Lithium battery cross-cell energy equalization system and equalization method thereof

Abstract

The invention relates to the technical field of lithium ion batteries, and discloses a lithium battery cross-cell energy equalization system and an equalization method thereof.The lithium battery cross-cell energy equalization system comprises a top layer module, an acquisition module and an equalization module, and the acquisition module and the equalization module are both electrically connected with the top layer module; the top layer module comprises a power supply unit, a CAN communication unit and a single board ID identification unit. The acquisition module comprises an acquisition unit; the equalization module comprises an equalization execution unit, an equalization current setting unit and an MCU control unit, the top layer module further comprises a safety monitoring unit, a bidirectional forward topological structure and a high-frequency transformer coupling mode are adopted, the energy transfer time is greatly shortened while + / -3A constant current transmission is achieved, the equalization efficiency and the system response capability are improved, and the system reliability is improved. And the safety monitoring unit and the MCU are adopted to form a dual-redundancy protection structure, so that automatic power-off and alarm reporting can be realized in abnormal states such as over-temperature, over-current, failure and the like, and thermal runaway is effectively prevented.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a lithium battery cross-cell energy balancing system and its balancing method. Background Technology

[0002] To promote green development and lifestyles, it is essential to comprehensively advance low-carbon and circular development in key areas, strengthen energy management in high-energy-consuming industries, and enhance energy conservation in buildings and transportation. Inconsistency imbalance has become a major challenge and a key area for technological breakthroughs in battery pack applications; battery safety is also a significant obstacle to the high-quality development of new energy vehicles. Therefore, establishing an efficient energy conversion architecture and improving the reliability and safety design of the equalization system are currently necessary measures. Furthermore, with the development of advanced sensing technologies, the accuracy of SOC equalization can be improved by utilizing data collected from multiple sensors, and monitoring and state estimation can be performed based on fundamental parameters such as electrothermal dependence. However, these parameters may not reflect problems in a timely manner when potential faults occur inside the battery, but could be precursors to thermal runaway or battery failure.

[0003] Traditional early warning mechanisms primarily rely on threshold judgments, such as excessively high voltage or abnormal temperature. However, this simple threshold judgment cannot capture the gradual changes in battery state, making it difficult to identify potential fault risks in advance. Furthermore, limited sampling accuracy and frequency may lead to inaccurate or untimely monitoring of battery state. Although mainstream bidirectional active equalization technologies can generally achieve energy conversion efficiencies of 85-90%, their hardware structures are extremely complex and redundant, increasing reliability risks associated with complex control logic. Moreover, the "drop the handkerchief" adjacent equalization scheme requires energy transfer cell by cell, drastically increasing the cost of large-scale systems, extending equalization time, and reducing reliability. Summary of the Invention

[0004] (a) Technical problems to be solved This invention proposes a solution that systematically addresses core issues in lithium-ion battery pack applications, such as inconsistency imbalance, low energy efficiency, poor dynamic response, and insufficient reliability, through architectural innovation, key component optimization, and intelligent control strategies. This provides a breakthrough solution for the safe and efficient operation of high-energy-density battery packs.

[0005] (II) Technical Solution The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A lithium battery cross-cell energy balancing system and its balancing method, comprising a top-level module, a data acquisition module, and a balancing module, wherein the data acquisition module and the balancing module are both electrically connected to the top-level module; The top-level module includes a power supply unit, a CAN communication unit, and a single-board ID identification unit; The acquisition module includes an acquisition unit; The equalization module includes an equalization execution unit, an equalization current setting unit, and an MCU control unit.

[0006] Based on the above technical solution, the present invention can be further improved as follows.

[0007] Preferably, the equalization execution unit includes a plurality of equalization boards and a dual equalization component disposed on the equalization boards.

[0008] Preferably, the dual equalization component includes a transformer and a switching matrix component.

[0009] Preferably, the switch matrix assembly includes a controller and a pair of MOSFETs.

[0010] Preferably, the top-level module further includes a security monitoring unit.

