Excitation current automatic adjusting system for lithium battery internal resistance detection

Abstract

The invention discloses an excitation current determination method for a lithium battery internal resistance detection system, and specifically belongs to the technical field of lithium battery internal resistance detection. In the method, a cluster-level internal resistance detection host generates and outputs initial excitation current to a lithium battery; the internal resistance detection host processor determines an excitation current control signal based on the battery charging and discharging current of the lithium battery; the excitation current control function circuit determines an excitation current driving signal based on the excitation current control signal; the excitation current driving circuit generates excitation current based on the excitation current driving signal and outputs the excitation current to the lithium battery; the excitation current control function circuit adjusts the excitation current control signal based on the excitation current detected in real time so as to update the excitation current driving signal, and the excitation current driving circuit adjusts the excitation current based on the updated excitation current driving signal and outputs the adjusted excitation current to the lithium battery. Therefore, the lithium battery internal resistance can be accurately calculated by the package-level internal resistance detector.

Description

Technical Field

[0001] This application relates to the field of lithium battery internal resistance detection technology, and in particular to an automatic excitation current adjustment system for lithium battery internal resistance detection. Background Technology

[0002] In the energy storage field, numerous batteries are connected in series and parallel to form massive battery packs. However, the complexity of battery production and usage makes parameters such as internal resistance, voltage, and capacity highly susceptible to variation. Online detection of battery AC internal resistance is therefore crucial. On one hand, battery internal resistance accurately reflects the degree of battery degradation and maximum usable capacity, far surpassing parameters such as voltage, current, and temperature. It is also closely linked to battery charging and discharging efficiency and rate; increased internal resistance slows down charging and discharging, leading to energy loss. On the other hand, in the series operation mode of lithium batteries, the performance of individual cells affects the overall battery structure; abnormal cells can even accelerate the degradation of other cells, making monitoring the internal resistance of individual cells imperative. Simultaneously, AC internal resistance plays a significant role in evaluating battery performance under high-frequency, dynamic changing scenarios. It can promptly detect internal faults such as electrode aging and electrolyte drying, perfectly suited to the frequent charging and discharging and high-current operating conditions of energy storage power stations. Furthermore, it is key to proactively preventing thermal runaway risks; real-time monitoring can identify degraded batteries early, preventing potential problems.

[0003] Currently, related products are scarce, and most are integrated into BMS systems, becoming mere background parameters. Their insufficient accuracy makes them unsuitable for independently evaluating battery performance and failing to meet the demands of precise battery management. Furthermore, as the charging and discharging current increases, the smaller excitation current is affected or even overwhelmed, impacting the accuracy of AC internal resistance measurement and potentially rendering it undetectable. Therefore, there is an urgent need to develop an automatic excitation current adjustment system for lithium battery internal resistance detection to address these issues. Summary of the Invention

[0004] In view of this, this application provides a method for determining the excitation current for a lithium battery internal resistance detection system. The internal resistance detection host can generate a precise alternating current and inject it non-destructively into the battery pack or battery cluster to provide an excitation current for online internal resistance detection. The pack-level internal resistance detector can collect the cell voltage in real time and receive the host excitation current value, thereby accurately calculating the internal resistance of the lithium battery.

[0005] Specifically, the following technical solutions are included:

[0006] This application provides a method for determining the excitation current in a lithium battery internal resistance detection system. The lithium battery internal resistance detection system includes a battery pack, a pack-level internal resistance detector, and a cluster-level internal resistance detection host. The pack-level internal resistance detector collects the cell voltage when an excitation current flows through the battery pack, detects the lithium battery internal resistance, and transmits the lithium battery internal resistance to the cluster-level internal resistance detection host. The cluster-level internal resistance detection host includes an internal resistance detection host processor, an excitation current control function circuit, an excitation current drive circuit, and an excitation current detection function module. The method includes:

[0007] The cluster-level internal resistance detection host generates and outputs the initial excitation current to the lithium battery.

