An online battery internal resistance measurement device and method

Abstract

An online battery internal resistance measurement device and method, including a battery to be tested, a circuit where the battery to be tested is located, and a load in the circuit where the battery to be tested is located; including a first inductor and a second inductor arranged in cooperation with the circuit where the battery to be tested is located, the first inductor is wound with a current measurement coil for measuring alternating current and a current feedback coil for replacing the load shunt current in the circuit where the battery to be tested is located. The present application integrates two measurement structures according to different operating conditions, one is a direct injection form, which is suitable for the measurement of large loads; the other is an indirect injection form using a second inductor, which is suitable for the measurement of small loads. Since the internal resistance of a battery is not completely consistent under different operating conditions, the integrated setting of the two measurement methods can greatly improve the convenience, as well as the reliability and stability of the persistent online measurement of the internal resistance.

Description

Technical Field

[0001] The present application relates to an online battery internal resistance measurement device and method. Background Art

[0002] The internal resistance of a battery refers to the resistance encountered by the current flowing through the battery when the battery is working. It includes ohmic internal resistance and polarization internal resistance. Polarization internal resistance includes electrochemical polarization internal resistance and concentration polarization internal resistance. The internal resistance of a battery refers to the resistance encountered by the current flowing through the battery when the battery is working. It is generally divided into AC internal resistance and DC internal resistance. Since the internal resistance of a rechargeable battery is very small, when measuring the DC internal resistance, the electrode capacity is polarized, resulting in polarization internal resistance, so its true value cannot be measured. However, measuring its AC internal resistance can eliminate the influence of polarization internal resistance and obtain the true internal value. The AC internal resistance test method is: using the characteristic that the battery is equivalent to an active resistor, give the battery a constant current of 1KHz, 50mA, and perform a series of processing such as voltage sampling, rectification and filtering to accurately measure its resistance value. The current measurement methods are mostly open-circuit measurement methods. It is difficult to make accurate measurements in some situations where it is not appropriate or even impossible to disconnect the battery. In addition, the resistance of the battery is constantly changing. In some situations where more frequent and regular resistance monitoring is required, there are not many methods and equipment available. Summary of the invention

[0003] In order to solve the above problems, the present application proposes, on the one hand, an online battery internal resistance measurement device, including a battery to be tested, a circuit where the battery to be tested is located, and a load in the circuit where the battery to be tested is located; including a first inductor and a second inductor arranged in cooperation with the circuit where the battery to be tested is located, the first inductor is wound with a current measuring coil for measuring alternating current and a current feedback coil for replacing the load shunt current in the circuit where the battery to be tested is located, and the second inductor is wound with an excitation current coil for receiving external current input; the battery to be tested is electrically connected to a main AC power supply unit, and also includes a voltage meter for measuring the voltage value provided by an AC voltage supply unit; a current meter for measuring the current in the current measuring coil and a secondary AC power supply unit for providing auxiliary AC current to the current feedback coil and the excitation current coil. The present application integrates two measurement structures according to different operating conditions. One is a direct injection form, which is suitable for the measurement of large loads; the other is an indirect injection form using a second inductor, which is suitable for the measurement of small loads. Since the internal resistance of the battery is not completely consistent under different operating conditions, the integration of two measurement methods can greatly improve the convenience, as well as the reliability and stability of the persistent online measurement of the internal resistance.

[0004] Preferably, the first inductor is a first semicircular magnetic core and a second semicircular magnetic core that can be opened and closed; the second inductor is a third semicircular magnetic core and a fourth semicircular magnetic core that can be opened and closed; and it also includes two oppositely arranged first snap-fit ​​shells and second snap-fit ​​shells, the first semicircular magnetic core and the third semicircular magnetic core are arranged in the first snap-fit ​​shell, and the second semicircular magnetic core and the fourth semicircular magnetic core are arranged in the second snap-fit ​​shell.

[0005] Preferably, a Hall sensor is provided on the first inductor.

[0006] Preferably, it further comprises a polarity selection circuit, and the Hall sensor, the primary AC power supply unit, the secondary AC power supply unit, the voltage measuring device, and the current measuring device are electrically connected to the polarity selection circuit.