[0011] Preferably, the balancing process of the lithium-ion battery pack active balancing system specifically includes the following steps: Step 1: After the power is turned on, the power supply unit will step down the external input 12~60V voltage to output 5V to power the CAN communication unit, safety monitoring unit, single board ID identification unit, acquisition unit, equalization execution unit, equalization current setting unit and MCU control unit. Step 2: After the MCU control unit starts up, it executes the initialization program and detects the DIP switch or the single-board ID recognition unit to read the system ID address. Then, the MCU control unit initializes the timer interrupt and sets the time interval for periodically performing data sampling and equalization judgment. Step 3: The MCU control unit receives real-time battery data from the acquisition unit via the CAN communication unit, or reads historical data such as battery voltage, temperature, SOC, battery type, and cycle count, and stores it in RAM cache for subsequent equalization decisions. Step 4: The MCU control unit activates the acquisition unit to collect the current equalization current and the current actual temperature for safety judgment and current limiting control; Step 5: The MCU control unit analyzes the voltage, temperature and historical status of all individual batteries to determine if any cells have overheated. If an abnormality is found, the safety monitoring unit enters protection mode and sends fault information to other units or the host computer via the CAN communication unit. If no abnormality is found, proceed to step 6. Step 6: The MCU control unit compares the voltage of each cell to determine if any single cell has an excessively high voltage. If a high-voltage cell is found, the MCU control unit connects the positive and negative terminals of the corresponding cell to the equalization execution unit, and at the same time selects a low-voltage cell to connect to the equalization execution unit, thus forming a complete energy transfer path. Step 7: The MCU control unit injects the high-voltage battery cell into the low-voltage battery cell by activating the equalization execution unit, forming a bidirectional constant current energy transfer; the acquisition unit collects current data in real time, and the equalization current setting unit adjusts the current magnitude to keep the output current at ±3A until the voltage difference between the high-voltage battery cell and the low-voltage battery cell is lower than the set threshold, at which point the equalization stops. Step 8: The MCU control unit judges the voltage of a certain cell. If the voltage of a certain cell is too low and cannot reach the average voltage requirement, the low-voltage cell is connected to the equalization execution unit, and other high-voltage cells are also connected to the equalization execution unit. Then, the equalization execution unit injects the power of the high-voltage cells into the low-voltage cell to achieve charging equalization. Step 9: After the equalization process is completed, the MCU control unit uses the current voltage, current and temperature data of each cell to calculate the SOC, and calculates the remaining capacity of all individual cells and the total remaining capacity of the battery pack, providing a basis for the next equalization or fault analysis. Step 10: The user manually sets whether to start active balancing via the host computer or external CAN command. The system will determine whether the start conditions are met and perform the balancing operation; otherwise, the MCU control unit will remain in monitoring state, waiting for the next round of sampling interruption or host request to trigger the balancing function, while updating the current battery status information and balancing module operation status in real time on the local or remote interface.

[0012] (III) Beneficial Effects Compared with the prior art, the technical solution of this application has the following beneficial technical effects: 1. This invention sets up a hierarchical architecture to perform balanced management of battery packs at different levels. The multi-mode strategy can flexibly adjust the balancing method according to the real-time status of the battery, effectively solving the problem of inconsistent states of individual cells within the battery pack.

[0013] 2. By setting up dual equalization components, the system can still maintain normal operation when a single component fails, thus improving the reliability of the system.

[0014] 3. The modular design of this invention allows the number of modules to be flexibly increased or decreased as needed, while the CAN bus cascading enables efficient communication and collaborative work between multiple modules, improving the system's scalability.

[0015] 4. By adopting a bidirectional forward topology and a high-frequency transformer coupling method, this invention achieves ±3A constant current transmission while significantly shortening the energy transfer time, thereby improving equalization efficiency and system response capability.

[0016] 5. This invention adopts a dual-redundant protection structure by using a safety monitoring unit and an MCU, which can automatically cut off power and report alarms under abnormal conditions such as over-temperature, over-current, and failure. At the same time, it has self-diagnostic capabilities and can judge potential risk points such as the working status of MOSFETs and abnormal temperature rise of transformers in real time, effectively preventing thermal runaway.

