Thomas Wagner, UL
As Business Manager Automotive at UL (Underwriters Laboratories), Thomas Wagner outlined new standards available or under development to ensure the fire safety of electric cars.
Testing is component based, and most parts in e-vehicles are the same as those in combustion engine vehicles, except for fuel systems replaced by batteries and high voltage charging and drive chains. UL94 V0 thus remains the main test for many materials, with other tests used for certain standards or certain applications, such as burning behaviour (FMVSS 302), GWFI Glow Wire Flammability Index, CTI comparative tracking index and IPT inclined plane tracking.
New developments underway include:
- Extension of FMVSS 302 beyond interior materials to cover e.g. electronic components and multi-materials components such a display screens
- Adaptation and extension of IPT to assess electrical performance under high voltages (up to 7 000 V), including electrical tracking resistance (amperage, tracking path length), burning, hole formation.
It is key to remember that UL and other organisations provide tests, but requirements (level of achievement in the test) are defined by component or vehicle manufacturers, as a function of their own fire safety or other performance specifications, or of industry or regulatory standards.
Battery fire testing
In discussion, it was noted that UL 2580 (resistance of battery to simulated abuse conditions, such as impacts or accidents) includes testing of battery resistance to an external fire. This standard, as well as SAE J2464 and SAE J2929 also address toxic and flammable emissions.
Ruiz et al. 2018 provide a detailed assessment of testing standards and regulations for e-vehicle battery abuse testing. This includes analysis of fire tests for battery cell, pack and whole vehicle. They conclude that, given the importance of toxic and flammable emissions, further standards work should be developed to define testing, guidance and protocols.
“A review of international abuse testing standards and regulations for lithium ion batteries in electric and hybrid electric vehicles”, V. Ruiz et al., Renewable and Sustainable Energy Reviews 81 (2018) 1427–1452, http://dx.doi.org/10.1016/j.rser.2017.05.195
Nicolas Dupont & Laurent Tribut
Electric vehicle charging poses specific fire and overheating risks, in particular fast charging stations, because of high power supply use without surveillance, especially for installations in humid atmospheres or outdoors.
A range of standards, not yet harmonised, specify electrical, design, mechanical and fire safety characteristics:
- IEC 61851, UL 2594, 2231, 2202, SAE J2293 for charging stations
- IEC 62196, UL 2251, SAE J1772 for charging plugs and sockets. These are more challenging, in particular for electrical properties.
Demanding material requirements include: electrical insulation and safety (e.g. dielectric strength, touch current, Proof Tracking Index PTI 175V), resistance to water, UV, impact, solvents (cleaning) and temperature, ageing for rubber seals and marking durability. Additionally, for sustainability reasons, Schneider Electric requires halogen-free materials and recycled materials when they are available.
Fire performance can be GWFI 650°C in IEC 61851, or UL94 V1, V2, FT2 to 5V, for different parts in UL 2594. UL94-V5 is a stringent rating asking for resistance to a 500W burner. In addition, UL 2202 requires flame spread rating < 200 for larger components (surface > 0.93 m2 or one dimension > 1.83) using UL 723 Steiner Tunnel or ASTM E162 radiant panel. IEC and UL requirements are different, but each of them constitutes an “ecosystem” with installation requirements, product standards and horizontal standards which have proven to be safe.
Schneider Electric – electrical car charging https://www .se.com/ww/en/product-category/1800-electrical-car-charging/