Recently, in the article "How to Choose an Electric Drive Axle for Electric Heavy-Duty Trucks" published by TRION, a reader commented: "Don't use electric axles on construction sites." This comment sparked a new discussion: Which application scenarios are more suitable for electric heavy-duty trucks to use an e axle system?
To address this question, TRION has reviewed the main application scenarios of electric heavy-duty trucks and analyzed how the technical characteristics of these scenarios align with the configuration and performance of electric truck axles. This article aims to provide reference guidance for users when selecting and applying truck drive axles.
01 Drive Modes of Electric Heavy-Duty Trucks: Advantages and Disadvantages
At present, electric heavy-duty trucks mainly adopt two drive modes.
1. Central Drive
In a central drive configuration, the motor and transmission (powertrain) are installed in the middle of the frame and connected to the drive axle via a drive shaft. This layout is consistent with that of traditional fuel-powered vehicles.
Advantages:
Central drive offers high reliability and low cost. Components such as the drive shaft, rear axle, and suspension are shared with conventional fuel vehicles. Because these parts are mass-produced and standardized, tooling costs have already been amortized, resulting in lower procurement costs. In addition, the motor and transmission are mounted at the center of the frame using four-point suspension, which helps reduce damage from impact and vibration.
In electric heavy-duty trucks with centralized drive, the motor and gearbox are installed in the middle of the chassis.
Disadvantages:
This configuration occupies internal frame space, making it difficult to arrange under-mounted batteries and limiting battery capacity expansion. It also involves many components and low integration, which is unfavorable for overall vehicle lightweighting. Moreover, power transmission relies on the drive shaft, and energy loss occurs at each universal joint, resulting in lower transmission efficiency and relatively higher energy consumption.
2. Electric Drive Axle
In this configuration, the motor and transmission are integrated directly into the drive axle, resulting in a compact structure and high transmission efficiency.
Tesla Semi electric heavy-duty truck's electric drive axle configuration: 2 drive axles + 3 electric motors
TRION believes that the greatest value of the electric axle lies in its ability to fundamentally change the traditional layout of commercial vehicles, making the overall structure more streamlined. It allows full utilization of the frame interior for under-mounted battery installation, thereby lowering the vehicle's center of gravity and improving handling performance. Another advantage is reduced weight, which contributes to overall vehicle lightweighting-an especially important factor for electric heavy-duty trucks. A third advantage is lower energy loss, which directly reduces total vehicle power consumption.
However, EV axles require entirely new designs, involving numerous stamping dies, casting molds, as well as fixtures and gauges for production and assembly. In addition, the current installation rate remains low (according to TRION's estimates, less than 10% of electric heavy-duty trucks), resulting in relatively high costs for EV axle kits. As adoption continues to increase, the cost of electric drive axles is expected to gradually return to a more reasonable level.
The electric drive axle requires a completely new design, resulting in low production volume and higher costs.
02 Application Scenarios and Suitability of Electric Drive Axles
An 8x4 electric dump truck for engineering and transportation scenarios, operating under harsh driving conditions.
1. Engineering Transportation Scenarios
Typical vehicles include 8×4 electric dump trucks, 8×4 electric concrete mixers, and electric mining trucks. Road conditions in engineering transportation often include dirt roads, gravel roads, cement roads, and asphalt roads. In some regions, electric dump trucks and mining trucks are frequently overloaded, causing severe road damage. Dirt and gravel roads can develop deep ruts, increasing the risk of the lowest point of the truck drive axle striking the ground.
Because the motor and transmission on electric drive axles typically use aluminum casings, impacts with hard objects can easily cause casing damage, leading to motor or transmission replacement and significantly higher maintenance costs. In addition, the electric axle is mounted below the suspension as part of the unsprung mass, which can increase impact loads transmitted to the frame and cab when operating on rough roads.
TRION's recommendation:
Electric heavy-duty trucks used in harsh engineering transportation conditions are generally not well suited for electric drive axles.
The motor and gearbox housings are made of aluminum alloy, which is easily damaged if struck by hard objects.
2. Resource-Based Transportation Scenarios
This category mainly includes the transportation of sand, gravel, coal, and ore. Road conditions typically consist of uneven surfaces in loading yards, provincial roads, national highways, and expressways. Yard roads usually have localized potholes rather than deep ruts, and the lowest point of the electric truck axle is unlikely to contact the ground.
At present, 6×4 electric heavy-duty trucks are mainly used in resource-based transportation, with single-charge ranges generally within 220 kilometers. If users prioritize low purchase cost, have limited annual mileage, and are less sensitive to energy consumption, a central drive solution may be sufficient. However, for long annual mileage and higher efficiency requirements, an e axle system is recommended.
TRION suggests:
When selecting large-capacity electric heavy-duty trucks for resource transportation, ground clearance of the electric drive axle should exceed 260 mm;
Motor and transmission casings should use steel materials to reduce the risk of cracking during impact;
The transmission should offer 3 or 4 gears to handle starting, acceleration, steep climbs, and high-speed operation;
The electric axle should be equipped with a PTO interface. Dump trucks used for sand and gravel transportation require a hydraulic pump driven via PTO to operate the tipping mechanism.
The electric drive axle has a ground clearance of more than 260mm, and the housing is made of cast steel and has a power take-off interface.
3. Express and Parcel Transportation Scenarios
To further reduce operating costs, many express and parcel logistics companies have replaced routes within 400 kilometers with electric heavy-duty trucks. According to TRION's research, these operators place strong emphasis on energy consumption. If a vehicle travels more than 250,000 kilometers per year and average energy consumption decreases from 1.6 kWh/km to 1.3 kWh/km, electricity costs can be reduced by approximately 60,000 yuan, assuming an average electricity price of 0.8 yuan/kWh.
Electric heavy-duty trucks used for express delivery and freight transport utilize a battery-at-the-bottom layout combined with an electric drive axle.
Express and parcel transportation is conducted entirely on expressways, making it the most suitable application scenario for electric drive axles. TRION recommends the following configurations:
The vehicle should adopt a multi-motor drive strategy. For example, installing three or four motors across two drive axles. During starting and acceleration, two motors operate; during high-speed cruising, one or two motors operate for optimal efficiency; during climbing, all motors provide maximum power; and during downhill driving, multiple motors perform regenerative braking, with braking force reaching up to 48% of maximum power output to ensure safety.
Illustration: The electric heavy-duty truck uses two electric drive axles and three motors, employing a multi-motor drive strategy.
Expressways typically have maximum gradients of around 5%, so a 2-speed transmission is sufficient, with no need for 3- or 4-speed designs.
To pursue lightweight design, aluminum alloy casings are recommended for motors and transmissions.
To reduce impact and vibration transmitted to the frame and cab, and to improve the reliability and service life of the electric drive axle, rear air suspension and wide-base medium-pressure tires are recommended.
Conclusion
TRION believes that electric axles represent the future development direction of electric heavy-duty trucks. Users should select the configuration and performance of electric drive axles based on their actual application scenarios. As installation rates continue to rise, EV axle costs will gradually decrease. From a total cost of ownership (TCO) perspective, when annual mileage exceeds 150,000 kilometers, the energy-saving advantages of electric truck axles become significant, allowing the initial price difference to be recovered within one to two years.
