UL 1642 Section 17 Heating Test Service

Test Basis

Based on Section 17 Heating Test of ul 1642 Safety Standard for Lithium Batteries, this is a mandatory thermal abuse test for cells. It simulates the thermal stability of cells in a long-term high-temperature environment and evaluates whether the cells experience thermal runaway, fire, or explosion under continuous high-temperature incubation conditions.

Preparation Requirements Before Testing

1. Sample Preparation

• (1) Sample Quantity: 5 brand-new cells per group. Lithium-ion cells shall be in a fully charged state. Lithium polymer cells require two groups of 5 cells each; one group fully charged and the other discharged to the manufacturer's specified end-of-discharge voltage for separate testing.

• (2) Pre-treatment: Charge the cells to 100% SOC according to the standard 6.1 charging procedure, and let them rest in a 20°C ± 5°C environment for 1 to 4 hours until the cell temperature reaches equilibrium with the environment. The appearance must have no damage, swelling, seal cracking, or tab damage.

• (3) Cells for Special Operating Conditions: For cells with a manufacturer's nominal maximum operating temperature > 100°C, the heating and incubation temperature must be increased accordingly. The maximum incubation temperature for lithium metal cells shall not exceed 170°C ± 2°C.

2. Environmental Protection

The test must be conducted in an explosion-proof and ventilated oven equipped with smoke exhaust, pressure relief, and fire extinguishing devices. The cells shall be placed on an insulated isolation surface without contacting each other to prevent a chain reaction of thermal runaway.

3. Equipment and Tooling Parameters

• (1) Oven: Gravity natural convection or forced circulation hot air oven with a temperature control accuracy of ± 2°C.

• (2) Heating Rate: 5°C/min ± 2°C/min.

• (3) Standard Incubation Reference Temperature: 130°C ± 2°C, with an incubation duration of 10 minutes.

• (4) Monitoring Equipment: K-type thermocouple attached to the cell casing for temperature measurement, voltage recorder, and timing device.

Test Procedures

1. Initial Setup: Stabilize the initial oven temperature at 20°C ± 5°C. Place the temperature-stabilized cells onto the insulated surface inside the oven, attach the temperature-measuring thermocouples, and record the initial voltage and temperature.

2. Heating Phase: Start the oven heating program to heat up at a uniform rate of 5°C/min ± 2°C/min to the reference temperature of 130°C ± 2°C. For special high-temperature cells, increase the incubation temperature as required, with an upper limit of 170°C ± 2°C for lithium metal cells.

3. Incubation Phase: Once the target temperature is reached, maintain a constant temperature for 10 minutes. Continuously monitor the cell surface temperature and voltage changes throughout the entire process.

4. Cooling Phase: After the incubation phase ends, turn off the heating and allow the oven to cool naturally to a room temperature of 20°C ± 5°C.

5. Inspection: Remove the cells after they have cooled to room temperature. Inspect their appearance and sealing, and check for any leakage, swelling, or cracking. Completely record any phenomena such as smoking, splashing, fire, or explosion throughout the entire process.

Acceptance Criteria

All 5 samples must simultaneously meet the following requirements throughout the entire process and the cooling inspection phase. If any single sample fails, the test is judged as a failure.

1. No Fire or Explosion: No fire and no explosion throughout the entire process; no casing rupture, high-temperature material ejection, or open flame combustion.

2. No Leakage or Disassembly: No continuous electrolyte leakage, cell disassembly, or massive ejection from the explosion-proof valve.

3. No Structural Damage Post-Cooling: After cooling, the cells shall have no severe swelling, penetrating cracks in the casing, or exposure of internal electrode assemblies.