Meaning
Transport safety standards mandate environmental stress testing to ensure lithium cells endure rapid temperature swings without experiencing structural leakage or electrical failure. The thermal cycling test T.2 is a mandatory safety evaluation mandated by the United Nations Manual of Tests and Criteria Section 38.3 for transport clearance. This test governs transport regulatory compliance, applying to individual cells and battery packs prior to public transport, and ending once compliance certification is granted.
Test Sequence
Environmental test chambers subject test units to extreme temperature swings between seventy-five degrees Celsius and negative forty degrees Celsius. The thermal cycling test T.2 requires storing test samples at seventy-five degrees for at least six hours, followed by storage at negative forty degrees for at least six hours, repeating this cycle ten consecutive times. Thermal transition times between temperature extremes must not exceed thirty minutes, imposing severe mechanical shock on cell seals, casing joints and internal current collectors.
Following thermal cycling, test units undergo a twenty-four hour rest period before visual inspection and electrical verification.
Pass Threshold
Evaluation standards require zero mass loss, zero leakage, no venting, no disassembly and no fire following environmental exposure. Open circuit voltage after testing must remain within ten percent of pre-test baseline values.
Shipping Compliance
Transport carriers refuse battery shipments lacking verified UN 38.3 test completion certificates. Test documentation protects shipping lines from thermal runaway hazards during commercial air, ocean and ground transport.
