Meaning
Chemical discharge events occur when a battery cell releases internal vapors during the rigorous environmental and mechanical testing required for transport certification. This un 38.3 off-gassing typically involves the escape of volatile organic compounds through the safety vent or a compromised seal. If a cell exhibits this behavior without a fire or explosion, it is recorded as a mass loss or a venting event.
The test standards define the exact threshold for weight reduction that determines if a cell remains compliant. Such failures indicate that the cell design cannot withstand the pressures of high altitude or vibration.
Venting Threshold
Specific criteria for mass loss determine whether the release of gas constitutes a failure of the safety protocols. For a small cell, a loss of more than zero point one percent of its initial mass during un 38.3 off-gassing is considered a failure. This measurement is taken after each of the eight test sequences to ensure the integrity of the housing is maintained.
The loss of electrolyte through the vent can occur without a visible flame, but the change in weight provides an objective measure of the leak. Every sample must pass this check to receive the certification needed for international shipping.
Thermal Runaway
Excessive heat generated during the short circuit or overcharge phases of the test often leads to a sudden release of pressure. During un 38.3 off-gassing, the temperature of the cell casing must be monitored to ensure it does not exceed the maximum limits allowed by the protocol. A rapid rise in temperature suggests that the internal chemistry is becoming unstable and could lead to a fire.
The vented gases are frequently flammable and pose a risk to the test environment and the personnel involved. If the cell remains intact but leaks, the test is still failed under the criteria for leakage or venting. Proper insulation and cooling systems are required in the test chamber to manage these risks.
Mass Loss
Accurate weighing before and after the thermal cycles and mechanical shocks identifies the smallest breach in the cell containment. This check for un 38.3 off-gassing uses the same high precision balances found in quality control labs. If the mass remains within the tolerance, the cell is deemed to have maintained its hermetic seal under the stress of transport.
These results are documented in the test report which accompanies every shipment of lithium batteries. The failure of a single cell in the test group requires a full redesign of the cell or the safety vent. Every test report provides a clear record of the stability and integrity of the battery design.
