Electric-Truck Battery Enclosures Balance Demands

Lightweight construction is very important, but durability and safety requirements cannot be compromised.

April 1, 2021

Ryan Gehm

Light weight is a definite consideration for the Freightliner eCascadia’s battery-enclosure design, which employs aluminum, but durability also is a critical factor. (Daimler Trucks North America)

Manufacturers of battery-electric commercial trucks have similar requirements for their battery enclosures as do their passenger-vehicle counterparts. Lightweight construction is very important, but durability and the ability to protect components and occupants in crashes and the event of a fire are paramount. The Volvo VNR Electric features an all-metal cab construction, and the battery enclosure is made from stainless steel. The protection plates and mounting arrangements are made from casted and steel materials.

Durability requirements and occupant protection drove material selection for the Volvo VNR Electric’s battery enclosure. (Volvo Trucks North America)

“These metals were chosen due to the technical requirements needed to support the batteries, durability demands, and to provide protection to cab occupants and vehicle components,” said Brett Pope, director of electric vehicles, Volvo Trucks North America. “In the overall development of an electric Class 8 truck, lightweight components are utilized where feasible to maximize payload and to affect the load distribution on the axles. However, we will not compromise the safety of our vehicles, so the protection of the occupants of the cab will always be our top priority.”

The Volvo VNR Electric’s battery enclosure is made from stainless steel. The protection plates and mounting arrangements are made from casted and steel materials. (Volvo Trucks North America)

Freightliner takes a similar approach with the design of its battery-pack enclosures for the eM2 and eCascadia trucks. “Weight is always a consideration in trucking, but safety is an even more important factor,” said Alex Voets, Freightliner eMobility sales and product strategy manager. Aluminum is the material of choice for Freightliner’s current generation of EV battery enclosures. Engineers designed the side-impact protection of the batteries to distribute the forces along the structure, providing a lightweight structure with maximum safety, Voets said.

Navistar employs a mixed-material approach for its electric-truck battery enclosures. The underside of the medium-duty eMV prototype is shown. (SAE/Ryan Gehm)

Navistar employs a mixed-material approach for its electric-truck battery enclosures. “We currently use multiple materials in our battery enclosures – composites, stamped steel, and aluminum being the most common,” said Zilai Zhao, director of eMobility Engineering at Navistar. “Safety, weight, durability, cost, dielectric separation, thermal performance, and manufacturability are all considerations when selecting battery-enclosure materials. Our goal is to balance these considerations while optimizing the design for that particular vehicle’s duty cycle.”

Weight is always an important factor when selecting materials, said Zhao, especially because less weight equals more range, better acceleration, and more payload. “The challenge is to remove the weight without compromising the vehicle’s durability and performance – all at an acceptable cost,” he said.

Navistar continuously evaluates different materials for use with battery enclosures. “As electric vehicles continue to grow, the industry supply base is constantly offering new materials and technologies with different use cases and advantages depending on the application,” Zhao said.