Electronics Production |
Testing lithium ion batteries essential to product safety
Manufacturers and suppliers of lithium ion cells and batteries can have their products thoroughly tested in a new test laboratory in Karlstein (Germany), which the batteryuniversity.eu with the support of BMZ Batterien-Montage-Zentrum has put into operation.
In the laboratory cells at 0 to 5 V with up to 10/120 A as well as batteries at 0 to 60 V with up to 200 A or to 12 kW can be tested. Furthermore, the batteryuniversity.eu can perform complete UN Transport Tests including specialist support in the event that a redesign of the battery packs is necessary with the issuance of expert reports and certificates required for the transport of lithium ion cells or batteries.
According to Sven Bauer, founder of batteryuniversity.eu and managing director of BMZ, it was decided to take this step, not least because of the significantly more stringent transport regulations for lithium ion cells and batteries that came into effect from January 1, 2009. Despite the well-known risks during transport and storage of lithium batteries, some manufacturers, suppliers and transport companies still consciously or unknowingly ignore the regulations. Sven Bauer considers this to be highly dangerous. “Lithium in powder or dust form can self ignite at around 20°C room temperature. Lithium as a solid material ignites in the air when the melting point of 179°C is reached; however, once this point is reached a metallic fire that can not be extinguished develops quickly with temperatures in excess of 2000°C.”
Sven Bauer adds that lithium also reacts intensively in contact with water. It does not sink, but rather floats on the water surface. This forms a highly inflammable hydrogen gas and highly caustic lithium hydroxide. Explosions in closed rooms could occur by ignition of the hydrogen. Furthermore, the water dissolves lithium hydroxide and takes on its caustic characteristics. “In addition to due caution in handling of this material, the only protection against these undesired effects are extensive test procedures, in which all possible transport risks are simulated in advance in the laboratory,” commented Sven Bauer.
Since 2003, all lithium cells and batteries, independent of the system and lithium content, must be tested according to special, mandatory safety standards. The accumulators may absolutely not be placed on the market without qualified proof of these tests.
Since the beginning of last year, numerous new regulations for the transport of lithium-based cells and batteries have to be observed. Not only that lithium cells and batteries are now generally classified as “Class 9 Hazardous Materials” (dangerous goods), but also the regulations for registration, packaging, labeling, handling and accompanying documents have to some extent changed significantly. For example, a distinction is now drawn between lithium ion and lithium metal batteries/cells. A decisive factor is also how and in what the respective cell or battery has been packed.
The complexity of the whole issue is shown by the fact that a total of six new UN shipping names with new numbers have been assigned for it: UN 3480 Lithium ion batteries (including lithium polymer batteries), UN 3481 Lithium ion batteries packed with equipment, UN 3481 Lithium ion batteries contained in equipment, UN 3090 Lithium metal batteries (including lithium alloy batteries), UN 3091 Lithium metal batteries packed with equipment and UN 3091 Lithium metal batteries contained in equipment.
General requirement for the approval of lithium cells and/or batteries for transport is, however, always proof of successful tests in accordance with the United Nations "Recommendations on the Transport of Dangerous Goods Manual of Test and Criteria" Part III, subsection 38.3. It is irrelevant whether possible exemptions can be exercised or the cells/batteries are classified as Class 9, and hence must adhere to the hazardous materials regulations in their entirety.
batteryuniversity.eu with the support of BMZ have so far invested around 1.2 million Euros in personnel and laboratory equipment in order to be able to fully perform all necessary UN Transport Tests for lithium cells and batteries. This investment would hardly ever pay off for companies that are not exclusively involved with the manufacture or assembly of battery packs. In addition, according to Sven Bauer; most of the persons concerned lack the necessary detailed technical knowledge for such tests. It is necessary to have many years of practical experience with different lithium ion technologies in order to assess the safety of battery packs. What happens when this knowledge is missing has been shown in a series of experimental test with third-party products. “More than 10 percent of the tested batteries did not conform to the current legal safety requirements. We are not only talking here about a fine of up to 50,000 Euros, which could be imposed if regulations are violated. In the event of damage, the responsible persons must also expect that they will be held accountable for substantial destruction of property, severe injury to any person or even, in the worst case, death.” Ultimately, for those not wanting to take this potential existence-threatening risk, there is no other alternative to the statutory complex test procedures, commented Sven Bauer.
