Battery internal resistance measuring device

Abstract

The utility model provides a battery internal resistance measuring device in the technical field of batteries. The battery internal resistance measuring device comprises an MCU (Microprogrammed Control Unit), a battery voltage acquisition circuit, a battery current acquisition circuit and an alternating current signal acquisition circuit, the MCU is respectively connected with the battery voltage acquisition circuit, the battery current acquisition circuit and the alternating current signal acquisition circuit; the battery voltage acquisition circuit comprises a divider resistor R1, a divider resistor R2, a divider resistor R3, a divider resistor R4, a sampling resistor R5, an optocoupler OC1, an optocoupler OC2, an optocoupler OC3, an optocoupler OC4, an operational amplifier U1, an isolation operational amplifier U2 and an operational amplifier U3. The battery internal resistance measuring device has the advantage that the battery internal resistance measuring precision is greatly improved.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, in particular to a battery internal resistance measuring device. Background Art

[0002] The internal resistance of a battery is an important parameter that affects its performance. If the internal resistance of a battery is large, a large amount of Joule heat will be generated, causing the battery temperature to rise, resulting in a decrease in the battery discharge operating voltage and a shortened discharge time, which will affect the battery performance and life, etc. Therefore, there is a need to measure the internal resistance of the battery.

[0003] To measure the internal resistance of a battery, traditional measuring devices use a DC discharge method, which involves discharging a large current instantaneously through the battery, measuring the instantaneous voltage drop on the battery, and then calculating the internal resistance of the battery using Ohm's law. Although traditional measuring devices have been widely used in practice, they suffer from poor measurement accuracy.

[0004] Therefore, how to provide a battery internal resistance measurement device to improve the accuracy of battery internal resistance measurement has become a technical problem that needs to be solved urgently. Summary of the invention

[0005] The technical problem to be solved by the utility model is to provide a battery internal resistance measuring device to improve the accuracy of battery internal resistance measurement.

[0006] The utility model is implemented as follows: a battery internal resistance measuring device comprises an MCU, a battery voltage acquisition circuit, a battery current acquisition circuit and an AC signal acquisition circuit;

[0007] The MCU is respectively connected to the battery voltage acquisition circuit, the battery current acquisition circuit and the AC signal acquisition circuit;

[0008] The battery voltage acquisition circuit includes a voltage-dividing resistor R1, a voltage-dividing resistor R2, a voltage-dividing resistor R3, a voltage-dividing resistor R4, a sampling resistor R5, an optical coupler OC1, an optical coupler OC2, an optical coupler OC3, an optical coupler OC4, an operational amplifier U1, an isolation operational amplifier U2 and an operational amplifier U3;

[0009] The voltage-dividing resistor R1, the voltage-dividing resistor R2, the voltage-dividing resistor R3, the voltage-dividing resistor R4, the operational amplifier U1, the isolation operational amplifier U2, the operational amplifier U3 and the MCU are connected in series in sequence; the optocoupler OC1 is connected in parallel with the voltage-dividing resistor R1, the optocoupler OC2 is connected in parallel with the voltage-dividing resistor R2, the optocoupler OC3 is connected in parallel with the voltage-dividing resistor R3, and the optocoupler OC4 is connected in parallel with the voltage-dividing resistor R4; the optocoupler OC4 and the sampling resistor R5 are both connected to the operational amplifier U1; the optocoupler OC1, the optocoupler OC2, the optocoupler OC3 and the optocoupler OC4 are all connected to the MCU.

[0010] Further, the battery current acquisition circuit includes a voltage-dividing resistor R14, a voltage-dividing resistor R15, a voltage-dividing resistor R16, a voltage-dividing resistor R17, a sampling resistor R18, a MOS tube Q1, a MOS tube Q2, a MOS tube Q3, a MOS tube Q4, a MOS driver chip, an operational amplifier U5, an isolation operational amplifier U6, an operational amplifier U7 and a reference voltage chip;

[0011] The sampling resistor R18, the operational amplifier U5, the isolation operational amplifier U6, the operational amplifier U7 and the MCU are connected in series in sequence; the reference voltage chip is connected to the operational amplifier U5 and the isolation operational amplifier U6;

[0012] One end of the MOS transistor Q1, MOS transistor Q2, MOS transistor Q3 and MOS transistor Q4 are connected to the sampling resistor R18, and the other end is connected to one end of the voltage dividing resistor R14, the voltage dividing resistor R15, the voltage dividing resistor R16 and the voltage dividing resistor R17 respectively; the other ends of the voltage dividing resistor R14, the voltage dividing resistor R15, the voltage dividing resistor R16 and the voltage dividing resistor R17 are connected in series;

[0013] One end of the MOS driver chip is connected to the MOS transistor Q1 , the MOS transistor Q2 , the MOS transistor Q3 and the MOS transistor Q4 respectively, and the other end is connected to the MCU.

