Battery technology is evolving rapidly, and one of the most significant shifts is the move towards cell-to-chassis (CTC), also known as cell-to-body (CTB) integration. In this design, battery cells are embedded directly into the vehicle structure, removing traditional modules and packs.
This transition is part of a broader evolution in battery architecture, often referred to as Cell-to-X (C2X), where batteries move from modular systems to fully integrated structural components. As integration increases, so do gains in efficiency, weight reduction, and design flexibility.
While this approach improves energy density and enhances overall vehicle performance, it also introduces a critical challenge. When the battery becomes part of the vehicle itself, it becomes far less visible, harder to access, and more difficult to track across its lifecycle.
The Digital Battery Passport (DBP), introduced by the European Commission under Regulation (EU) 2023/1542, provides a robust solution. It ensures that even when batteries are physically “invisible”, their data remains accessible, traceable, and actionable.
What is Cell-to-Chassis Battery Integration
Cell-to-chassis integration represents the most advanced stage in battery integration. It builds on earlier architectures such as cell-to-module and cell-to-pack, where layers of packaging are progressively removed to improve efficiency.
In a cell-to-chassis system, individual battery cells are directly incorporated into the vehicle’s structural frame. This transforms the battery from a standalone component into a load-bearing part of the vehicle.
The result is a more compact and efficient design. Manufacturers can achieve higher energy density, improved structural rigidity, and reduced material use. It also opens up new possibilities in vehicle design, including lower profiles and optimised interior space.
Companies like BYD are exploring structural battery concepts, while Tesla has introduced structural battery packs that integrate cells into the vehicle body. These developments are shaping the next generation of electric vehicles.
Why “Invisible” Batteries Create New Challenges
While CTC designs offer clear performance benefits, they significantly complicate how batteries are monitored, serviced, and tracked.
In traditional battery packs, modules can be removed, inspected, and replaced individually. With cell-to-chassis integration, access becomes limited. The battery is no longer a separate component but part of the vehicle’s structural core.
This shift introduces a new level of engineering complexity. The battery must now meet both energy storage and structural safety requirements. Crash performance, durability, and long-term reliability become closely tied to battery integrity.
Thermal management also becomes more demanding. Distributing and controlling heat across a structurally integrated system requires advanced cooling strategies to prevent performance loss or safety risks.
Serviceability is another concern. If damage occurs, repairing or replacing parts of the battery may require significant disassembly of the vehicle structure, increasing cost and complexity.
Most importantly, tracking battery identity and lifecycle data becomes more challenging without clear physical boundaries.
The International Energy Agency highlights the increasing complexity of battery systems and the growing need for improved lifecycle data management as technologies evolve.
The Role of the Digital Battery Passport in CTC Systems
The Digital Battery Passport ensures that each battery retains a persistent digital identity, regardless of how it is physically integrated into a vehicle.
Under the EU Battery Regulation, the passport includes key information on composition, performance, durability, safety, and lifecycle events, all stored in a structured and machine-readable format.
In a cell-to-chassis context, this means that even if individual cells cannot be easily accessed, their data remains available. Manufacturers, service providers, and recyclers can retrieve critical information without direct physical access to battery components.
This digital layer becomes essential for maintaining visibility, accountability, and control across the battery lifecycle.
Maintaining Traceability Without Physical Access
One of the key advantages of the Digital Battery Passport is its ability to maintain traceability even when physical inspection is limited.
Each battery system is linked to a unique digital identifier, accessible through vehicle systems or secure data platforms. This allows stakeholders to trace the origin, composition, and usage history of the battery throughout its lifecycle.
In highly integrated designs such as CTC, this capability is critical. It supports regulatory compliance and ensures that battery systems remain transparent despite their physical inaccessibility.
It also reflects a broader industry shift, where data continuity replaces physical visibility as the foundation of lifecycle management.
Supporting Maintenance and Data-Driven Diagnostics
In cell-to-chassis systems, traditional maintenance approaches are no longer sufficient. Physical inspection is often limited, so operators must rely more heavily on data-driven diagnostics.
The Digital Battery Passport supports this shift by providing access to historical and operational data. When combined with onboard systems such as Battery Management Systems (BMS), it enables more accurate fault detection and performance analysis.
If an issue arises, passport data can help determine whether it is linked to manufacturing conditions, usage patterns, or environmental factors. This improves maintenance efficiency and supports safer operation over time.
It also enables early detection of hidden risks, which is particularly important in structurally integrated systems where faults may not be immediately visible.
Implications for Recycling and End-of-Life Processing
Recycling integrated battery systems presents new technical and operational challenges. Separating materials from a structural battery is more complex than dismantling traditional modular packs.
The Digital Battery Passport helps address this by providing recyclers with detailed information about battery composition, materials, and structure. This enables more efficient processing and improves the recovery of valuable raw materials.
It also supports the development of advanced dismantling strategies and recycling processes that are better suited to highly integrated designs.
The European Commission emphasises that improved traceability and data access are key to achieving circular economy objectives in battery value chains.
Ensuring Compliance in Advanced Battery Architectures
As battery designs become more complex, ensuring compliance with EU regulations becomes more demanding.
The Digital Battery Passport provides a consistent framework for capturing, sharing, and verifying battery data across stakeholders. This ensures that even highly integrated systems meet requirements for transparency, sustainability, and safety.
For manufacturers, this supports alignment with regulatory expectations from the earliest design stages. For regulators, it enables more effective monitoring of battery performance and lifecycle data.
How BASE Supports Cell-to-Chassis Battery Traceability
At BASE, we recognise that next-generation battery architectures require equally advanced digital infrastructure. Our Digital Battery Passport framework is designed to maintain traceability even in highly integrated systems such as cell-to-chassis designs.
By enabling structured data capture, secure data exchange, and interoperability across the value chain, BASE ensures that battery information remains accessible throughout its lifecycle. Advanced analytics further support insights into performance, degradation, and safety.
This allows stakeholders to manage batteries more effectively, even when physical access is limited, supporting maintenance, compliance, and circularity.
Looking Ahead
Cell-to-chassis integration represents a major step forward in battery design, offering improved efficiency, performance, and design flexibility. It also reflects a broader shift towards tighter integration between battery systems and vehicle architecture.
At the same time, it introduces new challenges in visibility, traceability, and lifecycle management.
Digital Battery Passports provide the foundation needed to address these challenges. By ensuring continuous access to reliable data, they enable confident management of even the most integrated battery systems.
As electric vehicles continue to evolve, combining advanced engineering with robust digital systems will be essential for building safe, sustainable, and compliant mobility solutions.
The BASE project has received funding from the Horizon Europe Framework Programme (HORIZON) Research and Innovation Actions under grant agreement No. 101157200.
References
EU Battery Regulation (Regulation EU 2023/1542) https://eur-lex.europa.eu/eli/reg/2023/1542/oj
EU Battery Regulation Detailed Text https://eur-lex.europa.eu/eli/reg/2023/1542/2023-07-28/eng
International Energy Agency – Global EV Outlook 2023 https://www.iea.org/reports/global-ev-outlook-2023
European Commission – Circular Economy https://environment.ec.europa.eu/topics/circular-economy_en
World Economic Forum – What is cell-to-body technology and what does it mean for the EV industry: https://www.weforum.org/stories/2024/02/cell-to-body-electric-vehicles/