Carriage and shipment of some kinds of lithium batteries may be prohibited aboard certain types of transportation (particularly aircraft) because of the ability of most types of lithium batteries to fully discharge very rapidly when short-circuited, leading to overheating and possible explosion in a process called thermal runaway. Most consumer lithium batteries have built-in thermal overload protection to prevent this type of incident, or are otherwise designed to limit short-circuit currents. Internal shorts from manufacturing defect or physical damage can lead to spontaneous thermal runaway.
The maximum size of each battery (whether installed in a device or as spare batteries) that can be carried is one that has an equivalent lithium content (ELC) not exceeding 8 grams per battery. Except, that if only one or two batteries are carried, each may have an ELC of up to 25 g The ELC for any battery is found by multiplying the ampere-hour capacity of each cell by 0.3 and then multiplying the result by the number of cells in the battery. The resultant calculated lithium content is not the actual lithium content but a theoretical figure solely for transportation purposes. When shipping lithium ion batteries however, if the total lithium content in the cell exceeds 1.5 g, the package must be marked as “Class 9 miscellaneous hazardous material”.
Although devices containing lithium-ion batteries may be transported in checked baggage, spare batteries may be only transported in carry-on baggage. They must be protected against short circuiting, and example tips are provided in the transport regulations on safe packaging and carriage; e.g., such batteries should be in their original protective packaging or, “by taping over the exposed terminals or placing each battery in a separate plastic bag or protective pouch”. These restrictions do not apply to a lithium-ion battery that is a part of a wheelchair or mobility aid (including any spare batteries) to which a separate set of rules and regulations apply.
Some postal administrations restrict air shipping (including EMS) of lithium and lithium-ion batteries, either separately or installed in equipment. Such restrictions apply in Hong Kong, Australia and Japan. IATA provides details in its Lithium Battery Guidance document.
On 16 May 2012, the United States Postal Service (USPS) banned shipping anything containing a lithium battery to an overseas address, after fires from transport of batteries. This restriction made it difficult to send anything containing lithium batteries to military personnel overseas, as the USPS was the only method of shipment to these addresses; the ban was lifted on 15 November 2012. United Airlines and Delta Air Lines excluded lithium-ion batteries in 2015 after an FAA report on chain reactions.
Starting on 15 January 2018, several major U.S. airlines banned smart luggage with non-removable batteries from being checked in to travel in the cargo hold due to the risk of fire. Some airlines continued to mistakenly prevent passengers from bringing smart luggage as a carry on after the ban went into effect.
Several smart luggage companies have been forced to shut down as a result of the ban.