Battery management system capable of monitoring internal resistance of each battery

Abstract

The invention discloses a battery management system capable of monitoring the internal resistance of each battery. The battery management system comprises an MCU module, a CAN communication module, a power supply module, a constant-voltage and constant-current output module, an alternating-current signal generation circuit and change-over switch module and a signal acquisition and change-over switch module, the MCU module is respectively connected with the CAN communication module, the power supply module, the constant-voltage constant-current output module, the alternating-current signal generation circuit and change-over switch module and the signal acquisition and change-over switch module, and the alternating-current signal generation circuit and change-over switch module and the signal acquisition and change-over switch module are respectively connected with a tested battery cell; the power supply module is connected with the constant-voltage and constant-current output module, and the constant-voltage and constant-current output module is connected with the alternating-current signal generation circuit and the change-over switch module. Internal resistance on-line monitoring is introduced into the battery management system, the digital models of the SOC and the SOH are corrected in real time, the estimation precision of the SOC and the SOH is improved, and therefore the energy utilization rate of the whole energy storage system and the vehicle-mounted power battery system is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of energy storage, and in particular relates to a battery management system capable of monitoring the internal resistance of each battery. Background Art

[0002] At present, the development of battery management systems is mainly concentrated in the fields of energy storage, consumer electronics and new energy vehicles. With the production and manufacturing of new energy vehicle power batteries and energy storage and their high requirements for safety, efficient, reliable and safe battery management systems (BMS) are gaining more and more attention.

[0003] The main functions of the existing battery management system (BMS) management system include: real-time monitoring of battery physical parameters: battery status estimation; online diagnosis and early warning: charge, discharge and pre-charge control; balance management and thermal management. The battery management system (BMS) is mainly to improve the utilization rate of the battery, prevent the battery from overcharging and over-discharging, extend the battery life, and monitor the battery status.

[0004] Battery degradation and failure are mostly caused by internal problems such as material aging, plate corrosion, sulfation crystallization, and water loss. They cannot be measured directly, but they will cause the internal resistance of the battery to increase. These internal problems can often be manifested through changes in internal resistance. Therefore, battery internal resistance is a very important parameter. Many important information of the battery, such as capacity, SOC, SOH, etc., can be reflected through internal resistance. Although the existing BMS system has made a lot of safety-related designs for battery system safety, the starting reference conditions of these designs are all estimated conditions for the battery status. Therefore, the existing BMS management system has the following defects:

[0005] (1) The battery internal resistance cannot be measured online in real time;

[0006] (2) The abnormal internal resistance of the battery cannot be discovered in time, and as the internal resistance of the battery continues to increase, the health of the battery is affected;

[0007] (3) The change of battery internal resistance during long-term operation of the system leads to inaccurate SOC estimation, and the battery capacity cannot be effectively utilized;

[0008] (4) The internal resistance increases with the system operation time, and the system cannot recognize it. In terms of safety, it is easy to cause thermal runaway, causing a fire in the system and burning the entire system. Summary of the invention

[0009] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a battery management system that introduces online internal resistance monitoring in a battery management system, corrects the digital models of SOC and SOH in real time, improves the estimation accuracy of SOC and SOH, and thus improves the energy utilization rate of the entire energy storage system and the on-board power battery system, and can monitor the internal resistance of each battery.

[0010] The objective of the present invention is achieved through the following technical solutions: a battery management system capable of monitoring the internal resistance of each battery, comprising an MCU module, a CAN communication module, a power module, a constant voltage and constant current output module, an AC signal generating circuit and a switching switch module, and a signal acquisition and switching switch module; the MCU module is respectively connected to the CAN communication module, the power module, the constant voltage and constant current output module, the AC signal generating circuit and the switching switch module, and the signal acquisition and switching switch module, and the AC signal generating circuit and the switching switch module, and the signal acquisition and switching switch module are respectively connected to the tested battery cell; the power module is connected to the constant voltage and constant current output module, and the constant voltage and constant current output module is connected to the AC signal generating circuit and the switching switch module.

[0011] The MCU module includes an MCU chip, an active crystal oscillator, a connector, an indicator light LED1, and an LC filter circuit; the MCU chip adopts STM32G473VET6.

[0012] The AC signal generating circuit and switching switch module include MOS tubes Q1-Q16, inductor L9, analog switches U7 and U8, connector J6, multiple resistors and capacitors, and the analog switches U7 and U8 both use TMUX1308A chips; 2 pins of MOS tubes Q1-Q16 are connected in parallel to the inductor L9, and the other end of L9 is connected to the constant voltage and constant current output module; 3 pins of MOS tubes Q1-Q16 are respectively connected to the positive electrode of the tested battery cell through connector J6;

[0013] Pin 1 of MOS tubes Q1~Q16 is the control signal input pin, and pin 1 of MOS tubes Q1~Q7 is connected to pins 13, 14, 15, 12, 1, 5, 2, and 4 of U7 respectively; pin 1 of MOS tubes Q8~Q15 is connected to pins 13, 14, 15, 12, 1, 5, 2, and 4 of U8 respectively; the MCU chip drives the analog switches U7 and U8 to control the switches of MOS tubes Q1~Q16 to generate a 1kHz frequency AC signal, which is injected into the positive electrode of the battery cell under test through pin 3 of MOS tubes Q1~Q16.

[0014] The signal acquisition and switching module includes MOS tubes Q17-Q32, resistors R70-R135, capacitors C55-C77, analog switches U10 and U11, multiplexer U9 and connector J7; the analog switches U10 and U11 both use TMUX1308A chips, and the multiplexer U9 uses CD74HC4067M96 chips;

[0015] Pin 2 of MOS tubes Q17~Q32 is connected to the negative electrode of the tested cell through connector J7; Pin 3 of MOS tubes Q17~Q32 is connected to sampling resistors R76~R81, R88~R93, R103~R106 respectively, one end of sampling resistors R76~R81, R88~R93, R103~R106 is connected to GND, and the other end is connected to pins 9, 8, 7, 6, 5, 4, 3, 2, 23, 22, 21, 20, 19, 18, 17, 16 of U9 in sequence; pins 10, 11, 14, 13 of U9 are connected to pins 17, 18, 19, 20 of MCU chip respectively; pin 1 of U9 is connected to pin 2 of MCU chip after resistor R107 is connected in series. 1 pins, pin 1 of MOS tubes Q17~Q24 are connected to pins 13, 14, 15, 12, 1, 5, 2, 4 of U10 respectively; pin 1 of MOS tubes Q25~Q32 are connected to pins 13, 14, 15, 12, 1, 5, 2, 4 of U11 respectively; pins 6, 3, 9, 10, 11 of U10 are connected to pins 56, 55, 57, 58, 59 of MCU chip respectively, and pins 6, 3, 9, 10, 11 of U11 are connected to pins 68, 69, 67, 66, 65 of MCU chip respectively. The MCU chip drives analog switches U10 and U11 to control the switches of MOS tubes Q17~Q32, and the signal on the sampling resistor is sent to the MCU through the multiplexer U9.

