Rethinking the high-voltage cable assembly: pre-validated and ready to install 

Q&A with Marc Moser, HUBER+SUHNER

Ask what’s holding back electric truck and bus production and you’ll usually hear about battery supply or software. Less often mentioned: the orange highvoltage cable running between the battery, inverter, e-axle and charging port. As commercial EV volumes climb, that highvoltage power distribution has become a real constraint, and the old way of building it, one bespoke harness at a time, is straining to keep up.

The argument of HUBER+SUHNER is that the fix isn’t another custom harness but a standardized, pre-validated modular cable assembly that arrives ready to install. The company calls its version mCAY, short for modular cable assembly. Launched in 2024, the mCAY is built on the RADOX® high voltage cable line.

Charged recently chatted with HUBER+SUHNER’s Marc Moser to learn more.

Charged: Give us a quick introduction to the RADOX modular cable assemblies.

Marc Moser: RADOX® is our brand of thin-wall, robust high voltage (HV) cable, and it’s the foundation for a reliable HV cable assembly. From there, our production line handles the cutting, stripping and termination of qualified HV connector systems, either our own EV-C or other validated third-party connectors, and finishes with proper end-of-line testing. The result is an mCAY built under one roof: short lead times, available either as a standard part number or as a modular assembly you configure yourself in our variant configurator.

Charged: Orange HV cables often get wrapped in a corrugated tube. Why is that, and how do you strip that out?

Moser: The HV cable assembly is usually separate from the low voltage signaling harness. You have to account for where the components sit, the inverter and the power distribution unit (PDU) that splits and routes high voltage power to the vehicle’s subsystems, for example. So you can route the charging and drive paths cleanly and fix them in place properly.

Traditionally the orange HV cable also has to be wrapped in a corrugated tube, because the cables underneath use soft insulation. RADOX® doesn’t need that. It’s a robust cable, with the abrasion resistance, electrical performance and environmental performance, such as UV resistance, to run unprotected. And that protection isn’t free: it changes the cable’s derating. Derating means lowering the current a cable can safely carry as heat builds up. Trapped heat forces you to either run less current or move to a bigger conductor.

We measured and simulated it and found that a 95 mm² cable inside a corrugated tube can be replaced by a 70 mm² cable in free air. Both heat up to 139 °C carrying 500 A. Dropping the tube also allows a smaller bend radius, which makes routing easier. Omitting the use of a tube around the cables also makes the HV cable assembly solution cheaper since there are significant cost savings in manufacturing.

Charged: With a modular assembly, what can an OEM still customize?

Moser: What’s customized tends to be the add-ons: clamps for fixation points, tubing, or extra taping where a cable needs more protection. Some applications also call for special cable or connector designs. An e-axle is the obvious case, where dynamic movement, high vibration and a harsh environment can demand a purpose-built solution. An e-axle packages the motor, power electronics and gearing into one driveline unit, so its cabling is in near-constant motion.

Charged: For an engineer weighing this against a conventional custom harness, where do the biggest time savings show up?

Moser: Evaluating and testing HV systems is complex and costly. Proving that the connector terminated to the cable holds up to high voltage performance and is sealed correctly, to the relevant ISO standard or to an OEM’s own standards, is a long road. With mCAY we’ve already walked it: the evaluation, the testing and the product safety are guaranteed as part of the assembly.

Charged: Your materials mention accelerated homologation— the formal certification that a part meets the regulations needed to put it on the road. How does a modular assembly concretely cut that burden for truck or bus OEMs?

Moser: RADOX®HV cables have been proven in the commercial vehicle market for years, so they’re already well recognized. The connector interfaces, chosen either by the OEM or by the supplier of the battery, PDU, inverter or e-motor, then define the type of assembly you need. Because every component in the assembly is already approved, homologation goes quickly.

Every assembly runs through a complete, approved build process, and a final inspection and test is what makes it qualified and ready to install.

Charged: What do engineers most often get wrong about cable shielding in HV systems?

Moser: Our shielding know-how comes out of the rail industry, where shielded cable has been used for decades, and that’s the basis for the electromagnetic compatibility (EMC) shield on the orange automotive RADOX® cables. EMC is a system’s ability to work without emitting or being disrupted by electromagnetic interference.

The point engineers often miss is that “100% coverage” of a shield doesn’t automatically give you good performance. What matters is transfer impedance and screening attenuation over the frequency range. Both are standard measures of how well a shield actually blocks interference, and coverage alone doesn’t capture them. Just as important is the long-term reliability of where the shield terminates at the connector.

Charged: Commercial EVs run very different duty cycles than passenger cars. How did you design these assemblies for trucks and buses specifically, rather than adapting passenger-EV practice?

Moser: Some of the standard HV connectors from the passenger-car world simply aren’t reliable enough for harsh-duty use. The cables often need ADR approval (the European agreement governing road transport of dangerous goods), or flammability certification to ECE R118 (the UN regulation on the burning behavior of materials used in commercial-vehicle and bus interiors).

And most commercial-vehicle makers add their own testing and requirements on top of the ISO standards.

Charged: Where does a modular assembly make the most sense today, from prototypes to low-volume production?

Moser: The quickest win is availability, when someone needs a first prototype fast, for whatever purpose. But mCAY isn’t only for production or mid-size projects with selected HV assemblies. It’s also for testing. If you’re developing a PDU, you need cables to test it, and those test assemblies are easy to overlook when a new PDU program kicks off.

The third case is small- to medium-series production to the automotive IATF standard (the auto industry’s quality-management standard for production parts).

Charged: What’s the most common misconception engineers have when they first hear “modular” for high-voltage power distribution?

Moser: Probably that “modular” means you buy the components and assemble them yourself. That’s not it. You select the components in the variant configurator, define the length and the connector on each end, and we ship a proven, tested HV solution, with no tooling charges or other extra cost to the customer.

Charged: What does it look like when an OEM comes to you for a fast prototype build?

Moser: One OEM had selected components for its first prototype build and urgently needed a small batch of different HV cable assemblies. We turned the first functional assemblies around quickly, in-house, using both electromagnetic pulse technology (EMPT) and standard mechanical crimping. EMPT uses a high-energy magnetic pulse to join the connector to the conductor without heat, an alternative to mechanical crimping.

On top of that, we recommended the fixing points and ran short simulations. This optimizes our RADOX® solution for the dynamic application and allows us to select the right cable cross section for the best results in an ideal derating behavior within vehicle charging paths.

Learn more: The variant configurator and the full RADOX HV range are on the HUBER+SUHNER site.