E-Mobility Engineering 015 l EMotive Scarab off-road truck dossier l In Conversation: Giulio Ornella l Hall effect and magnetic sensors focus l Challenge of batteries for heavy-duty EVs l Alpha Motor Corporation digest l Automated charging insight l HVAC systems focus

fleet of heavy commercial vehicles have certain impacts on how the battery management systems (BMSs) for such systems should be designed. For instance, end-users typically demand a very high lifetime and ruggedness in their battery packs. “That is especially true for trucks, and will probably drive high requirements on the quality and thus cost of the microcontrollers and internal data storage systems chosen,” says Dr Busche. Dr Beckmann adds, “The testing for the BMS is sometimes even more extensive compared to those of passenger EV BMSs. Another main difference is that we need to control a multi-pack system most of the time since most of our customers use several battery packs. We have also therefore developed options for the multi-pack with our Vehicle Interface Box [VIB] and Vehicle Interface Gateway [VIG].” Both are designed for master BMS functionality with central CAN comms interfaces between an EV and its battery systems, as well as 12-14 V inputs and 400 or 800 V compatibility. The VIB is configurable for managing up to 10 packs, while the VIG can manage up to 18. It is also critical that BMSs and EV comms networks comply with all the internationally accepted standards for safety and performance. “Both roadcar EVs and heavy-duty commercial buses and trucks must comply with ISO 26262,” says Sylvain Chonavel, Leclanche’s chief engineer for on/off highway and rail vehicles. “And we use CAN bus on truck packs, and Modbus on marine and stationary projects.” Manufacturing Generally, the manufacturing of battery packs for heavy-duty commercial applications will be similar to those intended for light-duty or consumer EV packs. The relationships between cell chemistries and form factors has noteworthy implications for the ideal types of cells to use in electrified trucks, buses and coaches. Heavy-duty commercial EVs generally require large battery capacities as well as relatively high power (compared with packs for cars and light utility vehicles) for the energy density configuration of the cell design. “With these in mind, the ability to extract heat from the battery packs is very important, so optimising the internal resistance of the cells is critical,” says Blanc. “From a design point of view, cylindrical cells have a rather high internal resistance, resulting in more heat needing to be removed. Their surface area-to-capacity ratio is also much lower than in other cell formats, meaning a smaller area for heat exchanges to take place and extract that heat. “As with pouch cells, prismatic cells have a much lower internal resistance than cylindrical cells. However, prismatic cells tend to be thicker than pouch cells, meaning that the centre of the cell will see higher temperatures than those in pouch cells, and with a higher temperature gradient. “This will have an impact on cell ageing, as in a more asymmetric ageing within the cell. Pouch cells meanwhile require more complex mechanical structures for integration in battery packs, as they do not have any mechanical structure for supporting themselves. “Other considerations will come into play, such as the internal structure of the electrode layering, but the main focus for heavy-duty EV packs moving forward will be mostly on prismatic and pouch formats.” Dr Busche notes however that commercial EV customers are among the most sensitive to safety concerns, so integrated safety features typical of cylindrical cells such as overpressure current interrupt devices and rupture valves could still make them highly desirable in such contexts (adding that prismatic cells often feature these too). Also, being highly standardised makes them easily ‘exchangeable’ between different suppliers and packs without mechanical incompatibilities arising. Battery management The high volume and maintenance costs associated with electrifying a Advanced automation systems combined with skilled manual workers can be critical for safe and efficient pack manufacturing (Courtesy of Webasto) 48 Autumn 2022 | E-Mobility Engineering