Lithium battery internal resistance test system

Abstract

The utility model discloses a lithium battery internal resistance test system, comprising a sampling resistor; the control unit is used for generating a driving signal; the switch unit, the first pole of the lithium battery, the switch unit, the sampling resistor and the second pole of the lithium battery are sequentially connected in series, and the switch unit is further connected with the control unit and used for being closed according to a driving signal so that the first pole of the lithium battery, the switch unit, the sampling resistor and the second pole of the lithium battery can form a loop; the voltage sampling unit is connected with the lithium battery and is used for acquiring a voltage signal of the lithium battery; the current sampling unit is connected with the sampling resistor and is used for acquiring a current signal flowing through the sampling resistor; the control unit is further connected with the voltage sampling unit and the current sampling unit so as to obtain a voltage signal and a current signal. The driving signal is generated through the control unit, the driving signal is a voltage signal, a fixed sampling resistor is adopted, and the lithium battery adjusts the amplitude of the discharging current through different driving signals, so that the magnitude of the discharging current of the lithium battery can be adjusted at will.

Description

Technical Field

[0001] The utility model belongs to the technical field of lithium battery internal resistance testing, and in particular relates to a lithium battery internal resistance testing system. Background Art

[0002] In the prior art, the main methods for testing the internal resistance of lithium batteries are: (1) AC injection method: During measurement, an AC current signal with a fixed amplitude is injected into the lithium battery, and the AC frequency is usually 1kHz. The corresponding AC voltage is measured, and then the internal resistance of the lithium battery is calculated according to Ohm's law. This method is easily interfered by ripple current and noise. Therefore, the test accuracy of the AC injection method is low, and the measurement accuracy is usually 1% to 2%. (2) DC discharge method: The battery is connected to an external load to discharge the battery for a short time, and the voltage and short-time discharge current at both ends of the lithium battery are detected, and then the internal resistance of the lithium battery is calculated according to Ohm's law. This method has strong anti-interference ability, is not easily affected by noise, and has a slightly higher test accuracy, and the measurement accuracy is usually 0.1% to 0.2%. Since this test method requires the connection of an external load during the test, the lithium battery must be tested in a static or offline state, and cannot be tested online, and is not suitable for lithium battery automatic production lines. In addition, since the discharge current of lithium batteries of different specifications is different, different external loads are required in the conventional test method, and more test equipment is required, and the test work is relatively cumbersome. Utility Model Content

[0003] In order to overcome the above technical defects, the utility model provides a lithium battery internal resistance testing system, which can realize the test without using different external loads.

[0004] The utility model is realized by the following scheme:

[0005] A lithium battery internal resistance testing system, comprising:

[0006] Sampling resistor;

[0007] A control unit, for generating a driving signal;

[0008] A switch unit, wherein the first pole of the lithium battery, the switch unit, the sampling resistor, and the second pole of the lithium battery are sequentially connected in series, and the switch unit is also connected to the control unit and is used to close according to the driving signal so that the first pole of the lithium battery, the switch unit, the sampling resistor, and the second pole of the lithium battery form a loop;

[0009] A voltage sampling unit is connected to the lithium battery and is used to obtain a voltage signal of the lithium battery;

[0010] A current sampling unit, connected to the sampling resistor, for acquiring a current signal flowing through the sampling resistor;

[0011] The control unit is also connected to the voltage sampling unit and the current sampling unit to obtain the voltage signal and the current signal.

[0012] As a further improvement of the present invention, the switch unit comprises:

[0013] A D / A conversion circuit is connected to the control unit, and the control unit controls the D / A conversion circuit to generate a standard voltage signal to obtain the driving signal;

[0014] A current amplifier circuit, a first pole of a lithium battery, the current amplifier circuit, the sampling resistor, and a second pole of the lithium battery are sequentially connected in series, and the current amplifier circuit is used to close according to the driving signal and amplify the current flowing through the sampling resistor.

[0015] As a further improvement of the present invention, the switch unit further includes:

[0016] The error amplifier circuit is connected to the D / A conversion circuit, the current power amplifier circuit, and the current acquisition unit, and is used to obtain the current feedback signal flowing through the sampling resistor. The error amplifier circuit performs error amplification on the standard voltage signal and the current feedback signal to obtain the drive signal and send it to the current power amplifier circuit.

