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As these regulations have become more stringent, battery manufacturers, vehicle manufacturers, and battery testing laboratories need to be familiar with these standards and test procedures in regard to LI batteries. Today, there is a wide range of safety standards for LIBs associated with operational and environmental aspects, referring to voltage, temperatures, and mechanical damage that can cause problems safety problems with LIBs. The international standard for electrical, mechanical, environmental, and abuse tests is the UN 38.3 that combines several transportation tests. An important EU and Japan standard for LI-batteries is the ECE R100 Rev.2, for the US there is the UL 2580 standard.
Some of the most important standards and the related test and measurement procedures are pointed out and – in part - discussed here:
- ECE R100 | Type testing
- Vibration test
- Heat shock and cycle test
- Vibration and mechanical integrity
- Fire resistance
- External short circuit protection
- Overcharge protection
- Protection against excessive discharge
- Overheating protection
Batteries classified by the United Nations as Class 9 dangerous goods must meet the requirements necessary for the safe transport of lithium cells and batteries (by air, sea and land). This standard, which is recognised by regulatory and customs authorities around the world, is also seen as an important gateway to access global markets. From a technical perspective, UN 38.3 testing can be carried out at cell, module or pack level and is a combination of rigorous mechanical, electrical and, most importantly, environmental testing to assess the stability of a battery during transport.
As Lithium-ion batteries are used in a wide range of battery-powered devices, they can, when improperly designed, present different hazards. Therefore, testing the safety and performance of lithium batteries to standards such as UN 38.3 is of enormous importance to ensure that they are safe for battery transport so that they can legally enter foreign markets.
The test criteria include eight tests (T1 – T8) that all focus on specific transportation hazards.
UN 38.3 testing for the shipment and transport of batteries:
- Height simulation
- Thermal test
- External short circuit
- Impact test
- Overload test
- Forced discharge
Many of the LIBs’ safety concerns are because the devices are voltage and temperature sensitive.
The UL 2580 is the US standard for safety for batteries for use in electric vehicles. It is comprised of several tests, three are pointed out here, to name just a few for better understanding.
Large current battery short circuit:
Operation with fully charged samples. The sample is short-circuited with a total circuit resistance ≤ 20 mΩ. Spark ignition detects the presence of flammable gas concentrations in the sample and there must be no signs of explosion or fire. In addition, the vapours escape to the outside only through the ventilation openings or systems provided for this purpose. There is no rupture of the housing and no visible signs of electrolyte leakage. If the LIB remains functional after the short circuit test, it is subjected to a charge and discharge cycle according to the manufacturer's specifications. Short circuit tests can be performed on sub-assemblies instead of a whole electrical energy storage assembly (EESA).
is performed on fully charged samples and simulates the effects of a vehicle impact on the integrity of the EESA. As with the short circuit test, spark ignition is used to determine the presence of flammable gas concentrations inside the sample, and there must be no evidence of explosion or fire. No toxic gas is released.
Battery cell crush (vertical):
performed on fully charged samples. The force applied in the crush test shall be limited to 1000 times the battery weight. As in the squeeze test, spark ignition is used to determine the presence of flammable gas concentrations inside the sample and there shall be no evidence of explosion or fire. No toxic gas is released.
Safety criteria for electric vehicle (EV) traction batteries will be considered differently, and each OEM will have its own approach tailored to its vehicle platform. Nevertheless, two goals are fundamental to all efforts:
- The failure rate of cells leading to thermal runaway must become extremely rare.
- The propagation of thermal runaway from cell to cell, leading to cascading failure of a battery module or pack, must not be allowed.
Efforts have been made in the past to trade battery safety for lower energy. The aim of this roadmap is to identify opportunities, where high energy and safety can be achieved simultaneously. If this, for example, is a priority in research and development (R&D), this will enable the development of cells and batteries that provide long-range and sufficient safety for use in electric vehicles.
Author: Rolf Spellmeyer, Business Development Expert E-Mobility
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