Eight test procedures are compulsory for lithium cells and six test procedures for lithium batteries. 16 to 24 production-ready battery packs are required for the six test procedures, conducted in a certain sequence, on lithium batteries.
"Test T.1: Altitude simulation" is the first test. This test simulates air transport under low-pressure conditions. Test cells and batteries are stored at a pressure of 11.6 kPa or less for at least six hours at an ambient temperature of 20 ± 5°C. Cells and batteries meet this requirement (as is also the case for the second, third and fourth tests) if there is no mass loss, no leakage, no venting, no disassembly, no rupture and no fire and if the open circuit voltage of each test cell or battery after testing is not less than 90% of its voltage immediately prior to this procedure.
The second test "Test T.2: Thermal test" assesses cell and battery seal integrity and internal electrical connections. The test is conducted using rapid and extreme temperature changes. Test cells and batteries are stored for at least six hours at a test temperature equal to 75 ± 2°C, followed by storage for at least six hours at a test temperature equal to -40 ± 2°C.
The maximum time interval between test temperature extremes is 30 minutes. This procedure is repeated 10 times, after which all test cells and batteries are stored for 24 hours at ambient temperature of 20 ± 5°C. For large cells and batteries the duration of exposure to the test temperature extremes should be at least 12 hours.
"Test T.3: Vibration" is the third test and simulates vibration during transport. Cells and batteries are firmly secured to the platform of the vibration machine. The vibration is a sinusoidal waveform with a logarithmic sweep between 7 Hz and 200 Hz and back to 7 Hz traversed in 15 minutes. This cycle is repeated 12 times for a total of 3 hours for each of three mutually perpendicular mounting positions of the cell.
A particular challenge, especially for large battery packs, is "Test T.4: Shock", which simulates possible impacts during transport. Test cells and batteries are secured to the testing machine by means of a rigid mount which support all mounting surfaces of each test battery. Each cell or battery is subjected to a halfsine shock of peak acceleration of 150 gn and pulse duration of 6 milliseconds. Each cell or battery is subjected to a total of 18 shocks from different directions. However, large cells and large batteries are subjected to peak acceleration of 50 gn and pulse duration of 11 milliseconds.
Special safety measures are required for "Test T.5: External short circuit". The cell or battery to be tested is temperature stabilized so that its external case temperature reaches 55 ± 2°C and then the cell or battery is subjected to a short circuit condition with a total external resistance of less than 0.1 ohm. Cells and batteries meet this requirement if - during the at least one hour short circuit condition and further six hours observation - their external temperature does not exceed 170 °C and there is no disassembly, no rupture and no fire.
"Test T.7: Overcharge", evaluates the ability of a rechargeable battery to withstand an overcharge condition. Eight packs are overcharged with twice the manufacturer's recommended maximum continuous charge current and 1.2 (packs <18V) to 2 times the recommended charge voltage or 22V (packs >18V) for 24 hours and then observed for a further seven days. The long observation period is intended to prevent that with batteries overcharged some time before transportation, later in the case of internal short circuits in the cells fire breaks out.
Lithium battery packs are only approved for transport after proof of having passed these six test procedures. Lithium cells must pass additional tests as follows: "Test T.6: Impact" and "Test T.8: Forced discharge".
Special provisions in the regulations provide "exceptions" or "eased transportation" for lithium ion battery packs with a rating of not more than 100 Wh or cells of not more than 20 Wh and lithium metal battery packs with a lithium content of no more than 2 grams or cells with no more than 1 gram. Subject to compliance with Special Provisions 188 and 230 of ADR/RID, ADNR, IMDG Code and Packing Instructions 965 - 970, Part 2 of IATA Dangerous Goods Regulations, transportation of these lithium cells and batteries is not subject to other rules and regulations.
In order to be authorized for "eased transportation" - in other words, without having to fully comply with the dangerous goods regulations - packages must be labeled with a special label including e.g. an emergency telephone number. Each consignment must be accompanied with a document with an indication that the package contains lithium ion or lithium metal cells or batteries, a flammability hazard exists if the package is damaged and special procedures should be followed in the event the package is damaged, to include inspection and repacking if necessary.