[0017] As a further improvement of the utility model, the utility model also includes:

[0018] The A / D conversion unit is connected to the switch unit, the voltage sampling unit and the control unit, and is used to convert the voltage signal of the analog quantity of the voltage sampling unit and the current signal of the analog quantity of the current sampling unit into the voltage signal and the current signal of the analog quantity of the digital quantity.

[0019] As a further improvement of the present utility model, the sampling resistor is a precision resistor, and the current detection end of the precision resistor is respectively connected to the negative electrode of the lithium battery and the switch unit;

[0020] The current sampling unit comprises:

[0021] A first operational amplifier circuit, wherein a non-inverting terminal thereof is connected to a voltage detection terminal of the precision resistor;

[0022] A second operational amplifier circuit, a non-inverting terminal of which is connected to a voltage detection terminal of the precision resistor;

[0023] A third operational amplifier circuit, wherein the output terminal and the inverting input terminal of the first operational amplifier circuit are connected to the non-inverting terminal of the third operational amplifier circuit, and the output terminal and the inverting input terminal of the second operational amplifier circuit are connected to the non-inverting terminal of the third operational amplifier circuit; and the output terminal of the third operational amplifier circuit is connected to the control unit.

[0024] As a further improvement of the present utility model, the voltage sampling unit comprises:

[0025] A fourth operational amplifier circuit, wherein a non-inverting input terminal thereof is connected to a positive electrode of a lithium battery;

[0026] A fifth operational amplifier circuit, wherein a non-inverting input terminal thereof is connected to a positive electrode of a lithium battery;

[0027] A sixth operational amplifier circuit, wherein the inverting terminal and the output terminal of the fourth operational amplifier circuit are connected to the non-inverting input terminal of the sixth operational amplifier circuit, and the inverting terminal and the output terminal of the fifth operational amplifier circuit are connected to the non-inverting input terminal of the fifth operational amplifier circuit; and the output terminal of the sixth operational amplifier circuit is connected to the control unit.

[0028] As a further improvement of the present invention, the D / A conversion circuit comprises:

[0029] A D / A conversion chip, whose input end is connected to the control unit;

[0030] a seventh operational amplifier circuit, whose input end is connected to the output end of the D / A conversion chip, and whose output end is connected to the error amplifier circuit;

[0031] The first voltage reference chip is connected to the D / A conversion chip.

[0032] As a further improvement of the present invention, the error amplification circuit comprises:

[0033] an eighth operational amplifier circuit, an input end of which is connected to the A / D conversion unit;

[0034] A ninth operational amplifier circuit, whose input end is connected to the D / A conversion circuit and the output end of the eighth operational amplifier circuit, and whose output end is connected to the switch unit.

[0035] As a further improvement of the present invention, the A / D conversion unit comprises:

[0036] An A / D conversion chip, whose input end is connected to the control unit, and whose output end is connected to the voltage sampling unit and the current sampling unit;

[0037] The second voltage reference chip is connected to the A / D conversion chip.

[0038] As a further improvement of the present invention, the switch unit comprises:

[0039] A resistor, wherein the output end of the error amplifier circuit is connected to one end of the resistor;

[0040] NMOS tube, the other end of the resistor is connected to the gate of the NMOS tube, the source of the NMOS tube is connected to the positive electrode of the lithium battery, and the drain of the NMOS tube is connected to the current sampling unit.

[0041] Compared with the prior art, the beneficial effects of the utility model are as follows: a driving signal is generated by a control unit, wherein the driving signal is a voltage signal, and a fixed sampling resistor is used. The lithium battery adjusts different discharge current amplitudes through different driving signals, so that the discharge current of the lithium battery (i.e., the current passing through the sampling resistor) can be adjusted arbitrarily, and testing can be achieved without using different external loads. At the same time, a voltage sampling unit and a current sampling unit are provided to realize the collection of voltage and current, thereby providing a hardware platform for the subsequent realization of the internal resistance of the lithium battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The specific implementation of the utility model is further described in detail below with reference to the accompanying drawings, wherein:

[0043] Figure 1 This is a schematic diagram of the overall structure of the lithium battery internal resistance testing system of the utility model;

[0044] Figure 2 It is a structural schematic diagram of the D / A conversion circuit and the error amplification circuit of the utility model;

[0045] Figure 3 It is a structural schematic diagram of the current power amplifier circuit and the current sampling unit of the utility model;

[0046] Figure 4 It is a structural schematic diagram of the A / D conversion unit and the voltage sampling unit of the utility model.

