E-Mobility Engineering 014 l InoBat Auto dossier l In Conversation: Brandon Fisher l Battery monitoring focus l Supercapacitor applications insight l Green-G ecarry digest l Lithium-sulphur batteries insight l Cell-to-pack batteries focus

Sophisticated technologies are becoming necessary for faster monitoring of cell behaviour. Nick Flaherty reports Smarter and faster M onitoring the performance of battery cells in a pack is pushing the limits of technology in many ways. Increasing the accuracy and reliability of the monitoring in the hostile environment of a battery pack, at voltages of more than 800 V and in fluctuating temperatures, is a considerable challenge. New ways of getting the data back quickly and reliably to a battery management system (BMS) are therefore being developed, to provide long-term data on them for later use in applications other than vehicles. Then there are new ways to probe the performance of a battery pack through a digital model. Technology to measure the performance more accurately of all the parts of a pack, including the swelling of cells, can be captured during development and used throughout the pack’s lifetime. That creates new ways to monitor the performance of the pack during operation, giving vehicle developers and operators enhanced visibility of their system designs. Rechargeable battery packs, particularly ones based on lithium- ion cells, prematurely deteriorate in performance if any of the cells are allowed to over-discharge. As a pack becomes fully discharged, the voltage drop of the weakest cell(s) can overtake the internal chemical potential, and the cell terminal voltage becomes negative with respect to the normal voltage. In such a condition, irreversible chemical processes begin altering the internal material characteristics that originally provided the cell’s charge storage capability, so subsequent charge cycles of the cell do not retain the original energy content. Once a cell is impaired, it is more likely to suffer from less efficient charging cycles in subsequent use, making the problem worse and shortening the useful cycle life of the pack. That is critical for the users of EVs of all kinds who want to get the most out of the battery pack, whether it is maximum range or longer operating times. Measurement technology is key to identifying battery problems, and relies partly on having a detailed model of the pack (Courtesy of InnovationLabs) 32 Summer 2022 | E-Mobility Engineering