Battery Control and Managementkkkkkk.pptx

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1. 电池控制与管理 BATTERY CONTROL AND MANAGEMENT 电池管理系统 (BMS)、充电控制、热管理、安全监控及状态估计 电池管理系统 (BMS)、充电控制、热管理、安全监控及状态估计 报告日期: 2025-10-28 电动汽车电池技术

2. Introduction to Battery Management Systems (BMS) What is BMS? Battery Management System (BMS) is the control unit for batteries, monitoring and managing their parameters to ensure optimal performance and safety. Key Functions: Battery Protection Prevents overcharging, overdischarging, and overtemperature conditions Performance Optimization Optimizes battery performance within safe operating limits Vehicle Interface Acts as an interface between battery and vehicle control units State Estimation Estimates and controls SOC, SOH, and SOF BMS Challenges Parameter Dependencies Battery parameters are interrelated and dependent on usage and environmental history, making prediction complex Real-time Requirements Must respond to dynamic driving conditions in real-time, requiring fast processing and control Safety & Lifespan Protection Must ensure safe operation while maximizing battery lifespan through proper management Fault Detection Need to identify internal and external fault causes and issue warnings promptly 2 / 11

3. BMS Functions and Operations BMS Control Unit Workflow BMS Operation BMS combines battery electrochemical/material limitations with dynamic driving conditions to control charging/discharging currents in real-time. It uses various devices to track parameters and includes diagnostic tools to identify internal/external causes of battery faults. Core Functions Protection Prevents overcharging, overdischarging, overtemperature, and other abusive conditions that could damage the battery or create safety hazards. Performance Optimization Optimizes battery performance within safe operating limits by controlling voltage, current, and temperature parameters. Communication Interface Acts as an interface between the battery and vehicle control units, facilitating data exchange and system integration. State Function Estimation Estimates and controls SOC (State of Charge), SOH (State of Health), and SOF (State of Function) to optimize battery usage. Diagnostics & Fault Tracking Includes diagnostic and service tools to identify internal or external causes of battery faults, track safety issues, and provide early warnings of potential problems. 3 / 11

4. Charging Control Methods Constant Current (CC) Applies a fixed current based on battery capacity. Simple but requires robust termination control. Voltage Control: Monitors voltage change (ΔV/Δt) to detect battery full state Temperature Control: Uses temperature change (ΔT/Δt) to terminate charging Risk of overcharging without proper termination Constant Voltage (CV) Maintains voltage at preset limit, allowing higher current. Suitable for fast charging. Higher Current: Allows maximum current until voltage limit reached Fast Charging: More suitable for quick charging applications May cause high current spikes if not properly managed CC-CV Method Combines both methods for optimal charging. First CC, then CV as voltage approaches limit. Stages: I (Max Current) → II (Current Decreases) → III (Low Current) Advantages: Fast charging with battery protection Best balance of charging speed and battery safety CC-CV Charging Stages: I Maximum current flows until voltage limit is reached II Current gradually decreases as voltage approaches full charge III Low current maintains battery at full charge and compensates for self-discharge 4 / 11

5. Thermal Management Why Temperature Matters Optimal Range Battery performance is best between +20°C and +40°C Performance Impact Higher temperatures improve reaction rates and capacity Temperature Gradients Minimize temperature differences between cells Heat Generation Three sources: activation losses, concentration losses, and ohmic losses -20°C +20°C +40°C +80°C Thermal Management Strategies Active Cooling Use cooling systems to remove excess heat during operation Heating Elements Implement heating mechanisms for cold environment operation Thermal Interface Optimize thermal conductivity between battery cells and cooling system Temperature Monitoring Continuous monitoring of cell temperatures and gradients Charge Management Adjust charging rates based on temperature conditions Thermal management directly impacts battery safety and lifespan 5 / 11

6. Thermal Runaway Prevention Causes of Thermal Runaway Overcharging Excessive charging can cause electrolyte decomposition and gas generation Overheating External heat sources or poor thermal management can lead to rapid temperature rise Mechanical Impact Physical damage can cause internal short circuits and heat generation Internal Short Circuit Manufacturing defects or particle contamination can lead to internal shorts Detection Methods Temperature Monitoring Continuous monitoring of cell temperature to detect abnormal rise rates Voltage Analysis Monitoring for voltage anomalies that may indicate thermal runaway BMS Diagnostics Advanced algorithms to detect patterns indicating thermal events 0°C 40°C 80°C 150°C Prevention Strategies Thermal Management Maintain optimal temperature range and minimize temperature gradients Proper Charging Algorithms Implement adaptive charging based on temperature and SOC Safety Mechanisms CID at 120-130°C, PTC function to reduce current 6 / 11