[0017] 6. This invention combines a high-precision acquisition module with a dynamic SOC model (based on the fusion of multiple parameters such as voltage, current, and temperature). The system supports accurate balanced control under complex fluctuating conditions such as acceleration and deceleration of electric vehicles and charging and discharging of energy storage, thereby improving the accuracy of SOC estimation and the consistency control capability.

[0018] 7. This invention utilizes a modular design to be compatible with different battery string numbers, supports hot-swapping and cascading deployment, and can be flexibly applied to various scenarios such as electric vehicles, grid energy storage, rail transit, and AGVs. Attached Figure Description

[0019] Figure 1 This is a system block diagram of the present invention; Figure 2 This is a flowchart of the present invention; Figure 3 This is the PCB layout of the present invention; Figure 4 This is a simulation diagram of the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Step 1: After the power is turned on, the power supply unit (using TLC3630) steps down the external input 12~60V voltage to output 5V, providing power to the entire equalization board. Sub-units including the main control MCU, current sampling operational amplifier, MOS array controller (using EMB1428Q), DC / DC controller (using EMB1499Q) and CAN communication chip (using CTM1050) are all powered and activated.

[0022] Step 2: After the MCU (using MC9S12P128) starts up, it executes the initialization program, which initializes the internal Flash, ADC sampling unit, I / O ports, SPI bus interface, CAN communication interface, etc. in sequence; at the same time, it configures the two coprocessors EMB1499Q and EMB1428Q through SPI, and detects the DIP switch or resistor array to read the board ID address; the MCU also initializes the timer interrupt and sets the time interval for periodically performing data sampling and equalization judgment.

[0023] Step 3: The MCU receives real-time battery data from the acquisition unit via the CAN communication unit (using CTM1050), and can also read historical data from the internal Flash, such as battery voltage, temperature, SOC, battery type, cycle count, etc., and store it in RAM cache for subsequent equalization decisions.

[0024] Step 4: The MCU enables the ADC unit to sample, reads the voltage signal across the sampling resistor (1mΩ), amplifies it through a differential operational amplifier, and inputs it into the ADC channel to calculate the current equalization current; at the same time, it acquires the output voltage of the temperature sensor (NTC), inputs it into the ADC channel through a voltage divider circuit, converts it into the actual temperature, and uses it for safety judgment and current limiting control.

[0025] Step 5: The MCU analyzes the voltage, temperature and historical status of all individual cells to determine if any cells have abnormal conditions such as overvoltage, undervoltage or overtemperature. If an abnormality is found, the MCU immediately shuts down the PWM output of the EMB1499Q and disconnects all MOS channels controlled by the EMB1428Q, enters the protection state, and sends fault information to other equalization units or the host computer through the CAN communication unit.

[0026] Step 6: If there is no abnormality, the MCU compares the voltage of each cell to determine if there is a single cell with an excessively high voltage. If a high-voltage cell is found, the MCU controls the EMB1428Q via SPI to turn on the MOS switch corresponding to that cell, so that its positive and negative terminals are connected to the main side of the DC / DC transformer. At the same time, it selects the MOS path corresponding to a low-voltage cell and connects it to the secondary side, thus forming a complete energy transfer path.

[0027] Step 7: The MCU configures the EMB1499Q controller via SPI to start the DC / DC converter. The main side absorbs the high-voltage battery cell's charge, which is coupled to the secondary side through the transformer. Then, the energy is injected into the low-voltage battery cell through the MOS matrix, forming a bidirectional constant current energy transfer. The MCU collects the current data on the sampling resistor in real time and adjusts the PWM duty cycle to achieve closed-loop control, keeping the output current at ±3A until the voltage difference between the two is lower than the set threshold (e.g., 15mV), at which point the balancing stops.

