The rapid evolution of electric vehicle (EV) architectures is creating new challenges for power interconnects, particularly busbars. One of the most significant trends in e-mobility is the push toward higher power density, which necessitates more compact and energy-efficient systems.
This drive for miniaturization directly supports improved battery efficiency, lowers overall energy consumption, and extends vehicle range.
Additionally, there’s a continual migration from 400 to 800-volt (V) battery architectures, with some systems potentially moving toward 1200 V (Figure 1). This higher voltage enables faster charging times and potentially greater powertrain efficiency, while also minimizing resistive losses and allowing for lighter-weight cable harnesses by reducing current for the same power output.
Figure 1. Advancing EV architectures demand more compact, energy-efficient systems.
Compounding these advances is the increasing adoption of faster switching devices, which are transitioning from traditional silicon-based technology to wide-bandgap materials, such as silicon carbide (SiC) and gallium nitride (GaN).
While these devices enhance electrical efficiency and performance, particularly in inverters operating with high currents (200–400+ A) and high voltages (800–1200+ V), they also generate a substantial amount of heat, making liquid cooling of the electric motors essential for effective thermal management.
The current trend towards fully integrated powertrain systems, where components such as inverters, onboard chargers, dc-dc converters, and electric motors are combined into single units, further intensifies the need for efficient cooling and robust interconnect designs within constrained spaces.
These developments underscore the importance of innovative solutions for managing thermal and mechanical stresses, as well as enhancing electrical efficiency, in the ongoing evolution of the automotive electrification market.
Thermal and mechanical stability
One promising approach is the use of flexible busbar designs, which help manage thermal stress and vibration within electric motors (Figure 2). Deploying one flexible busbar for each of the three phases of the motor significantly reduces the impact of thermal cycling and mechanical strain, improving long-term reliability.
Figure 2. Flexible busbar design with stacked copper lamels for managing thermal stress and vibration.
“A flexible busbar is intelligently designed to be easily bent and shaped, making it ideal for tight spaces,” explains Dominik Pawlik, director of Product Management at ENNOVI, a manufacturer of EV interconnect and thermal management solutions. “Its construction involves multiple layers of copper or aluminium, known as stacked lamels, which are precisely welded at the terminals. This unique layered structure enables the busbars to be bent with an extremely small radius, providing crucial design flexibility.”
For longer busbar applications, engineers are also turning to hybrid designs that combine a rigid busbar with a smaller welded portion of flexible busbar. This ensures cost efficiency while still delivering flexibility where it’s most needed.
Sealing and manufacturing efficiency
The interface between liquid-cooled components and dry electrical connections presents another critical challenge: preventing coolant leakage. Traditional sealing methods, such as epoxy potting or rubber O-rings, can add cost and complexity or degrade over time.
“Recognizing these limitations, we developed an innovative busbar sealing technology that prevents coolant leakage in hybrid and EV drivetrain applications,” says Pawlik. “ENNOVI-SealTech offers two primary sealing methods, giving design engineers flexibility for different busbar shapes and parameters.”
The shrink tubing method uses an inner glue layer that melts and adheres to the busbar during shrinking, with an outer polyolefin layer that bonds into molded parts during injection moulding.
“This ensures a tight, durable seal that integrates seamlessly into the manufacturing process,” he adds.
As an alternative, adhesive tape offers strong adhesion to metal and plastic, while maintaining elasticity and temperature resistance during the injection molding process. It compresses under pressure and rebounds to form a strong seal, delivering reliability without the need for additional potting steps.
“These sealing methods not only maintain superior performance under extreme conditions, but they also lower production costs by eliminating secondary processes,” he explains.
Figure 3. Innovative sealing technology ensures reliability and stability in extreme conditions.
Testing has validated the absence of leakage under thermal aging at 150° C for 1,000 hours and thermal shock cycling from -40° to +150° C for 600 cycles, along with comprehensive leak tests.
A holistic approach to electrification
The pace and direction of electrification vary significantly across global markets, and any successful strategy must address both EVs and hybrids.
“The path to EV adoption is not uniform, and many markets are still hybrid-first,” says Pawlik. “A successful strategy requires a dual focus on both hybrids and EVs to support the diverse needs of the automotive industry.”
Organizational agility is also crucial in this rapidly evolving sector.
“Flexibility allows us to respond quickly to dynamic customer needs, localize development, and adapt product roadmaps to regional differences,” he shares. “Europe is showing a strong shift toward EVs, but PHEVs remain a transition. North America favors hybrids due to range anxiety, while China pushes EVs aggressively under supportive policy.”
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