[0047] Marking description: 1. Control unit; 2. Switch unit; 21. D / A conversion circuit; 211. Seventh operational amplifier circuit; 22. Current power amplifier circuit; 23. Error amplifier circuit; 231. Eighth operational amplifier circuit; 232. Ninth operational amplifier circuit; 3. Voltage sampling unit; 31. Fourth operational amplifier circuit; 32. Fifth operational amplifier circuit; 33. Sixth operational amplifier circuit; 4. Current sampling unit; 41. First operational amplifier circuit; 42. Second operational amplifier circuit; 43. Third operational amplifier circuit; 5. A / D conversion unit; 100. Lithium battery. DETAILED DESCRIPTION

[0048] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0049] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In the description of the present utility model, it should also be noted that, unless otherwise clearly specified and limited, the terms "setting" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal connection of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0050] According to the test specification of IEC61960, the internal resistance of lithium batteries is tested according to the following steps:

[0051] (1) After the lithium battery is discharged at a constant current of I1 = 0.2It for 10 seconds, the discharge current I1 and the corresponding discharge voltage U1 are measured respectively;

[0052] (2) After the lithium battery is discharged at a constant current of I2 = 1.0It for 1 second, the discharge current I2 and the corresponding discharge voltage U2 are measured respectively;

[0053] (3) Lithium battery DC internal resistance

[0054] Among them, It is the nominal discharge current of the lithium battery.

[0055] The utility model discloses a lithium battery internal resistance test system, which can meet the requirements of IEC61960, adopt the discharge current and corresponding voltage of the lithium battery to provide hardware support for the subsequent calculation of the internal resistance of the lithium battery, such as Figure 1 As shown, the lithium battery internal resistance test system includes: a sampling resistor RS, a control unit 1, a switch unit 2, a voltage sampling unit 3, and a current sampling unit 4; the control unit 1 is used to generate a driving signal; the positive electrode of the lithium battery 100, the switch unit 2, the sampling resistor RS, and the negative electrode of the lithium battery 100 are connected in series in sequence, and the switch unit 2 is also connected to the control unit 1, and is used to close according to the driving signal so that the positive electrode of the lithium battery 100, the switch unit 2, the sampling resistor RS, and the negative electrode of the lithium battery 100 form a loop; the voltage sampling unit 3 is connected to the lithium battery 100 to obtain the voltage signal of the lithium battery 100; the current sampling unit 4 is connected to the sampling resistor RS to obtain the current signal flowing through the sampling resistor RS; the control unit 1 is also connected to the voltage sampling unit 3 and the current sampling unit 4 to obtain the voltage signal and the current signal.

[0056] The utility model can be connected to a background calculation unit for use. The calculation unit can be implemented by a single-chip microcomputer or a computer. The voltage signal and the current signal are obtained by the lithium battery internal resistance test system and sent to the calculation unit. The calculation unit is used to calculate the internal resistance of the lithium battery.

[0057] The switch unit 2 includes: a D / A conversion circuit 21 and a current amplifier circuit 22; wherein the D / A conversion circuit 21 is connected to the control unit 1, and the control unit 1 controls the D / A conversion circuit 21 to generate a standard voltage signal to obtain a driving signal; the positive electrode of the lithium battery 100, the current amplifier circuit 22, the sampling resistor RS, and the negative electrode of the lithium battery 100 are connected in series in sequence, and the current amplifier circuit 22 is used to close according to the driving signal and amplify the current flowing through the sampling resistor RS.

[0058] Preferably, the D / A conversion chip U1 is implemented using a 16-bit D / A conversion chip U1, so that the accuracy of the discharge currents I1 and I2 output by the lithium battery BAT can reach 0.01%. The control unit 1 is connected to the D / A conversion chip U1 through an SPI interface, and controls the D / A conversion chip U1 to generate a set DC standard voltage signal I-SIGN through an embedded software code.

[0059] In order to achieve precise control of the lithium battery discharge circuit, the utility model also includes: an error amplifier circuit 23, the error amplifier circuit 23 is connected to the D / A conversion circuit 21, the current power amplifier circuit 22, and the current acquisition unit 4, and is used to obtain the current feedback signal of the output current of the lithium battery BAT. The error amplifier circuit 23 performs error amplification on the DC standard voltage signal I-SIGN and the current feedback signal to obtain a drive signal I-DRIVE and send it to the current power amplifier circuit 22.