[0016] The beneficial effects of the present invention are:

[0017] 1. The present invention introduces online internal resistance monitoring in the battery management system, which can monitor the change of battery internal resistance in real time.

[0018] 2. SOC estimation is generally calculated using the ampere-hour integration method. Changes in the battery's internal resistance will affect changes in the current, thereby affecting the accuracy of SOC estimation. Through real-time monitoring of the inside of the resistor, the SOC estimation model can be corrected in real time to improve the SOC estimation accuracy.

[0019] 3. Through real-time monitoring of the battery's internal resistance, the battery's SOH digital model can be continuously corrected in real time to improve the accuracy of SOH estimation, thereby improving the energy utilization of the entire energy storage system and the on-board power battery system.

[0020] 4. The present invention can monitor the change of battery internal resistance online in real time, which is of great significance in terms of safety. Thermal runaway of the battery is generally caused by overcharging or external factors. Regardless of the factor, the internal resistance of the battery can intuitively warn the user in advance, thereby avoiding safety accidents. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the overall structure of the battery management system of the present invention;

[0022] Figure 2 A circuit diagram of the MCU module of the present invention;

[0023] Figure 3 is the circuit diagram of the LC filter circuit;

[0024] Figure 4 This is the circuit diagram of the active crystal oscillator (G1);

[0025] Figure 5 is the circuit diagram of the connector (J2);

[0026] Figure 6 This is the circuit diagram of indicator LED1;

[0027] Figure 7 This is the circuit diagram of the CAN communication module;

[0028] Figure 8 This is the circuit diagram of connector J5;

[0029] Fig. 9 This is the circuit diagram of the 5V voltage conversion circuit;

[0030] Fig.10 Circuit diagram of 3.3V voltage conversion circuit

[0031] Fig.11 This is the circuit diagram of the constant voltage and constant current output module;

[0032] Fig.12 This is the circuit diagram of MOS tubes Q1 to Q16;

[0033] Fig.13 This is the circuit diagram of connector J6;

[0034] Fig.14 is the circuit diagram of the analog switch U7;

[0035] Fig.15 is the circuit diagram of the analog switch U8;

[0036] Fig.16 This is the circuit diagram of MOS tubes Q17 to Q32;

[0037] Fig.17 This is the circuit diagram of connector J7;

[0038] Fig.18 is a circuit diagram of the multiplexer U9;

[0039] Fig.19 is a circuit diagram of the analog switch U10;

[0040] Fig. 20 is a circuit diagram of the analog switch U11;

[0041] Fig.21 The circuit diagram of the power pin decoupling filter circuit;

[0042] Fig. 22 This is the circuit diagram of the watchdog circuit. DETAILED DESCRIPTION

[0043] The battery internal resistance detection scheme can be generally classified into two categories: DC discharge method and AC injection method.

[0044] The essence of the DC discharge method is to add an external load to the battery to make it discharge with a large current, detect the voltage drop at both ends of the battery while discharging, and obtain the internal resistance of the battery through the ratio of the voltage drop of the battery to the value of the large current. It has the following disadvantages:

[0045] (1) It is impossible to detect the internal resistance of the battery online, so the online working status of the battery cannot be determined; and this method takes too long to detect the internal resistance, which increases the risk for systems that require uninterrupted power supply;

[0046] (2) The detection process requires high current discharge, which will inevitably damage the battery. If the frequency of battery detection is too high, the damage to the battery will accumulate, which will in turn affect the battery performance;

[0047] (3) The DC method is too repetitive and cumbersome to be used in practical applications.

[0048] The AC injection method applies an AC current signal of a fixed frequency to the battery, measures the voltage value fed back from both ends of the battery, and subtracts the DC component therefrom. Based on the ratio of the fed back voltage value to the injected current value, the internal resistance of the battery is obtained. When the AC injection method detects the internal resistance of the battery, the battery does not need to be taken offline, and online detection of the internal resistance is achieved. In addition, the AC current injected by this method is much smaller than the discharge current of the DC discharge method, so the impact on the battery is also much smaller than that of the DC discharge method. Combining the two detection methods, the present invention selects the internal resistance detection method of the AC injection method.

[0049] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0050] like Figure 1 As shown, a battery management system capable of monitoring the internal resistance of each battery of the present invention includes an MCU module, a power module, a constant voltage and constant current output module, an AC signal generating circuit and a switching switch module, a signal acquisition and switching switch, and a CAN communication module;

[0051] The MCU module is respectively connected to the power module, the constant voltage and constant current output module, the AC signal generation circuit and the switching switch module, the signal acquisition and switching switch and the CAN communication module;

[0052] The MCU module includes an MCU chip (U4), an active crystal oscillator (G1), a connector (J2), an indicator light LED1, and an LC filter circuit; the MCU chip adopts STM32G473VET6, such as Figure 2 As shown;

[0053] The LC filter circuit includes magnetic bead inductors L5 and L6, capacitors C16, C17, C19, and C20. Figure 3 As shown; the magnetic bead inductors L5 and L6 are connected in series, and the two non-connected ends of L5 and L6 are called free ends, and the free end of L5 is connected to the 3.3V power supply (VCC3V3) provided by the power module; capacitors C16 and C17 are connected in parallel, one end of the two parallel capacitors is connected to the free end of L6, and the other end is grounded; the connection end of the parallel capacitors of C16 and C17 and L6 is connected to the 37th pin of the MCU chip; the connection ends of L5 and L6 are respectively connected to the power pins of the MCU chip, the active crystal oscillator, the connector, and the indicator LED1, providing a 3.3V power supply (VDD3V3) for the MCU chip, the active crystal oscillator, the connector, and the indicator LED1; capacitors C19 and C20 are connected in parallel, one end of the parallel capacitor is connected to the connection end of L5 and L6, and the other end is grounded; through the coordination of inductance and capacitance, an LC filtering circuit is formed to provide reliable power supply for the MCU chip.

[0054] like Figure 4 As shown, the active crystal oscillator (G1) uses OT32258MJBA4SL, the 2nd pin of the active crystal oscillator G1 is grounded, the 4th pin is connected to one end of the capacitor C18, and the 4th pin is connected to the 3.3V power supply (VDD3V3), and the other end of the capacitor C18 is grounded; the 3rd pin of the active crystal oscillator G1 is connected in series with the resistor R10 and then connected to the 12th pin of the MCU chip, and the 1st pin is left floating;

[0055] like Figure 5 As shown, the connector (J2) is the program download and program simulation debugging interface of U4. J2 adopts TH-MTB111-10S. Pin 2 of the connector is connected to a 3.3V power supply (VDD3V3), and pin 4 is connected to capacitor C21 and then grounded; pin 4 of the connector is connected to pin 14 of the MCU chip in series with resistor R12, pin 6 is connected to pin 90 of the MCU chip in series with resistor R14, pin 3 is connected to pin 91 of the MCU chip in series with resistor R13, pin 5 is connected to pin 78 of the MCU chip in series with resistor R15, pin 7 is connected to pin 76 of the MCU chip in series with resistor R16, and pin 9 is connected to pin 77 of the MCU chip; resistors R12, R13, R14, R15, and R16 are all pull-up resistors, and the other ends of them are connected to pins 1 and 2 of the connector respectively.