7. Battery Safety Monitoring Battery safety monitoring involves comprehensive tracking of mechanical, electrical, thermal, and chemical parameters to ensure safe operation throughout the battery's lifecycle. Mechanical Monitoring Vibration & Impact: Detects mechanical abuse from collisions or vibrations that could damage battery cells Physical Damage: Identifies external damage that might compromise battery integrity Vehicle Integration: Ensures proper mechanical integration to prevent battery movement during operation Electrical Monitoring Current & Voltage: Monitors for abnormal current flow and voltage levels that could indicate faults Internal Short Circuits: Detects dangerous internal electrical paths that can lead to thermal runaway Fuse Monitoring: Tracks fuse status to ensure proper protection circuits are intact Thermal Monitoring Temperature Distribution: Tracks temperature across battery cells to identify hotspots Thermal Runaway Prevention: Detects rapid temperature increases that could lead to thermal events Cooling System: Monitors cooling system performance to maintain optimal battery temperature Chemical Monitoring Gas Detection: Identifies harmful gases that may indicate chemical degradation or thermal events Electrolyte Stability: Assesses electrolyte condition to prevent dangerous chemical reactions Self-Discharge: Monitors leakage currents that could indicate chemical imbalance 7 / 11

8. State of Charge (SOC) Estimation SOC Definition: Ratio of available capacity to maximum capacity SOC(t) = Q(t)/Q N × 100 Current Counting Integrates current over time to estimate charge SOC(t) = SOC(0) - (1/C) ∫I(t)dt Requires precise current measurement High sampling frequency needed Affected by temperature and self-discharge Voltage Lookup Tables Compares battery voltage to reference tables Limited accuracy for flat discharge curves Simple implementation Requires calibration Voltage hysteresis affects accuracy Model-Based Uses battery models with inputs from current, voltage, temperature Often uses Kalman filtering Higher accuracy More complex Requires extensive testing Key Challenges Temperature affects capacity and voltage Requires real-time processing Battery aging affects parameters 8 / 11

9. State of Health (SOH) and State of Function (SOF) State of Health (SOH) SOH represents the battery's health condition compared to its original state, indicating capacity degradation over time. Measured as a percentage of original capacity Typically evaluated over months or years Affected by charge/discharge cycles and calendar age Key parameters: capacity, internal resistance, efficiency State of Function (SOF) SOF represents the battery's functional capabilities at a specific moment, focusing on real-time performance metrics. Determines available power capability in milliseconds Critical for vehicle control unit decisions Monitors for abnormal conditions that could affect performance Updates continuously during operation Key Insight: Both SOH and SOF are essential for optimizing battery usage, ensuring performance, and predicting remaining useful life. SOH provides historical context, while SOF delivers real-time functionality. 9 / 11

10. Battery Cell Balancing Why Balancing is Important Uniform Characteristics Ideal battery operation requires all cells to have identical capacity, SOC, and temperature Causes of Imbalance: Manufacturing Variations: Initial differences in cell characteristics Environmental Factors: Uneven thermal conditions during operation Internal Resistance: Cells with higher resistance experience different C-rates Consequences of Imbalance: Cells may reach cutoff voltage before others, leading to overcharging Reduced overall battery capacity and shortened lifespan Safety risks including overcharging, overdischarging, and thermal runaway Balancing Techniques Purpose of Balancing To equalize cell voltages and SOC to extend battery life and ensure safety Passive Balancing: Uses fixed or switched resistors to discharge higher voltage cells Active Balancing: Transfers charge between cells using capacitors, more efficient than passive balancing 10 / 11

11. Future Trends in Battery Management As battery technology advances, so do the methods to manage and optimize their performance. Here are key emerging trends: Advanced Algorithms Fuzzy logic methods for estimating battery state with noisy current data Self-learning adaptive approaches for improved accuracy Weighted estimation combining multiple SOC estimation methods Enhanced Safety Improved fault detection for thermal runaway prevention Advanced insulation monitoring for electrical safety Multi-level safety mechanisms with hierarchical protection Monitoring Advances Reference electrodes for more accurate voltage determination Standard deviation and error metrics for SOC estimation accuracy Enhanced models with improved convergence time The future of battery management lies in intelligent systems that learn and adapt, ensuring optimal performance, safety, and longevity. 11 / 11