Effective from 1 January 2009, the latest version of the Technical Instructions for the Safe Transport of Dangerous Goods by Air issued by the International Civil Aviation Organization (ICAO) added UN serial numbers for dangerous goods, and lithium batteries are classified as lithium-ion batteries (UN 3090 and UN 3091) and lithium metal batteries (UN 3480 and UN 3481). The regulation states that lithium batteries cannot be transported by air if they are not accompanied by a test report or certificate of approval based on UN38.3.
UN 38.3 refers to Part 3, paragraph 38.3 of the United Nations Manual of Tests and Criteria for the Transport of Dangerous Goods, which requires lithium batteries to pass height simulation, high and low temperature cycling, vibration test, shock test, external short circuit at 55°C, impact test, overcharge test, and forced discharge test, before transportation to ensure the safety of lithium batteries.
Forced discharge means that the battery discharges the internal stored power. When the voltage reaches a certain value, continued discharge will cause over-discharge. It will destroy the crystalline structure of the positive and negative electrodes of the battery, degrading the thermal stability of the two electrodes. The negative electrode produces a large amount of hydrogen gas, which catalyses the decomposition of the organic electrolyte. When the temperature is high enough, the positive electrode will decompose and produce a large quantity of hydrocarbons, which will eventually lead to the rupture of the battery, resulting in fire.
Real case scenario
A test required a 3,7 V battery cell to undergo a forced discharge at 500 A. An ITECH T6030D-80-900 high-power DC power supply was used. The PSU was set to 12 V/510 A and connected in series with the battery cell. An IT8912A-150-1200 high-performance DC electronic load, with constant current set to 500 A, was used to discharge the cell.
The sense function of the load was switched on, and through the remote measurement terminal, the voltage of the battery cell could be read back in real time. The voltage and current data used for this experiment was then recorded through the supporting software. The data was then analysed, and conclusions drawn, once the experiment was complete.
ITECH DC power supplies and loads can be used to test all types of battery chemistries. Besides the models mentioned above, there are also bi-directional DC power supplies and the ITS5300 battery testing system for different battery testing options.
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