[0056] like Figure 6As shown, the indicator light LED1 is a 4-pin LED lamp, whose pin 1 is connected to the resistor R19, and the pin 4 is connected to the resistor R18; the other ends of R18 and R19 are connected (to limit the current and avoid damage to LED1), and the other ends of R18 and R19 are both connected to a 3.3V power supply (VDD3V3); the pins 2 and 3 of the indicator light LED1 are respectively connected to the pins 60 and 61 of the MCU chip.

[0057] MCU chip U4 controls the generation, modulation, collection and analysis of AC constant current and constant voltage signals, and enables switch control, and calculates the internal resistance of the battery cell through the collected information; capacitors C16~C28 realize U4 peripheral power supply energy storage and high-frequency interference signal filtering, providing reliable and clean power supply to U4 and its periphery; resistors R12~R17 and J2 constitute U4's program download and debugging interface, and resistors R12~R17 configure U4 debugging pins to ensure that U4 is stable and reliable during debugging; resistors R18 and R19 are current limiting resistors of LED1, and LED1 realizes U4's working status indication function.

[0058] The CAN communication module consists of a CAN chip U5, a magnetic bead L8, a common mode inductor L7, resistors R21, R22, R2, 4R25, capacitors C29, C31, C32, TVS tubes TVS2 to TVS4, and a jumper J3. Figure 7 As shown, U5 uses the SN65HVD232DR chip.

[0059] Pin 1 of U5 is connected to pin 73 of MCU chip through resistor R21, and outputs CAN1-TXD signal to MCU chip. The end of resistor R21 connected to MCU chip is provided with test point TP4; Pin 4 of U5 is connected to pin 72 of MCU chip through resistor R25, and receives CAN1-RXD signal output by MCU chip. The end of resistor R25 connected to MCU chip is provided with test point TP5;

[0060] Pin 2 of U5 is grounded, and pin 3 is connected to one end of magnetic bead L8. The other end of magnetic bead L8 is connected to a 3.3V power supply (VDD3V3, provided by the output end of the LC filter circuit); capacitors C31 and C32 are connected in parallel, and one end of the parallel capacitor is connected between magnetic bead L8 and pin 3 of U5, and the other end is grounded; pins 6 and 7 of U5 are connected to ports 1 and 2 of common-mode inductor L7 respectively; three TVS tubes TVS2, TVS3 and TVS4 are connected in series in sequence, and the connection ends of TVS2 and TVS3 are connected to the third port of common-mode inductor L7 and the jumper wire respectively. The 1st port of J3 is connected, and the 2nd port of jumper J3 is connected in series with resistor R22; the connection ends of TVS3 and TVS4 are respectively connected to the fourth port of common mode inductor L7 and resistor R24; the other ends of resistors R22 and R24 are both connected to one end of capacitor C29, and the other end of capacitor C29 is respectively connected to the free ends of TVS2 and TVS4 and grounded; wherein, the connection ends of TVS2 and TVS3, and the connection ends of TVS3 and TVS4 (CANH and CANL signals) are respectively connected to the subsequent circuits through connector J5, and the circuit of connector J5 is as shown in FIG. Figure 8 shown.

[0061] The power supply module in the present invention is composed of two parts: a 5V voltage conversion circuit and a 3.3V voltage conversion circuit (VCC3V3).

[0062] The 5V voltage conversion circuit includes a power chip U1, a connector J1, diodes D1 to D3, a fuse F1, capacitors C1 to C7, resistors R1 to R5, a light-emitting diode D4, a TCS tube TVS1 and a common-mode inductor L2. Fig. 9As shown. The power chip U1 uses TPS5430DDA. The 1-pin of the common-mode inductor L2 is connected to the negative electrode of the capacitor C2 and the positive electrode of the diode D3 respectively. The negative electrode of the diode D3 is connected to the 2-pin of the connector J1. The 3-pin of the common-mode inductor L2 is connected to the positive electrode of the capacitor C2 and the fuse F1 respectively. The other end of the fuse F1 is connected to the negative electrode of the diode D1. The positive electrode of the diode D1 is connected to the 2-pin of the connector J1. The connector J1 is connected to an external 9-36V DC power supply. The 2-pin of the common-mode inductor L2 is connected to the negative electrode of the capacitor C3, the 6-pin of U1 and the 9-pin of the connector J1 respectively. Pins, pin 4 of the common-mode inductor L2 are connected to the positive electrode of capacitor C3 and pin 7 of U1 respectively; capacitor C4 is connected in parallel between pins 7 and 9 of U1; resistor R2 and capacitor C7 are connected in parallel, one end of the parallel circuit is connected to pins 9 and 6 of U1, and the other end is connected to pin 5 of U1; pin 5 of U1 is connected in series with resistor R1 and then connected to pin 4 of the common-mode inductor L1, and pins 6 and 9 of U1 are also grounded; pin 1 of U1 is connected to capacitor C1 and inductor L1 in sequence, and the other end of inductor L1 is a voltage output interface, which outputs 5V voltage (VDD5V). Pin 8 of U1 is connected between capacitor C1 and inductor L1, the cathode of diode D2 is connected between pin 8 of U1 and inductor L1, and the anode of diode D2 is grounded; the anode of capacitor C6 is connected to the output end of inductor L1, and the cathode is grounded; resistors R3 and R5 are connected in series, and the two series resistors are connected in parallel with TCS tube TVS1, and one end of the parallel circuit formed is connected to the output end of inductor L1, and the other end is grounded; the series connection end of resistors R3 and R5 is connected to pin 4 of U1; a test interface TP1 is provided between capacitors C6 and C5. Resistor R4 is connected to the anode of light-emitting diode D4, the cathode of light-emitting diode D4 is grounded, and the other end of resistor R4 is connected to a 5V power supply provided by the output end of inductor L1.

[0063] The 3.3V voltage conversion circuit includes a power chip U2, an inductor L3, capacitors C8-C11, a resistor R6, and a light-emitting diode D5. Fig.10 As shown, its function provides a stable and reliable 3.3V working power supply for the whole system. The power chip U2 adopts TLV1117, and the 3rd pin of U2 is connected to the 5V power supply (VDD5V) through the inductor L3, which is provided by the output end of the inductor L1. Capacitors C10 and C11 are both connected between the 2nd and 1st pins of U2, and the 2nd and 4th pins of U2 are connected as the voltage output interface, outputting a 3.3V voltage (VDD3V3) to provide a 3.3V power supply for the other modules in the battery management system; capacitors C8 and C9 are connected in parallel, one end of the parallel capacitor is connected to the voltage output interface end, and the other end is grounded; a test interface TP2 is provided between capacitors C8 and C9; resistor R6 is connected to the positive pole of the light-emitting diode D5, and the negative pole of the light-emitting diode D5 is grounded, and the other end of the resistor R6 is connected to the 3.3V power supply, which is provided by the voltage output interface of U1.