[0008] The internal resistance detection host processor determines the excitation current control signal based on the battery charging and discharging current of the lithium battery;

[0009] The excitation current control function circuit determines the excitation current drive signal based on the excitation current control signal;

[0010] The excitation current drive circuit generates an excitation current based on the excitation current drive signal and outputs it to the lithium battery;

[0011] The excitation current detection module detects the excitation current in real time. The excitation current control circuit adjusts the excitation current control signal based on the detected excitation current. The excitation current control circuit updates the excitation current drive signal based on the adjusted excitation current control signal. The excitation current drive circuit adjusts the excitation current based on the updated excitation current drive signal and outputs the adjusted excitation current to the lithium battery.

[0012] In some embodiments, the method further includes:

[0013] The pack-level internal resistance detector detects the internal resistance of the lithium battery based on the excitation current and the cell voltage of the battery pack when the excitation current flows.

[0014] In some embodiments, the cluster-level internal resistance detection host further includes a battery charging and discharging current detection circuit, and the method further includes: the detection circuit detects the charging and discharging current of the lithium battery in real time, and sends the detected charging and discharging current of the lithium battery to the internal resistance detection host processor.

[0015] In some embodiments, the lithium battery internal resistance detection system includes a station control host, and the method further includes:

[0016] The cluster-level internal resistance detection host sends the detected lithium battery internal resistance to the station control host for storage, accident warning, and display.

[0017] In some embodiments, the excitation current includes adjusting the DC component, amplitude, frequency, and sampling multiple of the excitation current. The frequency range of the excitation current is 10~1000Hz. The amplitude of the excitation current is determined based on the amplitude of the charging and discharging current of the lithium battery. The amplitude of the excitation current is greater than or equal to 2A and less than 5A. The DC component of the excitation current is determined based on the initial output value of the current detection sensor in the excitation current detection function module when there is no turbulent current and the amplitude of the currently generated excitation current. The sampling frequency is 10~100 times the frequency of the excitation current signal.

[0018] In some embodiments,

[0019] The excitation current control function circuit adjusts the excitation current control signal based on the detected excitation current, including:

[0020] The excitation current control function module compares the currently detected excitation current with the excitation current control signal issued by the internal resistance detection host processor, and adjusts the excitation current control signal based on the obtained reference signal.

[0021] In some embodiments, the detected excitation current is compared with the excitation current control signal issued by the internal resistance detection host processor using an open-loop comparator or a hysteresis comparator.

[0022] In some embodiments, the packet-level internal resistance detector and the cluster-level internal resistance detection host communicate via a CAN bus or wirelessly.

[0023] In some embodiments, the cluster-level internal resistance detection host and the station control host communicate through wired or wireless networking. The wireless networking method is not limited to LoRa or Bluetooth, and the wired networking method is not limited to CAN bus or RS485 bus.

[0024] The beneficial effects of the technical solutions provided in this application include at least the following:

[0025] This application provides a method for determining the excitation current for a lithium battery internal resistance detection system. The cluster-level internal resistance detection host can generate a precise alternating current and inject it non-destructively into the battery pack or battery cluster to provide the excitation current for online internal resistance detection. The pack-level internal resistance detector can collect the cell voltage in real time and receive the host excitation current value, thereby accurately calculating the lithium battery internal resistance. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 A flowchart of the method for determining the excitation current of a lithium battery internal resistance detection system provided in this application;

[0028] Figure 2 A schematic diagram of the structure of the lithium battery internal resistance detection system in the excitation current determination method for the lithium battery internal resistance detection system provided in this application;

[0029] Figure 3 This application provides a cluster-level internal resistance detection host in the excitation current determination method for a lithium battery internal resistance detection system.

[0030] Figure 4 A schematic diagram of the non-reverse hysteresis comparator in the excitation current determination method for a lithium battery internal resistance detection system provided in this application.

