Electric Heavy-Duty Truck Design: Which E-Powertrain is Better?
Electric Heavy-Duty Truck Design: Which E-Powertrain is Better? At Brogen, we’ve spent a lot of time developing electric axle systems for commercial vehicles, particularly in heavy-duty applications like semi-trucks, tractors, and trailers. In this article, we’ll explore different electric powertrain systems, compare solutions, and discuss the pros and cons of each. 1. Types of E-Powertrain Systems Electric powertrain systems for heavy-duty vehicles can be categorized into three main configurations based on motor layout: Central Direct Drive: Direct drive motor Electric Drive Axles: Parallel-Axis E-Axle Coaxial E-Axle Vertical-axis E-Axle Distributed Drive Systems Wheel-End Drive Wheel-Hub Drive Each system offers unique advantages, and we’ll explore them in more detail below. But first, let’s look at some broader trends driving innovation in e-powertrain systems. 2. Key Trends in E-Powertrain Systems 2.1 Increasing Integration of E-Powertrain Systems More and more, motors, gearboxes, controllers, and other key components are being integrated into compact units. This not only reduces weight and space but also improves overall system efficiency and reliability. For example, our 360 kW drive assembly integrates the motor and gearbox into a single unit, which optimizes the layout for heavy-duty trucks and saves valuable space. Similarly, our 360 kW electric axle for heavy commercial vehicles combines the drive system, transmission, braking, and other key components into a compact, efficient assembly. Brogen 360 kW drive assembly for 40-ton to 90-ton HCV Brogen 360 kW E-axle for 4×2/6×2/6×4/8×4 HCV 2.2 Adoption of Dual-Motor E-Powertrain Systems Dual-motor setups are becoming increasingly popular, especially in high-end and specialized trucks. These systems offer better power distribution, improved energy efficiency, and enhanced performance for heavy loads. Our dual-motor drive assembly is a prime example, delivering continuous power during demanding conditions, such as hill climbs, while maximizing operational efficiency. Brogen Dual-Motor Drive Assembly for 55-180T HCV Brogen Dual-Motor 360 kW E-axle for 4×2/6×2/6×4/8×4 HCV 3. Central Direct Drive Systems: A Cost-Effective E-Powertrain Solution Central Direct Drive System Architecture Central Direct Drive System Examples Central direct drive systems are primarily used to convert traditional fuel-powered trucks into electric vehicles. In this configuration, the engine is replaced with an electric motor, along with an electric drive unit (EDU), battery packs, and other key components. The original chassis remains largely unchanged, making this solution adaptable for a wide range of commercial vehicles. Pros: Cost-Effective & Quick to Market: This is the most economical and fastest way to electrify existing vehicle platforms without extensive redesigns. Ease of Conversion: Many manufacturers opt for this approach as it allows them to enter the EV market without the significant financial and time investments required for developing a new platform. Cons: Limited Battery Space: Since the original chassis isn’t significantly altered, space for battery packs is restricted, which limits driving range and affects battery cooling system layout. Compromised Handling & Comfort: Converted models often have poor weight distribution, leading to increased braking distances and reduced driving comfort. Central direct drive systems are commonly used in short-distance transportation scenarios, such as ports, steel mills, power plants, and mines. They are less suited for medium- or long-distance travel. 4. Electric Drive Axles: Optimizing Space & Efficiency In contrast, electric drive axles (e-axles) eliminate the need for a drive shaft, reducing vehicle weight and improving system efficiency. E-axles also allow for better space optimization for battery packs, increasing driving range and better overall efficiency. Among the different types of electric drive axles, three main configurations stand out: parallel-axis, coaxial, and vertical-axis. Each configuration offers distinct advantages and challenges, making them suitable for various vehicle types and operational needs. 4.1 Parallel-Axis E-Axle Parallel-Axis E-Axle System Architecture Brogen Parallel-Axis E-Axle The parallel-axis electric drive axle is currently the most widely adopted configuration for electric axles in the market. In this system, the motor is positioned parallel to the axle, and the motor, drive axle, and AMT are integrated into a single unit. This design eliminates the need for a drive shaft, reducing overall system weight and improving transmission efficiency. Additionally, this configuration uses helical gears, which significantly enhance reverse braking capability—from the typical 30% to an impressive 100%. By removing traditional components such as the universal drive shaft, reducer, and suspension brackets, installation costs are significantly reduced compared to central direct drive systems. This compact design also saves weight and space, allowing for better battery placement and increased driving range. However, there are drawbacks. The large unsprung weight of the system, combined with its offset configuration, can negatively impact the vehicle’s handling, especially in heavy-duty applications. 4.2 Coaxial Electric Drive Axle Coaxial Electric Drive Axle Architecture Brogen Coaxial E-Axle The coaxial electric drive axle features a motor aligned directly with the axle housing. This configuration creates a more compact and concentrated power system, which optimizes the vehicle’s overall chassis layout. Due to its efficient space utilization, coaxial e-axles are ideal for smaller commercial vehicles like light vans and trucks weighing under 4.5 tons. However, their compact nature and lower power density make them unsuitable for heavy-duty vehicles, which require more robust power systems. 4.3 Vertical Axis Electric Drive Axle Vertical Axis Electric Drive Axle Architecture In the vertical axis electric drive axle, the motor is connected to the drive axle at a perpendicular angle. This setup offers some key advantages, such as lower installation costs and the efficient use of longitudinal space, which allows for better battery pack arrangement. Despite these benefits, there are significant trade-offs. The vertical axis design has lower transmission efficiency compared to parallel-axis e-axles, and its system power density is not as high. Additionally, the use of hypoid gears for speed reduction results in a smaller speed ratio and poorer performance in NVH (noise, vibration, and harshness). As a result, this configuration is more commonly used in medium- and heavy-duty commercial vehicles. 5. Distributed Drive Systems As electric vehicles continue to evolve, distributed drive systems are emerging as a powerful alternative to traditional powertrains. Distributed drive systems can be divided into two main types: wheel-end drive and wheel-hub drive. Each of these technologies offers distinct advantages, as well as unique challenges,