[0028] Step 8: If the MCU determines that the voltage of a certain cell is too low and cannot meet the average voltage requirement, it will reverse the energy flow path. The MOS array will conduct the low-voltage cell to the secondary side of the transformer, and other high-voltage cells will provide energy to the primary side. Then, the energy will be injected into the low-voltage cell through the DC / DC module to achieve charging balancing. This process is similar to Step 7, but the energy flow direction is reversed.

[0029] Step 9: After the equalization process is completed, the MCU uses the current voltage, current and temperature data of each cell to calculate the SOC, and calculates the remaining capacity of all individual cells and the total remaining capacity of the battery pack. It then updates the internal Flash storage to provide a basis for the next equalization or fault analysis.

[0030] Step 10: Users can manually set whether to start active balancing via the host computer or external CAN command. The system will determine whether the start conditions are met and execute the balancing operation; otherwise, the MCU will remain in monitoring mode, waiting for the next sampling interruption or host request to trigger the balancing function, while updating the current battery status information and balancing module operation status in real time on the local or remote interface. The MCU control unit will determine whether the start requirements are met and execute the balancing operation based on the following conditions: First, determine whether the voltage difference of all cells is greater than the set threshold ΔV_th (50mV); then confirm that the temperature value of all cells is within the set safe range (0℃ to 60℃); then assess the current system load status, and if there is a high dynamic condition (SOC change rate exceeds the threshold), the start will be postponed; then check whether the system has already performed the balancing operation within the set time window; finally, if a clear start or stop command is received from the host computer, the command will be processed first; only when all the above conditions are met can the MCU control unit execute the balancing operation; otherwise, it will maintain the monitoring mode, waiting for the next sampling interruption or external request to trigger the balancing function again, while updating the current battery status information and balancing module operation status in real time on the local or remote interface.

[0031] 1) Security monitoring unit Function: Even if the main controller or a certain channel fails during the equalization process, it can maintain the basic functions of the system and prevent abnormalities such as battery overheating and overcharging.

[0032] Functions: Redundant controllers participate in MOS switching control; implement fault tolerance mechanism, dual-channel parallel operation ensures uninterrupted energy balance.

[0033] Specific components: Monitoring driver: dual-channel EMB1428Q controller; Redundant switch: dual-channel AO4854 MOSFET group; Watchdog circuit.

[0034] 2). Single-board ID recognition unit Function: Enables the system to identify the physical number of each equalizer board, and to load and distribute the corresponding parameters.

[0035] Function: Configure a unique address via DIP switches or resistor array; provide a unique number to the main control MCU for CAN bus communication management.

[0036] Specific components: DIP switch (8-bit), resistor pull-high / pull-low array (e.g., 10kΩ), IO port read logic.

[0037] 3). Acquisition Unit (CSECU) Function: To collect the voltage and temperature information of each battery cell in real time and upload it to the main control or equalization unit.

[0038] Functions: Voltage sampling: 12-channel ADC conversion; Temperature detection: NTC thermistor voltage divider detection; CAN communication to send data to the equalization unit.

[0039] Specific components (some from CSECU, externally supplied): Precision resistor (1mΩ) for voltage division; Temperature sensor: 10kΩ NTC; ADC chip: such as ADS1115 (or ADC integrated inside the main controller).

[0040] 4). Equalizing current setting unit Function: Adjusts the current during battery balancing for each battery circuit, and dynamically adjusts the balancing speed according to the status.

[0041] Functions: Controls DC / DC operating mode to achieve constant current output; current feedback closed-loop control, sets target equalization current (±3A).

[0042] Specific components: Control chip: EMB1499Q; Current sampling resistor: 1mΩ precision sampling resistor; Operational amplifier + PWM modulation control loop.

[0043] 5). MCU control unit Function: As the core of the single-board control, it coordinates the communication and control of all modules and executes the balancing strategy.

[0044] Functions: Receive main control equalization commands; control the equalization module status (start / stop / current magnitude); collect and upload real-time feedback status.

[0045] Specific components: Main control chip: MC9S12P128 (Freescale); Built-in: SPI / CAN / ADC / I / O; Crystal oscillator, reset circuit, power supply decoupling capacitor.