[0060] Specifically, the error amplifier circuit 23 includes: an eighth operational amplifier circuit 231 and a ninth operational amplifier circuit 232, the input end of the eighth operational amplifier circuit 231 is connected to the A / D conversion unit 5; the input end of the ninth operational amplifier circuit 232 is connected to the D / A conversion circuit 21 and the output end of the eighth operational amplifier circuit 231, and the output end is connected to the switch unit 2.

[0061] The eighth operational amplifier circuit 231 includes: an eighth operational amplifier A8 and a resistor R2; the ninth operational amplifier circuit 232 includes: a ninth operational amplifier A9, a resistor R1, a resistor R3, and a resistor R4, the inverting input terminal of the eighth operational amplifier A8 is connected to the output terminal of the eighth operational amplifier A8, the non-inverting input terminal of the eighth operational amplifier A8 is connected to the current sampling unit 4, the output terminal of the eighth operational amplifier A8 is connected to the non-inverting input terminal of the ninth operational amplifier A9 through the resistor R2, the non-inverting input terminal of the ninth operational amplifier A9 is connected to the D / A conversion circuit 21 through the resistor R1, the inverting input terminal of the ninth operational amplifier A9 is grounded through the resistor R3, the output terminal of the ninth operational amplifier A9 is grounded through the resistors R4 and R3, and the output terminal of the ninth operational amplifier A9 is connected to the switch unit 2.

[0062] The error between the standard signal I-SING and the feedback signal I-FB of the current sampling unit 4 is amplified by the amplification circuit composed of the ninth operational amplifier, the resistor R3 and the resistor R4 to obtain the driving signal I-DRIVE of the linear amplifier circuit.

[0063] Furthermore, the utility model also includes: an A / D conversion unit 5, which is connected to the switch unit 2, the voltage sampling unit 3, and the control unit 1, and is used to convert the analog voltage signal of the voltage sampling unit 3 and the analog current signal of the current sampling unit 4 into digital voltage signals and current signals.

[0064] The sampling resistor RS is a precision resistor RS, and the current detection end of the precision resistor RS is connected to the negative electrode of the lithium battery BAT and the switch unit 2 respectively; Figure 3 As shown, the current sampling unit 4 includes: a first operational amplifier circuit 41, a second operational amplifier circuit 42 and a third operational amplifier circuit 43, the in-phase end of the first operational amplifier circuit 41 is connected to the voltage detection end of the precision resistor RS; the in-phase end of the second operational amplifier circuit 42 is connected to the voltage detection end of the precision resistor RS; the output end and the inverting input end of the first operational amplifier circuit 41 are connected to the in-phase end of the third operational amplifier circuit 43, the output end and the inverting input end of the second operational amplifier circuit 42 are connected to the in-phase end of the third operational amplifier circuit 43; the output end of the third operational amplifier circuit 43 is connected to the control unit 1.

[0065] Specifically, the first operational amplifier circuit 41 includes: a first operational amplifier A1, the second operational amplifier circuit 42 includes: a second operational amplifier A2, and the third operational amplifier circuit 43 includes: a third operational amplifier A3, a resistor R6, a resistor R7, a resistor R8, and a resistor R9. The non-inverting input terminal of the first operational amplifier A1 is connected to the voltage detection "+" terminal of the precision resistor RSRS, the inverting input terminal of the first operational amplifier A1 is connected to the output terminal of the first operational amplifier A1, and the output terminal of the first operational amplifier A1 is connected to the non-inverting input terminal of the third operational amplifier A3 through the resistor R6; the non-inverting input terminal of the second operational amplifier A2 is connected to the voltage detection "-" terminal of the precision resistor RS, the inverting input terminal of the second operational amplifier A2 is connected to the output terminal of the second operational amplifier A2, the output terminal of the second operational amplifier A2 is connected to the inverting input terminal of the third operational amplifier A3 through the resistor R7, and the non-inverting input terminal of the third operational amplifier A3 is connected to the error amplifier circuit 23 through the resistor R8.