[0007] Preferably, it also includes a first amplifier connected to the current feedback coil, a second amplifier connected to the voltage meter, the first amplifier and the second amplifier are respectively connected to the first filter; the main AC power supply unit, the secondary AC power supply unit, and the current feedback coil are respectively connected to the polarity selection circuit, the polarity selection circuit is connected to the second filter through a constant current power amplifier, the first filter is connected to the processor through an analog-to-digital converter, the second filter is connected to the processor through a digital-to-analog converter, and the processor is respectively connected to the input unit and the display unit.

[0008] On the other hand, the present application proposes an online battery internal resistance measurement method, providing a battery to be tested, a circuit where the battery to be tested is located, and a load in the circuit where the battery to be tested is located; estimating the ratio of the load equivalent resistance to the internal resistance of the battery to be tested, and if the ratio is greater than a first ratio, performing a direct injection measurement, and if the ratio is less than a second ratio, performing an indirect injection measurement; the first ratio is not less than the second ratio. The present application sets a first ratio and a second ratio so that online selection can be made during measurement. Of course, the first ratio can be equal to the second ratio. In this case, it is actually based on a limit value, and at this limit value, two measurement methods are selected. If automatic control is used, real-time and accurate monitoring and measurement of changes in battery internal resistance can be achieved.

[0009] Preferably, if the ratio is between the first ratio and the second ratio, the two measurement modes perform measurement operations sequentially.

[0010] Preferably, the direct injection measurement is performed using the following steps: first, an excitation current is input into the battery and the battery voltage is measured, and then the first inductor is adjusted using the current feedback coil on the first inductor so that the signal obtained by the current measurement coil is the total excitation current minus the excitation current shunted by the load, the excitation current passing through the battery is calculated, and then the internal resistance of the battery is calculated.

[0011] Preferably, the indirect injection measurement is performed by the following steps: first, an excitation current is input through the second inductor, then a current signal is measured through the first inductor, and a voltage change of the battery is measured, and then the internal resistance of the battery is calculated.

[0012] Preferably, the first ratio is 400-100, and the second ratio is 100-4.

[0013] This application can bring the following beneficial effects:

[0014] 1. According to different operating conditions, the present application integrates two measurement structures, one is a direct injection form, which is suitable for the measurement of large loads; the other is an indirect injection form using a second inductor, which is suitable for the measurement of small loads. Since the internal resistance of the battery is not completely consistent under different operating conditions, the integration of the two measurement methods can greatly improve the convenience, as well as the reliability and stability of the persistent online measurement of the internal resistance;

[0015] 2. This application sets the first ratio and the second ratio so that online selection can be made during measurement. Of course, the first ratio can be equal to the second ratio. In this case, the two measurement methods are actually selected based on a limit value. If automatic control is used, real-time and accurate monitoring and measurement of changes in battery internal resistance can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0017] Figure 1 A schematic diagram of this application;

[0018] Figure 2 This is a wiring terminal diagram of this application;

[0019] Figure 3 A schematic diagram of the inductor assembly part of the present application;

[0020] Figure 4 It is a schematic diagram of the constant current power amplifier part;

[0021] Figure 5 Schematic diagram for direct current injection measurement;

[0022] Figure 6 Schematic diagram of another state for direct current injection measurement;

[0023] Figure 7 Schematic diagram for indirect current injection measurement;

[0024] Figure 8 is a schematic diagram of a current measurement circuit;

[0025] Fig. 9 Schematic diagram of the voltage measurement circuit. DETAILED DESCRIPTION

[0026] In order to clearly illustrate the technical features of this solution, the present application is described in detail below through specific implementation methods and in conjunction with the accompanying drawings.

