Meaning
Environmental stress testing subjects transport packages containing lithium batteries to extreme temperature shifts to evaluate structural and electrical integrity. Executing un 38.3 thermal cycling involves storing fully charged cell samples at seventy-five degrees Celsius followed by negative forty degrees Celsius for specified duration intervals. Rapid temperature transitions create thermal expansion differentials that stress internal seals, electrical connections, and cell casings.
This test protocol verifies that cells remain safe against internal shorting or fluid leakage during transport.
Temperature Exposure
Test procedures require ten continuous thermal cycles between high and low extreme temperature limits. Conducting un 38.3 thermal cycling demands thermal chambers capable of shifting ambient air temperatures within thirty minutes. Dwell times ensure full thermal equilibrium throughout cell cores.
Pass Condition
Test samples must exhibit no mass loss, no leakage, no venting, no disassembly, and no fire. Completing un 38.3 thermal cycling requires open-circuit voltage retention above ninety-seven percent of pre-test values. Post-test electrical measurements confirm seal and separator stability.
Structural Response
Thermal expansion and contraction cycles strain cell crimps, headers, and polymeric pouch seals. Subjecting modules to un 38.3 thermal cycling uncovers mechanical flaws in welded interconnects before commercial shipping occurs. Package seal degradation leads to moisture ingress and cell failure.