[0064] like Fig.11 As shown, the constant voltage and constant current output module is used to convert a 5V power supply into a stable 3.6V voltage. It is composed of an inductor L4, a voltage regulator U3, resistors R7-R9, capacitors C12-C15, a light-emitting diode D6, and a diode D7. U3 uses a TPS7A02 chip; capacitors C14 and C15 are connected in parallel between the IN port and the GND port of U3, and serve as input energy storage and decoupling capacitors of U3; capacitors C12 and C13 are connected in parallel between the VOUT port and the GND port of U3, and serve as output energy storage and decoupling capacitors of U3; resistor R8 is connected between the IN port and the EN port of U3, and resistor R9 is connected between the EN port and the GND port of U3. Resistors R8 and R9 form a voltage divider circuit to achieve U3. 3 enable control; one end of the inductor L4 is connected to a parallel end of the capacitors C14 and C15 and the IN port of the chip U3, and the other end is connected to the 5V input voltage (VDD5V) provided by the power module. The inductor L4 and the capacitors C14 and C15 form the U3 input end LC filter circuit; the diode D7 is a switching diode with unidirectional conductivity; the positive electrode of the diode D7 is connected to the VOUT port of U3 and a parallel end of the capacitors C12 and C13, and the negative electrode is a voltage output interface, outputting a 3.6V voltage; a test interface TP3 is provided between the circuit connected to the capacitors C12 and C13 and the VOUT port. The resistor R7 is connected to the positive electrode of the light-emitting diode D6, the negative electrode of the light-emitting diode D6 is grounded, and the other end of the resistor R7 is connected to the 3.6V input voltage (VCC3V6, provided by the voltage output interface of D7). The resistor R7 and the light-emitting diode D6 form the output indication circuit of U3.

[0065] The AC signal generating circuit and the switching switch module include MOS tubes Q1-Q16, an inductor L9, analog switches U7 and U8, a connector J6, a plurality of resistors (R44-R69) and capacitors (C35-C54), and the analog switches U7 and U8 both use TMUX1308A chips; 2 pins of the MOS tubes Q1-Q16 are connected in parallel to the inductor L9, and the other end of L9 is connected to the constant voltage and constant current output module, and the constant voltage and constant current output module provides a 3.6V power supply for the AC signal generating circuit and the switching switch; Fig.12 As shown in the figure (due to the size of the figure, not all MOS tubes are drawn, only a part of them are cut out for display); the 3 pins of MOS tubes Q1~Q16 (C1~C16 interfaces) are connected to the positive electrode of the tested battery cell through connector J6 respectively. Connector J6 is as shown in the figure. Fig.13 shown.

[0066] Pin 1 (S1~S16) of MOS tubes Q1~Q16 is the control signal input pin, and pin 1 of MOS tubes Q1~Q7 is connected to pins 13, 14, 15, 12, 1, 5, 2, and 4 of U7 respectively. Fig.14As shown; the 1 pins of MOS tubes Q8 to Q15 are connected to the 13, 14, 15, 12, 1, 5, 2, and 4 pins of U8 respectively. Fig.15 As shown; the MCU chip drives the analog switches U7 and U8 to control the switches of the MOS tubes Q1 to Q16 to generate a 1kHz frequency AC signal, and the AC signal is injected into the positive electrode of the tested battery cell through the 3rd pin of the MOS tubes Q1 to Q16.

[0067] like Fig.14 As shown, pin 16 of U7 is connected to a 3.3V power supply (VCC3V3, provided by the power chip U2), and pin 8 is grounded; pin 6 of U7 is connected to pin 1 of the MCU chip, and pin 6 is also connected in series with resistor R60 before being connected to a 3.3V power supply; pins 3, 9, 10, and 11 of U7 are connected in series with resistors R62, R64, R66, and R68 in sequence and then connected to pins 15, 5, 4, and 3 of the MCU chip; resistor R44 and capacitor C39 are connected in series, resistor R45 and capacitor C40 are connected in series, resistor R46 and capacitor C41 are connected in series, and resistor R47 and capacitor C48 are connected in series. Capacitor C42 is connected in series, resistor R48 and capacitor C43 are connected in series, resistor R49 and capacitor C44 are connected in series, resistor R50 and capacitor C45 are connected in series, and resistor R51 and capacitor C46 are connected in series. The series ends of the above resistors and capacitors are connected to the 13, 14, 15, 12, 1, 5, 2, and 4 pins of U7 respectively. Resistors R44 to R51 are all pull-up resistors, and the other end of them is connected to the 3.3V power supply to ensure that the default output of U7 is high level. Capacitors C39 to C46 are all filter capacitors, and their function is to resist interference. The other end of capacitors C39 to C46 is grounded. Bypass capacitors C35 and C37 are connected in parallel, and one end of the parallel capacitor is connected to the 3.3V power input, and the other end is grounded.

[0068] like Fig.15As shown, the 16th pin of U8 is connected to the 3.3V power supply, and the 8th pin is grounded; the 6th pin of U8 is connected to the 2nd pin of the MCU chip, and the 6th pin is also connected in series with the resistor R61 and then connected to the 3.3V power supply; the 3rd pin, the 9th pin, the 10th pin and the 11th pin of U8 are connected in series with the resistors R63, R65, R67 and R69 in turn, and then connected to the 16th, 9th, 8th and 7th pins of the MCU chip; the resistor R52 and the capacitor C47 are connected in series, the resistor R53 and the capacitor C48 are connected in series, the resistor R54 and the capacitor C49 are connected in series, the resistor R55 and the capacitor C50 are connected in series, and the resistor R66 and the capacitor C51 are connected in series. R56 and capacitor C51 are connected in series, resistor R57 and capacitor C52 are connected in series, resistor R58 and capacitor C53 are connected in series, and resistor R59 and capacitor C54 are connected in series. The series ends of the above resistors and capacitors are connected to pins 13, 14, 15, 12, 1, 5, 2, and 4 of U8 respectively. Resistors R52 to R59 are all pull-up resistors, and the other end of them is connected to a 3.3V power supply to ensure that the default output of U8 is high level. Capacitors C47 to C54 are all filter capacitors, and their function is to resist interference. The other end of capacitors C47 to C54 is grounded. Bypass capacitors C36 and C38 are connected in parallel, and one end of the parallel capacitor is connected to the 3.3V power input, and the other end is grounded.

