 is soldered to the back of the patch 1 to connect to the measuring device. The copper wire 10 has a thickness of 2mm, a width of 5mm, and a length of 10mm. There are four spring sheets 80, with each pair of adjacent spring sheets 80 having an included angle of 45°. The spring sheets set at 45° with the patch form a spring claw. By deforming the spring sheets in different directions, when the motor drives the moving electrode plate to move and the patch is close to the positive and negative terminals of the battery, the patch can be tightly attached to the positive and negative terminals of the battery, reducing contact resistance.

[0044] Considering that the deformation displacement of the spring claw is not linearly related to the applied force, and that different forces will result in varying degrees of contact between the patch and the positive and negative terminals of the power battery, leading to different contact resistances and affecting measurement accuracy, a force sensor controls the motor drive. When the applied force is the same, the spring claw deforms at the same rate, resulting in consistent contact between the patch and the battery terminals, and thus, consistent contact resistance. This minimizes measurement errors caused by uncertain contact. Considering that the yield strength of the pure copper spring sheet varies greatly depending on its condition, to prevent excessive deformation of the spring sheet and damage to the patch due to excessive force, a stop command is sent to the power unit 5 when the force sensor 7 outputs a force of 2N.

[0045] The system resistance of the internal resistance testing device with the above structure can be reduced to about 0.03mΩ, which greatly reduces the resistance error caused by the measurement system and provides a prerequisite for eliminating the internal resistance testing method.

[0046] In one specific embodiment of the present invention, the specimen 00 is made of ultra-low carbon Inconel 625 alloy and includes two columnar specimens 00, such as... Figure 4 As shown, there are Type I and Type II specimens, respectively. The length L of the Type I specimen is 65±0.5mm and the diameter D is 18±0.2mm, while the length L of the Type II specimen is 70±0.5mm and the diameter D is 21±0.2mm. These two specimen specifications are designed based on 18650 batteries (Type I specimen) and 21700 batteries (Type II specimen).

[0047] Using the above-mentioned specimens can further eliminate measurement errors. The chemical composition of the ultra-low carbon Inconel 625 alloy, by weight percentage, meets the following requirements:

[0048] C: ≤0.02%, Cr: 20-23%, Nb+Ta: 3.15-4.15%, Fe: ≤5%, Mn: ≤0.5%, Mo: 8-10%, Si: ≤0.05%, S: ≤0.015%, P: ≤0.015%, Al: ≤0.4%, Ti: ≤0.4%, Co: ≤1.0%, Ni: ≥58%.

[0049] In the specific processing, the specimen 00 is a forging. Before processing, it undergoes solution heat treatment: vacuum heating to 10650-1100℃, holding at that temperature for 2 hours, and then water cooling. After testing, it is cut to the design dimensions. Care must be taken to use machining methods during cutting, and the deformation-hardened layer after processing must not exceed 0.5mm. At this point, the resistivity of the material can meet a relatively stable requirement of approximately ~1μΩ·m.

[0050] To further optimize the above technical solution, in order to ensure the uniformity of the electric field at the input and output terminals, both ends of the specimen 00 are encapsulated with a low-resistivity material. To ensure tight bonding and eliminate oxidation that may occur during heat treatment, the low-resistivity material is made of the same aluminum material as the battery casing, and vacuum plasma spraying is used with a spraying thickness of 0.2 mm. Calculations show that the resistance of the encapsulated aluminum material is 1 × 10⁻⁶. -6 The resistance is approximately mΩ, less than one ten-thousandth of the specimen's resistance, and can be ignored. At this point, the resistance of type I specimen is approximately 0.3 mΩ, and the resistance of type II specimen is approximately 0.25 mΩ, which is basically 8-10 times the resistance within the testing device, meeting the testing requirements.

[0051] This invention also provides a method for testing the internal resistance of an ultra-low internal resistance power battery. The method uses the aforementioned internal resistance testing device for ultra-low internal resistance power batteries to test the internal resistance of the batteries, and includes the following steps:

[0052] S1: Internal resistance test device internal resistance r:

[0053] When the type I specimen is loaded between the two patches and an external voltage is applied, according to Ohm's law, the internal resistance r of the device satisfies the following formula:

[0054]

[0055] In the formula: the unit of resistance r in the device is Ω; ρ is resistivity, the unit is Ω·m; V ocr This refers to the applied voltage, measured in volts (V). I Voltage on Type I specimen, in volts (V).

[0056] When the Type II specimen is loaded between the two patches and an external voltage is applied, the internal resistance r of the device satisfies the following formula:

[0057]

[0058] In the formula: r, ρ, and V ocr All are the same as in Formula 1; V II Voltage on type II specimen, in volts (V);

[0059] If the resistivity ρ is given, the resistance r of the device can be obtained by formula 1 or formula 2.

[0060] If the resistivity change caused by the external environment is considered, the resistivity must be obtained from actual measurements to further refine the test results. This is achieved by measuring the current I in the type I specimen. I Then, substituting the values ​​into the calculation formula for the Type II specimen, the resistance r of the device is obtained as shown in Formula 3:

[0061]

[0062] I I The current in the Type I specimen is expressed in A. The symbols in the remaining formulas are defined in the same way as in Formula 1 and Formula 2.

