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ENERGY STORAGE How to guarantee safe air transportation of lithium batteries By Benno Diemer On board an aeroplane, on the ground at an airport or inside a train, the consequences of an explosion or uncontrolled fire can be devastating. As a dense and combustible source of energy, a lithium battery would be capable of causing a blaze if it were misused, and its protection and safety circuits were disabled or faulty. An electrical fire caused by a battery cannot be doused with the small amounts of water available on board an aircraft, and requires specialist fire extinguishers. The potential for damage and loss of life if a battery catches fire on board an aircraft is evident. In fact, lithium batteries have been implicated in a small number of fires on board aeroplanes in the years up to 2013. This has resulted in a re-drawing of the regulations governing the transportation of lithium batteries on aircraft, which now require compliance with stricter instructions on the handling, preparation, packaging and labelling of lithium cells and batteries carried on-board aircraft. (Similar regulations apply to other modes of transport, such as rail, road and sea transport.) But this raises a number of questions for OEMs which transport lithium batteries as discrete parts, or equipment containing lithium batteries: How can OEMs ensure that they are in compliance with the many, complex regulations governing the airborne transportation of lithium batteries? And is compliance on its own sufficient to guarantee safe transportation? Fig. 1: approved label styles for lithium metal (primary) and lithium-ion batteries The function of the air transport regulations The latest version of the Lithium Battery Guidance Document from IATA (the International Air Transport Association, the trade association for the world’s airlines) is based on the provisions of two separate regulations: The 2013-2014 edition of the ICAO (International Civil Aviation Organization) Technical Instruction for the Safe Transport of Dangerous Goods by Air The 55th edition of the IATA Dangerous Goods Regulations (DGR) The rules reflect the known behaviour of lithium cells and batteries. The relevant failure mode for batteries in transportation (and therefore not in use) is normally a short circuit: this can cause a dangerous over-current event, resulting in over-heating which escalates until a cell or battery explodes and/or catches fire. One cause of short circuits is the ingress of dust or other particles inside a cell during the production process, impairing the separator layer between the anode and cathode. Reputable, brand-name cell manufacturers and battery manufacturers make and use known-good cells that keep the levels of contaminants to extremely low, safe levels. As of 1 January 2013, the DGR classification criteria for lithium batteries stipulate that cells and batteries must be manufactured under a quality management programme. Such a programme will provide for the production of high-quality cells posing an extremely low risk of dangerous internal contamination. A battery containing high-quality cells is still theoretically at risk of a short circuit caused by the making of an electrical connection between the positive and negative terminals on the case of the battery; or, in the case of a battery embedded in equipment, its accidental activation. This risk underlies most of the provisions with which OEMs must be concerned. Broadly, the regulations call for batteries to be packaged in such a way that insulation between the battery’s terminals is maintained from the battery’s production site to its final destination (in the case of discrete battery packs). This includes providing protection against the risk of contact with conductive materials in the same packaging that could lead to a short circuit. In the case of equipment containing an embedded battery, the packaging must prevent accidental activation, for instance by insulating the battery’s terminals from the terminals on the equipment side. In detail, the regulations require a discrete battery to be packed in a container, such as a blister pack, which completely encloses it, so that it cannot be directly handled in transit. This pack must then be contained in a strong and robust outer packaging which minimises the risk of accidental damage, and of the inner package shifting under the influence of shock or vibration Equipment containing a lithium battery pack must be packed in strong and robust packaging that prevents damage to and movement of the battery (unless the equipment itself achieves this end). The battery, or equipment containing a battery, must be handled in production by operators trained in the requirements of the DGR, who can ensure that each unit is packed in accordance with the provisions of the DGR. The packaging and packing process employed must be tested to verify that it satisfies the requirements of the DGR. The outer package must be labelled clearly to show that the package contains lithium batteries, that it must be handled with care (see Figure 1), that the contents are flammable, that special measures must be taken if the package is damaged, and providing a telephone number to call for information about the package (see Figure 2). Implementing these rules ensures that the battery leaves the factory inactive, and remains so throughout its journey. Even Benno Diemer is Risk Prevention Manager at VARTA Microbattery - www.varta-microbattery.com 46 Electronic Engineering Times Europe June 2014 www.electronics-eetimes.com


EETE JUN 2014
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