UN 38.3 Thermal Test

Cycling Protocol

Practitioners subject the objects under scrutiny to six hours of storage at seventy two degrees Celsius, followed by six hours of cooling to negative forty degrees Celsius. The sequence repeats ten times to reach a total of seventy two hours at each extreme. Air flow velocity across the battery surface remains constant during this duration to ensure even heat distribution across the device.

Technicians monitor the surface temperature of the battery to ensure it reaches equilibrium with the chamber environment before the timing sequence begins for each cycle. After the final shift, the battery rests for twenty four hours at room temperature while inspectors look for physical changes. A successful outcome demands that the open circuit voltage remains within ten percent of the starting value before the cycling started.

Validation Constraint

The procedure serves the aviation safety sector by isolating batteries prone to internal short circuits caused by expansion and contraction of electrodes. Cells that lack sufficient separator material often show signs of degradation when moving between these temperature boundaries. Manufacturers rely on this data to certify that their product design accommodates the harsh environmental shifts encountered in global logistics.

A passing grade on this specific assessment acts as a gateway for the broader certification package required for hazardous goods declarations. The data captured here prevents faulty units from entering the supply chain before the final assembly phase of a battery pack begins.

Outcome Requirement

Each tested battery must exhibit no mass loss beyond a specified threshold defined by the governing document. The exterior casing remains intact without signs of fire or explosion. Inspectors weigh the unit before and after the full sequence to track electrolyte evaporation or leakage that might remain invisible to the eye.

Voltage measurements confirm that the chemical stability of the lithium ions remains constant throughout the process. A battery pack that shows physical signs of heat distress fails the assessment regardless of whether the cell voltage stays within the acceptable range. The procedure establishes the threshold for safe transport of energy storage devices.