[0027] In the first embodiment, if Figure 1-2 As shown, an online battery internal resistance measuring device includes a battery to be tested 1, a circuit where the battery to be tested 1 is located, and a load 2 in the circuit where the battery to be tested 1 is located; including a first inductor 3 and a second inductor 4 arranged in cooperation with the circuit where the battery to be tested 1 is located, the first inductor 3 is wound with a current measuring coil 5 for measuring alternating current and a current feedback coil 6 for replacing the shunt current of the load 2 in the circuit where the battery to be tested 1 is located, and the second inductor 4 is wound with an excitation current coil 7 for receiving external current input; the battery to be tested 1 is electrically connected to a main alternating current supply unit 8, and also includes a voltage measuring device for measuring a voltage value provided by an alternating current voltage supply unit; a current measuring device for measuring the current in the current measuring coil 5 and a secondary alternating current supply unit for providing auxiliary alternating current to the current feedback coil 6 and the excitation current coil 7. The first inductor 3 is a first semicircular magnetic core 9 and a second semicircular magnetic core 10 that can be opened and closed; the second inductor 4 is a third semicircular magnetic core 11 and a fourth semicircular magnetic core 12 that can be opened and closed; it also includes two oppositely arranged first snap-fit ​​shells 13 and second snap-fit ​​shells 14, the first semicircular magnetic core 9 and the third semicircular magnetic core 11 are arranged in the first snap-fit ​​shell 13, and the second semicircular magnetic core 10 and the fourth semicircular magnetic core 12 are arranged in the second snap-fit ​​shell 14. A Hall sensor 26 is arranged on the first inductor 3. It also includes a polarity selection circuit 18, and the Hall sensor 26, the main AC power supply unit 8, the secondary AC power supply unit, the voltage measurement device, the current measurement device and the polarity selection circuit 18 are electrically connected. It also includes a first amplifier 15 connected to the current feedback coil 6, a second amplifier 16 connected to the voltage meter, the first amplifier 15 and the second amplifier 16 are respectively connected to the first filter 17; the main AC power supply unit 8, the secondary AC power supply unit, and the current feedback coil 6 are respectively connected to the polarity selection circuit 18, the polarity selection circuit 18 is connected to the second filter 20 through the constant current power amplifier 19, the first filter 17 is connected to the processor 21 through the analog-to-digital converter 22, the second filter 20 is connected to the processor 21 through the digital-to-analog converter 23, and the processor 21 is respectively connected to the input unit 24 and the display unit 25. The polarity selection circuit substantially plays a role in power conversion; the voltage meter and the current meter are substantially directly obtained by the processor after passing through the amplifier, the filter and the analog-to-digital converter.

[0028] In the second embodiment, during the specific operation, as shown in FIG. Figure 1 , Figure 3-Figure 9 As shown, for the processor of the present application, N sine wave data are output to the digital-to-analog converter strictly according to the fixed interval time t, and the digital-to-analog converter outputs a sine wave frequency f=1 / (t*N), and f takes a value of 1kHz. The processor can calculate new sine wave data to adjust the sine wave output amplitude, and the 1kHz sine wave is input to the filter, and low-pass filtering is performed to remove high-order harmonics. The sine signal is sent to the constant current power amplifier circuit, which converts the sinusoidal voltage signal into a sinusoidal constant current excitation signal.

[0029] For the constant current power amplifier part of the present application, this part of the circuit is composed of an error amplifier 101, a power amplifier 102, a current detection resistor 103, an instrument amplifier 104, and a range selection switch 105. The current signal on the current detection resistor is amplified by the instrument amplifier and sent to the error amplifier for comparison with the input sine wave signal. The error between the two signals is amplified and output to drive the power amplifier. The current on the current detection resistor changes accordingly, so that the signal after instrument amplification is precisely consistent with the input sine wave amplitude, but the polarity is opposite. The processor then selects a suitable range based on the detected AC excitation current passing through the battery to be tested 1 and the AC voltage drop generated by the AC excitation current at both ends of the battery to be tested 1 under the action of the internal resistance, so that the range switch is closed. After selecting the appropriate range, the processor adjusts the amplitude of the 1kHz sine signal and fine-tunes the output current. The AC excitation current passing through the battery to be tested 1 and the AC voltage drop generated by the AC excitation current at both ends of the battery to be tested 1 can reach more than 80% of the full range after passing through amplifiers 1 and 2, and the measurement will be more accurate.