[0014] Furthermore, the AC signal acquisition circuit includes an AC signal acquisition chip, an operational amplifier U8 and an isolation operational amplifier U9;

[0015] The AC signal acquisition chip, operational amplifier U8, isolation operational amplifier U9 and MCU are connected in sequence.

[0016] The advantages of the utility model are:

[0017] 1. By setting up an MCU, a battery voltage acquisition circuit, a battery current acquisition circuit and an AC signal acquisition circuit, the MCU is connected to the battery voltage acquisition circuit, the battery current acquisition circuit and the AC signal acquisition circuit respectively; and in the battery voltage acquisition circuit and the battery current acquisition circuit, a number of voltage divider resistors, optocouplers or MOS tubes are set. The MCU can connect voltage divider resistors of different resistance values ​​in series by controlling the optocouplers or MOS tubes, and then switch the measurement gears, thereby effectively improving the measurement accuracy.

[0018] 2. By setting up isolation amplifiers in the battery voltage acquisition circuit, battery current acquisition circuit and AC signal acquisition circuit, the security of data acquisition can be effectively improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described below in conjunction with the embodiments with reference to the accompanying drawings.

[0020] Figure 1The utility model discloses a circuit principle block diagram of a battery internal resistance measuring device.

[0021] Figure 2 The utility model is a circuit diagram of a battery voltage acquisition circuit.

[0022] Figure 3 The utility model is a circuit diagram of a battery current acquisition circuit.

[0023] Figure 4 The utility model is a circuit diagram of an AC signal acquisition circuit. DETAILED DESCRIPTION

[0024] The embodiment of the utility model solves the technical problem of poor measurement accuracy of battery internal resistance in the prior art by providing a battery internal resistance measurement device, and achieves the technical effect of greatly improving the accuracy of battery internal resistance measurement.

[0025] The technical solution in the embodiment of the utility model is to solve the above-mentioned problem, and the overall idea is as follows: by setting a plurality of voltage-dividing resistors, optocouplers or MOS tubes in the battery voltage acquisition circuit and the battery current acquisition circuit, the MCU can connect voltage-dividing resistors with different resistance values ​​in series by controlling the optocouplers or MOS tubes, and then switch the measurement gear to improve the measurement accuracy.

[0026] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0027] Please refer to Figures 1 to 4 As shown, a preferred embodiment of a battery internal resistance measuring device of the utility model includes an MCU, a battery voltage acquisition circuit, a battery current acquisition circuit and an AC signal acquisition circuit;

[0028] The MCU is used to control the work of the battery internal resistance measuring device. In specific implementation, it is sufficient to select an MCU that can realize this function from the prior art, and it is not limited to any model, such as an MCU of the STM32F103 series, and the control program is well known to those skilled in the art, and can be obtained by those skilled in the art without creative labor; the battery voltage acquisition circuit is used to acquire the battery voltage; the battery current acquisition circuit is used to acquire the battery current; the AC signal acquisition circuit is used to acquire the battery AC signal;

[0029] The MCU is respectively connected to the battery voltage acquisition circuit, the battery current acquisition circuit and the AC signal acquisition circuit;

[0030] The battery voltage acquisition circuit includes a voltage-dividing resistor R1, a voltage-dividing resistor R2, a voltage-dividing resistor R3, a voltage-dividing resistor R4, a sampling resistor R5, an optical coupler OC1, an optical coupler OC2, an optical coupler OC3, an optical coupler OC4, an operational amplifier U1, an isolation operational amplifier U2 and an operational amplifier U3;

[0031] The voltage-dividing resistor R1, the voltage-dividing resistor R2, the voltage-dividing resistor R3, the voltage-dividing resistor R4, the operational amplifier U1, the isolation operational amplifier U2, the operational amplifier U3 and the MCU are connected in series in sequence; the optocoupler OC1 is connected in parallel with the voltage-dividing resistor R1, the optocoupler OC2 is connected in parallel with the voltage-dividing resistor R2, the optocoupler OC3 is connected in parallel with the voltage-dividing resistor R3, and the optocoupler OC4 is connected in parallel with the voltage-dividing resistor R4; the optocoupler OC4 and the sampling resistor R5 are both connected to the operational amplifier U1; the optocoupler OC1, the optocoupler OC2, the optocoupler OC3 and the optocoupler OC4 are all connected to the MCU.