[0031] Figure 5 A schematic diagram of the output voltage of the hysteresis comparator in the excitation current determination method for a lithium battery internal resistance detection system provided in this application. Detailed Implementation

[0032] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0033] To make the technical solutions and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0034] This application provides a method for determining the excitation current in a lithium battery internal resistance detection system, which is applied to the lithium battery internal resistance detection system, such as... Figure 1 As shown, the lithium battery internal resistance detection system includes a battery pack, a pack-level internal resistance detector, and a cluster-level internal resistance detection host. The pack-level internal resistance detector is used to collect the cell voltage when the excitation current flows through the battery pack, detect the internal resistance of the lithium battery, and transmit the internal resistance of the lithium battery to the cluster-level internal resistance detection host. The cluster-level internal resistance detection host includes an internal resistance detection host processor, an excitation current control function circuit, an excitation current drive circuit, and an excitation current detection function module, such as... Figure 2 As shown, the method includes:

[0035] Step 101: The cluster-level internal resistance detection host generates and outputs an initial excitation current to the lithium battery.

[0036] The initial excitation current can be used to detect the static internal resistance of the battery cell online.

[0037] Step 102: The internal resistance detection host processor determines the excitation current control signal based on the battery charging and discharging current of the lithium battery.

[0038] The large charging and discharging current of the battery can cause impact interference to the excitation current. Increasing the amplitude of the excitation current can enhance its anti-interference capability. This ensures that the subsequent excitation current has sufficient anti-interference capability during product sampling, and that its amplitude is not too large.

[0039] Step 103: The excitation current control function circuit determines the excitation current drive signal based on the excitation current control signal.

[0040] The excitation current drive signal determined by the excitation current control signal can accurately provide the required excitation current.

[0041] Step 104: The excitation current driving circuit generates an excitation current based on the excitation current driving signal and outputs it to the lithium battery.

[0042] It generates a precise alternating current that is injected non-destructively into the battery pack or battery cluster, thereby providing a precise excitation signal for online internal resistance testing and ensuring the accuracy of internal resistance detection.

[0043] Step 105: The excitation current detection function module detects the excitation current in real time. The excitation current control function circuit adjusts the excitation current control signal based on the detected excitation current. The excitation current control function circuit updates the excitation current drive signal based on the adjusted excitation current control signal. The excitation current drive circuit adjusts the excitation current based on the updated excitation current drive signal and outputs the adjusted excitation current to the lithium battery.

[0044] By adjusting the excitation current control signal and real-time feedback detection of the actual excitation current, targeted control and modification of the excitation current can be achieved. This avoids the problem of decreased accuracy or even false alarms in lithium battery internal resistance detection when the battery charging and discharging current changes due to a constant excitation current, thereby ensuring the reliability and accuracy of online lithium battery internal resistance detection.

[0045] In some embodiments, the method further includes: a pack-level internal resistance detector detects the internal resistance of the lithium battery based on the excitation current and the cell voltage of the battery pack when the excitation current flows through it; the accurate excitation signal ensures the accuracy of the internal resistance detection.

[0046] In some embodiments, charging and discharging interference can be eliminated to optimize the detected lithium battery internal resistance results.

[0047] In some embodiments, the lithium battery internal resistance detection system includes a station control host. The method further includes: the cluster-level internal resistance detection host sending the detected lithium battery internal resistance to the station control host for storage, accident warning, and display. In some embodiments, the optimized internal resistance correction value is compared with the initial internal resistance value. If the difference is within the normal range, the detected lithium battery internal resistance result is sent to the station control host to inform the maintenance personnel; if it exceeds the range, the detected lithium battery internal resistance result and the corresponding alarm signal for exceeding the range are sent to the station control host to notify the maintenance personnel and ensure the safe and controllable operation of the lithium battery.

[0048] In some embodiments, the cluster-level internal resistance detection host further includes a battery charging and discharging current detection circuit, and the method further includes: the detection circuit detects the charging and discharging current of the lithium battery in real time, and sends the detected charging and discharging current of the lithium battery to the internal resistance detection host processor.

[0049] In some embodiments, the excitation current includes adjusting the DC component, amplitude, frequency, and sampling multiple of the excitation current. The frequency range of the excitation current is 10~1000Hz. The amplitude of the excitation current is determined based on the amplitude of the charging and discharging current of the lithium battery. The amplitude of the excitation current is greater than or equal to 2A and less than 5A because it is output by the internal resistance detection host processor. The output amplitude is limited by the power supply of the internal resistance detection host processor, that is, the maximum amplitude of this excitation current control signal cannot exceed the output upper limit of the internal resistance detection host processor. The DC component of the excitation current is determined based on the initial output value of the current detection sensor in the excitation current detection function module when there is no turbulent current and the amplitude of the currently generated excitation current. The sampling frequency is 10~100 times the frequency of the excitation current signal.

