E-mobility Guide

Injection moulding for e-mobility

With our extensive design capabilities, Rosti has been challenged to produce complex moulds and in-mould features for mass manufacturing in the swiftly growing e-mobility sector.

Injection moulding offers significant advantages in this industry, with applications for electric bikes, scooters, public transport vehicles, and cars. It is a repeatable, cost-effective, lightweight and rapid process, and production can be easily scaled up or down. These are ideal characteristics when seeking to guarantee consistent quality in high-volume manufacturing.

The modern battery carrier

The modern battery carrier has become a crucial element of effective thermal management in electric vehicles. Manufacturers face the challenge of maintaining cool temperatures for multiple batteries without relying on forced-air cooling. This has resulted in introducing a special channel structure inside the battery carrier that enables cooling fluid to flow through or around the battery cells. The carriers co-designed by Rosti include a channel structure that also facilitates transient cooling.

Rosti works with OEM clients to deliver packaged solutions in this area. By utilising our in-house, state-of-the-art mold flow simulation software, we help clients turn their concepts into reality. Half a billion carriers will be needed to meet the future requirements of the electric vehicle market. At Rosti, we are extremely proud to be leading the way.

Read more about our e-mobility projects below or download this white paper.

Why injection moulding is the perfect solution for mass-manufacturing e-mobility applications

Numerous factors are fuelling the rapid progress of e-mobility, not least of which are government regulations and environmental pressures. Furthermore, with the global commercial electric vehicle market predicted to grow at a compound annual growth rate of 39.9%—from 125,212 units in 2017 to 1,831,865 units by 2025—research and development in e-mobility is advancing faster than ever before.

Traditional internal combustion engine technology for powering vehicles is losing ground, with today’s OEMs developing new platforms across light-, medium- and heavy-duty e-mobility markets. These platforms are expected to perform just as well as their traditional equivalents. But that is not the only challenge; making the transition from low-volume prototype manufacturing using emerging technologies to the future’s demands for mass production is equally demanding.

Rosti is already active in the e-mobility and battery market, partnering with some of the world’s leading OEMs to utilise proven manufacturing techniques to confront the challenges of today’s production landscape. One such challenge is the battery pack carriers used within e-mobility platforms. Battery technology is key to enabling vehicles to travel further, and the not-so-simple battery carrier plays a significant part. In this article, Tony Austin, Technical Director at Rosti, explores the issues surrounding battery technology and explains why injection moulding ought to be the main method for OEMs in manufacturing.

The battery carrier’s role: past and present

Looking under the bonnet of a conventional ICE-powered vehicle will show that the battery carrier is quite a static component. Usually constructed from metal, its main function has been to support the traditional lead-acid battery and provide some protection in the event of an impact. However, as e-mobility vehicles have developed, the battery has become the system’s core.

Both vehicle reliability and range depend on the type of battery technology employed, so anything that could compromise battery performance—such as hot climates—must be addressed. Essentially, an increase in ambient temperature shortens the lifespan of e-mobility batteries: the hotter the batteries, the faster the chemical reactions, and the sooner the battery will self-discharge.

Independent tests have shown that a battery’s self-discharge rate doubles for every 10°C increase in temperature. It is also vital to protect batteries from overheating, which is the worst-case scenario and can cause rapid damage.

Introducing the 21st-century battery carrier

The modern battery carrier is now a key component in effective thermal management, and e-mobility OEMs are searching for new approaches to maintain cool temperatures for multiple batteries and move away from traditional forced-air cooling. This has resulted in a special channel structure within the carrier that enables cooling fluid to flow through or around the cells. Additionally, this channel structure enables transient cooling.

Rosti is collaborating with OEM clients to provide packaged solutions for this need. The latest battery carrier designs are often highly intricate, making it difficult to manufacture a finished component using traditional methods like CNC machining or pressing. Furthermore, 3D printing—hailed as a breakthrough for the future—still presents limitations in terms of the capital investment required. It also cannot fulfil the industry’s requirements for high-volume manufacturing. So, what is the alternative?

Injection moulding for electric vehicle battery carriers

In the injection moulding process, source material is melted and injected into a mould at high pressure. The part cools in the mould and is then ejected before the process begins again. But is injection moulding the best manufacturing process for electric vehicle battery carriers? For years, Rosti has been challenged by many OEMs—across a variety of markets—to design complex moulds featuring many in-mould characteristics, an expertise that would almost certainly be necessary for battery carriers used in e-mobility applications. For instance, Rosti can design the cooling channels as an integrated part of the moulding. Using in-house, state-of-the-art mould-flow simulation software, Rosti can bring ideas from concept to reality, producing in a single operation a component that incorporates all the required features for a 21st-century battery carrier.

But again, is injection moulding truly the right manufacturing process for battery carrier applications? Another way to approach this question is to consider the potential volumes required. If e-mobility reaches its full potential based on unit projections, then production volumes will be extremely high. This figure must also account for the large number of spare battery packs—and therefore carriers—that will be necessary, as well as power supply units needed for other markets.

Rosti suggests that neither CNC machining nor 3D printing will be able to handle such large volumes or deliver the target piece-part costs expected by OEMs. Instead, a repeatable, cost-effective and rapid process that also provides structural rigidity is required. This is where injection moulding offers significant advantages, including the ability to scale production as required.

It is true that upfront costs for injection moulding can sometimes be slightly higher due to tooling requirements, but the engineering advantages and economies of scale must be considered. Once the initial outlay has been amortised, the cost per unit with injection moulding is highly competitive. Moreover, the process is extremely repeatable—a valuable attribute when aiming for brand consistency and component reliability in high-volume production. Another benefit is that injection moulding can reduce the total number of parts required since it enables the integration of ancillary components such as brackets. This design flexibility clearly benefits the bill of materials and reduces production assembly time.

Does injection moulding provide the right materials?

For this application, it is essential to involve the raw material producer from the outset of the project. For example, there is a strong need to reduce weight in battery carrier applications; since it is not possible to make battery cells lighter, the carrier itself must be lightened. While injection-moulded solutions offer a lighter alternative to traditional metal carriers, will these components possess the necessary strength to support the battery and protect it from external factors? Rosti’s thorough consultations with raw material manufacturers ensure the correct material composition is selected—one that meets all the requirements for thin yet strong wall construction. In addition, the specified material always meets the UL-94VO flammability resistance standard, providing assurance of regulatory compliance in application.