As a core component of modern energy storage systems, lithium-ion battery charge/discharge
management directly affects the performance and service life of the equipment. For the battery
recycling, transportation and storage, performance testing and other scenarios of the discharge
needs, systematic discharge processing has become a key technical link to extend the life of the
battery and ensure operational safety. In this paper, we will deeply analyze the technical path
and operation standard of lithium-ion battery discharge, and provide a full-process
implementation plan.
Necessity and technical objectives of discharge processing
1.1 Safety Scenario Requirements
Transportation safety: to meet the International Air Transportation Association (IATA) regulations below 30%
state of charge (SOC) standards
Graduated utilization: realize single cell voltage equalization (±50mV error range) before restructuring of
battery packs
Recycling and dismantling: eliminating residual electrical energy and preventing the risk of ignition and
explosion caused by electrolyte decomposition.
1.2 Technical control index
Target voltage: adjusted according to the battery system, lithium iron phosphate (LFP) discharged to
2.5V, ternary materials (NCM) to 3.0V.
Current control: standard discharge rate is 0.2C, emergency discharge does not exceed 1C.
Temperature monitoring: maintain 15-35℃ working temperature zone throughout the whole process,
and interrupt immediately for abnormal temperature rise.
Standardized discharge process
2.1 Pre-processing diagnosis
Use the battery internal resistance tester to detect the initial state and record parameters such as open-circuit
voltage (OCV) and AC impedance (ACIR). Pre-treatment discharge is prioritized for batteries with voltage >3.7V
to prevent thermal runaway caused by direct high-current discharge in high charge state.
2.2 Active discharge technology program
Program 1: Constant current and constant voltage (CCCV) discharge
Configure programmable DC power supply, set the cut-off voltage (e.g. 3.0V) and maximum current (≤1C).
Paste thermocouples on the battery surface to monitor the temperature change in real time.
Typical time consumption: 1-4 hours (depending on initial SOC)
Option 2: Resistive Load Discharge
Select ceramic package power resistor, resistance value calculation formula: R=V²/(P×η) (η takes 0.8 safety factor)
Configuration of forced air cooling system to control the resistance temperature ≤ 80 ° C
Applicable scene: emergency discharge without professional equipment
2.3 Passive discharge management
Natural discharge method: the battery is placed in a constant temperature box at 25℃, and the
self-discharge rate is about 2-3% per month.
Charge transfer method: connect with the same specification low power battery pack for charge
equalization (need to be protected by anti-reverse current diode)
Key equipment selection and technical parameters
3.1 Specialized discharge equipment
Multi-channel battery discharge cabinet: support ≥ 8 channels in parallel, single-voltage sampling accuracy ± 1mV
Energy feedback system: adopts bi-directional DC/AC inverter, power feedback efficiency>85%.
Safety protection design: with over-voltage, over-current, reverse connection, over-temperature four protection
mechanisms
3.2 Homemade Discharge Tools
Cement resistor group: Combination of 10Ω/50W resistors to realize power expansion (example: 60V battery
needs to be configured with 6 series connections)
Intelligent monitoring module: add voltage acquisition board (ADS1115 chip) + temperature control relay
Safety operation standardization and risk prevention and control
4.1 Operator protection
Three-level protective equipment: anti-static clothing + acid-resistant gloves + goggles
Operating environment requirements: explosion-proof fume hood operation, equipped with CO₂ fire
extinguishers and sandboxes
4.2 Process risk point control
Voltage reversal: anti-dumbing interface design, differentiated management of red and black wire diameters.
Lithium precipitation monitoring: switch trickle mode when the voltage drops to 2.8V at the end of discharge (≤0.05C).
Gas emission: NCM system battery discharge produces trace CO, need to configure gas detector.
4.3 Disposal of abnormal conditions
Temperature alarm: cut off the circuit immediately when it exceeds 45℃, and move it to the explosion-proof box to cool down.
Voltage drop: terminate the discharge when the voltage drop is more than 10% within 30 seconds, and
investigate the internal short circuit.
Expansion and deformation: put into the steel explosion-proof container for 24 hours of isolation and observation.
Post-discharge processing and data management
5.1 Status Confirmation
Measure the terminal voltage of the battery using the four-wire method, and re-test the voltage return value after 2
hours of resting. Requirements:
Ternary battery recovery ≤ 0.05V, lithium iron phosphate ≤ 0.15V
The rate of change of internal resistance＜20% of the initial value.
5.2 Storage specification
Environmental conditions: temperature 20±5℃, humidity 30-60%RH.
Regular maintenance: recharge and discharge to the target voltage every 3 months.
Insulation treatment: electrodes with anti-short-circuit adhesive film, insert flame-retardant spacer between monoblocs
5.3 Data Traceability
Establish discharge file and record key parameters:
Discharge start and end time/temperature curve
Accumulated discharge capacity (Ah)
Voltage platform characteristic diagram
Special Scenario Application Program
6.1 Soft pack battery discharge
Customized fixture to prevent deformation, pressure control at 5-10kPa
Prioritize the use of contact temperature sensor (K-type thermocouple)
6.2 Module discharge
Configure active equalization module to control the temperature difference between cells <5℃.
Adopt liquid cooling plate to assist heat dissipation, with flow rate set at 2-3L/min.
6.3 Emergency energy discharge treatment
Salt water immersion method: 5% NaCl solution submerged battery (only after complete discharge)
Energy-discharging resistance method: Parallel connection of 100Ω high-power resistors to force discharge.
Through standardized discharge treatment, the efficiency of subsequent disassembly and reorganization
of lithium-ion batteries can be increased by 40%, and the rate of storage accidents can be reduced by 90%.
With the development of intelligent BMS technology, the future discharge management will realize cloud
monitoring and adaptive adjustment, promoting the upgrading of the safety level of the whole industrial
chain. Operators must strictly follow this guide to ensure that every technical detail is in place to realize
the double benefits of safety and economy.