If the thresholds of 20 Wh/100 Wh or 1 g/2 g lithium content are exceeded, the lithium ion cells and batteries must always be transported as dangerous goods of Class 9, Packing Group II in compliance with the packaging standards.
Sven Bauer sums it up in this way: “100% safety for the transport of lithium ion battery packs can never be achieved. However, with our test laboratory we have at least created conditions to come as close as possible to this goal.”
According to Sven Bauer, founder of batteryuniversity.eu and managing director of BMZ, it was decided to take this step, not least because of the significantly more stringent transport regulations for lithium ion cells and batteries that came into effect from January 1, 2009. Despite the well-known risks during transport and storage of lithium batteries, some manufacturers, suppliers and transport companies still consciously or unknowingly ignore the regulations. Sven Bauer considers this to be highly dangerous. “Lithium in powder or dust form can self ignite at around 20°C room temperature. Lithium as a solid material ignites in the air when the melting point of 179°C is reached; however, once this point is reached a metallic fire that can not be extinguished develops quickly with temperatures in excess of 2000°C.”
Sven Bauer adds that lithium also reacts intensively in contact with water. It does not sink, but rather floats on the water surface. This forms a highly inflammable hydrogen gas and highly caustic lithium hydroxide. Explosions in closed rooms could occur by ignition of the hydrogen. Furthermore, the water dissolves lithium hydroxide and takes on its caustic characteristics. “In addition to due caution in handling of this material, the only protection against these undesired effects are extensive test procedures, in which all possible transport risks are simulated in advance in the laboratory,” commented Sven Bauer.
Since 2003, all lithium cells and batteries, independent of the system and lithium content, must be tested according to special, mandatory safety standards. The accumulators may absolutely not be placed on the market without qualified proof of these tests.
Since the beginning of last year, numerous new regulations for the transport of lithium-based cells and batteries have to be observed. Not only that lithium cells and batteries are now generally classified as “Class 9 Hazardous Materials” (dangerous goods), but also the regulations for registration, packaging, labeling, handling and accompanying documents have to some extent changed significantly. For example, a distinction is now drawn between lithium ion and lithium metal batteries/cells. A decisive factor is also how and in what the respective cell or battery has been packed.
The complexity of the whole issue is shown by the fact that a total of six new UN shipping names with new numbers have been assigned for it: UN 3480 Lithium ion batteries (including lithium polymer batteries), UN 3481 Lithium ion batteries packed with equipment, UN 3481 Lithium ion batteries contained in equipment, UN 3090 Lithium metal batteries (including lithium alloy batteries), UN 3091 Lithium metal batteries packed with equipment and UN 3091 Lithium metal batteries contained in equipment.
General requirement for the approval of lithium cells and/or batteries for transport is, however, always proof of successful tests in accordance with the United Nations "Recommendations on the Transport of Dangerous Goods Manual of Test and Criteria" Part III, subsection 38.3. It is irrelevant whether possible exemptions can be exercised or the cells/batteries are classified as Class 9, and hence must adhere to the hazardous materials regulations in their entirety.
batteryuniversity.eu with the support of BMZ have so far invested around 1.2 million Euros in personnel and laboratory equipment in order to be able to fully perform all necessary UN Transport Tests for lithium cells and batteries. This investment would hardly ever pay off for companies that are not exclusively involved with the manufacture or assembly of battery packs. In addition, according to Sven Bauer; most of the persons concerned lack the necessary detailed technical knowledge for such tests. It is necessary to have many years of practical experience with different lithium ion technologies in order to assess the safety of battery packs. What happens when this knowledge is missing has been shown in a series of experimental test with third-party products. “More than 10 percent of the tested batteries did not conform to the current legal safety requirements. We are not only talking here about a fine of up to 50,000 Euros, which could be imposed if regulations are violated. In the event of damage, the responsible persons must also expect that they will be held accountable for substantial destruction of property, severe injury to any person or even, in the worst case, death.” Ultimately, for those not wanting to take this potential existence-threatening risk, there is no other alternative to the statutory complex test procedures, commented Sven Bauer.
Eight test procedures are compulsory for lithium cells and six test procedures for lithium batteries. 16 to 24 production-ready battery packs are required for the six test procedures, conducted in a certain sequence, on lithium batteries.