[0066] The precision resistor RS converts the current signal into a voltage signal, and the voltage signal is differentially input through the first operational amplifier A1 and the second operational amplifier A2; then the differential sampling and amplification circuit composed of resistors R6, R7, R8, R9 and the third operational amplifier A3 samples and amplifies the voltage signal of the precision resistor RS, thereby obtaining a current signal I-FB.

[0067] like Figure 4 As shown, the voltage sampling unit 3 includes: a fourth operational amplifier circuit 31, a fifth operational amplifier circuit 32 and a sixth operational amplifier circuit 33, the non-inverting input terminal of the fourth operational amplifier circuit 31 is connected to the positive electrode of the lithium battery BAT; the non-inverting input terminal of the fifth operational amplifier circuit 32 is connected to the positive electrode of the lithium battery BAT; the inverting terminal and the output terminal of the fourth operational amplifier circuit 31 are connected to the non-inverting input terminal of the sixth operational amplifier circuit 33, the inverting terminal and the output terminal of the fifth operational amplifier circuit 32 are connected to the non-inverting input terminal of the fifth operational amplifier circuit 32; the output terminal of the sixth operational amplifier circuit 33 is connected to the control unit 1.

[0068] The fourth operational amplifier circuit 31 includes: a fourth operational amplifier A4, the fifth operational amplifier circuit 32 includes: a fifth operational amplifier A5, and the sixth operational amplifier circuit 33 includes: a sixth operational amplifier, a resistor R10, a resistor R11, a resistor R12, and a resistor R13. The non-inverting input terminal of the fourth operational amplifier A4 is connected to the positive electrode of the lithium battery BAT, the reverse input terminal of the fourth operational amplifier A4 is connected to the non-inverting input terminal of the sixth operational amplifier A6 through the resistor R10, the reverse input terminal of the fourth operational amplifier A4 is connected to the output terminal of the fourth operational amplifier A4, the reverse input terminal of the fifth operational amplifier A5 is connected to the non-inverting input terminal of the sixth operational amplifier A6 through the resistor R11, the reverse input terminal of the fifth operational amplifier A5 is connected to the output terminal of the fifth operational amplifier A5, the non-inverting input terminal of the sixth operational amplifier A6 is connected to the A / D conversion unit 5 through the resistor R12, the output terminal of the sixth operational amplifier A6 is connected to the A / D conversion unit 5, and the reverse input terminal of the sixth operational amplifier A6 is grounded through the resistor R13. The voltage of the lithium battery BAT is differentially input through the fourth operational amplifier A4 and the fifth operational amplifier A5, and then passes through the differential sampling circuit composed of resistors R10, R11, R12, R13 and the sixth operational amplifier A6 to amplify the sampling signal, thereby obtaining the voltage signal V-FB of the lithium battery BAT.

[0069] like Figure 2 As shown, the D / A conversion circuit 21 includes: a D / A conversion chip U1, a seventh operational amplifier circuit 211 and a first voltage reference chip U1, the input end of the D / A conversion chip U1 is connected to the control unit 1; the input end of the seventh operational amplifier circuit 211 is connected to the output end of the D / A conversion chip U1, and the output end is connected to the error amplifier circuit 23; the first voltage reference chip U1 is connected to the D / A conversion chip U1.

[0070] Specifically, the seventh operational amplifier circuit 211 includes: a seventh operational amplifier A7 and a capacitor C1, the inverting input terminal of the seventh operational amplifier A7 is connected to the D / A conversion chip U1 through the capacitor C1, the non-inverting input terminal of the seventh operational amplifier A7 is connected to the D / A conversion chip U1 and grounded, the non-inverting input terminal of the seventh operational amplifier A7 is connected to the D / A conversion chip U1, and the output terminal of the seventh operational amplifier A7 is connected to the error amplifier circuit 23.

[0071] like Figure 3 As shown, the A / D conversion unit 5 includes: an A / D conversion chip U3 and a second voltage reference chip U4. The input end of the A / D conversion chip U3 is connected to the control unit 1, and the output end is connected to the voltage sampling unit 3 and the current sampling unit 4; the second voltage reference chip U4 is connected to the A / D conversion chip U3.

[0072] The analog voltage signal V-FB and the analog current signal I-FB are respectively connected to the input end of the multi-channel 16-bit A / D conversion chip U3, and are output to the control unit 1 after AD conversion to obtain the current voltage value and current value.

