I. Core Battery Types and Basic Cycle Life Specifications

　　1. Lithium Iron Phosphate Battery (Automotive/Industrial Grade)

　　Core Cycle Life Parameters

　　Depth of Discharge (DoD) 20%: Cycle life range 5000-7000 cycles, corresponding to a calendar life (average of 1 charge/discharge cycle per day) of 13.7-19.2 years, with a capacity fade of ≤1.5% per year.

　　Depth of Discharge (DoD) 50%: Cycle life range 3000-5000 cycles, corresponding to a calendar life (average of 1 charge/discharge cycle per day) of 8.2-13.7 years, with a capacity fade of ≤2.0% per year.

　　Depth of Discharge (DoD) 80%: Cycle life range 1500-3000 cycles, corresponding to a calendar life (average of 1 charge/discharge cycle per day) of 4.1-8.2 years, with a capacity fade of ≤3.2% per year.

　　Typical Configuration Reference: 48V 3000Ah The battery pack (14 series, 3 parallel configuration) achieved a measured cycle life of 2,200 cycles at 80% DoD, meeting the operational requirements of a 20kW system for over 10 years.

　　Test Standards and Conditions

　　Implementation Standards: GB/T 36276-2025 (Specification for Cycle Life of Lithium-ion Batteries for Energy Storage), UL 1642

　　Test Environment: 25±5°C, Charge Rate 0.2C (6A), Discharge Rate 0.5C (15A), Cut-off Voltage 2.5V (Discharge) / 3.65V (Charge)

　　End-of-Life Definition: Capacity decays to 80% of the rated value (mandatory threshold in the national standard).

　　2. Lead-Acid Batteries (Conventional/Improved)

　　Core Cycle Life Parameters

　　Conventional lead-acid batteries: 300-400 cycles (80% DoD), calendar life 2-3 years, annual degradation rate ≥15%;

　　Graphene-enhanced lead-acid batteries: 600-800 cycles (80% DoD), calendar life 3-4 years, annual degradation rate ≤10%;

　　Typical configuration reference: 2V 600Ah battery pack (110 cells), cycle life increased to 500 cycles at 50% DoD, suitable for low-frequency charging and discharging scenarios.

　　Test Standards and Conditions

　　Implementation Standard: GB/T 18332.1-2009 (Lead-Acid Battery Cycle Life Test)

　　Test Environment: 20-25°C, three-stage charging (constant current - constant voltage - float charge), avoiding deep discharge (DoD ≤ 70%).

　　II. Key Factors Influencing Cycle Life and Their Quantitative Impact

　　1. Depth of Charge and Discharge (DoD): The Most Core Influencing Factor

　　Lithium iron phosphate batteries have a cycle life of only 3,500 cycles at 100% DoD. This life doubles to 8,000 cycles at 50% DoD. Deep discharge accelerates lattice damage in the electrode material.

　　Lead-acid batteries are more sensitive to DoD. When discharged to 20% remaining charge, cycle life is 60% shorter than when discharged to 50%, which can easily lead to plate sulfation.

　　2. Ambient Temperature: Accelerates or Delays Aging

　　Optimum Operating Temperature: 5-35°C (LiFePO4), 15-25°C (Lead-acid);

　　Impact of Extreme Temperatures:

　　Above 45°C: LiFePO4 cycle life decreases by 30%/year, while lead-acid battery capacity decay increases to 20%/year;

　　Below -10°C: LiFePO4 cycle efficiency drops to 85%, shortening lead-acid battery cycle life to less than 200 cycles.

　　3. Charge/Discharge Rate: High-Frequency Fast Charging Accelerates Aging

　　LiFePO4: 1C fast charging (30A) reduces cycle life by 20% compared to 0.2C slow charging. Discharging at rates above 3C can cause a surge in internal resistance.

　　Lead-acid: Discharging at rates exceeding 0.3C can reduce cycle life by 40%, and plate softening is more likely to occur.

　　4. System Integration Impact: Consistency Determines Pack Lifespan

　　Battery Pack Series Unbalance: When cell voltage difference > 0.05V, cycle life decreases by 15%-20%, requiring active balancing via the BMS.

　　Poor Heat Dissipation: When battery cabinet temperature difference > 5°C, local cell cycle life can vary by up to 30%.

　　III. 20kW System Cycle Life Optimization Technical Specifications

　　1. BMS Intelligent Management Parameter Settings

　　DoD Threshold Control: Set to 80% for industrial scenarios (balancing capacity and lifespan), 60% for emergency scenarios (extending cycle times).

　　Balancing Current: ≥ 5A active balancing, ensuring cell voltage difference ≤ 0.03V within 100 cycles.

　　Protection Strategy: Immediate power-off for charging overvoltage (3.65V/cell) and discharging undervoltage (2.8V/cell). Forced cooling is activated at high temperatures (45°C).

　　2. Thermal Management System Compatibility Specifications

　　Air Cooling: Starts when ambient temperature > 40°C, wind speed ≥ 2m/s, temperature control accuracy ±3°C;

　　Liquid Cooling (High Power Scenario): Heat exchange efficiency ≥ 80W/(m²・K), controlling battery temperature between 25-35°C, increasing cycle life by over 30%.

　　3. Charge and Discharge Strategy Optimization

　　PV Priority Charging: Utilizes MPPT tracking (efficiency > 99%) to avoid shallow charging and discharging of the battery;

　　Peak and Valley Control: In industrial scenarios, discharge is avoided during the power frequency (50Hz) resonant period to reduce high-frequency stress on the battery.

　　IV. Lifespan Verification and Warranty Specifications

　　1. Factory Cycle Test Requirements

　　Lithium Iron Phosphate Batteries: Samples undergo 100 cycle tests, and a capacity decay of ≤2% is considered acceptable.

　　Lead-Acid Batteries: Samples undergo 50 cycle tests, and a capacity decay of ≤5% is considered acceptable.

　　2. Warranty Terms and Failure Determination

　　Lithium iron phosphate batteries: 5-year warranty, guaranteed cycle count ≥ 2000 (80% DoD). If actual cycle count is not reached and capacity degradation is > 20%, the battery cell will be replaced free of charge.

　　Lead-acid batteries: 1-2 year warranty, cycle count ≥ 300 (80% DoD). Plate sulfation or leakage will be considered failure.

　　3. Lifecycle Monitoring Indicators

　　Daily monitoring: Cell voltage (deviation ≤ 0.05V), cell temperature (≤ 45°C);

　　Annual monitoring: Cycle life degradation rate (≤ 3%/year), internal resistance growth rate (≤ 10%/year).

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