Battery thermal safety testing: a step in evaluating battery thermal stability
Battery thermal safety testingIt is the core link in evaluating the thermal stability of batteries under working conditions, and the process can be divided into three stages:
Preparation phase
Equipment selection: Equipped with a constant temperature box, adiabatic acceleration calorimeter, temperature sensor (accuracy ± 0.5 ℃), voltage/current monitoring device, combustion testing device, etc. For example, lithium battery testing needs to meet the GB/T31485 standard, while lead-acid batteries need to focus on cycle life and high-temperature float charging testing.
Sample pretreatment: The battery needs to be fully charged and left to stand for 24 hours, with SOC adjusted to above 95%, and insulation resistance and charge discharge performance checked. Pre treatment is required in an environment with a temperature of 22 ℃± 5 ℃ and a humidity of 10% -90% before testing.
Plan formulation: Set parameters based on testing objectives such as high-temperature storage, needle puncture triggering, and overcharge verification.
Test execution phase
Environmental simulation: Simulate scenarios through temperature cycling (such as -40 ℃ to 80 ℃), low pressure (11.6kPa simulating altitude of 15240m), vibration (7Hz-200Hz sweep frequency), and other methods.
Thermal runaway triggering: triggered by needle punching (steel needle diameter 3-8mm, speed 0.1-10mm/s), heating (power up to 300 ℃), overcharging (3C/10V), and other methods. For example, the heating test requires direct contact between the heating device and the surface of the battery, and continuous heating until 300 ℃ or thermal runaway occurs.
Data collection: Real time monitoring of temperature, voltage, current, air pressure, smoke and other parameters, with a sampling interval of ≤ 1 second. The thermal diffusion test requires recording the time for thermal runaway to spread to adjacent batteries, with a warning window of ≥ 15 minutes.
Result analysis stage
Performance evaluation: Obtain parameters such as thermal runaway initiation temperature, maximum temperature rise rate, adiabatic temperature rise, etc. through ARC testing, and evaluate thermal stability in combination with GB/T38661-2020.
Safety judgment: If the triggering conditions meet any of the following conditions: voltage drop ≥ 25%, temperature rise rate ≥ 1 ℃/s for 3 seconds, monitoring point reaching 300 ℃, etc., it is judged that a thermal event has occurred.
Report preparation: It should include test parameters, equipment calibration records, raw data curves, video evidence, and improvement suggestions, in accordance with the data format requirements of GB/T32960.3-2016.
2、 Key precautions
safety protection
Personnel protection: Operators are required to wear goggles and set up emergency eye wash stations, fire extinguishers (heptafluoropropane response time ≤ 10 seconds), and isolation passages in the test area.
Equipment safety: Testing equipment needs to be calibrated regularly, such as temperature sensor accuracy meeting the requirement of ± 2 ℃, and BMS system needs to have functional safety mechanism (FTTI ≤ 5 seconds).
Emergency plan: In case of thermal runaway, immediately initiate power-off, exhaust, and fire extinguishing procedures, and ensure that the driver and passengers have at least 15 minutes to evacuate.
Operating Specifications
Environmental control: The testing environment should maintain a temperature of 22 ℃± 5 ℃, humidity ≤ 90%, wind speed ≤ 2.5km/h, and avoid external interference.
Data management: The raw data needs to be encrypted and stored, and abnormal values should be removed during analysis. Dual sensor comparison verification should be used (if the temperature difference is greater than 5 ℃ for 5 seconds, it will be judged as invalid).
Standard compliance: International standards such as UN38.3 (Transportation Safety), IEC62660 (Electric Vehicles), UL9540 (Energy Storage Systems) must be followed, while domestic standards such as GB38031-2020 and GB/T40556-2021 must be met.
Special scenario response
Cold/high temperature environment: Low temperature testing needs to evaluate battery start-up performance (such as -30 ℃ discharge capacity retention), while high temperature testing needs to focus on thermal management efficiency (such as forced air cooling for ≥ 30 ℃/10 minutes).
Mechanical impact: Collision testing requires simulating real road conditions, such as a 9.1kg weight falling freely from a height of 610mm to impact the battery, ensuring that the shell is not cracked and the electrolyte is not leaked.
Recycling process: ISO22400 requires controlling the mechanical crushing temperature during disassembly, with wastewater COD ≤ 50mg/L to prevent secondary pollution.