Automotive
Driving the EV revolution T
By Marcus Sampson, business line manager for transport at TÜV SÜD, a global product testing and certification organisation
he battery management system on an EV consists of both hardware and software elements, which contribute to vehicle safety and performance. The hardware generally includes current sensing capabilities for state of charge (SoC) estimation and for safety. It must also detect leakage current faults, which could render the vehicle chassis “live” and therefore highly dangerous, if not lethal. Effective fusing will also provide overcurrent protection. A pre-charge element should be incorporated to energise circuits via current limiting components to minimise inrush currents. Relays and contactors will also provide safe and reliable connection/ disconnection to and from the vehicle. The software element of the battery management system provides the interface and communications to the vehicle (CAN bus). The incorporation of diagnostics and health software monitors SoC (under/over charge), which is important for control, safety and vehicle range estimation. State- of-health functions will also determine battery degradation over time and predict end of usable life. The software delivers control over the battery’s function, including electrical isolation, thermal management, charge/discharge and cell balancing. 5G will also be a driver of smart battery maintenance, using ‘Data Over the Air’ and ‘Software Over the Air’. This means that real-time data can be used to optimise battery charging and discharging, and support predictive maintenance and failures, as well as remote troubleshooting. On the fly software updates will deal with battery ageing and extreme operating conditions, such as hot or cold environments.
Battery design
Single battery cells typically come in three package styles, cylindrical, prismatic and pouch and can be particularly sensitive to mishandling, inappropriate packaging, deformation and contamination. They can also fail due to overcharging and extreme temperatures. Repeated overcharging of a battery cell can create unwanted electrical
16 February 2024
of lithium-ion batteries to power EVs, and education about their use and care, will also continue to grow.
Safety improvements Improvements in design, materials, construction, and manufacturing processes means that the safety of Li-ion has dramatically improved. However, ensuring their safety and reliability requires thorough and accurate testing, which includes:
Life cycle testing - verifies how long a battery lasts and demonstrates the quality of the battery. These tests include environmental cycle testing and calendar life testing.
Performance testing - demonstrates the efficiency of batteries, such as performance testing under various climatic conditions.
paths, as well as short circuits that grow and create instability. High temperatures can drive excessive ionic flow which damages the crystalline structure of the cathode and can ignite electrolyte. Meanwhile, charging at low temperatures can lead to metallic plating, creating instability through short circuits. When these individual cells are connected in series / parallel combinations (depending on end use requirements) the resulting modules deliver increased voltage and capacity. Although the individual cells are now mechanically “protected” with a mechanical support / enclosure, care must be taken due the potentially high voltages and high currents presented.
For EVs, large battery packs connect to the vehicle’s electric powertrain. These packs are constructed by connecting modules together, adding sensors and a battery management system. They deliver an extremely high voltage and can be moulded to fit the host vehicle and may also form part of its structure.
Safety tips for module and pack designs include: Use physical partitions and fire breaks to minimise fire propagation
Components in Electronics
Employ good thermal management Use pressure vents / relief mechanisms to safely deal with excessive pressures
Utilise sensors and a battery management system to identify abnormal behaviours
Use materials appropriate for foreseeable temperatures
Use constructions with adequate mechanical strength appropriate for the real world
Risk management
Batteries used in EVs present many electrical hazards, such as electric shock, arc flash burn, heatwave/fire burns and explosion. Of course, because of the energy requirements to power EVs, high voltage / high-capacity battery packs are needed.
It is therefore essential that people working with high voltage systems are aware of the potential dangers and protective measures. This applies to all employees - mechanics and technicians, cleaning staff, office workers, and vehicle owners - anyone who might come into contact with the vehicles. So, this is a real game changer for the EV market. As the global demand for innovation in EVs increases, so the need for qualified testing
Environmental and durability testing - demonstrates the quality and reliability of a battery through tests including vibration, shock, EMC, thermal cycling, corrosion, dust, salt and humidity.
Abuse testing - simulates extreme environmental conditions and scenarios to test batteries beyond limits.
Dynamic impact tests - simulates a real 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.
There’s no doubt that EV battery technology has developed at pace but nonetheless the requirements of industry to deliver this transition effectively and on time will require significant effort from all involved. There are still major challenges faced by EV battery manufacturers, but there are countless innovation opportunities. Of course, battery safety and testing must be a key consideration, making battery specifications and compliance ever more critical.
https://www.tuvsud.com/en-us/services/ testing/battery
www.cieonline.co.uk.uk
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