[0050] In some embodiments, the internal resistance detection host processor can be a microcontroller unit (MCU), and the upper limit of the output of the internal resistance detection host processor is the upper limit of the output of the MCU pins.

[0051] In some embodiments, the excitation current control function circuit adjusts the excitation current control signal based on the detected excitation current, including: the excitation current control function module compares the currently detected excitation current with the excitation current control signal issued by the internal resistance detection host processor, and adjusts the excitation current control signal based on the obtained reference signal.

[0052] In some embodiments, the packet-level internal resistance detector and the cluster-level internal resistance detection host communicate via a CAN bus or wirelessly. The internal resistance detection host and the internal resistance detector communicate in a network to transmit the excitation current and lithium battery internal resistance, replacing the traditional common-plate current sensor detection scheme. This saves costs, reduces size, simplifies network topology, and improves construction and maintenance efficiency.

[0053] In some embodiments, the cluster-level internal resistance detection host and the station control host communicate through wired or wireless networking. The wireless networking methods include, but are not limited to, LoRa and Bluetooth, while the wired networking methods include, but are not limited to, CAN bus and RS485 bus.

[0054] In some embodiments, the method can be applied to applications involving lithium batteries, such as energy storage power stations, low-altitude economy, and electric ships.

[0055] In some embodiments, the detected excitation current is compared with the excitation current control signal issued by the internal resistance detection host processor using an open-loop comparator or a hysteresis comparator.

[0056] In some embodiments, the control circuit that compares the detected excitation current with the excitation current control signal issued by the host processor for detecting the internal resistance of the reference excitation current using an open-loop comparator is specifically implemented as follows: Figure 3 As shown, the excitation current ( Figure 3 The IL_DET signal in the internal resistance detection host processor is related to the excitation current control signal. Figure 3 The excitation current (IL_ref) is compared with the excitation current control signal issued by the internal resistance detection host processor in comparator U3. The obtained reference signal is input to JK flip-flop U2. The switching frequency signal MCU_PWM given by the internal resistance detection host processor to control the excitation current also plays a role here. The three signals MCU_PWM, IL_ref, and IL_DET are fused through JK flip-flop U2, and the final output signal Driver_out is given to U1 to generate the excitation current drive control signals Driver_SH & Driver_SL to control the excitation current. This cyclic feedback control eventually stabilizes the excitation current.

[0057] In some embodiments, comparators U1 and U3 can be selected from devices with small offset voltages, such as LMV331IDBVR, LM193DR and TLV3501AIDBVR, to ensure that the differential input of the comparator differs significantly from its offset voltage and to avoid output fluctuations of the comparator.

[0058] It should be noted that, as Figure 5 As shown, the hysteresis comparator can generate two comparison thresholds, one for the rising process VIN1 and one for the falling process VIN2. The hysteresis magnitude is the difference between the two comparison thresholds. When the two inputs are very close, the hysteresis allows one voltage to quickly exceed the other, thus shifting the input voltage out of the output fluctuation range.

[0059] In some embodiments, such as Figure 4As shown, the hysteresis comparator can specifically be a non-inverting hysteresis comparator, and its specific principle is as follows:

[0060] Connecting two resistors R1 and R2 to the non-inverting terminal creates positive feedback. When the input VIN rises to VIN1, the output changes from low to high. VIN1 can be obtained using the following formula:

[0061] ;

[0062] When the input VIN1 drops to VIN2, the output changes from high to low. VIN2 can be obtained by the following formula:

[0063] ;

[0064] The hysteresis magnitude is the difference between VIN1 and VIN2:

[0065] .

[0066] In summary, the excitation current determination method for a lithium battery internal resistance detection system provided in this application embodiment can generate a precise alternating current in the cluster-level internal resistance detection host, which can be injected into the battery pack or battery cluster without damage, providing an excitation current for online internal resistance detection. The pack-level internal resistance detector can collect the cell voltage in real time and receive the host excitation current value, thereby accurately calculating the internal resistance of the lithium battery.