[0046] 6) Security Monitoring Unit Function: To monitor in real time whether the current, voltage, and temperature exceed the safety limits and determine whether to trigger the shutdown protection.

[0047] Functions: Real-time acquisition of equalization current and battery temperature; setting threshold alarm points to trigger MOS shutdown protection; indicator lights provide feedback on the current status.

[0048] Specific components: operational amplifier (OPA2333), voltage divider detection network, NTC thermistor.

[0049] A lithium battery cross-cell energy balancing system and its balancing method adopts a hierarchical architecture design, which consists of: power battery pack → acquisition board → CAN bus → balancing board → dual balancing components → individual cells.

[0050] Equalization board: Each group of 12 batteries is equipped with an independent equalization board, which is cascaded via CAN bus.

[0051] Dual equalization components: Each equalization board has two built-in equalization groups, each with 6 batteries, supporting parallel equalization.

[0052] Core module selection Dual equalization components: TI EMB1499Q + custom transformer, features: synchronous rectification, active clamping, 3A constant current output.

[0053] Switching matrix: AO4854 MOSFET pairs (on-resistance <10mΩ) and EMB1428Q controller are selected to support safe timing control.

[0054] Key parameters of the dual equalization component: transformer turns ratio: 1:1 (bidirectional symmetrical design), switching frequency: 100kHz (to reduce size and loss), filter capacitor: 470μF / 100V (output).

[0055] Power supply components: The selected chip is TI TLC3630 (9-36V input, 5V / 3.3V output), and the selected overvoltage protection device is (12V TVS diode) and the filter capacitor (100μF).

[0056] CAN communication component: Selected chip: CTM1050 (3000V isolation), terminating resistor: 120Ω (both ends of the bus).

[0057] Battery model: Based on Thevenin equivalent circuit: Parameter values: Open circuit voltage: 3.2-4.2V, internal resistance: 10mΩ, polarization capacitance: 1000F.

[0058] Balanced module model: Efficiency curve: 82% (3A load), response time: <50μs (current step).

[0059] Static equalization test: Initial voltage difference: 247mV → converged to 99mV (7000 seconds), SOC standard deviation: 4.2% → 1.8%.

[0060] Dynamic operating condition test: NEDC cycle: voltage difference convergence time is reduced by 40% compared to traditional solutions.

[0061] Pulse charge / discharge: Temperature rise <20℃ under 3A equalization current.

[0062] PCB layout strategy: Number of layers: 4 layers (top / bottom signal layers, middle power / ground layers) Layout rules: Power circuits and signal circuits are strictly isolated; MOSFETs and transformers are placed near heat dissipation copper foil; CAN signal lines are routed differentially and grounded.

[0063] Transformer: Vertical placement reduces EMI.

[0064] MOSFET: Heat sink area ≥ 2cm².

[0065] MCU: Located near the CAN interface to reduce signal trace length.

[0066] Sampling resistor: 1mΩ precision resistor, differential trace.

[0067] EMC design: Power input: π-type filter (10μF+100nF), CAN bus: common mode inductor (2mH) + TVS diode (SMBJ33A).

[0068] Grounding strategy: Analog ground and digital ground are connected at a single point, and a large area is covered to reduce impedance.

[0069] Functional test: Balancing current: 3A±0.1A (bidirectional); Energy efficiency: 82.5% (3A load).

[0070] Reliability testing: High and low temperature cycling: -40℃~85℃, 1000 cycles without failure; Vibration testing: 10-2000Hz, 2G acceleration, no poor contact.

[0071] Integration with BMS: CAN communication latency: <1ms; equalization command response time: <100ms.

[0072] In actual operating condition testing, the voltage difference during acceleration / braking of electric vehicles is controlled within 15mV.

[0073] Energy storage system charge / discharge: Cycle life extended to 5200 cycles.

[0074] Efficiency verification: According to actual measurements with a power meter, the input power is 12.3W and the output power is 10.1W under a 3A load, with an efficiency of 82.1%.

[0075] Lifetime verification: After 100,000 switching tests, the internal resistance of the MOSFET increased by less than 5%.