[0032] The battery current acquisition circuit includes a voltage-dividing resistor R14, a voltage-dividing resistor R15, a voltage-dividing resistor R16, a voltage-dividing resistor R17, a sampling resistor R18, a MOS tube Q1, a MOS tube Q2, a MOS tube Q3, a MOS tube Q4, a MOS driver chip, an operational amplifier U5, an isolation operational amplifier U6, an operational amplifier U7 and a reference voltage chip;

[0033] The sampling resistor R18, the operational amplifier U5, the isolation operational amplifier U6, the operational amplifier U7 and the MCU are connected in series in sequence; the reference voltage chip is connected to the operational amplifier U5 and the isolation operational amplifier U6;

[0034] One end of the MOS transistor Q1, MOS transistor Q2, MOS transistor Q3 and MOS transistor Q4 are connected to the sampling resistor R18, and the other end is connected to one end of the voltage dividing resistor R14, the voltage dividing resistor R15, the voltage dividing resistor R16 and the voltage dividing resistor R17 respectively; the other ends of the voltage dividing resistor R14, the voltage dividing resistor R15, the voltage dividing resistor R16 and the voltage dividing resistor R17 are connected in series;

[0035] One end of the MOS driver chip is connected to the MOS transistor Q1 , the MOS transistor Q2 , the MOS transistor Q3 and the MOS transistor Q4 respectively, and the other end is connected to the MCU.

[0036] The AC signal acquisition circuit includes an AC signal acquisition chip, an operational amplifier U8 and an isolation operational amplifier U9;

[0037] The AC signal acquisition chip, operational amplifier U8, isolation operational amplifier U9 and MCU are connected in sequence.

[0038] Working principle of this utility model:

[0039] The voltage-dividing resistor R1 of the battery voltage acquisition circuit is connected to the positive electrode of the battery, and the sampling resistor R5 is connected to the negative electrode of the battery; the voltage-dividing resistors R14, R15, R16, and R17 of the battery current acquisition circuit are connected to the positive electrode of the battery, and the sampling resistor R18 is connected to the negative electrode of the battery; the AC signal acquisition chip of the AC signal acquisition circuit is connected to the positive and negative electrodes of the battery.

[0040] The MCU collects the battery voltage, battery current and AC signal of the battery through the battery voltage collection circuit, battery current collection circuit and AC signal collection circuit respectively, and calculates the internal resistance of the battery by combining the battery voltage and battery current through the phase difference of the AC signal, specifically:

[0041] Step 1: The MCU turns on the MOS tube Q1, MOS tube Q2, MOS tube Q3 or MOS tube Q4 through the MOS driver chip to select the voltage divider resistor R14, voltage divider resistor R15, voltage divider resistor R16 or voltage divider resistor R17 to connect to the loop to select the gear position of the battery current collection circuit. Similarly, the gear position of the battery voltage collection circuit is selected through the optical coupler.

[0042] Step 2: The MCU collects the battery voltage through the battery voltage collection circuit:

[0043] In the battery voltage acquisition circuit, when the optocoupler is not turned on by default, the four groups of voltage dividers are connected in series to make the battery voltage acquisition within the maximum range; the voltage of the sampling resistor R5 is amplified by the operational amplifier U1, isolated by the isolation operational amplifier U2, and then amplified by the operational amplifier U3, and the battery voltage is acquired and calculated by the ADC of the MCU; since it is the maximum range, if the voltage acquisition is small, the MCU controls the optocoupler to close to bypass the voltage divider resistor. If the range is still large, the subsequent optocouplers are controlled to close until the appropriate gear is reached; the calculation formula of the battery voltage is:

[0044] V1=Vadc1*(Rf+R5) / R5 / A1;

[0045] Among them, Vadc1 represents the first voltage value collected by the MCU; A1 represents the first operational amplifier coefficient; V1 represents the battery voltage; Rf represents the sum of the resistance values ​​of the voltage divider resistors (R1, R2, R3, R4), and the resistance values ​​are different in different gears.

[0046] Step 3: The MCU collects the battery current through the battery current collection circuit:

[0047] In the battery current acquisition circuit, the sampling resistor has a fixed resistance. When current passes through, the sampling resistor has a certain voltage drop. The battery current can be calculated by collecting the voltage drop of the sampling resistor:

[0048] I = Vadc2 / Rc / A2;

[0049] Wherein, Vadc2 represents the second voltage value collected by the MCU; Rc represents the resistance value of the sampling resistor R18; A2 represents the second operational amplification factor; and I represents the battery current, that is, the discharge current.

[0050] Step 4: The MCU controls the MOS tube of the battery current collection circuit to continuously discharge on and off to generate an AC square wave signal with a fixed frequency, and collects the AC signal of the battery through the AC signal collection circuit.