[0030] As for the current feedback polarity and excitation signal injection mode, this part of the circuit consists of a current injection mode selection switch, a current feedback coil polarity selection switch, and a Hall sensor signal amplifier. The AC excitation current line number is coupled into the excitation signal injection mode selection switch through a DC isolation capacitor. When the second current injection mode is used, when the switch is closed in the direction of the coil, the AC excitation current will be directly coupled into the power line from the battery 1 to the load 2 to be tested. When the first current injection mode is used, the switch is closed in the direction of the switch, the AC excitation current, and then the current will be connected to the current detection coil 1 through the switch selection of the current feedback winding 1-3, 1-4.

[0031] When in use, there are two current injection methods. As for which one to choose, it is necessary to use an estimated value, or the ratio of the equivalent resistance of the load 2 to the resistance value of the battery 1 to be tested measured last time. If the ratio is greater than the first ratio, direct injection measurement is performed. If the ratio is less than the second ratio, indirect injection measurement is performed. The first ratio is not less than the second ratio. If it is between the two, direct injection measurement can be used first, and then indirect injection measurement, or vice versa. If there is no significant deviation between the two measurements, the average value of the two is taken.

[0032] The equivalent resistance of the load 2 powered by the battery 1 to be tested is usually not fixed. For example, the current consumed by the device in the standby state and the power-on state, the current consumed in the low-power mode and the full-power mode are very different, and the equivalent resistance varies in a wide range.

[0033] For example, the voltage of the battery 1 to be tested is 12V, the internal resistance is 100mΩ, the appliance is working in a low-power state, the battery 1 to be tested discharges 0.3A to the load 2, and the equivalent resistance value of the load 2 is 40Ω. Using the second current injection method, the AC excitation current is 50mA, and the voltage drop generated by the excitation current on the load 2 reaches 2V. Considering the voltage drop caused by the internal resistance of the battery 1 to be tested and the line resistance in the circuit, and the turn ratio of the current injection inductor and the power supply line of the battery 1 to the load 2 is 3:1, the use of the second current injection method will cause the voltage swing of the output signal of the constant current power amplifier circuit to exceed 6V. If the resistance of the load 2 is further increased, the voltage swing of the output signal of the power amplifier circuit will reach the power supply voltage of the tester, and the constant current signal will not be output normally, affecting the measurement accuracy. At this time, the first current injection method is used at both ends of the battery 1 to be tested, and the ratio of the AC excitation current passing through the battery 1 to be tested and the load 2 is 400:1. The excitation current diverted by the load 2 is then detected by the current detection coil 1, which improves the accuracy of the internal resistance test.

[0034] On the contrary, when the resistance of load 2 decreases, using the first current injection method, load 2 will shunt more AC excitation current, reducing the voltage drop across the battery 1 to be tested. For example, the voltage of battery 1 to be tested is 12V, the internal resistance is 100mΩ, the appliance works in a high-power state for a short time, the discharge current of battery 1 to be tested to load 2 is 30A, and the equivalent resistance value of load 2 is 0.4Ω. The AC excitation current is 50mA, and the ratio of the AC excitation current passing through battery 1 to be tested and load 2 is 4:1. The voltage drop across the battery 1 to be tested will be 0.8 times that of the second current injection method. Switching to the second current injection method, the total AC voltage drop on battery 1 to be tested and load 2 is only 25mV.

[0035] Direct current injection measurement, the detection principle of current detection coil 1 is as follows:

[0036] Coils 1-5 and 1-6 represent the power lines that pass through the current detection coil 1 and supply power to the load 2 from the battery 1 to be tested. Coils 1-3, 1-1, and 1-6 are the same-named terminals. Coils 1-3 and 1-4 have 1 turn, and coils 1-5 and 1-6 have 1 turn. Coils 1-1 and 1-2 have 100 turns. As shown in the figure above, the DC current that supplies power to the load 2 from the battery 1 to be tested enters 1-5 from the positive pole and flows out from 1-6. 3-1 and 3-2 are the positive and negative poles of the DC voltage measurement terminal of the battery 1 to be tested, respectively, and the AC voltage drop is sampled at the same time. We assume that the DC generates a fixed magnetic field in the magnetic ring at this time, so that the Hall element outputs a positive voltage signal and 3-1 is a positive voltage. The Hall output signal is amplified and sent to the processor. The processor controls the current feedback coil polarity selection switch to inject the AC excitation current into the battery 1 to be tested through ports 3-3 and 3-4. Entering from 1-3 and flowing out from 1-4, a part of the AC excitation current enters coils 1-5 and 1-6. At this time, since the number of turns of coils 1-3 and 1-4, 1-5 and 1-6 is the same but the current direction is opposite, the alternating magnetic field generated by the excitation current in the two coils is partially offset. The final remaining alternating magnetic field strength is the total AC excitation current minus the part shunted by load 2, and the corresponding AC signal is induced in coils 1-1 and 1-2 and sent to amplifier 2. For example, the voltage of the battery 1 to be tested is 12V, the internal resistance is 100mΩ, the appliance is working in a low power state, the battery 1 to be tested discharges 3A to load 2, and the equivalent resistance value of load 2 is 4Ω. The AC excitation current is 50mA. The excitation current passing through the battery 1 to be tested is i1=50*40 / 41mA, which is about 48.780mA. The current shunted by load 2 is i2=50 / 41mA, which is about 0.976mA. Therefore, the current output by 1-1 and 1-2 is i0=(i1-i2) / 100mA, which is approximately 0.47804mA.

[0037] As shown in the figure above, the current detection coil 1 is clamped on the negative power line of the battery 1 to be tested to supply power to the load 2. The DC current will enter the coil 1-5 from 1-6 and flow out. At this time, the Hall sensor outputs a negative voltage signal, and the voltage of the battery 1 to be tested measured at the 3-1 terminal is a positive voltage. At this time, the processor controls the current feedback coil polarity selection switch to make the AC excitation current enter from 1-4 and flow out from 1-3. The signals output by coils 1-1 and 1-2 correspond to the total AC excitation current minus the part diverted by load 2.

[0038] When the 3-1 terminal is at a negative voltage and the Hall output is at a positive voltage, the processor controls the current feedback coil polarity selection switch to allow the AC excitation current to enter from 1-4 and flow out from 1-3.

[0039] When the 3-1 terminal is a negative voltage and the Hall outputs a negative voltage, the processor controls the current feedback coil polarity selection switch to allow the AC excitation current to enter from 1-3 and flow out from 1-4.

[0040] Indirect current injection measurement:

[0041] Coils 2-3 and 2-4 represent the power lines passing through the current injection inductor, with 1 turn. Coils 2-1 and 2-2 have 4 turns.

[0042] After selecting the current injection inductor, the AC excitation current passes through coils 2-1 and 2-2 and is induced to 2-3 and 2-4. When measuring a large-capacity battery 1 to be tested or a group of batteries to be tested, a large excitation current is required because the internal resistance of the battery 1 to be tested is very small. For example, the voltage of the battery 1 to be tested is 12V, the internal resistance is 4mΩ, the discharge current to the load 2 is 200A, and the equivalent resistance of the load 2 is 0.06Ω. The excitation current can be amplified 4 times by the turns ratio of 2-1 and 2-2, 2-3 and 2-4 of 4:1, that is, when there is a 0.5A excitation current in 2-1 and 2-2, there will be a 2A induced excitation current in 2-3 and 2-4. When the induced excitation current passes through 1-5 and 1-6, it will induce the corresponding current on 1-1 and 1-2, i0=2 / 100A=0.02A current.

[0043] Measuring current:

[0044] The current detection terminal 1-1 is grounded, and 1-2 is connected to the inverting input terminal of the operational amplifier. There are multiple precision resistors and selection switches at the inverting input terminal and the output terminal. The corresponding resistor can be connected according to the current size, and the output terminal of the operational amplifier will output the corresponding voltage, u=i*R. The output voltage signal is then sent to the back stage for processing, and finally converted into a digital signal by an analog-to-digital converter. FFT is used to process the data to obtain information such as the amplitude, phase angle, etc. of the 1kHz AC excitation signal.