[0073] Preferably, the A / D conversion chip U3 is implemented using a 16-bit D / A conversion chip U1, so that the measurement accuracy of the voltage values ​​U1 and U2 of the lithium battery BAT can reach 0.01%. Combined with the accuracy of the D / A conversion chip U1, the accuracy of the test method of the utility model can reach more than 0.02%.

[0074] like Figure 3 As shown, the switch unit 2 includes: a resistor R5 and an NMOS tube Q1, the output end of the error amplifier circuit 23 is connected to one end of the resistor R5; the other end of the resistor R5 is connected to the gate of the NMOS tube Q1, the source of the NMOS tube Q1 is connected to the positive electrode of the lithium battery BAT, and the drain of the NMOS tube Q1 is connected to the current sampling unit 4.

[0075] Next, the utility model is further explained in conjunction with the specific implementation process, as follows:

[0076] The control unit 1 controls the D / A conversion circuit 21 through the SPI (serial peripheral interface) interface to generate a DC standard voltage signal I-SIGN; the I-SIGN signal and the output current feedback signal I-FB are error-amplified to generate a drive signal I-DRIVE; the NMOS tube Q1 is driven by the I-DRIVE signal to make the current amplifier circuit 22 output the corresponding current. The current is sampled using the precision resistor RSRS and the current sampling unit 4 to obtain the current feedback signal I-FB. The lithium battery provides output power for the switch unit 2.

[0077] The current sampling unit 4 and the lithium battery BAT form a programmable constant current source, the main function of which is to make the test current of the lithium battery BAT adjustable. By setting the standard voltage signal amplitude through the control unit 1, the discharge current amplitude of the lithium battery can be controlled. During the discharge of the lithium battery BAT, the discharge current is sampled in real time by the current sampling unit 4 to obtain the current signal; at the same time, the voltage at the positive and negative ends of the lithium battery BAT is sampled in real time by the voltage sampling unit 3 to obtain the voltage signal. Then the current signal and the voltage signal are input into the multi-input A / D conversion unit 5, and the sampling signals of the current signal and the voltage signal are converted into digital signals through the A / D conversion unit 5 and input into the control unit 1, and finally the current discharge current amplitude and voltage amplitude are obtained through the control unit 1.

[0078] The driving signal generated by the control unit 1 is a voltage signal, which drives the MOS tube in the current amplifier circuit 22, so that the lithium battery 100 outputs a linear current. The driving signal amplitude is proportional to the output current amplitude, so the lithium battery discharge current can be controlled by controlling the driving signal.

[0079] According to the test specification of IEC61960: set I1=0.2It and I2=1.0It through the control unit, and test the discharge current I1 and I2, voltage U1 and U2 of the lithium battery BAT respectively. Use formula (1) in the calculation unit to calculate the DC internal resistance Rdc of the lithium battery.

[0080] In summary, the utility model has the following beneficial effects:

[0081] 1. By using a fixed sampling resistor and changing the driving signal, there is no need to use the AC injection method, which eliminates the influence of ripple current and noise in the entire test process. With the high-precision 16-bit D / A conversion chip and 16-bit D / A conversion chip, the accuracy of lithium battery internal resistance test can be improved;

[0082] 2. Compared with the DC discharge method in the prior art, the internal resistance test of lithium batteries of different specifications does not require the use of different external loads, but only requires different voltage signals to achieve the test;

[0083] 3. Since there is no need to change different loads during the test, offline testing can be achieved to meet the assembly line test or automatic test of lithium batteries, overcoming the disadvantage that the DC discharge method cannot be tested online.

[0084] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A lithium battery internal resistance test system, It is characterized in that include: Sampling resistor; A control unit, for generating a driving signal; A switch unit, wherein the first pole of the lithium battery, the switch unit, the sampling resistor, and the second pole of the lithium battery are sequentially connected in series, and the switch unit is also connected to the control unit and is used to close according to the driving signal so that the first pole of the lithium battery, the switch unit, the sampling resistor, and the second pole of the lithium battery form a loop; A voltage sampling unit is connected to the lithium battery and is used to obtain a voltage signal of the lithium battery; A current sampling unit, connected to the sampling resistor, for acquiring a current signal flowing through the sampling resistor; The control unit is also connected to the voltage sampling unit and the current sampling unit to obtain the voltage signal and the current signal.