[0063] S2: Measuring the internal resistance of ultra-low internal resistance power batteries:

[0064] Subtracting the device's internal resistance from the measured internal resistance of the power battery gives the pure battery internal resistance, as shown in Formula 4:

[0065] r b =r t -r Formula 4

[0066] In the formula: r b The internal resistance of the ultra-low internal resistance power battery, in Ω; r t r is the measured internal resistance of the power battery, in Ω; r is the internal resistance of the device, in Ω.

[0067] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for testing the internal resistance of an ultra-low internal resistance power battery, comprising an internal resistance testing device for testing the internal resistance of the ultra-low internal resistance power battery, the internal resistance testing device including a measuring specimen and two patches for connecting to a measuring device, the two patches being able to contact the two ends of the battery under test or the specimen, the two patches being respectively disposed on a fixed plate and a movable plate, the fixed plate being fixed on a base, the movable plate being slidably engaged with the base, the movable plate being connected to a power component for driving the movable plate to move relative to the fixed plate; the battery under test is an ultra-low internal resistance power battery, the patches are made of conductive material, and the fixed plate, movable plate and base are all made of insulating material; The movable electrode plate slides in a groove on the base via a sliding block. The sliding block is connected to the power component via a force sensor. The force value measured by the force sensor controls the start and stop of the power component pushing the sliding block. The power component is driven by a motor. The patch is connected to the fixed electrode plate and the movable electrode plate respectively by elastic claws. The elastic claws are composed of multiple arc-shaped spring pieces, with two adjacent spring pieces set at an acute angle. One end of the spring piece is connected to the back of the patch, and the other end of the spring piece is engaged with the track groove on the surface of the fixed electrode plate or the movable electrode plate. Its features are, Includes the following steps: S1: Internal resistance test device internal resistance r: When the type I specimen is loaded between the two patches and an external voltage is applied, the internal resistance r of the device satisfies the following formula: In the formula: the unit of resistance r in the device is Ω; ρ is resistivity, the unit is Ω·m; V ocr This refers to the applied voltage, measured in volts (V). I V is the voltage on the Type I specimen; L is the length of the Type I specimen; S is the cross-sectional area of ​​the Type I specimen. 2 ; When the Type II specimen is loaded between the two patches and an external voltage is applied, the internal resistance r of the device satisfies the following formula: In the formula: r, ρ, and V ocr All are the same as in Formula 1; V II V is the voltage on the Type II specimen; L is the length of the Type II specimen; S is the cross-sectional area of ​​the Type II specimen. 2 ; If the resistivity ρ is given, the resistance r of the device can be obtained by formula 1 or formula 2; Otherwise, first measure the current I in the type I specimen. I Then, substituting the values ​​into the calculation formula for the Type II specimen, the resistance r of the device is obtained as shown in Formula 3: In the formula: I I L represents the current in the Type I specimen, in A; L is the length of the Type II specimen, in m. S is the cross-sectional area of ​​the type II specimen, in meters. 2 The definitions of symbols in the remaining formulas are the same as in Formula 1 and Formula 2. S2: Measuring the internal resistance of ultra-low internal resistance power batteries: Subtracting the device's internal resistance from the measured internal resistance of the power battery gives the pure battery internal resistance, as shown in Formula 4: r b =r t -r Formula 4 In the formula: r b The internal resistance of the ultra-low internal resistance power battery, in Ω; r t r is the measured internal resistance of the power battery, in Ω; r is the internal resistance of the device, in Ω.

2. The method for testing the internal resistance of an ultra-low internal resistance power battery according to claim 1, characterized in that: The spring sheet is a pure copper sheet with a width of 1mm, a length of 10mm, and a thickness of 0.5mm; the patch is connected to the measuring device via a copper wire with a thickness of 2mm, a width of 5mm, and a length of 10mm.

3. The method for testing the internal resistance of an ultra-low internal resistance power battery according to claim 1, characterized in that: When the force sensor outputs a force value of 2N, it sends a stop command to the power unit.

4. The method for testing the internal resistance of an ultra-low internal resistance power battery according to claim 1, characterized in that: The specimens are made of ultra-low carbon Inconel 625 alloy and include two columnar specimens, namely type I specimen and type II specimen. The length L of type I specimen is 65±0.5mm and the diameter D is 18±0.2mm. The length L of type II specimen is 70±0.5mm and the diameter D is 21±0.2mm.

5. The method for testing the internal resistance of an ultra-low internal resistance power battery according to claim 4, characterized in that: The chemical composition of the ultra-low carbon Inconel 625 alloy meets the following requirements by weight percentage: C: ≤0.02%, Cr: 20-23%, Nb+Ta: 3.15-4.15%, Fe: ≤5%, Mn: ≤0.5%, Mo: 8-10%, Si: ≤0.05%, S: ≤0.015%, P: ≤0.015%, Al: ≤0.4%, Ti: ≤0.4%, Co: ≤1.0%, Ni: ≥58%.

6. The method for testing the internal resistance of an ultra-low internal resistance power battery according to claim 4, characterized in that: The specimens were forgings, and before processing, they underwent solution heat treatment: vacuum heating to 10650-1100℃, constant temperature for 2 hours, water cooling, and then cutting to the design dimensions.

7. The method for testing the internal resistance of an ultra-low internal resistance power battery according to claim 4, characterized in that: The two ends of the specimen were encapsulated with a low resistivity material and vacuum plasma sprayed with a coating thickness of 0.2 mm.

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