[0045] The signals at the 3-1 and 3-2 terminals are blocked by capacitors and amplified by an instrument amplifier for the AC voltage drop. The signals are then sent to the subsequent stage for processing and finally converted into digital signals by an analog-to-digital converter. The data is processed by FFT to obtain the amplitude, phase angle and other information of the required 1kHz AC voltage drop signal.

[0046] The internal resistance of the battery 1 to be tested is calculated from the data of the AC voltage and current.

[0047] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. An online battery internal resistance measuring device, comprising a battery to be tested, a circuit where the battery to be tested is located, and a load in the circuit where the battery to be tested is located; characterized in that: The device comprises a first inductor and a second inductor which are arranged in cooperation with the circuit where the battery to be tested is located, wherein the first inductor is wound with a current measuring coil for measuring alternating current and a current feedback coil for replacing the load shunt current in the circuit where the battery to be tested is located, and the second inductor is wound with an excitation current coil for receiving external current input; the battery to be tested is electrically connected to the main alternating current supply part, and further comprises a voltage measuring device for measuring the voltage value provided by the alternating current voltage supply part; a current measuring device for measuring the current in the current measuring coil and a secondary alternating current supply for providing an auxiliary alternating current to the current feedback coil and the exciting current coil; The first inductor is a first semicircular magnetic core and a second semicircular magnetic core that can be opened and closed; the second inductor is a third semicircular magnetic core and a fourth semicircular magnetic core that can be opened and closed; and further comprises two oppositely arranged first clamping shells and a second clamping shell, wherein the first semicircular magnetic core and the third semicircular magnetic core are arranged in the first clamping shell, and the second semicircular magnetic core and the fourth semicircular magnetic core are arranged in the second clamping shell; A Hall sensor is provided on the first inductor; It also includes a polarity selection circuit, and the Hall sensor, the primary AC power supply unit, the secondary AC power supply unit, the voltage measurer, and the current measurer are electrically connected to the polarity selection circuit.

2. The on-line battery internal resistance measuring device according to claim 1, characterized in that: It also includes a first amplifier connected to the current feedback coil, a second amplifier connected to the voltage meter, the first amplifier and the second amplifier are respectively connected to the first filter; the main AC power supply unit, the secondary AC power supply unit, and the current feedback coil are respectively connected to the polarity selection circuit, the polarity selection circuit is connected to the second filter through a constant current power amplifier, the first filter is connected to the processor through an analog-to-digital converter, the second filter is connected to the processor through a digital-to-analog converter, and the processor is respectively connected to the input unit and the display unit.

3. An online battery internal resistance measurement method using the battery internal resistance measurement device according to claim 1, characterized in that: Provide a battery to be tested, a circuit where the battery to be tested is located, and a load in the circuit where the battery to be tested is located; The ratio of the load equivalent resistance to the internal resistance of the battery to be measured is estimated. If the ratio is greater than a first ratio, direct injection measurement is performed. If the ratio is less than a second ratio, indirect injection measurement is performed. The first ratio is not less than the second ratio.

4. The method for measuring the internal resistance of an online battery according to claim 3, characterized in that: If the ratio is between the first ratio and the second ratio, the two measurement methods perform measurement operations in sequence.

5. The method for measuring the internal resistance of an online battery according to claim 3, characterized in that: The direct injection measurement is performed in the following steps: first, an excitation current is input into the battery and the battery voltage is measured, and then the first inductor is adjusted using the current feedback coil on the first inductor so that the signal obtained by the current measurement coil is the total excitation current minus the excitation current of the load shunt, the excitation current passing through the battery is calculated, and then the internal resistance of the battery is calculated.

6. The method for measuring the internal resistance of an online battery according to claim 3, characterized in that: The indirect injection measurement is performed by the following steps: first, an excitation current is input through the second inductor, then a current signal is measured through the first inductor, and a voltage change of the battery is measured, and then the internal resistance of the battery is calculated.

7. The method for measuring the internal resistance of an online battery according to claim 3, characterized in that: The first ratio is 400-100, and the second ratio is 100-4.

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