2. The lithium battery internal resistance testing system according to claim 1, It is characterized in that The switch unit comprises: A D / A conversion circuit is connected to the control unit, and the control unit controls the D / A conversion circuit to generate a standard voltage signal to obtain the driving signal; A current amplifier circuit, a first pole of a lithium battery, the current amplifier circuit, the sampling resistor, and a second pole of the lithium battery are sequentially connected in series, and the current amplifier circuit is used to close according to the driving signal and amplify the current flowing through the sampling resistor.

3. The lithium battery internal resistance testing system according to claim 2, It is characterized in that The switch unit further comprises: The error amplifier circuit is connected to the D / A conversion circuit, the current power amplifier circuit, and the current acquisition unit, and is used to obtain the current feedback signal flowing through the sampling resistor. The error amplifier circuit performs error amplification on the standard voltage signal and the current feedback signal to obtain the drive signal and send it to the current power amplifier circuit.

4. The lithium battery internal resistance testing system according to claim 3, It is characterized in that Also includes: The A / D conversion unit is connected to the switch unit, the voltage sampling unit and the control unit, and is used to convert the voltage signal of the analog quantity of the voltage sampling unit and the current signal of the analog quantity of the current sampling unit into the voltage signal and the current signal of the analog quantity of the digital quantity.

5. The lithium battery internal resistance testing system according to any one of claims 1 to 4, It is characterized in that The sampling resistor is a precision resistor, and the current detection end of the precision resistor is connected to the negative electrode of the lithium battery and the switch unit respectively; The current sampling unit comprises: A first operational amplifier circuit, wherein a non-inverting terminal thereof is connected to a voltage detection terminal of the precision resistor; A second operational amplifier circuit, a non-inverting terminal of which is connected to a voltage detection terminal of the precision resistor; A third operational amplifier circuit, wherein the output terminal and the inverting input terminal of the first operational amplifier circuit are connected to the non-inverting terminal of the third operational amplifier circuit, and the output terminal and the inverting input terminal of the second operational amplifier circuit are connected to the non-inverting terminal of the third operational amplifier circuit; and the output terminal of the third operational amplifier circuit is connected to the control unit.

6. The lithium battery internal resistance testing system according to any one of claims 1 to 4, It is characterized in that The voltage sampling unit comprises: A fourth operational amplifier circuit, wherein a non-inverting input terminal thereof is connected to a positive electrode of a lithium battery; A fifth operational amplifier circuit, wherein a non-inverting input terminal thereof is connected to a positive electrode of a lithium battery; A sixth operational amplifier circuit, wherein the inverting terminal and the output terminal of the fourth operational amplifier circuit are connected to the non-inverting input terminal of the sixth operational amplifier circuit, and the inverting terminal and the output terminal of the fifth operational amplifier circuit are connected to the non-inverting input terminal of the fifth operational amplifier circuit; and the output terminal of the sixth operational amplifier circuit is connected to the control unit.

7. The lithium battery internal resistance testing system according to claim 3, It is characterized in that The D / A conversion circuit comprises: A D / A conversion chip, whose input end is connected to the control unit; a seventh operational amplifier circuit, whose input end is connected to the output end of the D / A conversion chip, and whose output end is connected to the error amplifier circuit; The first voltage reference chip is connected to the D / A conversion chip.

8. The lithium battery internal resistance testing system according to claim 4, It is characterized in that The error amplification circuit comprises: an eighth operational amplifier circuit, an input end of which is connected to the A / D conversion unit; A ninth operational amplifier circuit, whose input end is connected to the D / A conversion circuit and the output end of the eighth operational amplifier circuit, and whose output end is connected to the switch unit.

9. The lithium battery internal resistance testing system according to claim 4, It is characterized in that The A / D conversion unit comprises: An A / D conversion chip, whose input end is connected to the control unit, and whose output end is connected to the voltage sampling unit and the current sampling unit; The second voltage reference chip is connected to the A / D conversion chip.

10. The lithium battery internal resistance testing system according to claim 3, It is characterized in that The switch unit comprises: A resistor, wherein the output end of the error amplifier circuit is connected to one end of the resistor; NMOS tube, the other end of the resistor is connected to the gate of the NMOS tube, the source of the NMOS tube is connected to the positive electrode of the lithium battery, and the drain of the NMOS tube is connected to the current sampling unit.

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