Feature: Batteries
the crystalline structure of the battery’s cathode and can ignite its electrolyte. Meanwhile, charging at low
temperatures can lead to metallic plating, creating instability through short circuits. When these individual cells are connected in series or parallel combinations, the resulting modules deliver increased voltage and capacity. Although the individual cells are now mechanically “protected” within an enclosure, care must be taken due the potentially high voltages and currents. For EVs, large battery packs connect
to the vehicle’s electric powertrain. Tese packs are constructed by connecting modules together, adding sensors and a battery management system. Tey deliver an extremely high voltage and can be moulded to fit the host vehicle. Safety tips for module and pack designs
include: • Use physical partitions and fire breaks to minimise fire propagation;
• Use good thermal management; • Use pressure vents and relief mechanisms to safely deal with excessive pressures;
• Utilise sensors and a battery management system to identify abnormal behaviours;
• Use materials appropriate for the temperatures;
• Use constructions with adequate mechanical strength appropriate to the real world.
Risk management EV batteries present many electrical hazards: electric shock, arc flash burn, heatwave/fire burns and explosion, which could include shrapnel and molten metal. Of course, because of the energy requirements of EVs, high-voltage/ high-capacity battery packs are needed. Depending on the configuration, battery modules can be high voltage (> 50Vdc), therefore presenting an electric shock and energy hazard, and vehicle battery packs will certainly present both. It is therefore essential that people working with high voltage systems are aware of the potential dangers and protective measures. Tis applies to all employees – mechanics and technicians, cleaning staff, office workers and vehicle owners – anyone who might come into contact with the vehicles.
As the global demand for innovation
in EVs increases, so the need for qualified testing of lithium-ion batteries to power EVs and education about their use and care will also continue to grow.
Safety improvements Comparatively lightweight, long-lasting and with good performance, Li-ion batteries have proven invaluable in EV development. Improvements in design, materials, construction and manufacturing processes means that the safety of this type batteries has dramatically improved. However, ensuring their safety and reliability requires thorough and accurate testing, which includes: • Life cycle testing – verifying how long a battery lasts and to demonstrate the quality of the battery. Tese tests include environmental cycle testing and calendar life testing.
• Performance testing – which demonstrates the efficiency of batteries, such as performance testing under various climatic conditions.
• Environmental and durability testing – which demonstrates the quality and reliability of a battery through tests including vibration, shock, EMC, thermal cycling, corrosion, dust, salt and humidity.
• Abuse testing – which simulates extreme environmental conditions and scenarios that test batteries beyond their limits.
• Dynamic impact tests – which simulates a vehicle accident to determine the true safety performance of the battery when the car body is deformed.
• Transportation tests – UN 38.3 is a series of tests to verify the robustness of batteries against conditions encountered in shipment.
Global regulations Te creation of global standards for motor vehicles, including electric vehicles and rechargeable electrical energy storage systems (REESS), falls under the purview of the World Forum for the Harmonization Vehicle Regulations. Tis is a permanent working party of the Transport Division of the United
Nations Economic Commission for Europe (UNECE). Its primary objective is to establish globally-harmonised regulations, to remove international trade barriers, promote road safety and protect the environment. In the US, manufacturers must meet the Federal Motor Vehicle Safety Standards. UNECE Regulation No. 100 is officially
titled “Uniform provisions concerning the approval of vehicles regarding specific requirements for the electric power train”. Also referred to as R100, this regulation addresses the safety requirements specific to the electric power train of road vehicles, as well as those high-voltage components and systems that are “galvanically connected” to the high-voltage bus of the electric power train. Revision three of R100 will impose
several updated and new requirements designed for use in motor vehicles manufactured, sold or operated in the European Union and other countries. Tis includes a new overcurrent test, adjusted requirements at SoC level, as well as new requirements relating to thermal propagation. All of these are intended to ensure the integrity and safe operation of such systems under anticipated operating conditions, as well as to provide a higher level of safety for vehicle drivers and passengers. Although these additional requirements will increase the compliance burden for battery manufacturers, it will also ease the acceptance and use of battery packs with type approval, thereby broadening the market for manufacturers. Tere’s no doubt that EV battery
technology has developed apace but, nonetheless, for industry to deliver this transition effectively and on time will require significant effort from all involved. Tere are still major challenges faced by EV battery manufacturers and by the entire EV industry, but there are countless innovation opportunities. Of course, battery safety and testing must be a key consideration, with the need for longer range, reduced charging times and minimised battery degradation driving innovative designs and developments. Tis will make EV battery specifications and compliance ever more critical.
www.electronicsworld.co.uk June 2024 47
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