[0069] The signal acquisition and switching module includes MOS tubes Q17 to Q32, resistors R70 to R135, capacitors C55 to C77, analog switches U10 and U11, multiplexer U9 and connector J7; analog switches U10 and U11 both use TMUX1308A chips, and multiplexer U9 uses CD74HC4067M96 chips. The 2 pins of MOS tubes Q17 to Q32 are connected to the negative pole of the tested battery cell through connector J7. The structure of MOS tubes Q17 to Q32 is as follows: Fig.16 As shown in the figure (due to the size of the figure, not all MOS tubes are drawn, only a part of them is cut out for display), the structure of connector J7 is as follows Fig.17 As shown; the 3 pins of MOS tubes Q17~Q32 are connected to the sampling resistors R76~R81, R88~R93, R103~R106 respectively, one end of the sampling resistors R76~R81, R88~R93, R103~R106 is connected to GND, and the other end is connected to the 9th, 8th, 7th, 6th, 5th, 4th, 3rd, 2nd, 23rd, 22nd, 21st, 20th, 19th, 18th, 17th, 16th pins of U9 in sequence. The circuit of the multiplexer U9 is as shown Fig.18 As shown. U9's 10, 11, 14, 13 pins are connected to the 17, 18, 19, 20 pins of the MCU chip respectively; U9's 1 pin is connected in series with resistor R107 and then connected to the 21 pin of the MCU chip. The 1 pins of MOS tubes Q17 to Q24 are connected to the 13, 14, 15, 12, 1, 5, 2, 4 pins of U10 respectively, as shown. Fig.19As shown; the 1 pins of MOS tubes Q25~Q32 are connected to the 13, 14, 15, 12, 1, 5, 2, and 4 pins of U11 respectively. Fig. 20 As shown. Pins 6, 3, 9, 10, and 11 of U10 are connected to pins 56, 55, 57, 58, and 59 of the MCU chip, respectively. Pins 6, 3, 9, 10, and 11 of U11 are connected to pins 68, 69, 67, 66, and 65 of the MCU chip, respectively. The MCU chip drives analog switches U10 and U11 to control the switches of MOS tubes Q17 to Q32. The signal on the sampling resistor is sent to the MCU through the multiplexer U9 to realize signal acquisition, thereby realizing the measurement of the internal resistance of each battery.

[0070] like Fig.19 As shown, the 16th pin of U10 is connected to the 3.3V power supply (VCC3V3, provided by the power chip U2), and the 8th pin is grounded; the 6th pin of U10 is connected to the 56th pin of the MCU chip, and the 6th pin is also connected in series with the resistor R124 and then connected to the 3.3V power supply; the 3rd pin of U10 is connected in series with the resistor R129 and then connected to the 55th pin of the MCU chip, and the 3rd pin is also connected in series with the resistor R126 and then connected to the 3.3V power supply; the 9th pin, the 10th pin and the 11th pin of U10 are connected in series with the resistors R130, R132 and R134 in turn, and then connected to the 57th, 58th and 59th pins of the MCU chip; the resistor R108 and the capacitor C62 are connected in series, and the resistor R109 and the capacitor C63 are connected in series. The resistors R110 and C64 are connected in series, the resistors R111 and C65 are connected in series, the resistors R112 and C66 are connected in series, the resistors R113 and C67 are connected in series, the resistors R114 and C68 are connected in series, and the resistors R115 and C69 are connected in series. The series ends of the above resistors and capacitors are connected to the 13, 14, 15, 12, 1, 5, 2, and 4 pins of U10 respectively. The resistors R108 to R115 are all pull-up resistors, and the other ends thereof are connected to the 3.3V power supply to ensure that the default output of U10 is high level. The capacitors C62 to C69 are all filter capacitors, and their function is to resist interference. The other ends of the capacitors C62 to C69 are grounded. The bypass capacitors C58 and C60 are connected in parallel, and one end of the parallel capacitors is connected to the 3.3V power supply input, and the other end is grounded.

[0071] like Fig. 20As shown, the 16th pin of U11 is connected to the 3.3V power supply, and the 8th pin is grounded; the 6th pin of U11 is connected to the 68th pin of the MCU chip, and the 6th pin is also connected in series with the resistor R124 and then connected to the 3.3V power supply; the 3rd pin of U11 is connected in series with the resistor R128 and then connected to the 69th pin of the MCU chip, and the 3rd pin is also connected in series with the resistor R127 and then connected to the 3.3V power supply; the 9th pin, the 10th pin and the 11th pin of U11 are connected in series with the resistors R131, R133 and R135 in turn, and then connected to the 67th, 66th and 65th pins of the MCU chip; the resistor R116 and the capacitor C70 are connected in series, the resistor R117 and the capacitor C71 are connected in series, and the resistors R118 and Capacitor C72 is connected in series, resistor R119 and capacitor C73 are connected in series, resistor R120 and capacitor C74 are connected in series, resistor R121 and capacitor C75 are connected in series, resistor R122 and capacitor C76 are connected in series, and resistor R123 and capacitor C77 are connected in series, and the series ends of the above resistors and capacitors are connected to pins 13, 14, 15, 12, 1, 5, 2, and 4 of U11 respectively. Resistors R116 to R123 are all pull-up resistors, and the other end of them is connected to a 3.3V power supply to ensure that the default output of U11 is high level. Capacitors C70 to C77 are all filter capacitors, and their function is to resist interference. The other end of capacitors C70 to C77 is grounded. Bypass capacitors C59 and C61 are connected in parallel, and one end of the parallel capacitor is connected to the 3.3V power input, and the other end is grounded.

[0072] The overall process of internal resistance monitoring in the battery management system is as follows: the entire internal resistance detection includes several parts: AC signal injection, circuit signal detection, internal resistance calculation and communication. The AC signal injection is controlled by the software to output PWM waves from the MCU. The PWM waves control the on and off of MOS tubes Q1 to Q17 in turn through the 3rd pins of the analog switches U7 and U8, thereby outputting a sinusoidal AC signal. The sinusoidal AC signal is connected to the positive electrode of each battery cell through connector J6, thus completing the AC signal injection; the circuit signal detection measured signal is connected to the negative electrode of each battery cell by connector J7. The measured signal is controlled by the software to output a control signal from the MCU. The control signal is connected to the 3rd pins of the analog switches U10 and U11, and the output pins of the analog switches control the on and off of MOS tubes Q17 to Q32 in turn. The measured signal is turned on in sequence from the negative electrode of the battery cell through MOS tubes Q17~Q32, and through sampling resistors R76~R81, R88~R93, R103~R106. One end of the sampling resistor is connected to GND, and the other end is connected to the multiplexer U9. U9 sends the collected signal from U9's 1 pin through resistor R107 to MCU; calculate the internal resistance and use the signal collected by MCU through the sampling resistor and the Ohm's law resistance calculation formula R=U / I as the prototype formula to derive the battery internal resistance; finally, send the internal resistance detection data and voltage detection data to the host computer or other devices through the CAN communication interface. These functions need to be implemented through different subroutines, and during the operation of the MCU, the hardware and software need to work together to ensure the maximum working efficiency of the entire internal resistance online detection system.

