BET "Battery Electric Truck" Retrofit vs. Purpose design.

In the realm of developing Battery Electric Trucks (BETs), two design approaches find application. The "Retrofit Design" entails the integration of electric propulsion components into pre-existing, conventionally established trucks. Conversely, the "Purpose Design" charts a course for the complete reengineering of the truck.

The strategy behind the "Retrofit Design" is to metamorphose an existing product variant with minimal alterations into another variant. This method is deployed in the conversion of vehicles with internal combustion engines to those powered by electric propulsion. All components of the electric drive train find integration into an existing vehicle chassis. An existing concept serves as the foundation for an electrically propelled vehicle. The objective of this approach is swift market penetration, coupled with the advantage of diminished development and investment costs.

Batteries, electric motors, and various power electronics modules are installed at the positions originally occupied by the fuel tank and internal combustion engine. The existing chassis remains unadopted to the specific demands of an electric propulsion system, thereby leaving crucial degrees of freedom untapped and presenting substantial optimisation potential. Instances of this phenomenon manifest in the battery, constituting part of the Extended Energy Storage System (ESS), which suboptimal utilises the available spatial envelope. This inefficiency arises due to the considerable deviation in geometry between the ladder frame, fuel tank, and exhaust system, as opposed to the ideal battery arrangement. Decentralised and distributed battery layouts negatively impact both vehicle structure and the battery arrangement optimised for energy density. This, in turn, overlooks the lightweight potential inherent in geometry and material utilisation.

Due to the decentralised battery arrangement, inevitable variations in the power and thermal connections result in disparate line resistances and unnecessary heat losses. Mitigating these losses demands appropriate insulation, seeking to minimise or even eliminate thermal dissipation. However, this pursuit diminishes the volumetric efficiency and packing density of the Extended Energy Storage System (ESS). The integration of the battery into the frame exacerbates these challenges, occurring laterally or partially below. The exposed positioning of the ESS within the vehicle subjects it to various environmental influences, and the reduction of heat loss proves to be just one of the myriad disadvantages.

The ESS design must grapple with technical solutions and intricate precautions to ensure adequate safety in the event of a lateral impact or an accident. The structural reinforcement becomes imperative due to the increase in vehicle weight stemming from the addition of electric components. Elevated weight, coupled with mandated maximum axle loads, inevitably leads to reductions in payload capacity. The diminished payload, resulting from the substantial weight of the tractor unit, invariably translates to a degradation of the overall utility of the Battery Electric Truck (BET). This consequence proves highly detrimental to the swift expansion of locally emission-free freight transport, posing a significant challenge to the economic viability of the BET.

The significant advantages of the "Retrofit Design" lie in its swift market introduction, low development costs, and enhanced integration into existing production facilities for conventionally powered vehicles. Synergies can be harnessed through the incorporation of a considerable number of carryover components, proving advantageous for an established manufacturer. Notably, the component strategy favors the "Retrofit Approach," especially when pre-existing contracts with suppliers are often negotiated based on quantities and annual volumes, covering the planned overall production quantity.

However, potential additional costs stemming from alterations to the vehicle structure pose a notable disadvantage. Integrating the battery into a conventional ladder frame necessitates substantial redesigns and reconfigurations of the structure. Vital components such as cooling systems, brake modules, and steering assistance must be tailored to suit an electric vehicle, and the production process needs seamless integration into an existing assembly line. These adaptations are, however, constrained, just as the creative possibilities in vehicle development are limited. Consequently, establishing new production lines becomes imperative to meet the heightened demand for electric vehicles, entailing a substantial financial commitment.

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The "Purpose Design" presents an alternative developmental path, involving the creation of a new vehicle around the electric drive train. This approach allows for a high degree of innovation, enabling technological leaps for BETs and instigating the so-called disruption of existing technologies. This transformation typically unfolds along an S-curve, with the introduction of a new technology progressing moderately until it reaches a market share of >10%. Subsequently, exponential growth occurs, marked by annual doubling of market shares, leading to the disruption of the old and complete penetration of the new technology.

The purpose design facilitates a focused development strategy tailored to the electric drive train, achieving a magnitude-improved vehicle performance. This enhancement spans areas such as energy consumption, range, vehicle center of gravity, and payload capacity. In BETs, the vehicle's center of gravity is a crucial consideration in its design, especially given the significant weight proportion contributed by the Extended Energy Storage System (ESS), which can reach up to 50% of the total vehicle weight (resulting in ranges exceeding 1000 km).

