Electronic control units, or ECUs, drive the connections in a vehicle. The microprocessors support a variety of features, from airbag deployment and parking assistance to memory seats and power steering.

Additionally, a car’s sensors pick up information from around the vehicle and send that back to computerized systems to initiate action and to enable autonomous driving capabilities.

Brian Shay, Siemens

The car is becoming a kind “smartphone on wheels” according to an industry expert from Siemens. And a 65-mile-an-hour phone requires a greater number of ECUs.

“There was a time when we used to have one [ECU] per vehicle,” said Brian Shay, Portfolio Development Executive, Digital Manufacturing, at the simulation tech provider Siemens. “Now we have maybe 100 per vehicle.”

Shay spoke during a live Tech Briefs presentation titled Addressing the Challenges in Battery and Electrical Systems Manufacturing for EVs .

The increased complexity is driving more required connections on a vehicle’s wire harness, the vehicle's “central nervous system” according to Shaw. The wire harness is an organized collection of cables and connectors that send power and data throughout the vehicle.

More ECUs means more wires.

And to add to the complexity, an increasing number of cars are opting for an electric powertrain over a traditional internal combustion vehicle.

“As we move into the realm of the electric vehicle, this wire harness becomes even more complex and even more crucial,” Shay told a virtual crowd of Tech Briefs attendees.

During the live Q&A, a reader had the following question for Shay.

How different is the wire harness for an EV compared to a wire harness for traditional internal combustion vehicles?”

Read Shay’s edited response below.

Shay: The EV drivetrain system actually has its own wiring system in addition to the standard wiring harness that you would see in an internal combustion engine (ICE) vehicle. That drivetrain system is composed of the high voltage batteries, the inverters, and the motors. These are all connected via a high-voltage wire harness of its own. They’re shielded, because the high voltage creates electromagnetic noise that could interfere with things that are in the regular wire harness.

The EV wire harness itself, not including the EV drivetrain, is similar to [the one for] an internal combustion engine, but there are some additional components and complexities. So, that wire harness also has to connect to the EV drivetrain.

An example of that might be the frontal collision mitigation system in a vehicle.

In my car, if my vehicle thinks I’m in a situation where I need to brake. First, it flashes a sign on the instrument panel saying I should hit the brakes. And if I don’t hit the brakes, it hits the brakes for me. What you would see in an electric vehicle: It would go through the same process, but it would also communicate with the EV drive system to shut off the electric motors while I’m trying to do an emergency brake.

So, there’s communication going on between those two wiring systems: the traditional wire harness, which, for an electric vehicle, is a little more complex than an ICE vehicle, but not, say, twice as complex. There is communication going on, however, between those two sets of wiring systems.

What do you think? Share your questions and comments below.