[0073] The MCU module further includes a power pin decoupling filter circuit and a watchdog circuit. The power pin decoupling filter circuit is as follows: Fig.21 As shown, it includes parallel capacitors C22 to C28, one end of the capacitor is connected to the power pins of the MCU chip (6, 24, 36, 49, 64, 75, 100. Among them, pin 36 is the external reference voltage pin of the ADC inside the chip, and a resistor R20 is connected in series), and the other end is grounded. Its function is to decouple and filter the U4 power pin and provide a clean and reliable power supply for U4. Watchdog circuit as shown Fig. 22As shown. It includes reset chip U6, connector J4, capacitors C30 and C33, resistors R23, R26 and R27; reset chip U6 uses TPS3823, pin 1 of U6 is connected to one end of connector J4, the other end of connector J4 is connected to capacitor C33 and resistor R23 respectively, the other end of capacitor C33 is connected to pin 2 of U6, the other end of resistor R23 is connected to capacitor C30 and pin 5 of U6 respectively, the other end of capacitor C30 is grounded, and U5 is also connected to a 3.3V power supply; pin 3 of U6 is connected to resistor R27, pin 4 is connected to resistor R26, and the other ends of resistors R26 and R27 are connected to a 3.3V power supply. The watchdog circuit is used to ensure that U4 is reset when the chip U4 program runs away.

[0074] Taking the internal resistance measurement of one of the batteries as an example, the detailed formula of the internal resistance of a single battery is derived by using Ohm's law resistance calculation formula R=U / I as the prototype:

[0075] From the circuit principle, we know that the MOS tube, inductor and multiplexer in the circuit are not ideal devices and have internal resistance (described in the specification), so the total resistance in the entire internal resistance measurement loop is:

[0076] R 总 =R Q1 +C R +R Q17 +R76+U9 R +L9 R Formula①

[0077] From formula ①, we can get:

[0078] C R =R 总 -(R Q1 +…+R Q17 +R76+U9 R +L9 R ) formula ②

[0079] R Q1 The internal resistance of the MOS tube Q1 is injected with the signal, C R Battery internal resistance, R Q17 is the internal resistance of the signal acquisition MOS tube Q17, the resistor R76 is the sampling resistor, and U9 R Multiplexer channel resistor, L9 R Inductor L9 DC resistance.

[0080] Where R 总 =U 恒 / I 恒 Since the diode D7 is connected in series in the circuit, the characteristics of the diode show that there is a tube voltage drop, so the total resistance of the loop can be obtained by the following formula:

[0081] R总 =(U 恒 -U D7 ) / I 恒 Formula③

[0082] U 恒 with I 恒 are the output current and voltage of the constant voltage and constant current source U3.

[0083] Combining the above formulas and substituting formula ③ into formula ②, we get the following formula:

[0084] C R = (U 恒 -U D7 ) / I 恒 -(R Q1 +…+R Q17 +R76+U9 R +L9 R ) ④

[0085] The internal resistance C of the battery cell can be calculated by formula ④. R Calculate it.

[0086] The present invention conducts an in-depth study on the working mode of the energy storage BMS management system and the information that can be collected during the battery management process, thereby proposing a battery management system that can monitor the internal resistance of each battery. The patent of this invention mainly involves the monitoring of the internal resistance of batteries in industrial and commercial energy storage, large-scale industrial and commercial energy storage systems, household energy storage, outdoor portable energy storage, energy storage power stations and new energy vehicle power battery systems; especially the monitoring of the internal resistance of batteries in industrial and commercial energy storage, large-scale industrial and commercial energy storage systems, household energy storage, outdoor portable energy storage and energy storage power stations. It mainly solves the following technical problems:

[0087] (1) Online monitoring of the internal resistance of each battery in the energy storage battery system;

[0088] (2) In energy storage systems, batteries are in long-term operation, and abnormal batteries can be detected earlier based on changes in internal resistance;

[0089] (3) Improve the accuracy of battery SOC and SOH calculation by measuring internal resistance, so that the battery of the energy storage system can operate in the optimal state.

[0090] (4) Safety accidents caused by changes in internal resistance can be prevented by early warning.

[0091] (5) Based on the internal resistance of each battery, the abnormal battery cell can be accurately located by looking up the table.

[0092] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the present invention.

Claims

1. A battery management system capable of monitoring the internal resistance of each battery, characterized in that: It includes an MCU module, a CAN communication module, a power module, a constant voltage and constant current output module, an AC signal generating circuit and a switching switch module, and a signal acquisition and switching switch module; the MCU module is respectively connected to the CAN communication module, the power module, the constant voltage and constant current output module, the AC signal generating circuit and the switching switch module, and the signal acquisition and switching switch module; the AC signal generating circuit and the switching switch module, and the signal acquisition and switching switch module are respectively connected to the tested battery cell; the power module is connected to the constant voltage and constant current output module, and the constant voltage and constant current output module is connected to the AC signal generating circuit and the switching switch module.

2. A battery management system capable of monitoring the internal resistance of each battery according to claim 1, characterized in that: The MCU module includes an MCU chip, an active crystal oscillator, a connector, an indicator LED1, and an LC filter circuit; the MCU chip adopts STM32G473VET6; The LC filter circuit includes magnetic bead inductors L5 and L6, and capacitors C16, C17, C19, and C20; the magnetic bead inductors L5 and L6 are connected in series, and the two non-connected ends of L5 and L6 are called free ends, and the free end of L5 is connected to the 3.3V power supply provided by the power module; capacitors C16 and C17 are connected in parallel, and one end of the two parallel capacitors is connected to the free end of L6, and the other end is grounded; the connection end of the parallel capacitors C16 and C17 and L6 is connected to the 37th pin of the MCU chip; the connection ends of L5 and L6 are respectively connected to the power pins of the MCU chip, the active crystal oscillator, the connector, and the indicator LED1; capacitors C19 and C20 are connected in parallel, and one end of the parallel capacitor is connected to the connection end of L5 and L6, and the other end is grounded; The active crystal oscillator uses OT32258MJBA4SL. Pin 2 of the active crystal oscillator is grounded, and pin 4 is connected to one end of capacitor C18. Pin 4 is connected to a 3.3V power supply, and the other end of capacitor C18 is grounded. Pin 3 of the active crystal oscillator G1 is connected in series with resistor R10 and then connected to pin 12 of the MCU chip. The connector uses TH-MTB111-10S, with pin 2 of the connector connected to a 3.3V power supply, and pin 4 connected to capacitor C21 and then grounded; pin 4 of the connector is connected in series with resistor R12 and then connected to pin 14 of the MCU chip, pin 6 is connected in series with resistor R14 and then connected to pin 90 of the MCU chip, pin 3 is connected in series with resistor R13 and then connected to pin 91 of the MCU chip, pin 5 is connected in series with resistor R15 and then connected to pin 78 of the MCU chip, pin 7 is connected in series with resistor R16 and then connected to pin 76 of the MCU chip, and pin 9 is connected to pin 77 of the MCU chip; resistors R12, R13, R14, R15, and R16 are all pull-up resistors, and the other ends of them are connected to pins 1 and 2 of the connector respectively; The indicator light LED1 is a 4-pin LED lamp, whose pin 1 is connected to the resistor R19, and the pin 4 is connected to the resistor R18; the other ends of R18 and R19 are connected, and the other ends of R18 and R19 are both connected to a 3.3V power supply; the pins 2 and 3 of the indicator light LED1 are connected to the pins 60 and 61 of the MCU chip respectively.