The impact on vehicle dynamics like braking behaviour, and loading is particularly critical in a BET development due to high weight ratio. Additionally, special attention is directed towards the position of the kingpin — The coupling point between the tractor and the trailer relative to the rear axle in the longitudinal direction of the vehicle and its distance from the road surface. This is pivotal as all towing, brake and loading forces are transmitted during operation. The determination of permissible axle loads is subject to legal regulations, necessitating the assurance of a maximised residual load per axle, especially for the tractor's rear axle. The equation "Maximum Axle Load – Residual Load = Possible Payload at the Kingpin" defines the ultimate payload capabilities. Beyond customer and market requirements, competitive products and the manufacturer's market positioning wield significant influence over the vehicle concept and packaging.

A purpose design offers greater freedom to achieve innovations in vehicle concept and packaging, leading to a construction and production more aptly suited for the demands of BETs. This results in optimised driving characteristics and more efficient lightweight construction. Other influencing factors include the vehicle's application and safety concept. The design flexibility inherent in the "Purpose Design" allows for the targeted development goals of a vehicle platform and manufacturing processes tailored to a product family.

Exoskeleton designs provide greater flexibility in terms of customisation and adaptability. This can be advantageous for different vehicle types and applications without significant redesign. The production of complex exoskeleton structures may require advanced processes and technologies, potentially increasing initial manufacturing costs. However, advancements in manufacturing techniques can mitigate these costs over time.

One of the significant advantages of purpose design lies in the high degree of automation in production. Much faster process speeds can be achieved compared to retrofit design. Optimised design allows for the reduction and partial elimination of fasteners connection. Additional potential lies in manual tasks in hard-to-reach areas, which require rotation and pivoting fixtures in the production line. With a corresponding purpose design, these can be eliminated. In this context, electromobility, with geometrically simpler components like the "Electric Motor" and "Battery," offers the opportunity to develop a vehicle platform capable of generating diverse vehicle concepts with various body configurations. The absence of a combustion engine and fuel tank, replaced by relatively small electric motors in the axle area through a so-called wheel-near execution, along with an ideal battery integration, allows for the creation of smart weight distribution and vehicle solutions that positively impact the usable space.

The "Purpose Design" leads to increased development and investment costs for established manufacturers. Existing facilities must undergo extensive transformations and adaptations to manufacture a radically new purpose design. The number of carryover components is significantly restricted, requiring substantial investment in both resources and time to develop and negotiate costs for these components in large quantities. Therefore, it should be predominantly used as a design foundation for lead variant with simultaneous high production volumes.

In embracing the "Purpose Design" for BETs, we embark on a paradigm that transcends mere evolution, aiming for revolutionary strides in the realm of electromobility. The superiority of the "Purpose Design" over the "Retrofit Approach" is not a mere nuance; it is a seismic shift that resonates across various dimensions. The "Purpose Design" empowers us to engineer BETs with an unprecedented level of innovation, unshackling us from the constraints of conventional structures. It fosters a realm where the electric drive train is not an appendage but the very nucleus around which a new vehicle is meticulously crafted. This approach heralds a new era of technological leaps, enabling BETs to transcend boundaries and disrupt established norms.

The level of customisation and adaptability afforded by the "Purpose Design" is a game-changer. It allows for a vehicle platform and manufacturing processes fine-tuned for a product family, unleashing a spectrum of possibilities without the need for substantial redesigns. The inherent design flexibility facilitates a focus on BET-specific requirements, leading to best performance, extended range, favourable vehicle center of gravity, and enhanced payload capacity.

Exoskeleton structures within the "Purpose Design" not only provide a canvas for geometrically simpler components but also usher in a new era of manufacturing possibilities. The high degree of automation in production enables faster processes, reduced reliance on bolted connections, and the elimination of labor-intensive tasks in hard-to-reach areas. The result is not just efficiency; it's a leap towards a manufacturing future characterised by speed, precision, and adaptability.

Moreover, the "Purpose Design" positions itself as a catalyst for sustainable mobility. By strategically placing electric motors and batteries, it unlocks opportunities for smart weight distribution, positively impacting driving dynamics, safety, and the effective utilisation of vehicle space. The absence of a combustion engine and fuel tank frees up design possibilities, offering a canvas for diverse vehicle concepts that align with the evolving needs of the market.

While it is undeniable that the "Purpose Design" demands a more substantial upfront investment, the dividends it promises in terms of performance, innovation, and adaptability make it a superior choice for those envisioning the future of BETs. In this era of transformative change, the "Purpose Design" emerges not just as a design philosophy but as a manifesto for the pioneers shaping the trajectory of electric transport. It is not merely a step forward - It is a leap into a future where the road to electromobility is paved with purpose and possibility.