[0076] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0077] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A lithium battery cross-cell energy balancing system, characterized in that, It includes a top-level module, a data acquisition module, and a balancing module, with the data acquisition module and the balancing module both electrically connected to the top-level module; the top-level module includes a power supply unit, a CAN communication unit, and a single-board ID identification unit. The acquisition module includes an acquisition unit; The equalization module includes an equalization execution unit, an equalization current setting unit, and an MCU control unit.

2. The lithium battery cross-cell energy balancing system according to claim 1, characterized in that: The equalization execution unit includes several equalization boards and dual equalization components mounted on the equalization boards.

3. The lithium battery cross-cell energy balancing system according to claim 2, characterized in that: The dual equalization component includes a transformer and a switching matrix component.

4. A lithium battery cross-cell energy balancing system according to claim 3, characterized in that: The switching matrix assembly includes a controller and a pair of MOSFETs.

5. A lithium battery cross-cell energy balancing system according to claim 1, characterized in that: The top-level module also includes a security monitoring unit.

6. A balancing method for a lithium battery cross-cell energy balancing system according to any one of claims 1-5, characterized in that, The balancing process of the active balancing system for lithium-ion battery packs specifically includes the following steps: Step 1: After the power is turned on, the power supply unit will step down the external input 12~60V voltage to output 5V to power the CAN communication unit, safety monitoring unit, single board ID identification unit, acquisition unit, equalization execution unit, equalization current setting unit and MCU control unit. Step 2: After the MCU control unit starts up, it executes the initialization program and detects the DIP switch or the single-board ID recognition unit to read the system ID address. Then, the MCU control unit initializes the timer interrupt and sets the time interval for periodically performing data sampling and equalization judgment. Step 3: The MCU control unit receives real-time battery data from the acquisition unit via the CAN communication unit, or reads historical data such as battery voltage, temperature, SOC, battery type, and cycle count, and stores it in RAM cache for subsequent equalization decisions. Step 4: The MCU control unit activates the acquisition unit to collect the current equalization current and the current actual temperature for safety judgment and current limiting control; Step 5: The MCU control unit analyzes the voltage, temperature and historical status of all individual batteries to determine if any cells have overheated. If an abnormality is found, the safety monitoring unit enters protection mode and sends fault information to other units or the host computer via the CAN communication unit. If no abnormality is found, proceed to step 6. Step 6: The MCU control unit compares the voltage of each cell to determine if any single cell has an excessively high voltage. If a high-voltage cell is found, the MCU control unit connects the positive and negative terminals of the corresponding cell to the equalization execution unit, and at the same time selects a low-voltage cell to connect to the equalization execution unit, thus forming a complete energy transfer path. Step 7: The MCU control unit injects the high-voltage battery cell into the low-voltage battery cell by activating the equalization execution unit, forming a bidirectional constant current energy transfer; the acquisition unit collects current data in real time, and the equalization current setting unit adjusts the current magnitude to keep the output current at ±3A until the voltage difference between the high-voltage battery cell and the low-voltage battery cell is lower than the set threshold, at which point the equalization stops. Step 8: The MCU control unit judges the voltage of a certain cell. If the voltage of a certain cell is too low and cannot reach the average voltage requirement, the low-voltage cell is connected to the equalization execution unit, and other high-voltage cells are also connected to the equalization execution unit. Then, the equalization execution unit injects the power of the high-voltage cells into the low-voltage cell to achieve charging equalization. Step 9: After the equalization process is completed, the MCU control unit uses the current voltage, current and temperature data of each cell to calculate the SOC, and calculates the remaining capacity of all individual cells and the total remaining capacity of the battery pack, providing a basis for the next equalization or fault analysis. Step 10: The user manually sets whether to start active balancing via the host computer or external CAN command. The system will determine whether the start conditions are met and perform the balancing operation; otherwise, the MCU control unit will remain in monitoring state, waiting for the next round of sampling interruption or host request to trigger the balancing function, while updating the current battery status information and balancing module operation status in real time on the local or remote interface.

Images