3. A battery management system capable of monitoring the internal resistance of each battery according to claim 1, characterized in that: The CAN communication module is composed of a CAN chip U5, a magnetic bead L8, a common mode inductor L7, resistors R21, R22, R2, 4R25, capacitors C29, C31, C32; TVS tubes TVS2 to TVS4 and a jumper J3; U5 uses a SN65HVD232DR chip; Pin 1 of U5 is connected to pin 73 of the MCU chip through resistor R21, and pin 4 of U5 is connected to pin 72 of the MCU chip through resistor R25; Pin 2 of U5 is grounded, pin 3 is connected to one end of magnetic bead L8, and the other end of magnetic bead L8 is connected to a 3.3V power supply; capacitors C31 and C32 are connected in parallel, one end of the parallel capacitor is connected between magnetic bead L8 and pin 3 of U5, and the other end is grounded; pins 6 and 7 of U5 are respectively connected to ports 1 and 2 of common-mode inductor L7; three TVS tubes TVS2, TVS3 and TVS4 are connected in series in sequence, the connection ends of TVS2 and TVS3 are respectively connected to the third port of common-mode inductor L7 and port 1 of jumper J3, and resistor R22 is connected in series to port 2 of jumper J3; the connection ends of TVS3 and TVS4 are respectively connected to the fourth port of common-mode inductor L7 and resistor R24; the other ends of resistors R22 and R24 are both connected to one end of capacitor C29, and the other end of capacitor C29 is respectively connected to the free ends of TVS2 and TVS4 and grounded.

4. A battery management system capable of monitoring the internal resistance of each battery according to claim 1, characterized in that: The power supply module consists of two parts: a 5V voltage conversion circuit and a 3.3V voltage conversion circuit; The 5V voltage conversion circuit includes a power chip U1, a connector J1, diodes D1 to D3, a fuse F1, capacitors C1 to C7, resistors R1 to R5, a light-emitting diode D4, a TCS tube TVS1 and a common-mode inductor L2; the power chip U1 adopts TPS5430DDA, the 1st pin of the common-mode inductor L2 is respectively connected to the negative electrode of the capacitor C2 and the positive electrode of the diode D3, and the negative electrode of the diode D3 is connected to the 2nd pin of the connector J1; the 3rd pin of the common-mode inductor L2 is respectively connected to the capacitor C2 The positive electrode of the common mode inductor L2 is connected to the cathode of the capacitor C3, the 6th and 9th pins of U1, and the 4th pin of the common mode inductor L2 is connected to the anode of the capacitor C3 and the 7th pin of U1; the capacitor C4 is connected in parallel between the 7th and 9th pins of U1; the resistor R2 and the capacitor C7 are connected in parallel. One end of the circuit is connected to the 9th and 6th pins of U1, and the other end is connected to the 5th pin of U1; the 5th pin of U1 is connected in series with the resistor R1 and then connected to the 4th pin of the common mode inductor L1, and the 6th and 9th pins of U1 are also grounded; the 1st pin of U1 is connected to the capacitor C1 and the inductor L1 in sequence, and the other end of the inductor L1 is a voltage output interface that outputs a 5V voltage; the 8th pin of U1 is connected between the capacitor C1 and the inductor L1, and the cathode of the diode D2 is connected between the 8th pin of U1 and the inductor L1, and the diode The positive electrode of D2 is grounded; the positive electrode of capacitor C6 is connected to the output end of inductor L1, and the negative electrode is grounded; resistors R3 and R5 are connected in series, and the two series resistors are connected in parallel with TCS tube TVS1, and one end of the formed parallel circuit is connected to the output end of inductor L1, and the other end is grounded; the series connection end of resistors R3 and R5 is connected to pin 4 of U1; resistor R4 is connected to the positive electrode of light-emitting diode D4, and the negative electrode of light-emitting diode D4 is grounded, and the other end of resistor R4 is connected to a 5V power supply provided by the output end of inductor L1; The 3.3V voltage conversion circuit includes a power chip U2, an inductor L3, capacitors C8-C11, a resistor R6, and a light-emitting diode D5. The power chip U2 adopts TLV1117. Pin 3 of U2 is connected to a 5V power supply through the inductor L3, which is provided by the output end of the inductor L1; capacitors C10 and C11 are both connected between pins 2 and 1 of U2, and pins 2 and 4 of U2 are connected as a voltage output interface to output a 3.3V voltage; capacitors C8 and C9 are connected in parallel, one end of the parallel capacitor is connected to the voltage output interface end, and the other end is grounded; resistor R6 is connected to the positive electrode of the light-emitting diode D5, the negative electrode of the light-emitting diode D5 is grounded, and the other end of the resistor R6 is connected to a 3.3V power supply, which is provided by the voltage output interface of U1.

5. A battery management system capable of monitoring the internal resistance of each battery according to claim 1, characterized in that: The constant voltage and constant current output module is composed of an inductor L4, a voltage stabilizer U3, resistors R7-R9, capacitors C12-C15, a light-emitting diode D6, and a diode D7. U3 adopts a TPS7A02 chip; capacitors C14 and C15 are connected in parallel between the IN port and the GND port of U3; capacitors C12 and C13 are connected in parallel between the VOUT port and the GND port of U3; resistor R8 is connected between the IN port and the EN port of U3, and resistor R9 is connected between the EN port and the GND port of U3; one end of the inductor L4 is connected to a parallel end of capacitors C14 and C15 and the IN port of the chip U3, and the other end is connected to a 5V input voltage; the positive electrode of the diode D7 is connected to the VOUT port of U3 and a parallel end of capacitors C12 and C13, and the negative electrode is a voltage output interface, outputting a 3.6V voltage; resistor R7 is connected to the positive electrode of the light-emitting diode D6, the negative electrode of the light-emitting diode D6 is grounded, and the other end of the resistor R7 is connected to the 3.6V input voltage.