[0067] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the application disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only.

[0068] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A method for determining the excitation current in a lithium battery internal resistance detection system, characterized in that, An internal resistance detection system for lithium batteries is provided. The system includes a battery pack, a pack-level internal resistance detector, and a cluster-level internal resistance detection host. The pack-level internal resistance detector collects the cell voltage when an excitation current flows through the battery pack, detects the internal resistance of the lithium battery, and transmits the internal resistance data to the cluster-level internal resistance detection host. The cluster-level internal resistance detection host includes an internal resistance detection host processor, an excitation current control circuit, an excitation current drive circuit, and an excitation current detection module. The method includes: The cluster-level internal resistance detection host generates and outputs the initial excitation current to the lithium battery. The internal resistance detection host processor determines the excitation current control signal based on the battery charging and discharging current of the lithium battery; The excitation current control function circuit determines the excitation current drive signal based on the excitation current control signal; The excitation current drive circuit generates an excitation current based on the excitation current drive signal and outputs it to the lithium battery; The excitation current detection module detects the excitation current in real time. The excitation current control circuit adjusts the excitation current control signal based on the detected excitation current. The excitation current control circuit updates the excitation current drive signal based on the adjusted excitation current control signal. The excitation current drive circuit adjusts the excitation current based on the updated excitation current drive signal and outputs the adjusted excitation current to the lithium battery.

2. The method for determining the excitation current of a lithium battery internal resistance detection system according to claim 1, characterized in that, The method further includes: The pack-level internal resistance detector detects the internal resistance of the lithium battery based on the excitation current and the cell voltage of the battery pack when the excitation current flows.

3. The method for determining the excitation current of a lithium battery internal resistance detection system according to claim 1, characterized in that, The cluster-level internal resistance detection host also includes a battery charging and discharging current detection circuit, and the method further includes: the detection circuit detects the charging and discharging current of the lithium battery in real time, and sends the detected charging and discharging current of the lithium battery to the internal resistance detection host processor.

4. The method for determining the excitation current of a lithium battery internal resistance detection system according to claim 1, characterized in that, The lithium battery internal resistance detection system includes a station control host, and the method further includes: The cluster-level internal resistance detection host sends the detected lithium battery internal resistance to the station control host for storage, accident warning, and display.

5. The method for determining the excitation current of a lithium battery internal resistance detection system according to claim 1, characterized in that, The excitation current includes adjusting the DC component, amplitude, frequency, and sampling multiple of the excitation current. The frequency range of the excitation current is 10~1000Hz. The amplitude of the excitation current is determined based on the amplitude of the charging and discharging current of the lithium battery. The amplitude of the excitation current is greater than or equal to 2A and less than 5A. The DC component of the excitation current is determined based on the initial output value of the current detection sensor in the excitation current detection module when there is no turbulent current and the amplitude of the currently generated excitation current. The sampling frequency is 10~100 times the frequency of the excitation current signal.

6. The method for determining the excitation current of a lithium battery internal resistance detection system according to claim 1, characterized in that, The excitation current control function circuit adjusts the excitation current control signal based on the detected excitation current, including: The excitation current control function module compares the currently detected excitation current with the excitation current control signal issued by the internal resistance detection host processor, and adjusts the excitation current control signal based on the obtained reference signal.

7. The method for determining the excitation current of a lithium battery internal resistance detection system according to claim 6, characterized in that, The detected excitation current is compared with the excitation current control signal issued by the internal resistance detection host processor using an open-loop comparator or a hysteresis comparator.

8. The method for determining the excitation current of a lithium battery internal resistance detection system according to claim 1, characterized in that, The packet-level internal resistance detector and the cluster-level internal resistance detection host communicate via CAN bus or wirelessly.

9. The method for determining the excitation current of a lithium battery internal resistance detection system according to claim 4, characterized in that, The cluster-level internal resistance detection host and the station control host communicate through wired or wireless networking. The wireless networking methods include, but are not limited to, LoRa and Bluetooth, while the wired networking methods include, but are not limited to, CAN bus and RS485 bus.

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