The heat is on for battery transportation
Last year, the FAA (Federal Aviation Administration) in the USA issued a safety alert a month after UPS flight 006 crashed in Dubai.
In a statement, the FAA acknowledges that the plane’s cargo included large quantities of lithium batteries and that it believed it was prudent to advise operators of that fact.
Its safety alert recommended that airlines adopt new procedures to reduce the risk of onboard fire posed by lithium batteries. This included asking customers to identify bulk shipment on airway bills and store such items in ‘class C’ cargo compartments.
Lithium-ion does have a reputation for volatility. Evidence, including that from the FAA and negative stories in the press, is making transport companies such as couriers, airlines and cargo handlers, increasingly nervous about carrying lithium-ion batteries. However, new regulations, which cover transport by air, land and sea, are now in place to combat the industry’s concerns.
Testing to minimise hazards
The United Nations (UN) Manual of Tests and Criteria contains test methods and procedures to be used for the classification of dangerous goods according to the provisions of the UN’s Recommendations on the Transport of Dangerous Goods.
The fifth revised edition came into effect last year (2010) and includes a revised sub-section UN38.3. This contains the revised provisions for the testing and classification of lithium metal and lithium-ion batteries and was required as the use of lithium-ion batteries is becoming widespread in many technologies today. The Fifth Edition also covers larger batteries and cells to accommodate the increasing prevalence of electric vehicles and their power packs.
The provisions are used as the basis for transportation companies to accept batteries, and customs officials will check that the battery manufacturer’s self-declaration meets the requirement of UN38.3. However, with such a complex set of requirements, manufacturers often call on third-party specialists to verify compliance.
The rules of engagement
The tests must be conducted for each battery type prior to shipment and involve tests in various states of charge (discharged, charged, first charge cycle, 50th charge cycle). In all, eight tests are available, five of which are mandatory and apply to all cells and batteries, and three are dependent on whether a cell, battery or a rechargeable battery is being tested. Tests must be completed in a defined order, primarily as this creates a method for ageing the battery to replicate its real lifetime usage
Unlike most other standards and regulations that relate to product testing, the Fifth Edition requires that the test sequence must be repeated from the start if any of the five mandatory test phases are non-compliant. Not only does the product need ageing correctly, it could be that if you fix one problem, there is no assurance as to how that adaption will affect the results of the other tests within the test sequence.
So the entire test process needs to go back to square one, if a product fails any of the five mandatory test stages, and the manufacturer will have to provide new samples, as well as pay for tests to be re-conducted. This not only costs extra, it will also delay time to market for new products and could seriously impact a manufacturer’s profitability.
The UN Manual of Tests and Criteria was first introduced in 1984 and, since then, has been amended every two years. A common misconception has been that it is only the cell that needs to be tested. However, it has always been the case that both the cell and battery pack must be included in the tests unless otherwise stated in the UN Manual. In all cases, the test stage is passed if there is no change to the cell or battery’s integrity such as leakage, decomposition or explosion, usually over an extended period following the test. The following tests must be performed:
Test 1 – Altitude simulation
Simulates air transportation under low pressure conditions. During the test the battery is stored at 11.6K kPa or less for six hours at ambient temperature.
Test 2 - Thermal test
Assesses the cell and battery seal integrity and internal electrical connections using thermal cycling to simulate rapid and extreme temperature changes. The test requires 10 cycles between +75oC and -40oC, six hours per cycle with no more than 30 minutes between cycles, and then being observed for 24 hours at ambient temperature.
Test 3 – Vibration
Simulates vibration that the product may be subjected to during transportation and uses a sinusoidal waveform with a logarithmic sweep from 7 to 200 Hz and back over 15 minutes. The cycle must be repeated 12 times for a total of three hours in each of three perpendicular mounting positions of the cell or battery.
Test 4 – Shock
Imitates possible shock during transportation, with different test requirements according to the size of cells or batteries. The test includes a half-sine shock of peak acceleration of 150g and pulse duration of six milliseconds for small batteries. Each cell or battery is also subjected to three shocks in the positive and three in the negative direction of the three perpendicular mounting positions - a total of 18 shocks.
Test 5 – External short circuit
Once stabilised at 55oC, the battery is subjected to an external short circuit with an external resistance of less than 0.1 ohm for one hour and is then observed for six hours.
Test 6 – Impact
Replicates the kind of impact that might be expected in transportation and is only applicable to cells and not batteries. The test involves a 9.1kg mass being dropped from a height of 61cm onto a bar across the cell. The cell is then observed for six hours.
Test 7 – Overcharge
Evaluates how a rechargeable battery withstands overcharge. It is charged at twice the manufacturer’s recommended maximum continuous charge current for 24 hours and then observed for seven days.
Test 8 - Forced discharge
The test evaluates cells’ ability to withstand a forced discharge at an initial current equal to the maximum discharge current specified by the manufacturer, and then being observed for seven days.
Packaging correctly
In order to identify potential transportation hazards, the Manual of Tests and Criteria divides dangerous goods into nine classes. Class 9 defines the packaging specification, markings, labelling, and shipping documentation requirements for lithium-ion cells and batteries that have a watt hour rating of more than 20Wh for cells or 100Wh for batteries. These products are required to have a safety vent and be packed in class II packaging (Class II packaging is classified as for medium danger substances with 1 being high danger and III low danger).
Lithium-ion cells and batteries that have a watt hour rating less than 20Wh or 100Wh respectively are exempt from these Dangerous Goods regulations. However, specific requirements for how they are packaged and documented remain, and the lithium ion cell or battery still needs to meet section 38.3.
The standard requires not only that the battery be tested, but its packaging as well. Such tests include drop, stacking and topple tests to ensure safety during transportation. The standard requires that the packaging must be of good quality, be compatible with its contents and able to withstand the normal conditions of transport. Most packaging is also required to meet specific performance tests dependent on the design-type of the packaging.
Batteries under 100Wh, for example, are required to be:
· Packed in strong outer packaging with the maximum weight of the packaged batteries not being more than 10kg when transported on aircraft.
· Completely enclosed by the inner packaging. Each package must also be able to withstand a 1.2 metre drop test without any damage to the battery and without shifting or release of the contents.
If batteries are prototypes or have been produced in low volumes, they do not need to be tested to section 38.3, but more stringent packaging requirements are still required and there will be a limit to the amount that can be shipped. If manufacturers do get their products and packaging tested successfully, however, they will gain economies of scale from shipping in larger volumes.
All lithium-ion batteries, whether they are considered dangerous goods or not, have strict labelling and documentation requirements. These are quite complex and include very specific requirements such as making it clear what the contents are, handling advice, procedures, should the packaging be damaged, and contact details of the manufacturer.
Packages must be marked with:
· Consignee name and address;
· Correct shipping name;
· Details about any handling requirements;
· Shippers name and address;
· UN number;
· UN packaging specification, and
· What the contents are – each package must therefore have a lithium-ion battery handling label.
Lithium-ion batteries listed as dangerous goods must also be accompanied by a Dangerous Goods Transport Document. This is a declaration that the consignment a transport company is being asked to convey complies with the safety regulations.
Although lithium-ion batteries are found in a growing number of applications, we must never forget that, while this chemistry provides great advantages, it can also be quite volatile and should be treated with respect. As more lithium-ion batteries are transported across air, sea and land, UN38.3 will help the industry to ensure that such volatile goods remain safe. The existence and use of the standard should also reduce the bad press that sometimes has both consumers and manufacturers questioning the long-term viability of lithium-ion batteries.
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