6. A battery management system capable of monitoring the internal resistance of each battery according to claim 1, characterized in that: The AC signal generating circuit and switching switch module include MOS tubes Q1-Q16, inductor L9, analog switches U7 and U8, connector J6, multiple resistors and capacitors, and the analog switches U7 and U8 both use TMUX1308A chips; 2 pins of MOS tubes Q1-Q16 are connected in parallel to the inductor L9, and the other end of L9 is connected to the constant voltage and constant current output module; 3 pins of MOS tubes Q1-Q16 are respectively connected to the positive electrode of the tested battery cell through connector J6; Pin 1 of MOS tubes Q1~Q16 is the control signal input pin, and pin 1 of MOS tubes Q1~Q7 is connected to pins 13, 14, 15, 12, 1, 5, 2, and 4 of U7 respectively; pin 1 of MOS tubes Q8~Q15 is connected to pins 13, 14, 15, 12, 1, 5, 2, and 4 of U8 respectively; the MCU chip drives analog switches U7 and U8 to control the switches of MOS tubes Q1~Q16 to generate 1kHz frequency AC signals, and the AC signals are injected into the positive electrode of the tested battery cell through pin 3 of MOS tubes Q1~Q16; Pin 16 of U7 is connected to a 3.3V power supply, and pin 8 is grounded; pin 6 of U7 is connected to pin 1 of the MCU chip, and pin 6 is also connected in series with resistor R60 before being connected to a 3.3V power supply; pins 3, 9, 10, and 11 of U7 are connected in series with resistors R62, R64, R66, and R68 in sequence before being connected to pins 15, 5, 4, and 3 of the MCU chip; resistor R44 and capacitor C39 are connected in series, resistor R45 and capacitor C40 are connected in series, and resistors R46 and Capacitor C41 is connected in series, resistor R47 and capacitor C42 are connected in series, resistor R48 and capacitor C43 are connected in series, resistor R49 and capacitor C44 are connected in series, resistor R50 and capacitor C45 are connected in series, and resistor R51 and capacitor C46 are connected in series, and the series ends of the above resistors and capacitors are connected to pins 13, 14, 15, 12, 1, 5, 2, and 4 of U7 respectively, and the other ends of resistors R44 to R51 are connected to a 3.3V power supply; the other ends of capacitors C39 to C46 are grounded; Pin 16 of U8 is connected to a 3.3V power supply, and pin 8 is grounded; pin 6 of U8 is connected to pin 2 of the MCU chip, and pin 6 is also connected in series with resistor R61 before being connected to a 3.3V power supply; pins 3, 9, 10, and 11 of U8 are connected in series with resistors R63, R65, R67, and R69 in sequence before being connected to pins 16, 9, 8, and 7 of the MCU chip; resistor R52 is connected in series with capacitor C47, resistor R53 is connected in series with capacitor C48, and resistor R54 and Capacitor C49 is connected in series, resistor R55 and capacitor C50 are connected in series, resistor R56 and capacitor C51 are connected in series, resistor R57 and capacitor C52 are connected in series, resistor R58 and capacitor C53 are connected in series, and resistor R59 and capacitor C54 are connected in series, and the series ends of the above resistors and capacitors are respectively connected to pins 13, 14, 15, 12, 1, 5, 2, and 4 of U8, and the other ends of resistors R52~R59 are connected to a 3.3V power supply; the other ends of capacitors C47~C54 are grounded.

7. A battery management system capable of monitoring the internal resistance of each battery according to claim 1, characterized in that: The signal acquisition and switching module includes MOS tubes Q17-Q32, resistors R70-R135, capacitors C55-C77, analog switches U10 and U11, multiplexer U9 and connector J7; the analog switches U10 and U11 both use TMUX1308A chips, and the multiplexer U9 uses CD74HC4067M96 chips; Pin 2 of MOS tubes Q17~Q32 is connected to the negative electrode of the tested cell through connector J7; Pin 3 of MOS tubes Q17~Q32 is connected to sampling resistors R76~R81, R88~R93, R103~R106 respectively, one end of sampling resistors R76~R81, R88~R93, R103~R106 is connected to GND, and the other end is connected to pins 9, 8, 7, 6, 5, 4, 3, 2, 23, 22, 21, 20, 19, 18, 17, 16 of U9 in sequence; pins 10, 11, 14, 13 of U9 are connected to pins 17, 18, 19, 20 of MCU chip respectively; pin 1 of U9 is connected to pin 2 of MCU chip after resistor R107 is connected in series. 1 pins are connected, the 1 pins of MOS tubes Q17~Q24 are connected to the 13, 14, 15, 12, 1, 5, 2, 4 pins of U10 respectively; the 1 pins of MOS tubes Q25~Q32 are connected to the 13, 14, 15, 12, 1, 5, 2, 4 pins of U11 respectively; the 6, 3, 9, 10, 11 pins of U10 are connected to the 56, 55, 57, 58, 59 of the MCU chip respectively, and the 6, 3, 9, 10, 11 pins of U11 are connected to the 68, 69, 67, 66, 65 of the MCU chip respectively. The MCU chip drives the analog switches U10 and U11 to control the switches of MOS tubes Q17~Q32, and the signal on the sampling resistor is sent to the MCU through the multiplexer U9; Pin 16 of U10 is connected to a 3.3V power supply, and pin 8 is grounded; pin 6 of U10 is connected to pin 56 of the MCU chip, and pin 6 is also connected in series with resistor R124 and then connected to a 3.3V power supply; pin 3 of U10 is connected in series with resistor R129 and then connected to pin 55 of the MCU chip, and pin 3 is also connected in series with resistor R126 and then connected to a 3.3V power supply; pins 9, 10, and 11 of U10 are connected in series with resistors R130, R132, and R134 in turn, and then connected to pins 57, 58, and 59 of the MCU chip; resistor R108 and capacitor C62 series, resistor R109 and capacitor C63 series, resistor R110 and capacitor C64 series, resistor R111 and capacitor C65 series, resistor R112 and capacitor C66 series, resistor R113 and capacitor C67 series, resistor R114 and capacitor C68 series, resistor R115 and capacitor C69 series, and the series ends of the above resistors and capacitors are connected to the 13, 14, 15, 12, 1, 5, 2, 4 pins of U10 respectively, and the other end of resistors R108~R115 is connected to a 3.3V power supply; the other end of capacitors C62~C69 is grounded; Pin 16 of U11 is connected to a 3.3V power supply, and pin 8 is grounded; pin 6 of U11 is connected to pin 68 of the MCU chip, and pin 6 is also connected in series with resistor R124 and then connected to a 3.3V power supply; pin 3 of U11 is connected in series with resistor R128 and then connected to pin 69 of the MCU chip, and pin 3 is also connected in series with resistor R127 and then connected to a 3.3V power supply; pins 9, 10, and 11 of U11 are connected in series with resistors R131, R133, and R135 in turn, and then connected to pins 67, 66, and 65 of the MCU chip; resistor R116 and capacitor C70 Series, resistor R117 and capacitor C71 series, resistor R118 and capacitor C72 series, resistor R119 and capacitor C73 series, resistor R120 and capacitor C74 series, resistor R121 and capacitor C75 series, resistor R122 and capacitor C76 series, resistor R123 and capacitor C77 series, and the series ends of the above resistors and capacitors are respectively connected to the 13, 14, 15, 12, 1, 5, 2, 4 pins of U11, and the other ends of resistors R116~R12 are connected to a 3.3V power supply; the other ends of capacitors C70~C77 are grounded.

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