[0051] Step 5: Based on the point position of the AC square wave signal, the MCU measures the phase change of the collected AC signal and then calculates the phase difference. Based on the collected battery voltage, battery current and phase difference, the internal resistance of the battery is calculated using the impedance calculation formula, which is:

[0052] When a controlled current is used, ΔI = Imax S in (2πft), the resulting voltage response (battery voltage) is: ΔV = Vmax S in (2πft + φ);

[0053] R=ΔU / ΔI=(U1-U2) / (I2-I1);

[0054] Among them, R represents the internal resistance of the battery; U1 represents the battery voltage before discharge; U2 represents the battery voltage at the end of discharge; I1 represents the current at the beginning of discharge; I2 represents the current at the end of discharge; φ represents the phase difference; Imax represents the maximum value of the battery current; Vmax represents the maximum value of the battery voltage; f represents the frequency of the AC signal; and t represents the charge and discharge time.

[0055] In summary, the advantages of the present invention are:

[0056] 1. By setting up an MCU, a battery voltage acquisition circuit, a battery current acquisition circuit and an AC signal acquisition circuit, the MCU is connected to the battery voltage acquisition circuit, the battery current acquisition circuit and the AC signal acquisition circuit respectively; and in the battery voltage acquisition circuit and the battery current acquisition circuit, a number of voltage divider resistors, optocouplers or MOS tubes are set. The MCU can connect voltage divider resistors of different resistance values ​​in series by controlling the optocouplers or MOS tubes, and then switch the measurement gears, thereby effectively improving the measurement accuracy.

[0057] 2. By setting up isolation amplifiers in the battery voltage acquisition circuit, battery current acquisition circuit and AC signal acquisition circuit, the security of data acquisition can be effectively improved.

[0058] Although the specific implementation methods of the present invention are described above, those skilled in the art should understand that the specific embodiments described are only illustrative and are not intended to limit the scope of the present invention. Equivalent modifications and changes made by those skilled in the art in accordance with the spirit of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A battery internal resistance measuring device, characterized in that: It includes an MCU, a battery voltage acquisition circuit, a battery current acquisition circuit and an AC signal acquisition circuit; The MCU is respectively connected to the battery voltage acquisition circuit, the battery current acquisition circuit and the AC signal acquisition circuit; The battery voltage acquisition circuit includes a voltage-dividing resistor R1, a voltage-dividing resistor R2, a voltage-dividing resistor R3, a voltage-dividing resistor R4, a sampling resistor R5, an optical coupler OC1, an optical coupler OC2, an optical coupler OC3, an optical coupler OC4, an operational amplifier U1, an isolation operational amplifier U2 and an operational amplifier U3; The voltage-dividing resistor R1, the voltage-dividing resistor R2, the voltage-dividing resistor R3, the voltage-dividing resistor R4, the operational amplifier U1, the isolation operational amplifier U2, the operational amplifier U3 and the MCU are connected in series in sequence; the optocoupler OC1 is connected in parallel with the voltage-dividing resistor R1, the optocoupler OC2 is connected in parallel with the voltage-dividing resistor R2, the optocoupler OC3 is connected in parallel with the voltage-dividing resistor R3, and the optocoupler OC4 is connected in parallel with the voltage-dividing resistor R4; the optocoupler OC4 and the sampling resistor R5 are both connected to the operational amplifier U1; the optocoupler OC1, the optocoupler OC2, the optocoupler OC3 and the optocoupler OC4 are all connected to the MCU.

2. A battery internal resistance measuring device as claimed in claim 1, characterized in that: The battery current acquisition circuit includes a voltage-dividing resistor R14, a voltage-dividing resistor R15, a voltage-dividing resistor R16, a voltage-dividing resistor R17, a sampling resistor R18, a MOS tube Q1, a MOS tube Q2, a MOS tube Q3, a MOS tube Q4, a MOS driver chip, an operational amplifier U5, an isolation operational amplifier U6, an operational amplifier U7 and a reference voltage chip; The sampling resistor R18, the operational amplifier U5, the isolation operational amplifier U6, the operational amplifier U7 and the MCU are connected in series in sequence; the reference voltage chip is connected to the operational amplifier U5 and the isolation operational amplifier U6; One end of the MOS transistor Q1, MOS transistor Q2, MOS transistor Q3 and MOS transistor Q4 are connected to the sampling resistor R18, and the other end is connected to one end of the voltage dividing resistor R14, the voltage dividing resistor R15, the voltage dividing resistor R16 and the voltage dividing resistor R17 respectively; the other ends of the voltage dividing resistor R14, the voltage dividing resistor R15, the voltage dividing resistor R16 and the voltage dividing resistor R17 are connected in series; One end of the MOS driver chip is connected to the MOS transistor Q1 , the MOS transistor Q2 , the MOS transistor Q3 and the MOS transistor Q4 respectively, and the other end is connected to the MCU.

3. A battery internal resistance measuring device as claimed in claim 1, characterized in that: The AC signal acquisition circuit includes an AC signal acquisition chip, an operational amplifier U8 and an isolation operational amplifier U9; The AC signal acquisition chip, operational amplifier U8, isolation operational amplifier U9 and MCU are connected in sequence.

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