"Test T.1: Altitude simulation" is the first test. This test simulates air transport under low-pressure conditions. Test cells and batteries are stored at a pressure of 11.6 kPa or less for at least six hours at an ambient temperature of 20 ± 5°C. Cells and batteries meet this requirement (as is also the case for the second, third and fourth tests) if there is no mass loss, no leakage, no venting, no disassembly, no rupture and no fire and if the open circuit voltage of each test cell or battery after testing is not less than 90% of its voltage immediately prior to this procedure.
The second test "Test T.2: Thermal test" assesses cell and battery seal integrity and internal electrical connections. The test is conducted using rapid and extreme temperature changes. Test cells and batteries are stored for at least six hours at a test temperature equal to 75 ± 2°C, followed by storage for at least six hours at a test temperature equal to -40 ± 2°C.
The maximum time interval between test temperature extremes is 30 minutes. This procedure is repeated 10 times, after which all test cells and batteries are stored for 24 hours at ambient temperature of 20 ± 5°C. For large cells and batteries the duration of exposure to the test temperature extremes should be at least 12 hours.
"Test T.3: Vibration" is the third test and simulates vibration during transport. Cells and batteries are firmly secured to the platform of the vibration machine. The vibration is a sinusoidal waveform with a logarithmic sweep between 7 Hz and 200 Hz and back to 7 Hz traversed in 15 minutes. This cycle is repeated 12 times for a total of 3 hours for each of three mutually perpendicular mounting positions of the cell.
A particular challenge, especially for large battery packs, is "Test T.4: Shock", which simulates possible impacts during transport. Test cells and batteries are secured to the testing machine by means of a rigid mount which support all mounting surfaces of each test battery. Each cell or battery is subjected to a halfsine shock of peak acceleration of 150 gn and pulse duration of 6 milliseconds. Each cell or battery is subjected to a total of 18 shocks from different directions. However, large cells and large batteries are subjected to peak acceleration of 50 gn and pulse duration of 11 milliseconds.
Special safety measures are required for "Test T.5: External short circuit". The cell or battery to be tested is temperature stabilized so that its external case temperature reaches 55 ± 2°C and then the cell or battery is subjected to a short circuit condition with a total external resistance of less than 0.1 ohm. Cells and batteries meet this requirement if - during the at least one hour short circuit condition and further six hours observation - their external temperature does not exceed 170 °C and there is no disassembly, no rupture and no fire.
"Test T.7: Overcharge", evaluates the ability of a rechargeable battery to withstand an overcharge condition. Eight packs are overcharged with twice the manufacturer's recommended maximum continuous charge current and 1.2 (packs <18V) to 2 times the recommended charge voltage or 22V (packs >18V) for 24 hours and then observed for a further seven days. The long observation period is intended to prevent that with batteries overcharged some time before transportation, later in the case of internal short circuits in the cells fire breaks out.
Lithium battery packs are only approved for transport after proof of having passed these six test procedures. Lithium cells must pass additional tests as follows: "Test T.6: Impact" and "Test T.8: Forced discharge".
Special provisions in the regulations provide "exceptions" or "eased transportation" for lithium ion battery packs with a rating of not more than 100 Wh or cells of not more than 20 Wh and lithium metal battery packs with a lithium content of no more than 2 grams or cells with no more than 1 gram. Subject to compliance with Special Provisions 188 and 230 of ADR/RID, ADNR, IMDG Code and Packing Instructions 965 - 970, Part 2 of IATA Dangerous Goods Regulations, transportation of these lithium cells and batteries is not subject to other rules and regulations.
In order to be authorized for "eased transportation" - in other words, without having to fully comply with the dangerous goods regulations - packages must be labeled with a special label including e.g. an emergency telephone number. Each consignment must be accompanied with a document with an indication that the package contains lithium ion or lithium metal cells or batteries, a flammability hazard exists if the package is damaged and special procedures should be followed in the event the package is damaged, to include inspection and repacking if necessary.
If the thresholds of 20 Wh/100 Wh or 1 g/2 g lithium content are exceeded, the lithium ion cells and batteries must always be transported as dangerous goods of Class 9, Packing Group II in compliance with the packaging standards.
Sven Bauer sums it up in this way: “100% safety for the transport of lithium ion battery packs can never be achieved. However, with our test laboratory we have at least created conditions to come as close as possible to this goal.”
