Battery tech for heavy-duty apps | Focus 39 Another benefit of having a modular battery pack mounted on the rear of the chassis is that it can improve weight distribution. With a more evenly distributed weight between the front and rear axles, the truck can provide more stable and predictable handling, particularly at high speeds or in adverse weather conditions. In cold weather, charging times can increase due to the lower efficiency of the battery, but a modular pack can be charged separately and then added to the main pack, reducing this and improving the overall efficiency of the EV. It can also include a built-in battery heater to warm it before use. The modular system can be easily scaled up or down, allowing customers to add or remove battery modules as their needs change. This can be valuable for commercial EVs, as it allows for the addition of capacity if the vehicle is used for longer trips or heavier loads. MW charging connectors The latest standard for megawatt charging connectors focuses on Class 6, 7 and 8 commercial vehicles, but could easily be used for buses, aircraft or other large battery electric vehicles (BEVs) with huge battery packs and the ability to accept a charge rate over 1 MW. The Megawatt Charging System (MCS) uses a single, conductive plug that supports up to 1250 V and 3000 A, and it is bidirectional, allowing vehicleto-grid (V2G) connections. The positioning of the connector on a truck is key, and this has been specified on the left side at roughly hip height, and it can be automated. A survey among vehicle manufacturers within the MCS subgroup resulted in inlet positions of between 2 m and 4.8 m, measured from the front of the vehicle. While heavy-duty equipment has large battery systems and needs high power chargers, the stress on the pack is not necessarily significant. For example, the latest electric buses have eight batteries with 880 kWh of storage, but with an 800 kW or megawatt charger that is a 1 C-Rate, which is low. By comparison, a car with an 80 kWh battery pack on a 350 kW charger has a 4.4 C-Rate. Fast chargers can be used with LFP and NMC heavy-duty packs, but have been more suitable for LTO chemistries, with higher power packs for tractors and construction equipment, which can support 10-40 C-Rates. MCS also offers more robust communication, reducing downtime related to charging failure. Commercial vehicles have specific driving patterns with mandated break times. These regulations state that drivers must take a break on occasion during their drive cycle; the exact time varies by location, but the aim is to fit the charging times into normal breaks in the duty cycle. Accessibility also has to be considered when installing MCS chargers in public infrastructure as they need to be accessible by large commercial vehicles requiring drive-through. The communication topology is an important part of the MCS specification. Following the OSI seven-layer model, one important part of the work involves defining a physical communication layer. Charging systems deployed around the world presently use physical layers with differing technologies, each with their own pros and cons. The physical layer of MCS natively supports TCP/IP-based communications to implement the ISO 15118 communication standard easily without the need of additional, complex middleware. ISO 15118 is the well-established standard, with many subgroups working on different implementation details. ISO 15118-2 has been in use throughout the charging industry for many years, but it has some limitations due to inconsistent interpretation and implementation. Other DIN and SAE protocols have also been used for years, but they have even more limitations. This has led to ISO 15118-20, which has been in use since 2022 as a complete and robust, globally available protocol. The maximum temperature limit of the pin/socket contacts for MCS is set to 100 C due to the following reasons: adequate testing results show that even at 100 C contact temperature, the permissible surface temperatures defined in IEC 62196 and UL2251 are maintained; increased ageing is less of a concern with the materials and surface treatments available now; and the E-Mobility Engineering | July/August 2024 The positioning of the charging system is key (Image courtesy of Freudenberg)
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