A.
I have written an article in the Dec mber 2011 issue of the “SPACE” magazine (Japanese language) about the transport of lithium batteries.

There, I had referred to the danger of “thermal runaway” of lithium batteries. Particularly for PI 965 and PI 968 where lithium cells/batteries are shipped as is, extra caution must be exercised. Lithium cells/batteries are liable to start a “thermal runaway” at a temperature of 230℃. Halon fire extinguishers equipped on the aircraft functions as fire extinguishers by cutting off the supply of air (oxygen) to the flame. Fire caused by thermal runaway of lithium batteries can only be extinguished by lowering the temperature. Halon do not act to reduce temperature. To reduce temperature, water is the best agent, but there is no abundant supply of water on an aircraft. Inferior quality lithium cells/batteries or cells/batteries which had not gone through the UN test pose great danger.

The shell of the cells/batteries swell up due to the pressure differential experienced in flight. The shell finally bursts and sends off highly flammable electrodes. Cells/batteries heat up to about 600℃ and enters into a thermal runaway. Neighboring cells/batteries heat up and results in a chain reaction of massive thermal runaways. 600℃ is the melting temperature of aluminum, a major structural material of an airplane. For cells/batteries packed with equipment (PI 966 and PI 969) and cells/batteries contained in equipment (PI 967 and PI 970) where cells/batteries are not adjacent to each other as in the case of PI 965 and PI 968, there are less chances of a contagious thermal runaway. Needless to emphasize, the cells/batteries must have passed the mandatory UN tests.

As result of technical advancement and modernization of life, the demand for lithium batteries have astronomically increased. The electric capacity of the cells/batteries have increased, while the size minimized, resulting for the shell of the cells/batteries to become thinner and thinner. At cruising altitude, cabin (cargo hold) pressure is Dec eased to about 80kPa or lower.

The pressure differential from ground pressure where the cells/batteries were manufactured increases to 20kPa or more. The thin shell of the cells/batteries will swell 20%. Inferior quality cells/batteries or those which had not gone through the mandatory UN tests cannot withstand this depressurization. They burst. The temperature rises and a thermal runaway starts. Unless there is water, there is no way to reduce the temperature. The reason why spare batteries are confined to cabin baggage is that when a thermal runaway should start cabin attendants can immediately cope with water.

PI 965 carries provisions for Non-Regulated cells/batteries in Section II. There, it makes particular reference to DGR 5.0.2.4、5.0.2.6.1 and 5.0.2.12.1 which must be met. In the Additional Requirements – Section II, it says: “Cells and batteries must be packed in inner packagings that completely enclose the cell and battery then packed in a strong outer packaging.” Of course, it will be better if each cells and battery are individually wrapped, but as long as the cells/batteries are protected from short circuit and the inner packagings are fully enclosed, there is no problem. A 1.2m drop test is mandatory.

Starting from 2013, the rule for PI 965 and PI 968 will become more sever. Please refer to the TOPICS column where details of the coming new rule is shown.