A European research consortium is developing a new battery pack for electric buses under the SIERRA project, focusing on nickel-rich nickel manganese cobalt (NMC) battery chemistry designed to deliver higher energy density and improved performance for heavy-duty transport.
The project is led by France’s CEA and brings together eleven partners from seven European countries. The initiative is funded through the European Union’s Horizon Europe programme with nearly €8 million in support.
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Participants aim to validate the battery system up to Technology Readiness Level 6, a stage intended to demonstrate the technology in a relevant environment and prepare it for future industrialisation.
Electric buses currently use several battery chemistries, including nickel-based NMC cells and lithium iron phosphate (LFP) batteries. Systems used in heavy-duty transport must meet strict requirements related to energy density, safety, durability, charging performance, and overall weight.
According to project partner AIT Austrian Institute of Technology, nickel-rich NMC cells offer significant potential to increase specific energy, but they also introduce new challenges related to thermal management, structural design, and monitoring.
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“Conventional battery pack architectures are increasingly reaching their limits in terms of safety, durability, and system weight,” AIT said.
The SIERRA project aims to address these challenges by developing a lightweight battery pack architecture with integrated cooling and advanced monitoring systems. Planned innovations include multiscale modeling for thermal and mechanical simulation, lightweight multi-material battery housings manufactured using a one-shot process, and multi-level monitoring systems for battery health and structural integrity.
Additional design features include integrated cooling systems and printed busbars intended to support high charging power and efficient operation across a wide range of conditions.
Researchers will also simulate the integration of the battery pack into electric buses using digital twin technology to evaluate system performance at the vehicle level.
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“In the SIERRA project, we use simulation-based methods at the battery pack and vehicle level to develop safe and energy-efficient lightweight battery concepts for heavy-duty transport,” said Mirza Popovac, project manager at AIT.
“This allows us to validate design decisions at an early stage and specifically improve the performance of future electric commercial vehicles,” he added.
Other partners in the project include Verkor, FEV France, Plastic Omnium Clean Energy Systems Research, Rina Consulting, Acondicionamiento Tarrasense Association, Asociacion de Investigacion Metalurgica del Noroeste, Gen 2 Carbon, Icomat, and associate partner FPT Motorenforschung.